This was a multi-institution study, and the first authors are from ...
In this paper, the authors find evidence that the bacteria Porphyro...
Periodontal disease, is an infection of the tissues that hold your ...
Here is a video from the company leading this study, Cortexyme, dis...
It is important to note the point that P. gingivalis is also found ...
P. gingivalis has been previously shown to be significantly associa...
Broad spectrum antibiotics cannot treat P. gingivalis, a motivation...
Tau is one of the main biomarkers for AD.
These key graphs demonstrate the presence of these P. gingivalis pa...
It is also important to note (as a limitation), that there is a dif...
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HEALTH AND MEDICINE
Porphyromonas gingivalis in Alzheimer’s disease brains:
Evidence for disease causation and treatment with
small-molecule inhibitors
Stephen S. Dominy
1
*
, Casey Lynch
1
*, Florian Ermini
1
, Malgorzata Benedyk
2,3
, Agata Marczyk
2
,
Andrei Konradi
1
, Mai Nguyen
1
, Ursula Haditsch
1
, Debasish Raha
1
, Christina Griffin
1
,
Leslie J. Holsinger
1
, Shirin Arastu-Kapur
1
, Samer Kaba
1
, Alexander Lee
1
, Mark I. Ryder
4
,
Barbara Potempa
5
, Piotr Mydel
2,6
, Annelie Hellvard
3,6
, Karina Adamowicz
2
, Hatice Hasturk
7,8
,
Glenn D. Walker
9
, Eric C. Reynolds
9
, Richard L. M. Faull
10
, Maurice A. Curtis
11,12
,
Mike Dragunow
11,13
, Jan Potempa
2,5
*
Porphyromonas gingivalis, the keystone pathogen in chronic periodontitis, was identified in the brain of Alzheimer’s
disease patients. Toxic proteases from the bacterium called gingipains were also identified in the brain of Alzheimer’s
patients, and levels correlated with tau and ubiquitin pathology. Oral P. gingivalis infection in mice resulted in
brain colonization and increased production of A
1–42
, a component of amyloid plaques. Further, gingipains were
neurotoxic in vivo and in vitro, exerting detrimental effects on tau, a protein needed for normal neuronal func-
tion. To block this neurotoxicity, we designed and synthesized small-molecule inhibitors targeting gingipains.
Gingipain inhibition reduced the bacterial load of an established P. gingivalis brain infection, blocked A
1–42
pro-
duction, reduced neuroinflammation, and rescued neurons in the hippocampus. These data suggest that gin-
gipain inhibitors could be valuable for treating P. gingivalis brain colonization and neurodegeneration in
Alzheimer’s disease.
INTRODUCTION
Alzheimer’s disease (AD) patients exhibit neuroinflammation con-
sistent with infection, including microglial activation, inflammasome
activation, complement activation, and altered cytokine profiles
(1,2). Infectious agents have been found in the brain and postulated
to be involved with AD, but robust evidence of causation has not
been established (3). The recent characterization of amyloid- (A)
as an antimicrobial peptide has renewed interest in identifying a
possible infectious cause of AD (4–6).
Chronic periodontitis (CP) and infection with Porphyromonas
gingivalis—a keystone pathogen in the development of CP (7)
have been identified as significant risk factors for developing A
plaques, dementia, and AD (8–12). A prospective observational
study of AD patients with active CP reported a notable decline in
cognition (Alzheimer’s Disease Assessment Scale—Cognitive and
Mini Mental State Examination scales) over a 6-month period com-
pared to AD patients without active CP, raising questions about
possible mechanisms underlying these findings (13). In Apoe
−/−
mice,
oral infection with P. gingivalis, but not with two other oral bacteria,
results in brain infection and activation of the complement pathway
(14). In transgenic mice overexpressing mutated human amyloid
precursor protein (hAPP-J20), oral infection with P. gingivalis
impairs cognitive function, increases the deposition of AD-like
plaques, and results in alveolar bone loss compared to control
hAPP-J20 mice (15). P. gingivalis lipopolysaccharide has been detected
in human AD brains (16), promoting the hypothesis that P. gingivalis
infection of the brain plays a role in AD pathogenesis (17).
P. gingivalis is mainly found during gingival and periodontal in-
fections; however, it can also be found at low levels in 25% of healthy
individuals with no oral disease (18). Transient bacteremia of P. gingivalis
can occur during common activities such as brushing, flossing, and
chewing, as well as during dental procedures (19), resulting in docu-
mented translocation to a variety of tissues including coronary ar-
teries (20), placenta (21), and liver (22). A recent study found that
100% of patients with cardiovascular disease had P. gingivalis arte-
rial colonization (23).
P. gingivalis is an asaccharolytic Gram-negative anaerobic bacte-
rium that produces major virulence factors known as gingipains,
which are cysteine proteases consisting of lysine-gingipain (Kgp),
arginine-gingipain A (RgpA), and arginine-gingipain B (RgpB).
Gingipains are secreted, transported to outer bacterial membrane
surfaces, and partially released into the extracellular milieu in solu-
ble and outer membrane vesicle (OMV)–associated forms (24,25).
Kgp and RgpA/B are essential for P. gingivalis survival and pathoge-
nicity, playing critical roles in host colonization, inactivation of host
defenses, iron and nutrient acquisition, and tissue destruction (24,26).
Gingipains have been shown to mediate the toxicity of P. gingivalis
1
Cortexyme, Inc., 269 East Grand Ave., South San Francisco, CA, USA.
2
Department
of Microbiology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian
University, Krakow, Poland.
3
Malopolska Centre of Biotechnology, Jagiellonian Uni-
versity, Krakow, Poland.
4
Division of Periodontology, Department of Orofacial Sci-
ences, University of California, San Francisco, San Francisco, CA, USA.
5
Department
of Oral Immunology and Infectious Diseases, University of Louisville School of Den-
tistry, Louisville, KY, USA.
6
Broegelman Research Laboratory, Department of Clinical
Science, University of Bergen, Bergen, Norway.
7
The Forsyth Institute, Cambridge,
MA, USA.
8
Harvard University School of Dental Medicine, Boston, MA, USA.
9
Coopera-
tive Research Centre for Oral Health Science, Melbourne Dental School and the Bio21
Institute of Molecular Science and Biotechnology, University of Melbourne, Melbourne,
Victoria, Australia.
10
Department of Anatomy with Radiology, Centre for Brain Research
and NeuroValida, Faculty of Medical and Health Sciences, University of Auckland,
Auckland, New Zealand.
11
Centre for Brain Research and NeuroValida, Faculty of Medi-
cal and Health Sciences, University of Auckland, Auckland, New Zealand.
12
Department
of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, Univer-
sity of Auckland, Auckland, New Zealand.
13
Department of Pharmacology, Faculty
of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
*These authors contributed equally to this work as co-senior authors.
†Corresponding author. Email: sdominy@cortexyme.com
Copyright © 2019
The Authors, some
rights reserved;
exclusive licensee
American Association
for the Advancement
of Science. No claim to
original U.S. Government
Works. Distributed
under a Creative
Commons Attribution
License 4.0 (CC BY).
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in endothelial cells, fibroblasts, and epithelial cells (27–29). More-
over, because treatment with broad-spectrum antibiotics rarely
eradicates P. gingivalis and may lead to resistance (30), gingipains
are implicated as narrow-spectrum virulence targets (24,3133).
Blocking gingipain proteolytic activity with short peptide analogs
reduces P. gingivalis virulence (34).
We hypothesized that P. gingivalis infection acts in AD patho-
genesis through the secretion of gingipains to promote neuronal
damage. We found that gingipain immunoreactivity (IR) in AD
brains was significantly greater than in brains of non-AD control
individuals. In addition, we identified P. gingivalis DNA in AD
brains and the cerebrospinal fluid (CSF) of living subjects diag-
nosed with probable AD, suggesting that CSF P. gingivalis DNA
may serve as a differential diagnostic marker. We developed and
tested potent, selective, brain-penetrant, small-molecule gingipain
inhibitors in vivo. Our results indicate that small-molecule inhibi-
tion of gingipains has the potential to be disease modifying in AD.
AD diagnosis correlates with gingipain load in brain
Tissue microarrays (TMAs) containing sex- and age-matched brain
tissue cores from the middle temporal gyrus (MTG) of both AD
patients and neurologically normal individuals were used for im-
munohistochemical (IHC) studies (tables S1 and S2). Gingipain-
specific antibodies, CAB101 and CAB102, targeting RgpB and Kgp,
respectively, were used to determine gingipain load in brain tissue
cores. Tau load in the TMAs was measured using an antibody
(DAKO A0024) that recognizes both nonphosphorylated and phos-
phorylated tau. RgpB and Kgp exhibited punctate intraneuronal
staining in tissue from AD brains (Fig.1,AandB, respectively). On
the basis of threshold analysis (see Materials and Methods), 96% (51
of 53) of AD samples were positive for RgpB and 91% (49 of 54) of
AD samples were positive for Kgp. The RgpB load was significantly
higher in AD brains than in nondemented control brains (Fig.1C),
and similarly, the Kgp load was significantly higher in AD brains
compared to nondemented control brains (Fig.1D).
We next stained for tau and found a highly significant correla-
tion between RgpB load and tau load (Fig.1E) and Kgp load and tau
load (Fig.1F). Tau pathology has been shown to correlate with cog-
nitive impairment in AD (35). We next stained the TMAs for ubiq-
uitin, a small protein tag that marks damaged proteins for degradation
by proteasomes (36) and accumulates in both tau tangles and A
plaques (37). There was a significant correlation between RgpB
load and ubiquitin load (Fig.1G) and Kgp load and ubiquitin load
(Fig.1H) in the TMAs. Of note, in nondemented control tissues, RgpB
staining was observed in 39% (18 of 46) of samples and Kgp staining
was observed in 52% (26 of 50) of samples. The correlation analyses
between the gingipain load and tau load (Fig.1,EandF) and between
the gingipain and ubiquitin load (Fig.1,GandH) in the nondemented
control samples revealed a continuum of gingipain and AD pathology
already present in the controls. These findings are consistent with
the concept of preclinical AD, i.e., the stage of disease when patho-
genesis has begun, but clinical symptoms are not yet present (38).
To further validate the gingipain IHC in the TMAs, we per-
formed a correlation analyses between the RgpB load and Kgp load
and found a significant correlation between the two different anti-
gens (Fig.1I). As a further IHC control, brain TMAs from several
different non-AD neurological diseases were probed with the CAB101
antibody. RgpB immunostaining on MTG TMAs of Parkinson’s
disease, Huntington’s disease, and amyotrophic lateral sclerosis re-
vealed no significant differences compared to controls (fig. S1). In
summary, both RgpB and Kgp antigens in brain independently
demonstrated a significant correlation with AD diagnosis, tau load,
and ubiquitin load.
RgpB colocalizes with neurons, astrocytes, and pathology in
AD hippocampus
In AD, the hippocampus is one of the first brain areas to be damaged.
Using a different antibody for RgpB than CAB101 (18E6 monoclonal;
see Materials and Methods), RgpB-IR was confirmed in neurons of
the dentate gyrus and CA3, CA2, and CA1 of AD hippocampus with
brightfield microscopy (Fig.2A). IHC analysis of a series of brains
from a university brain bank revealed a similar pattern of staining
for RgpB (fig. S2). Using immunofluorescence, RgpB-IR (CAB101)
colocalized primarily with neurons [microtubule-associated protein 2
(MAP2)] (Fig.2C) as well as occasional astrocytes, but not with
microglia (Iba1) (Fig.2D). In addition, RgpB colocalized with
pathology including tau tangles and intraneuronal A (Fig.2E).
Detection of Kgp in AD cerebral cortex
AD is also associated with atrophy of the gray matter of the cerebral
cortex. Brain lysates from the cerebral cortex of three AD brains
and six nondemented control brains were immunoprecipitated (IP)
with CAB102 and run on a Western blot (WB) (Fig.3B). The
CAB102 polyclonal antibody recognizes amino acids 22 to 400 of
Kgp, covering the propeptide and the N-terminal region of the cat-
alytic domain (see Materials and Methods). The WB from all three
AD brains revealed similar Kgp bands of molecular weights corre-
sponding to the molecular weights of Kgp bands from bacterial ly-
sates from P. gingivalis strains W83, ATCC33277, and FDC381
(Fig.3A). Strain HG66, which contains a mutation affecting the re-
tention of gingipains on its cell surface (39), demonstrated only a
single Kgp band at the molecular weight of the Kgp catalytic domain
(Fig.3A). The Kgp catalytic domain was identified at the proper mo-
lecular weight (40) in all of the AD brain samples (Fig.3B). In
addition, five of the six nondemented control brains demonstrated
Kgp banding patterns similar to the AD brains (Fig.3B), consistent
with our IHC data demonstrating a continuum of gingipain and AD
pathology present in nondemented control brains (Fig.1,D,F,andH).
In the sixth nondemented control brain sample (C6), the Kgp bands
were very faint, indicating near absence of Kgp (Fig.3B).
Identification of the P. gingivalis 16S rRNA and hmuY genes
in AD cerebral cortex
To further validate the Kgp protein detection data, we performed
quantitative polymerase chain reaction (qPCR) analysis on DNA
isolated from the same brain tissue used for the Kgp IP and WB
analysis. qPCR analysis using P. gingivalis 16S rRNA primers re-
vealed the presence of the P. gingivalis 16S rRNA gene in the AD
brains and five of the six nondemented control brains (Fig.3C).
Control brain C6, which exhibited near absence of Kgp bands in
Fig.3B above, was negative by qPCR for the P. gingivalis 16S rRNA
gene (Fig.3C). To further validate the 16S rRNA qPCR results, we
performed PCR analysis using primers for the hmuY gene, a gene
highly specific for P. gingivalis (41). All three AD brains and the five
nondemented control brains that were positive for the 16S rRNA
gene were also positive for the hmuY gene, and sequencing of the
hmuY PCR products confirmed the presence of P. gingivalis in brain
DNA (fig. S3). Because we were using a highly sensitive PCR method
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to detect low copy numbers of P. gingivalis DNA (see Materials and
Methods), we were concerned that nested amplification of a common
Gram-negative bacterium such as P. gingivalis in the presence of brain
DNA could be creating a false-positive signal. Therefore, as an ad-
ditional negative control, we used the same nested primer method
to attempt to detect another ubiquitous Gram-negative bacterium,
Helicobacter pylori (see Materials and Methods) (42). We tested the
three AD brain DNA samples and three of the P. gingivalis–positive
nondemented brain DNA samples for H. pylori. All six brain sam-
ples were negative for H. pylori using validated qPCR primers and
probe (fig. S3D) (43), indicating that our P. gingivalis PCR results
are not likely due to a PCR artifact. In summary, the identification
of P. gingivalis DNA in AD brains and Kgp-positive nondemented
control brains further validates the identification of Kgp in the same
brain tissue samples by IP and WB.
P. gingivalis DNA is present in the CSF of clinical AD patients
CSF is considered a “window” into brain infection, providing in-
sight into the neuropathogenesis of infectious agents (44). Hence,
we conducted a prospective pilot study using CSF collected from
AC
E
FD
B
IG
H
Control
Control
Fig. 1. Gingipain IR in brain correlates with AD diagnosis and pathology. (A and B) Representative TMA NVD005 containing brain tissue cores from the MTG of AD
patients and controls probed for RgpB (A) and Kgp (B) with antibodies CAB101 and CAB102, respectively. Higher magnification of representative tissue cores reveals
higher neuronal RgpB-IR and Kgp-IR in AD tissue cores than in control cores. (C) RgpB-IR and (D) Kgp-IR data from TMAs NVD005 and NVD003 show significantly higher load
in AD brain compared to controls. Mann-Whitney test, ***P < 0.0001; presented as geometric mean ± 95% confidence interval, n = 99 (C) and n = 104 (D). (E and F) Tau
load correlates to RgpB load (Spearman r = 0.674, P < 0.0001, n = 84) (E) and Kgp load (Spearman r = 0.563, P < 0.0001, n = 89) (F). Blue, control; red, AD. (G and H) Ubiquitin
load, a marker of AD pathology, correlates to RgpB load (blue, control; red, AD; Spearman r = 0.786, P < 0.0001, n = 99) (G) and Kgp load (Spearman r = 0.572, P < 0.0001,
n = 104) (H). (I) RgpB load correlates with Kgp load (Spearman r = 0.610, P < 0.0001, n = 99).
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10 patients diagnosed with probable AD who had mild to moderate
cognitive impairment (Fig.4D). CSF and matched saliva samples
were collected and analyzed for P. gingivalis DNA by qPCR detec-
tion of the hmuY gene (41). Positive and negative controls, similar
to the standard of care for detection of other brain infections in CSF,
were used (45,46). We were able to detect and quantify copies of the
hmuY gene by qPCR in CSF in 7 of the 10 clinically diagnosed AD
patients, with P. gingivalis load ranging from 10 to 50 copies/l of
CSF (Fig.4A), and the relative fluorescence intensity of the qPCR
products on agarose gel was consistent with the qPCR data (Fig.4C).
Sequencing of the endpoint PCR products from CSF confirmed the
presence of the hmuY gene (fig. S4). We then quantified the P. gingivalis
load in the matching saliva samples from all 10 patients. All 10 match-
ing saliva samples were positive for P. gingivalis by qPCR assay of
the hmuY gene (Fig.4B). As with the brain samples noted above, for
a PCR-negative control, we analyzed CSF samples for the presence of
H. pylori using methods with the same sensitivity as for P. gingivalis.
All of the CSF samples were negative for H. pylori (Fig.4C). The
CSF data provide additional evidence for P. gingivalis infection in
the brain of AD patients.
A
B
C
D
E
Fig. 2. RgpB colocalizes with neurons and pathology in AD hippocampus. (A) IHC using RgpB-specific monoclonal antibody 18E6 (representative images from a
63-year-old AD patient). The hippocampus shows abundant intracellular RgpB in the hilus (1), CA3 pyramidal layer (2), granular cell layer (3), and molecular layer (4).
High-magnification images from the indicated areas (1 to 4) exhibit a granular staining pattern consistent with P. gingivalis intracellular infection. Scale bars, 200 m
(overview), 50 m (1), and 10 m (2 to 4). (B) AD hippocampus stained with 18E6 (AD) compared to gingival tissue (gingiva) from a patient with periodontal disease as well as a
non-AD control and mouse IgG1 control (IgG1) in an adjacent hippocampal section. Scale bars, 50 m. (C) Immunofluorescent colabeling with CAB101 reveals granular
intraneuronal staining for RgpB (arrows) in MAP2-positive neurons in both the granular cell layer (GCL) and the pyramidal cell layer (CA1). Scale bars, 10 m. (D) Dense extra-
cellular RgpB-positive aggregates (arrowheads) were closely associated with astrocytes [glial fibrillary acidic protein (GFAP)]. There was no observed association of RgpB with
microglia (IBA1). Scale bars, 10 m. (E) RgpB was associated with paired helical filament Tau (PHF-Tau; arrows). RgpB-positive neurons negative for PHF-Tau (arrowheads)
were also seen. Intracellular A was often colocalized with RgpB (arrows). In some A-positive cells, RgpB could not be detected (arrowheads). Scale bars, 10 m.
AB
C
Fig. 3. Identification of P. gingivalis–specific protein and DNA in cortex from control and AD patients. (A) WB with four different strains of P. gingivalis and CAB102
detection of typical molecular weight bands for Kgp in bacterial lysates. (B) IP using brain lysates from nondemented controls (C1 to C6; ages 75, 54, 63, 45, 37, and 102 years,
respectively) and AD patients (AD1 to AD3; ages 83, 90, and 80 years, respectively) using CAB102 with subsequent WB reveals the ~50-kDa Kgp catalytic subunit (Kgp
cat
),
along with higher– and lower–molecular weight Kgp species seen in (A). (C) qPCR from DNA isolated from the same brain lysates as the protein samples analyzed in (B)
shows a positive signal in nondemented control (C1 to C5) and AD (AD1 to AD3) samples. Sample C6 from the 102-year-old nondemented control patient had no detect-
able qPCR signal in (C) and very faint bands indicating near absence of Kgp (B) (mean with SEM error bars of repeat qPCR runs).
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Tau is fragmented by gingipains
Because we identified colocalization of gingipain with tau tangles in
AD brain (Fig.2E), we were interested to see whether tau was a target
for gingipain proteolysis. Tau truncation and fragmentation have
been proposed to play a key role in inducing the formation of insol-
uble and hyperphosphorylated tau in AD (4749). To determine
whether gingipains cleave tau in a cell-based system, we used SH-
SY5Y cells that express high–molecular weight forms of tau (50).
Using the Tau-5 antibody as a probe, SH-SY5Y cells infected
with three different concentrations of P. gingivalis were examined at
three different time points. The results showed a dose-dependent
loss of soluble total tau within 1 hour of infection compared to unin-
fected cells, while cells infected with P. gingivalis gingipain–defective
mutants showed soluble tau levels similar to uninfected cells, indi-
cating that gingipains were responsible for the loss of the Tau-5 epitope
(Fig.5,AandB).
To characterize gingipain cleavage sites within tau, we incubated
recombinant tau-441 with purified protein containing the catalytic
domains of both Kgp and RgpB in combination and identified tau
cleavage fragments by mass spectrometry (MS). Following exposure
to 1 nM purified gingipains, we identified tau fragments covering
23% of the tau-441 amino acid sequence; at 10 nM gingipains, tau
fragments were generated covering 85% of the tau sequence (Fig.5D
and table S3). From the identified tau fragments, we were able to
deduce 14 RgpB cleavage sites and 30 Kgp cleavage sites within the
tau-441 protein (Fig.5D). Most of the Kgp cleavage sites (21 of 30)
were located C-terminal to position 222 in the tau protein. For RgpB,
the majority of cleavage sites (9 of 14) were located N-terminal to
position 222. Within the Tau-5 antibody epitope, which spans resi-
dues 210 to 230 in tau-441, we identified two RgpB cleavage sites
and two Kgp cleavage sites (Fig.5D,b). Thus, gingipain cleavages
within the Tau-5 antibody epitope were the likely cause of the loss
of the Tau-5 antibody signal and therefore tau protein detection af-
ter SH-SY5Y cells were infected with P. gingivalis.
We identified a mid-domain, RgpB-generated tau peptide fragment,
TPSLPTPPTR (residues 212 to 221), which is part of the Tau-5 epitope
(Fig.5D,g). This tau peptide is common to all tau isoforms and has
been used as an analyte to measure tau levels in CSF (51) and deter-
mine the turnover rate of tau in the human central nervous system
(CNS) (52). The TPSLPTPPTR fragment has been reported to be
increased 1.7-fold in AD CSF compared to non-AD CSF (51).
Kgp generated four unique tau peptide fragments containing the
hexapeptide sequence VQIVYK (Fig.5D,e) and two unique tau pep-
tide fragments containing the VQIINK sequence (Fig.5D,f). Tau
fragments containing these hexapeptide motifs have been shown to
be involved in tau tangle formation by nucleating paired helical fil-
aments (PHFs) from full-length tau (53,54).
Small-molecule gingipain inhibitors are neuroprotective
To determine whether gingipains are toxic to neurons in vitro, we ex-
posed differentiated SH-SY5Y cells to either RgpB or Kgp for 24 hours.
Combined application of RgpB and Kgp significantly increased cell
aggregation (Fig.6A). Pretreatment of gingipains with iodoacetamide,
an irreversible cysteine protease inhibitor, prevented gingipain-induced
aggregation, indicating that the proteolytic activity of the gingipains
was responsible for the morphological changes (Fig.6A).
On the basis of the cytotoxic activity of gingipains from P. gingivalis,
their presence in AD brain, and their critical role in bacterial survival
and virulence, we developed a library of potent and selective reversible
and irreversible small-molecule gingipain inhibitors. COR286 and
AB
CD
()
Fig. 4. Detection of P. gingivalis in CSF and oral biofluids from clinical AD subjects. (A) Detection and quantitation of P. gingivalis DNA by qPCR in CSF from subjects
with probable AD. (B) Detection and quantitation of P. gingivalis DNA by qPCR from matching saliva samples. (C) Top: PCR products detecting P. gingivalis from CSF in (A)
from all subjects run on agarose gel including negative and positive controls containing a synthetic DNA template. Faint or undetectable PCR products from subjects AD1,
AD3, and AD5 were below the limit of quantitation for copy number and not of sufficient quantity for sequence analysis. Bottom: qPCR products from CSF from the same
subjects for H. pylori. (D) Data table includes age and Mini Mental Status Exam (MMSE) score on subjects and sequence identity of PCR products to P. gingivalis hmuY DNA
sequence. Sequence data are included in fig. S4. NS, not sequenced.
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COR271 are irreversible inhibitors of arginine-specific (RgpA and
RgpB) and lysine-specific (Kgp) gingipains, respectively, both with
a median inhibitory concentration (IC
50
) of <50 pM. COR119 is a
reversible covalent Kgp inhibitor with an IC
50
of 10 nM.
To quantify protective effects of gingipain inhibitors, we infected
SH-SY5Y cells with the W83 strain of P. gingivalis at a multiplicity of
infection (MOI) of 400 for 48 hours, producing approximately 50%
cell death (Fig.6B). COR286 and COR271 were both effective in block-
ing P. gingivalis–induced cell death in a concentration-dependent
manner (Fig.6B). Broad-spectrum antibiotics, moxifloxacin and doxy-
cycline, even at concentrations that reduce bacterial survival in vitro
(55), did not protect the cells. We also tested the -secretase inhibitor
semagacestat (LY450139), which blocks the formation of A
1–42
(56),
to determine whether bacterial toxicity was mediated by P. gingivalis
induced A production, but it had no protective effect (Fig.6B).
We next assessed whether gingipains are neurotoxic in vivo and
whether inhibitors can penetrate the brain and prevent gingipain neu-
rotoxicity. Eight-week-old BALB/c mice were given a single adminis-
tration of gingipain inhibitors via a combination of COR271 by oral
gavage and COR286 subcutaneously, or both vehicles. Stereotactic in-
jection of a combination of Kgp and RgpB into the hippocampus was
performed 1.5 hours later. Seven days later, brains were analyzed for
neurodegeneration. Mice injected with gingipains had a significantly
greater number of degenerating neurons than saline-injected mice, but
the neurodegeneration could be blocked by pretreatment with a com-
bination of gingipain inhibitors COR286 and COR271 (Fig.6,CandD).
Oral infection of mice with P. gingivalis results in brain
infection and induction of A
1–42
We next wanted to understand whether oral exposure to P. gingivalis
would result in brain infiltration and induction of the stereotypical
AD marker A
1–42
. Aged 44-week-old BALB/c mice were orally in-
fected every other day over 6 weeks with P. gingivalis W83, Kgp knock-
out (Kgp) [kgp (602–1732) Em
r
] (57), or RgpA RgpB double
knockout (Rgp) (rgpA rgpB495-B Cm
r
, Em
r
) (58) P. gingivalis.
One W83-infected arm was administered the Kgp inhibitor COR119
three times per day subcutaneously over days 21 to 42. Endpoint PCR
analysis of mouse brains for P. gingivalis revealed that the bacteria
invaded the brain of all eight mice after oral infection for 6 weeks,
and colonization was decreased by gingipain knockout strains or treat-
ment with COR119 (Fig.7A). Mouse brain A
1–42
increased signifi-
cantly after oral infection with P. gingivalis compared to mock-infected
or COR119-treated mice (Fig.7B). Mice infected with Rgp or Kgp
strains of P. gingivalis had brain A
1–42
levels no different than mock-
infected, indicating that both gingipains were needed, either directly
or indirectly, to induce an A
1–42
response in vivo (Fig.7B).
A
1–42
has antibacterial effects against P. gingivalis
The significant A
1–42
response in the mouse brain to P. gingivalis
infection is consistent with reports demonstrating that A
1–42
is an
antimicrobial peptide (4,6). We therefore assayed whether A
1–42
interacts with P. gingivalis and decreases its viability in vitro. After
incubation of A
1–42
with P. gingivalis, A
1–42
colocalized with RgpB
on the surface of the bacterium (Fig.7C). Because A
1–42
is known
to disrupt cellular membranes, we hypothesized that A
1–42
might
disrupt the integrity of the P. gingivalis membrane to cause cell death.
In a separate experiment, we used an assay that can detect damaged
bacterial membranes and quantitate the amount of dead or dying
bacterial cells as a result of membrane damage. We found that the
proportion of dead and dying P. gingivalis bacterium significantly
increased after incubation with A
1–42
when compared to A
1–40
,
A
1–42
scrambled, and phosphate-buffered saline (PBS; Fig.7D).
A
B
C
D
Fig. 5. P. gingivalis and gingipains fragment tau. (A) WB analysis of total soluble tau in SH-SY5Y cells infected with increasing concentrations of wild-type (WT)
P. gingivalis strain W83 (P.g.) and P. gingivalis gingipain-deficient mutants either lacking Kgp activity (KgpIg-B) or lacking both Kgp and Rgp activity (K/RAB-A). Un-
infected SH-SY5Y cells (No P.g.) were used as a negative control. Glyceraldehyde-phosphate dehydrogenase (GAPDH) was used as a loading control. Total tau was moni-
tored with the monoclonal antibody Tau-5 at 1, 4, and 8 hours after infection. (B) Densitometry analysis of the total tau WB images. (C) WB analysis of rtau-441 incubated
with purified Kgp and RgpB catalytic domains combined (Gp) at various concentrations for 1 hour at 37°C. The blot was probed with tau monoclonal antibody T46.
(D) Gingipain cleavage sites in rtau-441 deduced from peptide fragments identified by MS for rtau-441 incubated with 1 or 10 nM gingipains. (a) T46 antibody epitope
(red). (b) Tau-5 antibody epitope (red). (c) N-terminal tau fragment. (d) C-terminal tau fragment. (e) Kgp-generated tau fragments containing the VQIVYK sequence.
(f ) Kgp-generated fragments containing the VQIINK sequence. (g) An RgpB-generated tau fragment. *Cleavage sites identified at 1 nM gingipains.
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Oral administration of a Kgp inhibitor effectively treats
P. gingivalis brain infection and prevents loss of
hippocampal Gad67
+
interneurons in vivo
We next wanted to measure the effects of gingipain inhibitors on
P. gingivalis load in the brain after oral infection of BALB/c mice. Eight-
week-old mice were orally infected every other day for 42 days with
P. gingivalis W83 [10
9
colony-forming units (CFU)] and were given
28 days of rest before study completion. Treatment, beginning after
brain infection was established, was administered during days 36 to
70 (Fig.7E). P. gingivalis DNA was identified by qPCR in the brain
of all infected mice at day 35, and copies of the P. gingivalis genome
significantly increased by day 70 (Fig.7F). The Kgp inhibitor COR271,
which has oral bioavailability and significant CNS penetration, ad-
ministered orally twice a day significantly reduced bacterial load in
the brain compared to the positive control infection arm and in com-
parison to baseline levels at 5 weeks (Fig.7F). The RgpB inhibitor
COR286, administered subcutaneously, was effective in reducing the
brain bacterial load at 10 weeks, but was not as effective as COR271
in reducing the bacterial load below baseline at 5 weeks (Fig.7F). The
broad-spectrum antibiotic moxifloxacin was also beneficial in pre-
venting the increase in brain colonization between day 35 and day 70
but was not effective in reducing the P. gingivalis load below the 5-week
baseline (Fig.7F). Combinations of COR271 with moxifloxacin or
COR286 did not improve efficacy over COR271 alone (Fig.7F).
Histological analysis of brains after the completion of the 10-week
study revealed a significant loss of Gad67
+
GABAergic interneurons
in the hippocampal dentate gyrus in the P. gingivalis infection group
compared to mock infection (Fig.7G). In AD, brain neuroimaging
and postmortem studies have shown variable disruption of the hip-
pocampal GABAergic system (59). Treatment with the Kgp inhibitor
COR271 alone, the RgpB inhibitor COR286 alone, a combination of
COR271 and COR286, COR271 plus moxifloxacin, and moxifloxacin
A
B
CD
Fig. 6. Small-molecule gingipain inhibitors protect neuronal cells against P. gingivalis– and gingipain-induced toxicity in vitro and in vivo. (A) Differentiated SH-
SY5Y neuroblastoma cells demonstrate cell aggregation after exposure to RgpB (10 g/ml), Kgp (10 g/ml), or both for 24 hours. The nonselective cysteine protease in-
hibitor iodoacetamide (IAM) blocks the gingipain-induced cell aggregation. (B) AlamarBlue viability assay shows that P. gingivalis (P.g.) is toxic to SH-SY5Y cells (MOI of
400) and that the small-molecule Kgp inhibitor COR271 and the RgpB inhibitor COR286 provide dose-dependent protection. The broad-spectrum antibiotics moxifloxa-
cin and doxycycline and the -secretase inhibitor semagacestat did not inhibit the cytotoxic effect of P. gingivalis. (C) Fluoro-Jade C (FJC) staining (green) in pyramidal
neurons of the CA1 region of the mouse hippocampus indicates neurodegeneration after stereotactic injection of gingipains. Counterstain with 4,6-diamidino-2-phenylindole
(DAPI) (blue). Scale bars, 50 m. (D) The total number of FJC-positive cells was determined from serial section through the entire hippocampus. Results demonstrate a
significant neuroprotective effect of gingipain inhibitors COR271 + COR286 after acute gingipain exposure in the hippocampus (*P < 0.05, n = 14). All graphs show the
mean with SEM error bars.
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AB
DC
E
FG
( )
D
×
,
Fig. 7. P. gingivalis invasion of the brain induces an A
1–42
response that is blocked by gingipain inhibition in mice. (A) P. gingivalis PCR product in mouse brains
after oral infection with P. gingivalis W83, with or without treatment with the Kgp inhibitor COR119, or infection with gingipain knockout strain RgpB or Kgp. Lanes 1
to 8 represent individual experimental animals. In the first lane (P.g.), P. gingivalis W83 was used as a positive control. (B) P. gingivalis W83–infected mice, but not COR119-
treated mice or mice infected with gingipain knockouts, had significantly higher A
1–42
levels compared to mock-infected mice (***P < 0.001, n = 40). (C) RgpB-IR (red)
colocalized with A
1–42
-IR (green) on the surface of P. gingivalis (D) A
1–42
, but not A
1–40
or A
1–42
scrambled, decreased viability of P. gingivalis (***P < 0.001, n = 12).
(E) Study design to quantitate the effect of gingipain inhibitors on brain P. gingivalis load. (F) qPCR results showed a substantial P. gingivalis copy number in the brain at
5 weeks, increasing 10-fold at 10 weeks (Inf. 10 week). All treatment groups showed a significant decrease in P. gingivalis load compared to vehicle-treated Inf. 10 week
mice (***P < 0.0001, n = 63). Treatment with the Kgp inhibitor COR271 resulted in a 90% reduction of P. gingivalis copy number. Comparing treatment groups to baseline
infection at the beginning of treatment (Inf. 5 week) showed a significant reduction with COR271 and COR286 (
##
P < 0.01,
#
P < 0.05) but not with moxifloxacin. (G) The
number of Gad67
+
interneurons in the dentate gyrus of the hippocampus was significantly decreased in the Inf. 10 week group (*P < 0.05, n = 120). This decrease was
reduced in all treatment groups, with COR271 and COR286 trending to better protection than moxifloxacin. (F) Geometric mean with 95% confidence interval. (B), (D),
and (G) show the mean with SEM error bars.
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alone, all beginning at day 36, reduced loss of the Gad67
+
interneu-
rons, with moxifloxacin-treated arms trending to decreased protec-
tion (Fig.7G).
COR388 treatment shows dose-dependent effects on brain
P. gingivalis infection, A
1–42
, and tumor necrosis factor–
levels in mice
On the basis of the superior performance of the highly potent and
specific Kgp inhibitor COR271 in the above in vivo mouse study in
clearing P. gingivalis brain infection and protecting Gad67
+
neurons
in the hippocampus compared to an Rgp inhibitor and a broad-
spectrum antibiotic, we developed the COR271 analog COR388.
Similar to COR271, COR388 is a highly potent (picomolar inhibi-
tion constant on Kgp) and selective irreversible small-molecule inhibi-
tor of Kgp, with superior oral pharmacokinetic and drug- appropriate
properties including significant CNS penetration.
In parallel, we also developed Kgp activity–based probes to
characterize COR388 Kgp target engagement in intact P. gingivalis
bacteria and biological tissue samples. We developed the fluores-
cent activity probe COR553 by combining a potent, small-molecule
irreversible Kgp inhibitor with Cy5 (Fig.8A) and validated its spec-
ificity and potency on Kgp in vitro (Fig.8,BtoD). COR553 bound
Kgp present in bacterial cultures of P. gingivalis but did not bind a
strain deficient in Kgp (Fig.8B). Preincubation of bacterial lysate
with Kgp antibody CAB102 depleted Kgp protein and COR553
binding from the lysate, while CAB102 antibody–bound complexes
contain Kgp and COR553 binding, confirming the identity of the
COR553 target (Fig.8C). Preincubation of P. gingivalis with 100 nM
COR388 before COR553 binding resulted in COR388 engagement
with the Kgp active site and a block of COR553 activity probe bind-
ing (Fig.8D). Using the COR553 probe, we demonstrated COR388
Kgp target engagement ex vivo in human oral subgingival plaque
samples obtained from patients with periodontal disease (table S4).
COR553 labeled Kgp present in plaque in four of the five sub-
jects. Preincubation with COR388 blocked probe binding to the
active site, while total Kgp protein was still detected by CAB102
(Fig.8E). High levels of Kgp in these plaque samples mirrored
detection of P. gingivalis DNA in the plaque samples (Fig.8F).
These same four subjects also had detectable levels of P. gingivalis in
saliva (Fig.8G).
A
E
HI JKL
FG
BC D
Fig. 8. COR388 target engagement and dose-dependent effects on brain P. gingivalis, A
1–42
, and TNF in mice. (A) COR553 fluorescent activity probe for Kgp.
(B) COR553 labeling of Kgp in P. gingivalis W83 strain and no labeling in mutant deficient in Kgp (Kgp). (C) W83 lysates labeled with COR553. Left lane, before immuno-
depletion; middle lane, after immunodepletion with anti-Kgp–conjugated beads; right lane, after elution from anti-Kgp–conjugated beads. (D) W83 strain titrated and
labeled with COR553 to determine the limit of bacterial detection. See Results for details. (E) Oral plaque samples from human subjects (CB1-5) with periodontal disease
were incubated ex vivo with COR553 probe with or without preincubation with COR388. COR553 probe and CAB102 detected Kgp strongly in three subjects (CB1, CB4,
and CB5) and weakly in one subject (CB3). COR388 preincubation blocked COR553 probe binding to Kgp. (F) qPCR analysis of plaque samples using hmuY gene–specific
primers identified P. gingivalis DNA in samples. (G) qPCR analysis of saliva samples. The bar graphs in (F) and (G) show the means and SEMs of three replicates. (H) COR388
treatment of W83 culture in defined growth medium reduced growth similarly to a Kgp-deficient strain (Kgp) over 43 hours. (I) Resistance developed rapidly to moxi-
floxacin but not COR388 with repeat passaging of bacterial culture. (J to L) Efficacy of COR388 at three oral doses of 3, 10, and 30 mg/kg twice daily in treating an estab-
lished P. gingivalis brain infection in mice. Reduction of brain tissue levels of P. gingivalis (J), A
1–42
(K), and TNF (L). The bar graphs show the means with SEM error bars.
***P < 0.001, **P < 0.01, *P < 0.05, t test with Dunn’s multiple comparison correction; n = 39.
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Using a defined growth medium, we showed that COR388 in-
hibited the growth of P. gingivalis, demonstrating that an inhibitor
of the Kgp virulence factor involved in generating nutrient amino
acids for energy acts as a narrow-spectrum antibiotic (Fig.8H). To
test for the potential for resistance to COR388, P. gingivalis was pas-
saged in the presence of COR388 or the broad-spectrum antibiotic
moxifloxacin. As shown in Fig.8I, P. gingivalis developed complete
resistance to moxifloxacin, with the minimum inhibitory concentra-
tion (MIC) increasing over 1000-fold in 12 passages. Resistance to
COR388 in two independent assays did not develop in this study. Effi-
cacy of COR388 was tested in vivo to treat an established P. gingivalis
brain infection in the mouse model described above for COR271
efficacy testing (Fig.7E). Similar to COR271, oral dosing of COR388
twice daily resulted in dose-dependent efficacy when administered to
an established P. gingivalis brain infection. Doses of 10 and 30 mg/kg
reduced P. gingivalis load, A
1–42
, and tumor necrosis factor– (TNF)
levels in brain tissue compared to those of infected animals treated
with vehicle (Fig.8,JtoL). The lowest dose of COR388 at 3 mg/kg
showed some reduction of brain P. gingivalis load but did not reduce
levels of brain A
1–42
or TNF (Fig.8,JtoL). Investigational new
drug application–enabling studies were completed with COR388,
and the compound is currently in clinical studies (ClinicalTrials.gov
NCT03331900).
DISCUSSION
The findings of this study offer evidence that P. gingivalis and gin-
gipains in the brain play a central role in the pathogenesis of AD,
providing a new conceptual framework for disease treatment. Ac-
cordingly, we demonstrate the presence of P. gingivalis DNA and
gingipain antigens in AD brains and show in vivo that oral admin-
istration of small-molecule gingipain inhibitors blocks gingipain-
induced neurodegeneration, significantly reduces P. gingivalis load
in the mouse brain, and significantly decreases the host A
1–42
re-
sponse to P. gingivalis brain infection.
Our identification of gingipain antigens in the brains of individ-
uals with AD and also with AD pathology but no diagnosis of de-
mentia argues that brain infection with P. gingivalis is not a result of
poor dental care following the onset of dementia or a consequence
of late-stage disease, but is an early event that can explain the pa-
thology found in middle-aged individuals before cognitive decline
(60). We also demonstrate that P. gingivalis bacterial load can be
detected in the CSF of clinical AD patients, providing further evi-
dence of P. gingivalis infection of the CNS.
The PCR analysis of P. gingivalis in the brain and CSF reported
here does not differentiate between P. gingivalis strains, and future
studies are needed to determine what P. gingivalis strains are pres-
ent in the brain and CSF and whether some strains might be more
virulent than others in causing disease. In addition, there is one other
species of Porphyromonas that is known to produce gingipains,
Porphyromonas gulae (61). P. gulae is a natural inhabitant of the oral
cavity of companion animals such as dogs, and a recent study demon-
strated that dogs can transmit P. gulae to the oral cavity of their
owners (62). Research is underway to determine whether P. gulae
may be contributing to the gingipain load in AD brains.
Evidence from our work reported here lends support to the emerg-
ing concept that A is an antimicrobial peptide (4–6), and mutations
(63,64) contributing to loss of this function could allow more ro-
bust infection with P. gingivalis and higher risk for disease. In addi-
tion, sustained high levels of antimicrobial A driven by chronic
P. gingivalis infection of the brain may be toxic to host cells, and
therefore, reduction of A levels after treatment of the P. gingivalis
infection should be beneficial. Furthermore, Down syndrome (DS),
the most common genetic cause of mental disability, has been used
to support A as a therapeutic target because of the notably high
prevalence of dementia with Alzheimer-type pathology in DS pa-
tients (greater than 50% after the age of 60) and the fact that the
amyloid precursor protein gene, which gives rise to A, is present
on chromosome 21, which is triplicated in DS (65). However, in sup-
port of our hypothesis, an aggressive form of periodontitis with rap-
id progression and onset as early as 6 years of age is associated with
DS, but not age-matched normal controls or other mentally handi-
capped patients of a similar age distribution (66). The occurrence of
P. gingivalis has been found to be significant in the subgingival plaque
of DS patients beginning around the age of 5 years when compared
to age-matched controls, indicating that P. gingivalis abnormally
colonizes DS patients in early childhood (67). The reason behind
DS patients being susceptible to P. gingivalis infection at such an
early age is unclear but may be due to the immunodeficiency that is
associated with DS (68). Research is needed to determine whether
P. gingivalis and gingipains are present in DS CSF and brain.
Although not specifically addressed in this report, once the oral
cavity is infected, P. gingivalis may access the brain and spread via a
number of pathways including (i) infection of monocytes followed
by brain recruitment (69,70), (ii) direct infection and damage to
endothelial cells protecting the blood-brain barrier (28), and/or (iii)
infection and spreading through cranial nerves [e.g., olfactory (71)
or trigeminal] to the brain. After entering the brain, we suggest that
P. gingivalis may spread slowly over many years from neuron to neu-
ron along anatomically connected pathways, similar to what has been
demonstrated for vascular cell-to-cell transmission of P. gingivalis (72).
Tau pathology has also been suggested to spread from neuron to
neuron (73), with a pattern resembling an infectious process. Our data
indicate that tau is a target of gingipain proteolysis, and we propose
that tau pathology seen in AD brains may be due to the transneuronal
spread of P. gingivalis, with direct damage of tau by gingipain pro-
teolysis as well as gingipain activation of human proteases that act
on tau. Gingipains have been shown to directly cleave procaspase-3 to
activate caspase-3 (74), a caspase that has been implicated in both
tau phosphorylation (75) and tau cleavage (76). Proteolysis of tau by
gingipains would be predicted to increase the turnover rate of tau
and trigger a compensatory increase in tau production rate to maintain
homeostasis in neurons infected by P. gingivalis. Recent research on
the kinetics of tau in the human CNS using the tau mid-domain
TPSLPTPPTR fragment as a reporter found that the production
rate of tau was increased in CSF of subjects with preclinical and
clinical AD (52). Our data demonstrating that both Kgp and RgpB
independently correlate with tau load in AD brains lend support to
the hypothesis that gingipains may be a driver of a compensatory
increase in tau production. Last, further research is needed to deter-
mine whether the gingipain-generated C-terminal tau fragments
containing the hexapeptide microtubule-binding domains that we
identified in vitro can drive tau filament formation in vivo.
Here, we have not addressed how P. gingivalis infection might
relate to apolipoprotein E4 (APOE4), the greatest genetic risk factor
for sporadic AD (77). Studies in mice deficient in APOE proteins
demonstrated an impaired innate immune response to the bacterial
pathogen Listeria monocytogenes (78), implicating APOE in normal
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innate immune function in vivo. It was recently reported that human
APOE is a target of gingipain proteolysis, and the authors suggested
that this mechanism could generate neurotoxic APOE fragments in
the AD brain (79). We propose that APOE4 may be more susceptible
to gingipain cleavage than APOE3 or APOE2 due to the presence of
more arginine residues, resulting in decreased innate immune func-
tion and the generation of neurotoxic fragments (80). The distinct
role of APOE in relation to P. gingivalis infection and targeting by
gingipains remains a focus of future studies.
Our identification of P. gingivalis in the CNS underscores the
importance of genetic findings linking innate immune response
genes to AD susceptibility, including TREM2 (81), TLR4 (82), CR1
(83), and NLRP3 (84). For example, recent studies have highlighted
the association between variants of triggering receptor expressed on
myeloid cells 2 (TREM2) and AD (81). TREM2 encodes a receptor
expressed on immune cells such as macrophages and microglia, with
heterozygous TREM2 variants conferring a risk of developing AD
similar to one copy of APOE4 (81). TREM2 has been shown to reg-
ulate inflammatory responses (85) and serve as a phagocytic recep-
tor for bacteria (86). TREM1, which shares homology with TREM2,
has also been linked to AD amyloid pathology and cognitive decline
(87). The risk-associated TREM1 allele was shown to decrease TREM1
surface expression on monocytes (87). P. gingivalis has been shown
to induce TREM1 gene expression (88), and it is therefore possible
that carriers of the TREM1 AD–associated allele have a reduced
ability to respond to infection by P. gingivalis. In addition, TREM1
is a target for gingipain proteolysis and degradation, with data show-
ing that Rgp can cleave soluble TREM1 from the cell surface and
that Kgp can degrade TREM1, actions that could induce chronic
inflammation (88). Additional research is needed to determine whether
TREM2 is involved in the innate immune response to P. gingivalis
and whether P. gingivalis and gingipains have similar effects on the
expression and degradation of TREM2 as they do for TREM1. In
summary, we propose that genetic polymorphisms of innate immune
system genes in essential immune pathways may result in defective
clearance of P. gingivalis and gingipains from the brain, resulting in
chronic, low-level infection and neuroinflammation in susceptible
individuals.
With regard to infection-induced neuroinflammation, inflam-
masomes, multiprotein complexes that act as intracellular innate
immune defense systems (89), have been shown to be activated in
AD brains (90). P. gingivalis has been shown to modulate inflam-
masome activity (91). Recent research indicates that A plaque for-
mation in AD is connected to the innate immune response through
activation of the NLRP3 inflammasome in microglia and release of
ASC specks that drive A assembly and deposition (92). Notably,
P. gingivalis was the first microbial pathogen shown to induce ASC
aggregation specks in P. gingivalis–infected primary human monocytes
through activation of the NLRP3 inflammasome (93). Inflammasomes
act in intracellular innate immune defense against intracellular
pathogens by activating interleukin-1 (IL-1) and IL-18, causing
cell death through pyroptosis and thereby eliminating the intracel-
lular niche for pathogen replication (94). Furthermore, recent reports
have shown that P. gingivalis OMVs, nanoscale proteoliposomes that
are enriched in gingipains and released into surrounding tissues, are
rapidly internalized into mammalian cells (95), where they drive
NLRP3 inflammasome activation and ASC speck formation and
cause cell death through pyroptosis (96,97). This research suggests
that P. gingivalis in the human brain, through release of OMVs enriched
in gingipains, could drive NLRP3 inflammasome activation, ASC
speck aggregation, and subsequent A plaque formation. In addi-
tion, recent evidence has shown that the NLRP1 inflammasome in
neurons can detect bacterial virulence factors such as proteases by
serving as a substrate for the pathogenic enzymes (98). We suggest
that intraneuronal gingipains may therefore drive neuronal NLRP1
activation, resulting in pyroptosis of neurons and activation of
caspase-1, leading to release of the neuroinflammatory interleukins
IL-1 and IL-18.
Last, we have shown that broad-spectrum antibiotics do not pro-
tect against P. gingivalis–induced cell death in vitro, whereas gingipain
inhibitors do. We also demonstrated in vivo that an orally adminis-
tered Kgp inhibitor is more effective than a high-dose subcutaneous
broad-spectrum antibiotic in clearing P. gingivalis from the brain.
It was recently demonstrated that a small-molecule inhibitor of a
Clostridium difficile cysteine protease virulence factor, TcdB, reduced
disease pathology in a mouse model of C. difficile–induced colitis
but did not reduce the C. difficile bacterial load (99). In contrast, we
report here that small-molecule inhibition of the cysteine protease
Kgp reduced not only disease pathology in mouse brain but also
P. gingivalis bacterial load. The mechanisms underlying the decrease
in P. gingivalis bacterial load in the brain by Kgp inhibitors are likely
due to reduction of Kgp-generated peptide nutrients essential for
the growth of this asaccharolytic bacterium (100) and blocking of
Kgp-dependent heme acquisition that is critical for P. gingivalis en-
ergy production (101,102). We have demonstrated that P. gingivalis
develops rapid resistance to a broad-spectrum antibiotic, moxiflox-
acin, but not to the Kgp inhibitor COR388. Therefore, with the
growing concern about widespread antibiotic resistance (103), and
severe side effects such as C. difficile colitis from broad-spectrum
antibiotic use (104), an antivirulence factor inhibition approach to
treatment of P. gingivalis is the most promising path while reducing
pressures for resistance.
In conclusion, we have designed an orally bioavailable, brain-
penetrant Kgp inhibitor currently being tested in human clinical
studies for AD. The present data indicate that treatment with a po-
tent and selective Kgp inhibitor will reduce P. gingivalis infection in
the brain and slow or prevent further neurodegeneration and accu-
mulation of pathology in AD patients.
MATERIALS AND METHODS
Study design
This study was conducted to investigate the prevalence of P. gingivalis
in the AD brain and to elucidate possible P. gingivalis–dependent
mechanisms of action for neurodegeneration and AD pathology. In
addition, we performed a series of preclinical studies to enable the
development of a therapeutic compound against P. gingivalis–induced
AD. To demonstrate the presence of gingipain antigens in the AD
brain, TMAs containing nondemented control and AD brain tissue
were used for IHC. To avoid potential bias and subjective elements
in assessing the results, stained TMAs were scanned and images were
analyzed for gingipain IR using the MetaMorph image analysis pro-
gram. Evidence for the presence of P. gingivalis in the AD brain was
further verified by IP, WB, and PCR. To demonstrate the presence
of P. gingivalis in the CNS of living patients prospectively diagnosed
with probable AD, CSF was analyzed for P. gingivalis by PCR. The
in vitro experiments to demonstrate P. gingivalis fragmentation of tau
analyzed by WB and MS were designed after detecting the correlation
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of increased tau load with gingipains in the TMAs and the colocal-
ization of gingipain with tau tangles in human AD brain. To study
the efficacy of gingipain inhibitors and neurodegenerative effects of
chronic P. gingivalis infection in vivo, we developed a mouse model
for chronic infection with P. gingivalis. The sample size for the mouse
model for brain infection with P. gingivalis was empirically deter-
mined on the basis of effect size and SD. A blinded observer per-
formed quantification of the loss of hippocampal GABAergic neurons
after P. gingivalis brain infection and the number of degenerating
neurons after intrahippocampal injection of gingipains. The efficacy
of the top lead compound, COR388, was determined in the brain by
qPCR for P. gingivalis–specific genes and by enzyme-linked immuno-
sorbent assay (ELISA) for A
1–42
and TNF. Animals were assigned
to each experimental group with an equal probability of receiving
vehicle or treatment.
Human tissue samples
The human postmortem brain tissue obtained from the Neurological
Foundation of New Zealand Human Brain Bank at the University of
Auckland was donated to the Brain Bank with family consent, and
its use for this study was approved by the University of Auckland
Human Participants Ethics Committee. The control cases had no
history of neurological abnormalities, and cause of death was unre-
lated to any neurological condition. Independent pathological anal-
ysis confirmed that any amyloid pathology was deemed normal for
age in the control cases selected for this study. Pathological analysis
was carried out on all AD cases used in this study to determine
pathological diagnosis and to assign pathological grades, which, to-
gether with a history of dementia, confirmed the diagnosis (tables S1
and S2).
Postmortem tissue samples collected under institutional review
board (IRB)–approved protocols were obtained from the University
of California Davis Alzheimer’s Disease Center, the University of
California San Francisco (UCSF) Neurosurgery Tissue Bank, Proteo-
Genex (Culver City, CA), and PrecisionMed (Solana Beach, CA).
Gingival tissue samples were collected from human volunteers with
chronic periodontal disease who provided signed informed consent
after the nature and possible consequences of the studies were ex-
plained under a University of California at San Francisco IRB–
approved protocol (approval no. 11-05608). CSF and saliva samples
were collected from human volunteers with a diagnosis of probable
AD who provided signed informed consent after the nature and
possible consequences of the studies were explained under an IRB-
approved protocol obtained from PrecisionMed (Solana Beach, CA).
Oral plaque and saliva samples were collected from human volun-
teers with chronic periodontal disease who provided signed informed
consent after the nature and possible consequences of the studies
were explained under an IRB-approved protocol obtained from the
Forsyth Institute (Cambridge, MA).
Animals
Specific pathogen–free (SPF) female BALB/c mice were purchased
from Envigo (UK) for the oral infection experiments with P. gingivalis.
Mice were maintained in individually ventilated cages and fed a
standard laboratory diet and water ad libitum under SPF conditions
within the animal care facility at Faculty of Biochemistry, Biophysics
and Biotechnology, the Jagiellonian University, Krakow, Poland. Mice
were kept under a 12-hour light/dark cycle at 22° ± 2°C and 60 ± 5
relative humidity. Control and bacterially infected mice were housed
in separate cages. To study A
1–42
levels in the brains of orally in-
fected mice and the efficacy of gingipain inhibitors to decrease
P. gingivalis infection of the brain, 40 (n = 8 per arm) 43- to 44-week-
old female BALB/c mice or 100 (n = 10 per arm) 8-week-old female
BALB/c mice were used, respectively. All the experiments were re-
viewed and approved by the I Regional Ethics Committee on Ani-
mal Experimentation, Krakow, Poland (approval nos. 164/2013 and
116/2016).
To study neurodegeneration after stereotactic injection of gin-
gipains into mouse hippocampus, fifteen 8-week-old male BALB/c mice
were purchased from Envigo (USA). Animals were group-housed
(n = 2 to 4 per cage) in plastic cages. Animals were maintained on a
12/12-hour light/dark cycle with the room temperature (RT) main-
tained at 22° ± 2°C and approximately 50% humidity and received
standard rodent chow and tap water ad libitum in the Brains On-Line,
LLC Animal Facility (South San Francisco, CA). Experiments were
conducted in accordance with the protocols approved by the Insti-
tutional Animal Care and Use Committee of Brains On-Line, LLC
(approval no. US16003).
Antibody production
Polyclonal antibodies CAB101 and CAB102 were produced by
GenScript USA Inc. (New Jersey) according to their express immu-
nization protocol. Briefly, immunogens were expressed in a bacterial
expression system and used for four consecutive immunizations of
four rabbits each. The immunogen sequences expressed are 401 to
736 residues for CAB101 (RgpB; GenBank: BAG33985.1) and 22 to
400 residues for CAB102 (Kgp; GenBank: BAG34247.1). After the
last immunization, sera were pooled and antigen affinity– purified.
Specific binding was tested on WBs, and nonspecific binding on hu-
man histology sections was controlled by coincubation of polyclonal
antibodies with their respective immunogens before IHC staining.
Human TMAs
Human brain TMAs comprised a total of 58 2-mm-diameter core
samples, 29 from dementia-free control individuals and 29 from AD
cases, each on two arrays (NVD003 and NVD005). Final sample
sizes reflect the loss of several samples from the slide during pro-
cessing (see tables S1 and S2).
IHC to detect gingipains, tau, and ubiquitin in human TMAs
TMAs were constructed from paraffin-embedded MTG blocks, as de-
scribed in detail by Narayan etal. (105). TMA sections were cut at a
thickness of 7 m and were annealed to slides by heating at 60°C for
1 hour. Sections were then dewaxed using xylene immersion in xylene
twice (1 hour and 10 min, respectively) and rehydrated using a stan-
dard graded ethanol series procedure. For IHC, slides were immersed
in sodium citrate antigen retrieval buffer (pH 6), heated at 121°C for
2 hours in 2100 Antigen Retriever (Aptum, Pick Cell Laboratories),
and then rinsed three times for 5 min in milliQH
2
O. For tau (1:20,000;
rabbit A0024, DAKO), IHC slides were immersed in 99% formic acid
for 5 min, rinsed three times in milliQH
2
O, and then treated as per
other slides. Slides were then incubated with an endogenous peroxi-
dase blocking solution (50% methanol, 1% H
2
O
2
, diluted in mQH
2
O)
for 20 min at RT. This was followed by three washes in PBS, and then
slides were incubated with blocking buffer (10% normal goat serum
in PBS) for 1 hour at RT. Primary antibodies mouse anti-ubiquitin
(1:2000; MAB1510, Chemicon), CAB101 (1:500), and CAB102 (1:500)
were applied for incubation overnight at 4°C.
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To detect antibody binding, slides were washed in PBS with Triton
X-100 for 5 min and then twice in PBS for 5 min each and incubated
with biotinylated goat anti-mouse or anti-rabbit antibodies (Sigma-
Aldrich) for 3 hours at RT. After further washing, they were incu-
bated for 1 hour at RT with Sigma Extravidin peroxidase at 1:1000
dilution and then washed and incubated with the peroxidase sub-
strate [3,3-diaminobenzidine with 0.04% Ni(NH
4
)
2
(SO
4
)
2
] to de-
velop the color change. Following PBS-milliQH
2
O washes (3 × 5 min
each), the slides were dehydrated in a graded ethanol series followed by
xylene and mounted under coverslips with DPX mounting medium.
Gingipain antibodies were optimized initially on formalin-fixed
paraffin-embedded sections of gingival tissue collected from peri-
odontal disease patients at the UCSF School of Dentistry under an
IRB-approved protocol. Testing was then performed on MTG (from
both postmortem control and AD human brains) and cerebellum
(negative control). Specificity of antibody staining was demonstrated
using positive and negative controls, secondary antibody only, iso-
type controls, and antigen pre-absorption. “No primary” antibody
controls were negative for staining. Stained slides were scanned at
10× objective using a MetaSystems VSlide slide scanner, and bright-
field images were analyzed for gingipain (and other markers) IR
using the MetaMorph image analysis program. For each marker, the
images were thresholded. Two thresholds for each core were deter-
mined: one to determine the total area of the core and the other to
determine the total area of the thresholded region. To determine
the load of staining per core, the thresholded area of staining was
divided by the total core area. This analysis controlled for varying
core sizes.
IHC of human AD brain sections for neurons, astrocytes,
and RgpB-IR
For 18E6 analysis, which recognizes a unique epitope within the im-
munoglobulin (Ig)–like domain of Arg-gingipain (RgpB) (58), IHC
was performed using the Ventana Benchmark XT automated slide
preparation system at the UCSF Brain Tumor Research Center tis-
sue core. For immunoperoxidase staining, after tissue sections (5 m
thickness) were deparaffinized (at 75°C; EZ-Prep, Ventana Medical
Systems), antigen retrieval was performed for 30 min [Cell Condi-
tioning 1 (pH 8.5), Ventana Medical Systems] at 95° to 100°C. H
2
O
2
(3%) (Thermo Fisher Scientific) was applied for 8 min to reduce
background staining. Antibody 18E6 (University of Georgia Mono-
clonal Antibody Facility) was incubated at RT for 32 min at 1:10
dilution. Staining was developed using the UltraView Universal
DAB Detection System (Ventana Medical Systems), and slides were
counterstained with hematoxylin.
For immunofluorescence, sections were deparaffinized in xylene
and rehydrated in a graded alcohol series. Heat-mediated antigen
retrieval was performed with citric buffer (pH 6.0) (H-3300, Vector
Laboratories). After PBS washes, sections were incubated in block-
ing solution, 5% donkey serum, and 0.3% Triton X-100 in PBS for
1 hour at RT. Sections were then incubated overnight at 4°C in
primary antibodies anti-MAP2 (1:500; ab5392, Abcam), CAB101
(1:500), anti-IBA1 (1:1000; ab97120, Abcam), anti–-amyloid, 17–24
(1:500; SIG-39200; 4G8, BioLegend), and anti-AT8 (1:2000; MN1020B,
Thermo Fisher Scientific) in 3% donkey serum and 0.3% Triton
X-100 in PBS. After PBS washes, slides were incubated with second-
ary antibody solution, either Alexa Fluor 647 goat anti-chicken
(1:200; A21449, Life Technologies) and Alexa Fluor 488 donkey anti-
rabbit (1:200; Jackson ImmunoResearch) mixed with anti–GFAP-
Cy3 (1:250; MAB3402C3, Millipore) or Cy3-donkey anti-rabbit
(1:200; Jackson ImmunoResearch), Alexa Fluor 488 donkey anti-
mouse (1:200; Jackson ImmunoResearch), and Alexa Fluor 647
donkey anti-goat (1:200; Jackson ImmunoResearch) in PBS with
0.3% Triton X-100 for 2 hours at RT. Sections were washed in PBS
and counterstained with 4,6-diamidino-2-phenylindole (DAPI)
(Invitrogen; D1306). Autofluorescence was quenched with TrueBlack
Lipofuscin Autofluorescence Quencher 1:20 in 70% ethanol (catalog
no. 23007, Biotium), and slides were mounted with ProLong Gold
Antifade (P36930, Thermo Fisher Scientific). Coimmunofluorescence
on P. gingivalis was performed by drying bacteria on SuperFrost
Plus microscope slides. Bacteria were immersed in 4% paraformal-
dehyde for 10 min, washed three times in PBS, and incubated in
formic acid for 7 min, followed by another three washes with PBS.
Cells were exposed to anti–-amyloid, 17–24 (1:500; SIG-39200; 4G8,
BioLegend) and CAB101 (1:500) in 3% donkey serum and 0.3% Triton
X-100 in PBS for 30 min at RT, followed by 30-min incubation in
Cy3-donkey anti-rabbit (1:200; Jackson ImmunoResearch) and Alexa
Fluor 488 donkey anti-mouse (1:200; Jackson ImmunoResearch) in
PBS, counterstained with DAPI, and coverslipped with ProLong Gold
Antifade (Thermo Fisher Scientific; P36930).
Histological analysis was performed on an Olympus BX61 motor-
ized microscope. Fluorescence images were taken with a sCMOS
camera (Zyla-5.5-USB3, Andor), and brightfield images were taken
on a color charge-coupled device camera (DP27, Olympus). Images were
processed for brightness and contrast correction, cropping, and ad-
dition of scale bars with CellSens 1.14 Dimension software (Olympus).
Human brain Kgp IP and WB
Brain tissue from each subject sample (cortex, 100 mg) was homog-
enized on ice in 1 ml of B-PER lysis buffer (Thermo Fisher Scientif-
ic) with proteinase inhibitor cocktail (Millipore) and then kept on
ice for 10 min. The bacteria control was prepared by pelleting 10
9
bacteria by centrifugation at 5000g for 10 min. Then, the pellet was
lysed in 1 ml of the same lysis buffer on ice for 10 min. All samples
were then centrifuged at 16,000g for 20 min at 4°C, and the super-
natant was collected. Protein concentration was measured using a
Pierce BCA assay kit (Thermo Fisher Scientific). One milligram of
total protein from each sample was denatured at 95°C for 5 min,
and then an equal volume of antibody binding and washing buffer
from the Dynabeads Protein G Immunoprecipitation Kit (Thermo
Fisher Scientific) was added. For the bacteria control, 10
7
bacteria
were used. For the brain sample spiked with bacteria, 1 mg of total
brain protein was mixed with bacterial lysate of 10
7
bacteria. The
samples were incubated with 10 g of rabbit polyclonal CAB102 anti-
body with rotation overnight at 4°C. The next day, prewashed
Dynabeads Protein G beads were incubated with 1 mg of bovine
serum albumin (BSA) in binding buffer for 30 min and then washed
three times with washing buffer. Then, samples were incubated with
Dynabeads with rotation for 30 min at RT. Samples were washed
four times with 200 l of washing buffer using magnetic rack. Beads
were then dissolved with 20 l of elution buffer and 10 l of NuPAGE
LDS sample buffer and 50 mM dithiothreitol (DTT) and heated at
70°C for 10 min. Then, IP proteins were eluted from the magnetic
beads using magnetic rack. Each sample (15 l) was then subjected
to SDS–polyacrylamide gel electrophoresis (PAGE) electrophoresis.
SDS-PAGE gel was subjected to WB analysis by using Trans-blot
Turbo transfer system (Bio-Rad) to transfer proteins to polyvinylidene
difluoride (PVDF) membrane. The membrane was then rinsed with
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tris-buffered saline (TBS) and then blocked with blocking buffer from
the Clean-Blot IP Detection Kit (Thermo Fisher Scientific) for 1 hour.
The blot was then incubated with 1:1000 primary antibody CAB102
overnight with rocking in blocking buffer at 4°C. The blot was then
washed three times with TBST buffer, 5 min each, and then incubated
with 1:250 dilution of Clean-Blot detection reagent [horseradish per-
oxidase (HRP)] in blocking buffer for 1 hour at RT. Blot was then
washed four times with TBST and then subjected to Pierce ECL de-
tection reagent and ChemiDoc imaging system.
qPCR analysis of P. gingivalis in human brain tissue
DNA was extracted and purified from postmortem cortex brain tis-
sues following the protocol described in the Blood and Tissue Kit
(Qiagen). Copy number of the P. gingivalis genome in brain DNA
samples was determined by qPCR with P. gingivalis–specific 16S
primers [(ACCCTTTAAACCCAATAAATC (forward) and ACGAG-
TATTGCATTGAATG (reverse)] and fluorescent-labeled probe
(CGCTCGCATCCTCCGTATTAC). The qPCR reaction mixture
contained 100 ng of brain DNA, 0.5 M primers/0.15 M probe, and
Kapa Fast qPCR Mix (Kapa Biosystems). PCR amplification was
performed using the following cycling parameters: 3 min at 95°C,
50 cycles of 3 s at 95°C, and 30 s at 60°C. Copy number was deter-
mined from the standard curve generated using a synthetic template.
Sequence analysis of P. gingivalis DNA amplified from
human brain tissue
For sequencing, an approximately 1-kb region of the P. gingivalis
genome encompassing the hmuY gene (except sequences correspond-
ing to the first six amino acids) was amplified from 50 ng of brain
DNA by PCR. PCR amplification (95°C/5 min; 95°C/20 s, 60°C/15 s,
and 72°C/1 min for 35 cycles; 72°C/2 min) was performed using the
KAPA HiFi HotStart ReadyMix PCR Kit (Kapa Biosystems) and
primers [TTCTCCGCACTCTGTGCATT (forward) and AGCACTTC-
GATTCGCTCGAT(reverse)] designed to amplify the hmuY gene
from the P. gingivalis genome. PCR products were run on 2% agarose
gel, and DNA bands close to the expected size (based on the PCR
product obtained from amplification of purified P. gingivalis DNA)
were excised from the gel (Fig.2F). DNA was extracted from the gel
pieces following the protocol described in the Gel Extraction Kit
(Qiagen). Approximately 5% of the eluted DNA was reamplified
using the same hmuY PCR primers. Sequencing of reamplified PCR
products was performed using nested primers (fig. S3).
qPCR analysis of P. gingivalis in human CSF and saliva
CSF and matching saliva samples were obtained from PrecisionMed
(Solana Beach, CA). Ten volunteer subjects, who were diagnosed with
probable AD and met the criteria of having a Mini Mental Status Exam
(MMSE) score of 20 or below, were serially enrolled in PrecisionMed’s
IRB-approved protocol for CSF collection in November 2017 and
donated CSF samples and matching saliva samples for P. gingivalis
PCR analysis.
CSF PCR method
DNA was extracted from 50 l of CSF using Puregene Core Kit A
(Qiagen). The final DNA pellet was dissolved in 50 l of DNA hy-
dration buffer. A preamplification PCR assay (20 cycles) was per-
formed with 5 l of CSF DNA and P. gingivalis hmuY gene–specific
H1.2 primers [GGTGAAGTCGTAAATGTTAC (H1.2 forward) and
TTGACTGTAATACGGCCGAG (H1.2 reverse)]. A serial dilution
of synthetic template DNA was also preamplified for the calculation
of copy number. The preamplified PCR products were diluted, and
a qPCR assay was performed with nested hmuY primers [GAAC-
GATTTGAACTGGGACA (H1.1 forward) and AACGGTAGTAG-
CCTGATCCA (H1.1 reverse)] and a probe (/56-FAM/TTCTGTCTT/
ZEN/GCCGGAGAATACGGC/3IABkFQ/). A serial dilution of the
same synthetic template DNA was included in the qPCR assay to
generate a standard curve and calculate starting copy number in CSF.
Saliva PCR method
DNA was extracted from 50 l of saliva using Puregene Core Kit A
(Qiagen). The final DNA pellet was dissolved in 50 l of DNA hy-
dration buffer. A qPCR assay was performed with 2 l of saliva DNA
and hmuY primers (H1.1) and the probe mentioned above. A serial
dilution of synthetic template DNA was included in the qPCR assay
to calculate starting copy number.
qPCR analysis of H. pylori in human brain and CSF
The preamplification and qPCR protocol used for detection of
H. pylori copy number in brain, CSF, and saliva samples were the same
as those used for detecting the P. gingivalis hmuY gene copy number
noted above. The qPCR primers and probe used for detection of H. pylori
copy number have previously been described (43). We designed two
primers [GATTAGTGCCCATATTATGGA (Hpy_outer_For) and
CTCACCAGGAACTAATTTAC (Hpy_outer_Rev)] for the pream-
plification step. These primers amplified a 217-bp fragment encom-
passing the region amplified by the qPCR primers. A synthetic DNA
of 240 bases encompassing the region amplified by outer primers
was used as a control for the preamplification step.
Effects of P. gingivalis infection on tau in SH-SY5Y cells
SH-SY5Y cells (~2.4 × 10
6
) were spin-inoculated with MOIs of 10,
50, and 100 with each of the following: P. gingivalis [American Type
Culture Collection (ATCC) BAA-308] [wild type (WT)], P. gingivalis
KgPIg-B, and P. gingivalis K/RAB-A. Uninfected SH-SY5Y cells
were used as a control. SH-SY5Y cells and P. gingivalis strains were
centrifuged at 1000g for 10 min at RT in Dulbecco’s modified Eagle’s
medium (DMEM)/F12 supplemented with 2 mM
l-glutamine and
BSA (200 g/ml), followed by incubation for 1, 4, and 8 hours, re-
spectively, in a CO
2
incubator. After the indicated incubation times,
cells were collected and cell pellets were lysed with 250 l of radio-
immunoprecipitation assay buffer supplemented with protease in-
hibitor cocktail for 10 to 15 min. Total protein (16 g) was used for WB.
WBs were probed with tau monoclonal antibody TAU-5 (Thermo-
MA5-12808). Glyceraldehyde-phosphate dehydrogenase (GAPDH)
was used as an internal reference.
Tau-441 incubation with gingipains and WB
Tau-441 (2N4R) (rPeptide, T-1001-1; molecular weight, 45.9 kDa)
(2 g) was reconstituted in 1% NH
4
OH and digested by 100, 10, 1,
and 0.1 nM Kgp/RgpB in working buffer [20 nM sodium phosphate
and 1 mM DTT (pH 7.5)]. Digestion reactions were performed for
1 hour at 37°C; reactions were stopped with protease inhibitor
(P8340, Sigma-Aldrich). Proteins were separated by electrophoresis
at 70 V for 15 min and then at 85 V for 1.5 hours on a 10% Criterion
TGX precast gel (Bio-Rad, 5671033) (Bio-Rad, Criterion vertical
electrophoresis cell) and electroblotted overnight onto a PVDF
membrane at 10 V (Bio-Rad, Criterion Blotter). Blot was blocked
with BLOTTO (87530, Thermo Fisher Scientific) for 1 hour and
probed with primary antibody anti-Tau46 (13-6400, Thermo Fisher
Scientific) at 1:1000 dilution in 3% BSA in TBS for 2 hours. Blot was
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then washed three times for 10 min each with TBST (28630, Thermo
Fisher Scientific) and then incubated with secondary antibody HRP
goat anti-mouse (1:50,000; 31439, Thermo Fisher Scientific) in 3%
BSA in TBS for 30 min. After further washing, blot was washed
three times for 10 min with TBST, and blot staining was visualized
using chemiluminescence detection (34096; SuperSignal West Femto,
Thermo Fisher Scientific).
Liquid chromatography–MS/MS analysis of
gingipain-generated tau cleavage products
Tau samples treated with 1 nM Kgp/RgpB or 10 nM Kgp/RgpB were
analyzed by 1D Nano LC-MS/MS (JadeBio, San Diego, CA). A reversed-
phase column (200 m × 20 cm C
18
2.5 m 130 Å) was generated in-
house and coupled online to a Q Exactive mass spectrometer (Thermo
Fisher Scientific, Bremen, Germany). Peptides were separated by a
linear gradient from 95% buffer A [0.1% formic acid (FA) in water]/5%
buffer B [0.1% FA in acetonitrile (ACN)] to 60% buffer A/40% buf-
fer B over 150 min at 500 nl/min. The mass spectrometer was oper-
ated in a data-dependent TOP20 mode with the following settings:
mass range, 400 to 2000 mass/charge ratio (m/z); resolution for MS
1
scan, 70,000 full width at half maximum (FWHM); resolution for MS
2
scan, 17,500 FWHM; isolation width, 3 m/z; NCE, 27; underfill ratio,
1%; dynamic exclusion, 15 s. Raw MS/MS spectra were searched
against UniProt Human + P. gingivalis + decoy sequence databases.
False discovery rate was <0.1% at the peptide level.
Small-molecule gingipain inhibitor characterization
Structure-based design was used to develop a library of gingipain
inhibitors, which were tested on purified Kgp and RgpB to assess
potency and determine inhibition constants. The detailed chemical
synthesis and structure of compounds in the relevant series of argi-
nine gingipain inhibitors including COR286 can be found in In-
ternational Patent Application PCT/US2015/054050 and PCT/
US2016/061197. The detailed chemical synthesis and structure of
compounds in the structural series for lysine gingipain inhibitors
including COR119, COR271, and COR388 can be found in PCT/
US2016/061197. The capacity of compounds to inhibit the activity
of lysine or arginine gingipain was measured in a fluorogenic assay.
The assay was performed in buffer [100 mM tris-HCl, 75 mM NaCl,
2.5 mM CaCl
2
, 10 mM cysteine, and 1% dimethyl sulfoxide (DMSO)
(pH 7.5)] for 90 min at 37°C. Kgp, RgpB, and RgpA were isolated
from culture of P. gingivalis, as described by Potempa and Nguyen (39).
The fluorogenic substrate for Kgp was 10 M Z-His-Glu-Lys-MCA
and for RgpA and RgpB was 10 M Boc-Phe-Ser-Arg-MCA. Trypsin
buffer was 10 mM tris and 10 mM CaCl
2
(pH 8.0), and the substrate
was Z-Gly-Gly-Arg-AMC. COR286 has an IC
50
of ≤20 pM on pu-
rified RgpB and an IC
50
of 300 pM on structurally related RgpA but
no significant inhibition of Kgp. COR119 has an IC
50
of 10 nM on
Kgp, with COR271 and COR388 having IC
50
values of ≤50 pM on
Kgp. All have no significant activity on RgpB. All compounds show
negligible inhibition of trypsin with IC
50
values of ≥10 M. COR271
and COR388 were profiled more extensively on a series of cellular
proteases, and no biologically meaningful activity (IC
50
> 10 M) was
detected on these enzymes including cathepsin S, calpain, tryptase,
thrombin, plasmin, FXa, FVIIa, BACE1, DPP4, proteasome, deu-
biquitinating peptidases, and caspase family enzymes.
A Morrison inhibition constant (K
i
) was determined for COR271
and COR388, and both display a K
i
of <0.01 nM. Enzyme kinetic
studies were performed to determine the mode of inhibition of the
compounds by monitoring recovery of enzyme activity following
dilution of existing enzyme/inhibitor complexes. COR119 is a re-
versible inhibitor, and COR271 and COR388 display irreversible
binding kinetics. COR286 contains an identical catalytic binding
site mechanism as COR271. The enzyme progress curves from this
study were used to estimate K
off
and T
1/2
(half-life) of the reversible
enzyme complex with COR119. Fitting the progress curve allows an
estimate of K
off/obs
(min
−1
) of 0.032 and T
1/2
of 22 min for COR119.
A K
off
value for COR271 and COR388 cannot be calculated, as their
binding is irreversible.
The COR553 activity probe was prepared by the copper-catalyzed
azide-alkyne cycloaddition reaction (106) between an azide deriva-
tive of the irreversible Kgp inhibitor COR553 and an alkyne amide
derivative of the Cy5 fluorophore. The COR553 probe forms an ir-
reversible covalent bond with a catalytic cysteine residue in the ac-
tive site of Kgp by displacement of a phenol leaving group.
Effect of gingipain inhibitors on P. gingivalis toxicity
in SH-SY5Y cells
Human neuroblastoma SH-SY5Y cells at 13 passages were cultured
in complete medium [DMEM/F12 (Invitrogen) supplemented with
2 mM
l-glutamine (Invitrogen), 10% heat-inactivated fetal bovine
serum (10099141, Invitrogen), and 1% penicillin-streptomycin
(Invitrogen)] in a 5% CO
2
incubator (Thermo Fisher Scientific). Cells
were seeded at a density of 2 × 10
4
to 4 × 10
4
cells per well (200 l of
1 × 10
5
to 2 × 10
5
cells/ml) in 96-well black/flat-bottom plates
(Greiner) manually coated with collagen type I and then incubated
in a CO
2
incubator at 37°C.
When cells reached 70 to 80% confluency (~6 × 10
4
cells per
well), they were challenged with P. gingivalis with or without COR271,
COR286, moxifloxacin (32477, Fluka), doxycycline (D9891-5G, Sigma-
Aldrich), or semagacestat (S1594, SELLECK) at various concentrations.
On the day of testing, the stock solution was diluted by eight
serials of twofold dilution in DMSO (Sigma-Aldrich) in a sterile
V-bottom 96-well plate (WIPP0280, Axygen) from well 2 to well 10.
Well 11 contained DMSO only. From well 2 to well 11, the concen-
trations were 12.8, 6.4, 3.2, 1.6, 0.8, 0.4, 0.2, 0.1, 0.05, and 0 mg/ml.
This was the compound mother plate, with each well containing
200× testing concentrations of compound in DMSO. Then, 6 l
from the mother plate was transferred into a 96-deep-well plate
filled with 594 l of complete medium–penicillin/streptomycin
(1:100 dilution) to 2× testing concentration (128, 64, 32, 16, 8, 4, 2,
1, 0.5, and 0 g/ml). This was the working solution.
P. gingivalis (ATCC BAA-308) was inoculated from −80°C stock
onto a brain heart infusion agar (BD-211065). The plate was incu-
bated for 72 hours at 37°C in an anaerobic workstation (YQX-II,
Shanghai Yuejin). The atmosphere was kept at 80% N
2
, 10% CO
2
,
and 10% H
2
.
On the day of testing, plates were processed in ambient atmo-
sphere. Bacteria were harvested and suspended in complete medium–
penicillin/streptomycin (without penicillin/streptomycin). Suspension
was adjusted using a Siemens MicroScan turbidity meter (Siemens)
to 0.5 turbidity, which is equivalent to ~6 × 10
8
CFU/ml. Bacterial
suspension was diluted in complete medium–penicillin/streptomycin
to a final bacterial density of 6 × 10
8
CFU/ml (for MOI of 1:1000)
including one well with no bacteria as a negative control.
Cells in the testing plate were washed once with 200 l of com-
plete medium–penicillin/streptomycin. Then, 100 l of working solu-
tion and 100 l of bacterial suspension were added. The final testing
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concentrations were 64, 32, 16, 8, 4, 2, 1, 0.5, 0.025, and 0 g/ml with
1% DMSO. The testing plates were incubated at 37°C in a 5% CO
2
incubator for 24 hours.
Cell viability was determined using AlamarBlue (Invitrogen).
Cells in the testing plates were washed twice using complete medium–
penicillin/streptomycin to remove bacteria in the suspension. Then,
220 l of AlamarBlue/medium mix (consisting of 200 l of complete
medium–penicillin/streptomycin and 20 l of AlamarBlue) was added
to each well of the testing plates. The testing plates were then incu-
bated in a 37°C CO
2
incubator for fluorescent reduced AlamarBlue to
develop. The fluorescent signal from the reduced AlamarBlue (exci-
tation, 530 nm/emission, 590 nm) was read after 6 hours, before
saturation, on a SpectraMax M2e plate reader (Molecular Devices).
Stereotactic injection of gingipains in mouse hippocampus
A 7-day study was designed to detect gingipain-induced hippocam-
pal neurodegeneration with Fluoro-Jade C (FJC), a fluorescent stain
that has been shown to exhibit maximum staining of degenerating
neurons 1 week after a neurotoxic insult (107). Fifteen 8-week-old
male BALB/c mice (Envigo) were used in the study. Animals were
group-housed (n = 2 to 4 per cage) in plastic cages. Animals were
maintained on a 12/12-hour light/dark cycle, with the RT main-
tained at 22° + 2°C and approximately 50% humidity, and received
standard rodent chow and tap water ad libitum.
Mice were anesthetized using isoflurane (2%, 800 ml/min O
2
).
Bupivacaine/epinephrine was used for local analgesia, and carpro-
fen was used for perioperative/postoperative analgesia. A solution
of RgpB (5 g/ml) + Kgp (5 g/ml) + 5 mM
l-cysteine was prepared in
sterile saline. Bilateral injections of 0.5 l were made into coordinates
from bregma: anteroposterior −2.0, lateral ±1.5, and ventral −1.4 mm
from dura at a rate of 0.1 l/min with a 5-min rest period using a
Hamilton syringe (10-l syringe with corresponding 30-gauge blunt
tip needle; model no. 80308) and the stereotactic micromanipulator
(Ultra Micro Pump III with Micro4 Controller, World Precision
Instruments). When compound delivery was complete, the needle
was left in place for 5 min and then withdrawn such that it took
approximately 1 min to fully withdraw the needle.
Mice received a single administration of vehicle or drug 1.5 hours
before stereotactic gingipain injection. Inhibitor-treated mice received
COR271 (100 mg/kg) in PBS by oral gavage and COR286 (20 mg/kg)
in 25% pluronic F127 subcutaneously at a dose volume of 5 and
10 ml/kg, respectively. Vehicle-treated mice received either PBS or
pluronic.
Seven days later, mice were anesthetized with isoflurane (2%,
800 ml/min O
2
) and perfused with PBS. Brains were harvested,
fixed in 10% formalin, embedded in paraffin, and sectioned at 5 m.
Serial sections 200 m apart through the entire hippocampus
were stained with the FJC Ready-to-Dilute Staining Kit (Biosensis)
according to the manufacturer’s protocol, and FJC-positive cells
in the CA1 area were counted on an Olympus BX61 motorized
microscope.
Growth of P. gingivalis W83
P. gingivalis [W83 (ATCC, Rockville, MD), Kgp (kgp), and Rgp
(rgpArgpB495-B Cm
r
, Em
r
] (57,58) was streaked on tryptic soy
broth (TSB) agar plates [5% sheep blood, supplemented with
l-cysteine
(0.5 mg/ml), hemin (5 g/ml), and vitamin K (0.5 g/ml)] and grown
under anaerobic conditions at 37°C for 5 to 7 days. Samples were then
inoculated in TSB with hemin, vitamin K, and
l-cysteine (TSB-HKC)
until mid-log phase OD
600
(optical density at 600 nm) of 0.5 to 0.7.
Bacteria were washed in PBS and prepared at a final concentration
of 1 × 10
10
cells/ml in PBS + 2% methylcellulose.
P. gingivalis oral infection in mice
Experimental periodontitis was induced by ligature placement.
During the procedure, mice were anesthetized with an intraperito-
neal injection of ketamine (200 mg/kg; VetaKetam, Poland) and
xylazine (10 mg/kg; Sedasin, Biowet, Poland), and the eyes were lu-
bricated with ointment (Puralube Vet; PharmaDerm, Melville, NY).
Next, a 5-0 silk ligature (Roboz Surgical Instrument Co., MD, USA)
was tied around the upper maxillary left and right second molar.
Suture was applied and tied gently to prevent damage to the peri-
odontal tissue. The ligature was left in position for the entire exper-
imental period so that inflammation could be constantly induced by
colonization of bacteria inside of it.
Experiment 1
To study A
1–42
levels in the brains of orally infected mice, 40 (n = 8
per arm) 43- to 44- week-old female BALB/c mice were infected for
6 weeks every other day. For infection, 100 l of the bacterial solu-
tion was applied topically to the buccal surface of the maxillae.
COR119 in 2% DMSO/PBS was administered three times a day by
subcutaneous injection starting on day 21 and continuing through
day 42. Vehicle-treated animals received DMSO only. To further
define the role of gingipains in the induction of brain A
1–42
, mice
were infected with P. gingivalis W83 (WT) or P. gingivalis lacking
Kgp (kgp) or the Rgp-null P. gingivalis mutant strain (Rgp) (58).
After 6 weeks, the mice were euthanized and perfused with PBS,
and brains were harvested and frozen in liquid nitrogen.
Experiment 2
To study the efficacy of gingipain inhibitors to decrease P. gingivalis
infection of the brain, 100 (n = 10 per arm) 8-week-old female BALB/c
mice were infected for 6 weeks every other day as described above.
The mice received gingipain inhibitors or moxifloxacin for 5 weeks
(days 36 to 70). COR271 was administered orally twice daily in PBS
at 10 mg/kg; COR286 was administered subcutaneously twice daily
in 25% pluronic F127 (10 mg/kg; Sigma-Aldrich, USA). Moxifloxacin
(Sigma-Aldrich, USA) was administered subcutaneously twice daily
in PBS at 10 mg/kg. Vehicle-treated animals received PBS or pluronic
only. A group of mock-infected and P. gingivalis W83 (WT)–infected
mice were euthanized on day 35 to gather baseline measurements
before the start of treatment. After 10 weeks, P. gingivalis W83 (WT)–
infected mice and mice infected with bacteria ± gingipain inhibitors
or moxifloxacin were euthanized, and the brain and serum were
harvested and frozen in liquid nitrogen
.
Experiment 3
To study the efficacy of gingipain inhibitors to decrease P. gingivalis
infection of the brain, 70 (n = 10 per arm) 8-week-old female BALB/c
mice were infected for 6 weeks every other day as described above.
The mice received COR388 (3, 10, or 30 mg/kg) or COR271 (10 mg/kg)
twice daily in PBS for 5 weeks (days 36 to 70) by oral administra-
tion. Vehicle-treated animals received PBS only. Mice were eutha-
nized on day 35 or day 70, and one brain hemisphere and serum were
frozen in liquid nitrogen, while one brain hemisphere was fixed in
10% formalin.
A ELISA
Brain samples (posterior half of the left hemisphere) were homoge-
nized in radioimmunoprecipitation assay buffer (VWR), and A
1–42
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was quantified with a Novex Mouse Beta Amyloid 1-42 (A42) ELISA
kit (Thermo Fisher Scientific, USA) according to the manufacturer’s
specifications.
ELISA assays for TNF
Brain lysate was quantified for TNF with ProcartaPlex Chemokine
Convenience Panel 1 (Thermo Fisher Scientific) on a Luminex plat-
form following the manufacturer’s protocol and with a V-PLEX Proin-
flammatory Panel 1 Mouse kit (Meso Scale Diagnostics, Rockville,
MD). Results from both assays were corrected for protein content
and normalized to the mock group, and the means of both assays
were analyzed as a combined dataset.
Endpoint PCR analysis of P. gingivalis in mice brain tissue
Bacterial DNA was extracted from mouse brains using DNeasy
Blood & Tissue Kits (Qiagen, Germany) according to the manufac-
turer’s protocols. The concentration of DNA was measured using a
NanoDrop 2000 (Thermo Fisher Scientific, USA). Bacterial DNA
was amplified with 16S ribosomal RNA (rRNA) primers for the
W83 strain of P. gingivalis [AGGCAGCTTGCCATACTGCG (for-
ward) and ACTGTTAGCAACTACCGATGT (reverse)]. PCR am-
plification was conducted in a 12-l reaction volume including 3 l
of brain DNA (80 ng of DNA), 6 l of EconoTaq PLUS Green 2×
Master Mix (Lucigen, USA), 0.6 l (10 M) of each primer (GenoMed,
Poland), and 1.8 l of H
2
O (Thermo Fisher Scientific, USA). Forty
cycles of amplification were performed in a DNA thermal cycler
(TProfessional TRIO, Biometra, Germany) consisting of 3 min for
95°C, 20 s for 95°C, 30 s for 57°C, 30 s for 72 °C, and 5 min for
72°C. The amplified product was identified by electrophoresis in a
1.5% agarose gel (BioShop, Canada). The DNA was stained with
ethidium bromide, visualized under short wavelength transillumina-
tor, and photographed in runVIEW imager (BIOCOMdirect, UK).
A
1–42
binds to the surface of P. gingivalis
Recombinant A (1-42) Ultra-Pure, Ammonium Hydroxide (rProtein)
was prepared as stock solutions (1 mg/ml) in 1% NaNH
4
. P. gingivalis
was washed in PBS and incubated at 10
8
CFU/ml in A (10, 30,
and 100 g/ml) for 1 hour at RT and ambient oxygen. For IHC, a
10-l solution was dried on a SuperFrost Plus glass slide (VWR)
fixed in 4% paraformaldehyde for 10 min. Slide was then rinsed
with PBS and dH
2
O, exposed to formic acid, and, after washing with
PBS, incubated for 2 hours in PBS, 0.3% Triton X-100, and primary anti-
bodies CAB102 (1:1000) and 4G8 (1:1000; BioLegend). Fluorescence
labeling was performed with Alexa Fluor 488 donkey anti-rabbit
(1:200; Jackson ImmunoResearch) and Cy3 donkey anti-goat
(1:200; Jackson ImmunoResearch) in PBS. Slides were mounted
with ProLong Gold Antifade (Thermo Fisher Scientific). Images were
taken on an Olympus BX61 microscope with a Zyla 5.5 sCMOS
camera (Andor).
Antimicrobial effects of A on P. gingivalis
Recombinant A (1-40, 1-42, 1-42 scrambled) Ultra-Pure, Ammo-
nium Hydroxide (rProtein) was prepared as 0.2 mM stock solutions
in 1% NaNH
4
. A peptides were added to P. gingivalis cultures at a
final concentration of 20 mM and kept at 37°C under anaerobic con-
ditions for 24 hours. Cells were washed in PBS and stained with the
LIVE/DEAD BacLight Bacterial Viability Kit (Thermo Fisher Scientific)
according to the manufacturer’s protocol. Fluorescence intensity was
quantified on a PerkinElmer Envision Plate reader.
qPCR analysis of P. gingivalis in mouse brain tissue
DNA was extracted from brain tissue using the DNeasy Blood &
Tissue Kit (Qiagen, Germany) according to the manufacturer’s pro-
tocol. TaqMan qPCR was performed with Kapa Probe fast qPCR
Mix (Rox Low) on a Bio-Rad CFX96 Real-Time System C1000
Touch ThermalCycler with the forward (5-AGCAACCAGCTAC-
CGTTTAT-3) and reverse (5-GTACCTGTCGGTTTACCATCTT-3)
primers and 6-FAM-TACCATGTTTCGCAGAAGCCCTGA-TAMRA
as the detection probe. The primers were based on single copy of
P. gingivalis arginine–specific cysteine-proteinase gene (108). Dupli-
cate samples were assayed in a total volume of 10 l, containing 100 ng
of template brain genomic DNA solution, TaqMan Universal PCR
Master Mix (2×) (Kapa Biosystems, USA), and the specific set of
primers (final concentration, 5 M) and probe (final concentration,
4 M) (GenoMed, Poland), corresponding to 562.5 nM of forward
and reverse primers and 100 nM of the probe. After an initial incu-
bation step of 2 min at 50°C and denaturation for 95°C for 20 s, 40
PCR cycles (95°C for 20 s and 60°C for 30 s) were performed. The
number of copies of the P. gingivalis genome was calculated by
matching C
q
values with a standard curve prepared from serial dilu-
tions of cultured P. gingivalis W83 (WT).
Quantification of hippocampal Gad67
+
interneurons
Anti-GAD67 antibody, clone 1G10.2 (MAB5406, MilliporeSigma),
was used at a dilution of 1:2000 for IHC. Quantification of Gad67
+
interneurons was performed with CellSens 1.5 Software. The area of
the hilus was defined as the area between the blades of the dentate
gyrus connected by a straight line on the open side. The number of
cells on every 40th section through the hippocampus was counted. The
results are presented as the number of cells per volume of tissue.
Preparation of P. gingivalis lysates for gel electrophoresis
Bacteria (10
8
) were collected and centrifuged at 5000g for 10 min at
4°C. The supernatant was discarded. Bacterial cell pellet was lysed
with 1 ml of B-PER lysis buffer (Thermo Fisher Scientific) on ice for
10 min and then centrifuged for 10 min at 14,000g at 4°C. The su-
pernatant containing protein lysate was collected.
COR553 activity probe labeling of Kgp
P. gingivalis lysate, purified Kgp, or human subgingival plaque sam-
ples were incubated with 1 M of Cy5 probe COR553 for 1 hour at
37°C with shaking. For COR388-treated samples, 1 M COR388
was added for 30 min at 37°C before the addition of COR553. Then,
samples were denatured with NuPAGE LDS sample buffer (Thermo
Fisher Scientific) containing 50 mM DTT at 95°C for 10 min and
subjected to SDS-PAGE with Criterion 4 to 15% precast gel (Bio-Rad)
and tris/glycine/SDS running buffer (Bio-Rad). Gel was run at 75 V
for 10 min and then at 125 V for 1.5 hours, followed by Cy5 visual-
ization with ChemiDoc imaging system (Bio-Rad).
IP of Kgp labeled with COR553
For IP of Cy5-labeled Kgp, the samples were incubated with 10 g of
rabbit polyclonal CAB102 antibody with rotation overnight at 4°C, in-
cubated with prewashed Dynabeads Protein G beads with rotation for
20 min at RT, washed, and magnetically separated. Beads were then
dissolved with 20 l of elution buffer and 10 l of NuPAGE LDS sample
buffer and 50 mM DTT and heated at 70°C for 10 min, eluting the IP
proteins. Samples were then subjected to SDS-PAGE, and Cy5 probe
signals were visualized with a ChemiDoc imaging system (Bio-Rad).
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WB analysis of COR553-labeled samples
After imaging with Cy5 detection, the same gels were transferred to
PVDF membranes and immunoblotted with anti-Kgp antibody
CAB102. Membranes were blocked with 3% BSA TBST buffer for at
least 1 hour, incubated with 1:1000 CAB102 for 2 hours at RT or
overnight at 4°C in blocking buffer, and visualized with goat anti-
rabbit IgG HRP-conjugated antibody (#31462, Thermo Fisher Sci-
entific) and chemiluminescent detection using SuperSignal West
Femto (Thermo Fisher Scientific) and a ChemiDoc imaging system.
Collection and processing of human saliva and subgingival
plaque samples
Oral subgingival plaque and saliva samples were obtained from five
human subjects with periodontal disease under an IRB-approved
clinical protocol. An unstimulated saliva sample (about 1 ml) was
obtained by collection into a sterile 15-ml falcon tube following a
2-min water rinse. Samples were collected at a consistent time of
day to avoid diurnal effects and were kept cold during and following
collection. After collection was complete, the cap of the tube was
tightly screwed and transferred to −80°C.
Two subgingival plaque samples per site were collected from
periodontal sites of four periodontal teeth with ≥6 mm pocket
depth using Endodontic absorbent paper points (size, 40). The sam-
pling sites were gently air-dried and isolated with cotton pellets to
avoid saliva contamination. The paper points were inserted in the
pockets for 30 s until resistance was felt. Paper points were held with
pliers, removed from the site, and placed into prelabeled 1.5-ml mi-
crocentrifuge tubes. Samples were eluted from the paper points by
placing them in 100 l of B-PER lysis buffer in a low-bind 1.5-ml
tube, flicking the tube at one flick per second for 30 s, discarding the
paper point, and snap-freezing the samples in liquid nitrogen. Each
plaque sample was processed in this manner separately but com-
bined for analysis. Twenty microliters of the eluate was used for
COR553 probe labeling, 5 l was used for BCA protein determina-
tion, and 2 l was used for qPCR.
qPCR detection of P. gingivalis copy number in saliva and
subgingival plaque of human subjects
DNA was extracted from 50 l of Saliva using Puregene Core Kit A
(Qiagen). The final DNA pellet was dissolved in 50 l of DNA hy-
dration buffer. A qPCR assay was performed with 2 l of saliva
DNA and hmuY primers [GAACGATTTGAACTGGGACA (H1.1
forward) and AACGGTAGTAGCCTGATCCA (H1.1 reverse)] and
a probe (/56-FAM/TTCTGTCTT/ZEN/GCCGGAGAATACGGC/
3IABkFQ/). A serial dilution of synthetic template DNA was in-
cluded in the qPCR assay to calculate the copy number of P. gingivalis
in saliva. qPCR was performed on 2 l of neat eluate of subgingival
plaque (no DNA extraction). The primers and methods were the
same as those used for saliva above.
Determination of Kgp-dependent growth of P. gingivalis
P. gingivalis [WT (ATCCBAA-308) and KgPIg-B] was inoculated
from stocks into 20 ml of prereduced modified TSB medium [TSB +
yeast extract (5 mg/ml),
l-cysteine (0.5 mg/ml), hemin (5 g/ml),
and vitamin K1 (1 g/ml)] and incubated at 37°C for 48 hours an-
aerobically in a Coy type C vinyl chamber. Prereduction of all solu-
tions used was done by transferring the liquids to an anaerobic
chamber for >16 hours immediately after autoclaving. On the day
of the experiment, the primary culture was diluted to obtain OD
of 0.2 to 0.25 using a Siemens MicroScan turbidity meter in the
prereduced modified TSB medium and incubated for 6 hours to
reach log phase (OD of approximately 0.5 to 0.6) at 37°C. Then, the
bacteria were collected by centrifuging at 4000 rpm for 10 min and
washed. Pellets were diluted to 3 × 10
8
to 5 × 10
8
CFU/ml, and 10 ml
of these diluted cultures was transferred into conical tubes and cen-
trifuged. The resultant pellet was resuspended using 10 ml of de-
fined medium to assess growth. The defined medium consists of the
following: salt base supplement [10.0 mM NaH
2
PO
4
, 10.0 mM KCI,
2 mM citric acid, 1.25 mM MgCl
2
, 20.0 M CaCl
2
, 0.1 M Na
2
MoO
4
,
25.0 M ZnCl
2
, 50.0 M MnCl
2
, 5.0 M CuCl
2
, 10.0 M CoCl
2
, and
5.0 M H
3
BO
3
(pH 7.0)] with 20 mM -ketoglutarate, 3% BSA, he-
min (5 g/ml), and vitamin K (1 g/ml). Fifty microliters of 100×
COR388 stock prepared in DMSO was added to the bacterial sus-
pension (3 × 10
8
to 5 × 10
8
CFU/ml) for each strain with a final
concentration of 500 nM. Vehicle cultures were treated with 0.1%
DMSO. The bacteria were incubated at 37°C in the anaerobic cham-
ber, and OD was measured at 0, 21, and 43 hours to generate a time
course of culture growth.
Assessment of in vitro resistance of P. gingivalis
P. gingivalis (ATCC BAA-308) and P. gingivalis Kgp knockout were
thawed, and a culture of OD
600
= 1.2 (equals 3 × 10
9
to 5 × 10
9
CFU/ml)
was prepared as described above. Resistance was assessed by incu-
bation of 16 serial passages of P. gingivalis in the defined medium
listed previously, and resistance to COR388 was performed simulta-
neously with cultures incubated with the broad-spectrum antibiotic
moxifloxacin. Because COR388 does not completely inhibit P. gingivalis
growth in vitro, we defined MIC as the minimum COR388 concen-
tration that produced a partial inhibition cutoff, specifically >50%
inhibition compared to nontreated cultures. Resistance was assessed
in two standard methods, with the final data reported as an average
of both methods. Cultures were first prepared with drug and moxi-
floxacin in a range of doses passaging each time for 17 passages and
monitoring MIC with each passage. In a separate study, drug con-
centrations were gradually increased between passages. The lowest
drug concentration that inhibited >50% growth was recorded as the
MIC, inoculum from this passage used for the next passage, and
assessed at a new drug concentration using the highest drug con-
centration that was sublethal and raising the concentrations through-
out the test as needed.
Statistical analysis
Data were analyzed with GraphPad Prism version 7.02 for Windows
(GraphPad Software, La Jolla, CA, USA; www.graphpad.com). Outliers
were detected with the ROUT method (Q = 0.2%) and removed from
further analysis. Outliers were not removed from data presented in
Fig.1. To determine whether the data were normally distributed, we
performed a Shapiro-Wilk test. If P values were below 0.05, then the
data were considered nonparametric and analyzed by Mann-Whitney
test or Kruskal-Wallis one-way analysis of variance (ANOVA) fol-
lowed by Dunn’s post hoc test. Parametric data were analyzed by
unpaired t test or by one-way ANOVA followed by Dunnett’s mul-
tiple comparisons test. Correlations were analyzed with Spearman’s
correlation coefficient.
SUPPLEMENTARY MATERIALS
Supplementary material for this article is available at http://advances.sciencemag.org/cgi/
content/full/5/1/eaau3333/DC1
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Fig. S1. CAB101 analysis of non-AD neurological disease brain microarrays.
Fig. S2. RgpB IHC in hippocampal samples from nondemented and AD patients.
Fig. S3. Sequencing of P. gingivalis hmuY PCR products from AD brains.
Fig. S4. Sequencing of P. gingivalis hmuY PCR products from clinical AD CSF.
Table S1. NVD003 AD and control TMA patient data.
Table S2. NVD005 AD and control TMA patient data.
Table S3. Tau fragments identified by MS after gingipain exposure.
Table S4. Demographic information of patients with CP who donated saliva and subgingival
plaque samples.
REFERENCES AND NOTES
1. T. Wyss-Coray, J. Rogers, Inflammation in Alzheimer disease—A brief review of the
basic science and clinical literature. Cold Spring Harb. Perspect. Med. 2, a006346
(2012).
2. V. Kaushal, R. Dye, P. Pakavathkumar, B. Foveau, J. Flores, B. Hyman, B. Ghetti, B. H. Koller,
A. C. LeBlanc, Neuronal NLRP1 inflammasome activation of Caspase-1 coordinately
regulates inflammatory interleukin-1-beta production and axonal degeneration-
associated Caspase-6 activation. Cell Death Differ. 22, 1676–1686 (2015).
3. F. Mawanda, R. Wallace, Can infections cause Alzheimer's disease? Epidemiol. Rev. 35,
161–180 (2013).
4. D. K. V. Kumar, S. H. Choi, K. J. Washicosky, W. A. Eimer, S. Tucker, J. Ghofrani, A. Lefkowitz,
G. McColl, L. E. Goldstein, R. E. Tanzi, R. D. Moir, Amyloid- peptide protects against
microbial infection in mouse and worm models of Alzheimer’s disease. Sci. Transl. Med. 8,
340ra72 (2016).
5. S. J. Soscia, J. E. Kirby, K. J. Washicosky, S. M. Tucker, M. Ingelsson, B. Hyman, M. A. Burton,
L. E. Goldstein, S. Duong, R. E. Tanzi, R. D. Moir, The Alzheimer’s disease-associated
amyloid -protein is an antimicrobial peptide. PLOS ONE 5, e9505 (2010).
6. P. Spitzer, M. Condic, M. Herrmann, T. J. Oberstein, M. Scharin-Mehlmann, D. F. Gilbert,
O. Friedrich, T. Grömer, J. Kornhuber, R. Lang, J. M. Maler, Amyloidogenic amyloid--
peptide variants induce microbial agglutination and exert antimicrobial activity. Sci. Rep.
6, 32228 (2016).
7. R. P. Darveau, G. Hajishengallis, M. A. Curtis, Porphyromonas gingivalis as a potential
community activist for disease. J. Dent. Res. 91, 816–820 (2012).
8. E. K. Kaye, A. Valencia, N. Baba, A. Spiro III, T. Dietrich, R. I. Garcia, Tooth loss and
periodontal disease predict poor cognitive function in older men. J. Am. Geriatr. Soc. 58,
713–718 (2010).
9. M. Gatz, J. A. Mortimer, L. Fratiglioni, B. Johansson, S. Berg, C. A. Reynolds, N. L. Pedersen,
Potentially modifiable risk factors for dementia in identical twins. Alzheimers Dement. 2,
110–117 (2006).
10. P. S. Stein, M. Desrosiers, S. J. Donegan, J. F. Yepes, R. J. Kryscio, Tooth loss, dementia and
neuropathology in the Nun study. J. Am. Dent. Assoc. 138, 1314–1322; quiz 1381–2
(2007).
11. A. R. Kamer, E. Pirraglia, W. Tsui, H. Rusinek, S. Vallabhajosula, L. Mosconi, L. Yi, P. McHugh,
R. G. Craig, S. Svetcov, R. Linker, C. Shi, L. Glodzik, S. Williams, P. Corby, D. Saxena,
M. J. de Leon, Periodontal disease associates with higher brain amyloid load in normal
elderly. Neurobiol. Aging 36, 627–633 (2015).
12. J. M. Noble, L. N. Borrell, P. N. Papapanou, M. S. V. Elkind, N. Scarmeas, C. B. Wright,
Periodontitis is associated with cognitive impairment among older adults: Analysis of
NHANES-III. J. Neurol. Neurosurg. Psychiatry 80, 1206–1211 (2009).
13. M. Ide, M. Harris, A. Stevens, R. Sussams, V. Hopkins, D. Culliford, J. Fuller, P. Ibbett,
R. Raybould, R. Thomas, U. Puenter, J. Teeling, V. H. Perry, C. Holmes, Periodontitis and
cognitive decline in Alzheimer’s disease. PLOS ONE 11, e0151081 (2016).
14. S. Poole, S. K. Singhrao, S. Chukkapalli, M. Rivera, I. Velsko, L. Kesavalu, S. Crean, Active
invasion of porphyromonas gingivalis and infection-induced complement activation in
ApoE
−/−
mice brains. J. Alzheimers Dis. 43, 67–80 (2015).
15. N. Ishida, Y. Ishihara, K. Ishida, H. Tada, Y. Funaki-Kato, M. Hagiwara, T. Ferdous,
M. Abdullah, A. Mitani, M. Michikawa, K. Matsushita, Periodontitis induced by bacterial
infection exacerbates features of Alzheimer’s disease in transgenic mice. NPJ Aging
Mech. Dis. 3, 15 (2017).
16. S. Poole, S. K. Singhrao, L. Kesavalu, M. A. Curtis, S. Crean, Determining the presence of
periodontopathic virulence factors in short-term postmortem Alzheimer’s disease brain
tissue. J. Alzheimers Dis. 36, 665–677 (2013).
17. S. K. Singhrao, A. Harding, S. Poole, L. Kesavalu, S. Crean, Porphyromonas gingivalis
periodontal infection and its putative links with Alzheimer’s disease. Mediators Inflamm.
2015, 137357 (2015).
18. A. L. Griffen, M. R. Becker, S. R. Lyons, M. L. Moeschberger, E. J. Leys, Prevalence of
Porphyromonas gingivalis and periodontal health status. J. Clin. Microbiol. 36, 3239–3242
(1998).
19. L. Forner, T. Larsen, M. Kilian, P. Holmstrup, Incidence of bacteremia after chewing, tooth
brushing and scaling in individuals with periodontal inflammation. J. Clin. Periodontol.
33, 401–407 (2006).
20. J. Mahendra, L. Mahendra, V. M. Kurian, K. Jaishankar, R. Mythilli, Prevalence of
periodontal pathogens in coronary atherosclerotic plaque of patients undergoing
coronary artery bypass graft surgery. J. Maxillofac. Oral Surg. 8, 108–113 (2009).
21. J. Katz, N. Chegini, K. T. Shiverick, R. J. Lamont, Localization of P. gingivalis in preterm
delivery placenta. J. Dent. Res. 88, 575–578 (2009).
22. M. Ishikawa, K. Yoshida, H. Okamura, K. Ochiai, H. Takamura, N. Fujiwara, K. Ozaki, Oral
Porphyromonas gingivalis translocates to the liver and regulates hepatic glycogen
synthesis through the Akt/GSK-3 signaling pathway. Biochim. Biophys. Acta 1832,
2035–2043 (2013).
23. J.-L. C. Mougeot, C. B. Stevens, B. J. Paster, M. T. Brennan, P. B. Lockhart, F. K. B. Mougeot,
Porphyromonas gingivalis is the most abundant species detected in coronary and femoral
arteries. J. Oral Microbiol. 9, 1281562 (2017).
24. Y. Guo, K.-A. Nguyen, J. Potempa, Dichotomy of gingipains action as virulence factors:
From cleaving substrates with the precision of a surgeon’s knife to a meat chopper-like
brutal degradation of proteins. Periodontol. 2000 54, 15–44 (2010).
25. M. J. Gui, S. G. Dashper, N. Slakeski, Y.-Y. Chen, E. C. Reynolds, Spheres of influence:
Porphyromonas gingivalis outer membrane vesicles. Mol. Oral Microbiol. 31, 365–378
(2016).
26. D. Grenier, S. Roy, F. Chandad, P. Plamondon, M. Yoshioka, K. Nakayama, D. Mayrand,
Effect of inactivation of the Arg- and/or Lys-gingipain gene on selected virulence and
physiological properties of Porphyromonas gingivalis. Infect. Immun. 71, 4742–4748
(2003).
27. P. G. Stathopoulou, J. C. Galicia, M. R. Benakanakere, C. A. Garcia, J. Potempa, D. F. Kinane,
Porphyromonas gingivalis induce apoptosis in human gingival epithelial cells through a
gingipain-dependent mechanism. BMC Microbiol. 9, 107 (2009).
28. S. M. Sheets, J. Potempa, J. Travis, C. A. Casiano, H. M. Fletcher, Gingipains from
Porphyromonas gingivalis W83 induce cell adhesion molecule cleavage and apoptosis in
endothelial cells. Infect. Immun. 73, 1543–1552 (2005).
29. J. A. Kinane, M. R. Benakanakere, J. Zhao, K. B. Hosur, D. F. Kinane, Porphyromonas
gingivalis influences actin degradation within epithelial cells during invasion and
apoptosis. Cell. Microbiol. 14, 1085–1096 (2012).
30. T. F. Flemmig, E. Milián, H. Karch, B. Klaiber, Differential clinical treatment outcome after
systemic metronidazole and amoxicillin in patients harboring Actinobacillus
actinomycetemcomitans and/or Porphyromonas gingivalis. J. Clin. Periodontol. 25,
380–387 (1998).
31. J. Travis, J. Potempa, Bacterial proteinases as targets for the development of second-
generation antibiotics. Biochim. Biophys. Acta 1477, 35–50 (2000).
32. A. E. Clatworthy, E. Pierson, D. T. Hung, Targeting virulence: A new paradigm for
antimicrobial therapy. Nat. Chem. Biol. 3, 541–548 (2007).
33. C. T. Supuran, A. Scozzafava, A. Mastrolorenzo, Bacterial proteases: Current therapeutic
use and future prospects for the development of new antibiotics. Expert Opin. Ther. Pat.
11, 221–259 (2001).
34. T. Kadowaki, A. Baba, N. Abe, R. Takii, M. Hashimoto, T. Tsukuba, S. Okazaki, Y. Suda,
T. Asao, K. Yamamoto, Suppression of pathogenicity of Porphyromonas gingivalis by
newly developed gingipain inhibitors. Mol. Pharmacol. 66, 1599–1606 (2004).
35. P. T. Nelson, I. Alafuzoff, E. H. Bigio, C. Bouras, H. Braak, N. J. Cairns, R. J. Castellani,
B. J. Crain, P. Davies, K. Del Tredici, C. Duyckaerts, M. P. Frosch, V. Haroutunian,
P. R. Hof, C. M. Hulette, B. T. Hyman, T. Iwatsubo, K. A. Jellinger, G. A. Jicha, E. Kovari,
W. A. Kukull, J. B. Leverenz, S. Love, I. R. Mackenzie, D. M. Mann, E. Masliah, A. C. McKee,
T. J. Montine, J. C. Morris, J. A. Schneider, J. A. Sonnen, D. R. Thal, J. Q. Trojanowski,
J. C. Troncoso, T. Wisniewski, R. L. Woltjer, T. G. Beach, Correlation of Alzheimer disease
neuropathologic changes with cognitive status: A review of the literature. J. Neuropathol.
Exp. Neurol. 71, 362–381 (2012).
36. A. Hershko, A. Ciechanover, The ubiquitin system. Annu. Rev. Biochem. 67, 425–479
(1998).
37. C. T. Chu, J. L. Caruso, T. J. Cummings, J. Ervin, C. Rosenberg, C. M. Hulette, Ubiquitin
immunochemistry as a diagnostic aid for community pathologists evaluating patients
who have dementia. Mod. Pathol. 13, 420–426 (2000).
38. R. Sperling, E. Mormino, K. Johnson, The evolution of preclinical Alzheimer’s disease:
Implications for prevention trials. Neuron 84, 608–622 (2014).
39. J. Potempa, K.-A. Nguyen, Purification and characterization of gingipains. Curr. Protoc.
Protein Sci. Chapter 21, Unit 21.20 (2007).
40. J. Potempa, R. Pike, J. Travis, The multiple forms of trypsin-like activity present in various
strains of Porphyromonas gingivalis are due to the presence of either Arg-gingipain or
Lys-gingipain. Infect. Immun. 63, 1176–1182 (1995).
41. A. Gmiterek, H. Wójtowicz, P. Mackiewicz, M. Radwan-Oczko, M. Kantorowicz,
M. Chomyszyn-Gajewska, M. Frąszczak, M. Bielecki, M. Olczak, T. Olczak, The unique hmuY
gene sequence as a specific marker of Porphyromonas gingivalis. PLOS ONE 8, e67719
(2013).
42. B. Linz, F. Balloux, Y. Moodley, A. Manica, H. Liu, P. Roumagnac, D. Falush, C. Stamer,
F. Prugnolle, S. W. van der Merwe, Y. Yamaoka, D. Y. Graham, E. Perez-Trallero,
on January 17, 2020http://advances.sciencemag.org/Downloaded from
Dominy et al., Sci. Adv. 2019; 5 : eaau3333 23 January 2019
SCIENCE ADVANCES
|
RESEARCH ARTICLE
20 of 21
T. Wadstrom, S. Suerbaum, M. Achtman, An African origin for the intimate association
between humans and Helicobacter pylori. Nature 445, 915–918 (2007).
43. C. Schabereiter-Gurtner, A. M. Hirschl, B. Dragosics, P. Hufnagl, S. Puz, Z. Kovách,
M. Rotter, A. Makristathis, Novel real-time PCR assay for detection of Helicobacter pylori
infection and simultaneous clarithromycin susceptibility testing of stool and biopsy
specimens. J. Clin. Microbiol. 42, 4512–4518 (2004).
44. S. S. Spudich, A. C. Nilsson, N. D. Lollo, T. J. Liegler, C. J. Petropoulos, S. G. Deeks,
E. E. Paxinos, R. W. Price, Cerebrospinal fluid HIV infection and pleocytosis: Relation to
systemic infection and antiretroviral treatment. BMC Infect. Dis. 5, 98 (2005).
45. Y. Yamamoto, PCR in diagnosis of infection: Detection of bacteria in cerebrospinal fluids.
Clin. Diagn. Lab. Immunol. 9, 508–514 (2002).
46. M. J. Espy, J. R. Uhl, L. M. Sloan, S. P. Buckwalter, M. F. Jones, E. A. Vetter, J. D. C. Yao,
N. L. Wengenack, J. E. Rosenblatt, F. R. Cockerill III, T. F. Smith, Real-time PCR in clinical
microbiology: Applications for routine laboratory testing. Clin. Microbiol. Rev. 19,
165–256 (2006).
47. H. Yin, J. Kuret, C-terminal truncation modulates both nucleation and extension phases
of fibrillization. FEBS Lett. 580, 211–215 (2006).
48. B. Kovacech, M. Novak, Tau truncation is a productive posttranslational modification of
neurofibrillary degeneration in Alzheimer’s disease. Curr. Alzheimer Res. 7, 708–716
(2010).
49. S. Taniguchi-Watanabe, T. Arai, F. Kametani, T. Nonaka, M. Masuda-Suzukake, A. Tarutani,
S. Murayama, Y. Saito, K. Arima, M. Yoshida, H. Akiyama, A. Robinson, D. M. A. Mann,
T. Iwatsubo, M. Hasegawa, Biochemical classification of tauopathies by immunoblot,
protein sequence and mass spectrometric analyses of sarkosyl-insoluble and
trypsin-resistant tau. Acta Neuropathol. 131, 267–280 (2016).
50. D. Uberti, C. Rizzini, P. F. Spano, M. Memo, Characterization of tau proteins in human
neuroblastoma SH-SY5Y cell line. Neurosci. Lett. 235, 149–153 (1997).
51. T. McAvoy, M. E. Lassman, D. S. Spellman, Z. Ke, B. J. Howell, O. Wong, L. Zhu, M. Tanen,
A. Struyk, O. F. Laterza, Quantification of tau in cerebrospinal fluid by immunoaffinity
enrichment and tandem mass spectrometry. Clin. Chem. 60, 683–689 (2014).
52. C. Sato, N. R. Barthélemy, K. G. Mawuenyega, B. W. Patterson, B. A. Gordon,
J. Jockel-Balsarotti, M. Sullivan, M. J. Crisp, T. Kasten, K. M. Kirmess, N. M. Kanaan,
K. E. Yarasheski, A. Baker-Nigh, T. L. S. Benzinger, T. M. Miller, C. M. Karch, R. J. Bateman,
Tau kinetics in neurons and the human central nervous system. Neuron 97, 1284–1298.e7
(2018).
53. M. von Bergen, P. Friedhoff, J. Biernat, J. Heberle, E.-M. Mandelkow, E. Mandelkow,
Assembly of protein into Alzheimer paired helical filaments depends on a local
sequence motif (
306
VQIVYK
311
) forming structure. Proc. Natl. Acad. Sci. U.S.A. 97,
5129–5134 (2000).
54. J. Stöhr, H. Wu, M. Nick, Y. Wu, M. Bhate, C. Condello, N. Johnson, J. Rodgers, T. Lemmin,
S. Acharya, J. Becker, K. Robinson, M. J. S. Kelly, F. Gai, G. Stubbs, S. B. Prusiner,
W. F. DeGrado, A 31-residue peptide induces aggregation of tau’s microtubule-binding
region in cells. Nat. Chem. 9, 874–881 (2017).
55. S. Eick, W. Pfister, Efficacy of antibiotics against periodontopathogenic bacteria within
epithelial cells: An in vitro study. J. Periodontol. 75, 1327–1334 (2004).
56. E. Portelius, H. Zetterberg, R. A. Dean, A. Marcil, P. Bourgeois, M. Nutu, U. Andreasson,
E. Siemers, K. G. Mawuenyega, W. C. Sigurdson, P. C. May, S. M. Paul, D. M. Holtzman,
K. Blennow, R. J. Bateman, Amyloid-
1–15/16
as a marker for -secretase inhibition in
Alzheimer’s disease. J. Alzheimers Dis. 31, 335–341 (2012).
57. M. Sztukowska, A. Sroka, M. Bugno, A. Banbula, Y. Takahashi, R. N. Pike, C. A. Genco,
J. Travis, J. Potempa, The C-terminal domains of the gingipain K polyprotein are
necessary for assembly of the active enzyme and expression of associated activities.
Mol. Microbiol. 54, 1393–1408 (2004).
58. K.-A. Nguyen, J. Travis, J. Potempa, Does the importance of the C-terminal residues in the
maturation of RgpB from Porphyromonas gingivalis reveal a novel mechanism for protein
export in a subgroup of Gram-Negative bacteria? J. Bacteriol. 189, 833–843 (2007).
59. K. Govindpani, B. Calvo-Flores Guzman, C. Vinnakota, H. J. Waldvogel, R. L. Faull,
A. Kwakowsky, Towards a better understanding of GABAergic remodeling in Alzheimer’s
disease. Int. J. Mol. Sci. 18, E1813 (2017).
60. W. Fornicola, A. Pelcovits, B.-X. Li, J. Heath, G. Perry, R. J. Castellani, Alzheimer disease
pathology in middle age reveals a spatial-temporal disconnect between amyloid- and
phosphorylated tau. Open Neurol. J. 8, 22–26 (2014).
61. J. C. Lenzo, N. M. O’Brien-Simpson, R. K. Orth, H. L. Mitchell, S. G. Dashper, E. C. Reynolds,
Porphyromonas gulae has virulence and immunological characteristics similar to those of
the human periodontal pathogen Porphyromonas gingivalis. Infect. Immun. 84,
2575–2585 (2016).
62. Y. Yamasaki, R. Nomura, K. Nakano, S. Naka, M. Matsumoto-Nakano, F. Asai, T. Ooshima,
Distribution of periodontopathic bacterial species in dogs and their owners. Arch. Oral
Biol. 57, 1183–1188 (2012).
63. L. Sun, R. Zhou, G. Yang, Y. Shi, Analysis of 138 pathogenic mutations in presenilin-1 on
the in vitro production of A42 and A40 peptides by -secretase. Proc. Natl. Acad.
Sci. U.S.A. 114, E476–E485 (2017).
64. R. Zhou, G. Yang, Y. Shi, Dominant negative effect of the loss-of-function -secretase
mutants on the wild-type enzyme through heterooligomerization. Proc. Natl. Acad.
Sci. U.S.A. 114, 12731–12736 (2017).
65. W. B. Zigman, D. A. Devenny, S. J. Krinsky-McHale, E. C. Jenkins, T. K. Urv, J. Wegiel,
N. Schupf, W. Silverman, Alzheimer’s disease in adults with Down syndrome. Int. Rev. Res.
Ment. Retard. 36, 103–145 (2008).
66. P. J. Cichon, L. B. Crawford, W. D. Grimm, Early-onset periodontitis associated with
Down’s syndrome—Clinical interventional study. Ann. Periodontol. 3, 370–380 (1998).
67. A. Amano, T. Kishima, S. Kimura, M. Takiguchi, T. Ooshima, S. Hamada, I. Morisaki,
Periodontopathic bacteria in children with Down syndrome. J. Periodontol. 71, 249–255
(2000).
68. G. Ram, J. Chinen, Infections and immunodeficiency in Down syndrome. Clin. Exp.
Immunol. 164, 9–16 (2011).
69. M. B. Giacona, P. N. Papapanou, I. B. Lamster, L. L. Rong, V. D. D’Agati, A. M. Schmidt,
E. Lalla, Porphyromonas gingivalis induces its uptake by human macrophages and
promotes foam cell formation in vitro. FEMS Microbiol. Lett. 241, 95–101 (2004).
70. M. Coureuil, H. Lécuyer, S. Bourdoulous, X. Nassif, A journey into the brain: Insight into
how bacterial pathogens cross blood-brain barriers. Nat. Rev. Microbiol. 15, 149–159
(2017).
71. B. R. Talamo, W.-H. Feng, M. Perez-Cruet, L. Adelman, K. Kosik, V. M.-Y. Lee, L. C. Cork,
J. S. Kauer, Pathologic changes in olfactory neurons in Alzheimer’s disease. Ann. N. Y.
Acad. Sci. 640, 1–7 (1991).
72. L. Li, R. Michel, J. Cohen, A. DeCarlo, E. Kozarov, Intracellular survival and vascular
cell-to-cell transmission of Porphyromonas gingivalis. BMC Microbiol. 8, 26 (2008).
73. T. E. Cope, T. Rittman, R. J. Borchert, P. S. Jones, D. Vatansever, K. Allinson, L. Passamonti,
P. Vazquez Rodriguez, W. R. Bevan-Jones, J. T. O’Brien, J. B. Rowe, Tau burden and the
functional connectome in Alzheimer’s disease and progressive supranuclear palsy. Brain
141, 550–567 (2018).
74. S. Urnowey, T. Ansai, V. Bitko, K. Nakayama, T. Takehara, S. Barik, Temporal activation of
anti- and pro-apoptotic factors in human gingival fibroblasts infected with the
periodontal pathogen, Porphyromonas gingivalis: Potential role of bacterial proteases in
host signalling. BMC Microbiol. 6, 26 (2006).
75. J. Chu, E. Lauretti, D. Praticò, Caspase-3-dependent cleavage of Akt modulates tau
phosphorylation via GSK3 kinase: Implications for Alzheimer’s disease. Mol. Psychiatry
22, 1002–1008 (2017).
76. P. Sandhu, M. M. Naeem, C. Lu, P. Kumarathasan, J. Gomes, A. Basak, Ser
422
phosphorylation blocks human Tau cleavage by caspase-3: Biochemical implications
to Alzheimer’s Disease. Bioorg. Med. Chem. Lett. 27, 642–652 (2017).
77. E. H. Corder, A. M. Saunders, W. J. Strittmatter, D. E. Schmechel, P. C. Gaskell,
G. W. Small, A. D. Roses, J. L. Haines, M. A. Pericak-Vance, Gene dose of apolipoprotein
E type 4 allele and the risk of Alzheimer’s disease in late onset families. Science 261,
921–923 (1993).
78. S. E. Roselaar, A. Daugherty, Apolipoprotein E-deficient mice have impaired innate
immune responses to Listeria monocytogenes in vivo. J. Lipid Res. 39, 1740–1743 (1998).
79. J. Lönn, S. Ljunggren, K. Klarström-Engström, I. Demirel, T. Bengtsson, H. Karlsson,
Lipoprotein modifications by gingipains of Porphyromonas gingivalis. J. Periodontal Res.
53, 403–413 (2018).
80. F. M. Harris, W. J. Brecht, Q. Xu, I. Tesseur, L. Kekonius, T. Wyss-Coray, J. D. Fish, E. Masliah,
P. C. Hopkins, K. Scearce-Levie, K. H. Weisgraber, L. Mucke, R. W. Mahley, Y. Huang,
Carboxyl-terminal-truncated apolipoprotein E4 causes Alzheimer’s disease-like
neurodegeneration and behavioral deficits in transgenic mice. Proc. Natl. Acad. Sci. U.S.A.
100, 10966–10971 (2003).
81. T. R. Jay, V. E. von Saucken, G. E. Landreth, TREM2 in neurodegenerative diseases.
Mol. Neurodegener. 12, 56 (2017).
82. P. Minoretti, C. Gazzaruso, C. D. Vito, E. Emanuele, M. P. Bianchi, E. Coen, M. Reino,
D. Geroldi, Effect of the functional toll-like receptor 4 Asp299Gly polymorphism on
susceptibility to late-onset Alzheimer’s disease. Neurosci. Lett. 391, 147–149 (2006).
83. N. Brouwers, C. Van Cauwenberghe, S. Engelborghs, J.-C. Lambert, K. Bettens,
N. Le Bastard, F. Pasquier, A. G. Montoya, K. Peeters, M. Mattheijssens, R. Vandenberghe,
P. P. Deyn, M. Cruts, P. Amouyel, K. Sleegers, C. Van Broeckhoven, Alzheimer risk
associated with a copy number variation in the complement receptor 1 increasing
C3b/C4b binding sites. Mol. Psychiatry 17, 223–233 (2012).
84. M.-S. Tan, J.-T. Yu, T. Jiang, X.-C. Zhu, H.-F. Wang, W. Zhang, Y.-L. Wang, W. Jiang, L. Tan,
NLRP3 polymorphisms are associated with late-onset Alzheimer’s disease in Han
Chinese. J. Neuroimmunol. 265, 91–95 (2013).
85. X. Gao, Y. Dong, Z. Liu, B. Niu, Silencing of triggering receptor expressed on myeloid
cells-2 enhances the inflammatory responses of alveolar macrophages to
lipopolysaccharide. Mol. Med. Rep. 7, 921–926 (2013).
86. E.-N. N’Diaye, C. S. Branda, S. S. Branda, L. Nevarez, M. Colonna, C. Lowell, J. A. Hamerman,
W. E. Seaman, TREM-2 (triggering receptor expressed on myeloid cells 2) is a phagocytic
receptor for bacteria. J. Cell Biol. 184, 215–223 (2009).
on January 17, 2020http://advances.sciencemag.org/Downloaded from
Dominy et al., Sci. Adv. 2019; 5 : eaau3333 23 January 2019
SCIENCE ADVANCES
|
RESEARCH ARTICLE
21 of 21
87. J. M. Replogle, G. Chan, C. C. White, T. Raj, P. A. Winn, D. A. Evans, R. A. Sperling,
L. B. Chibnik, E. M. Bradshaw, J. A. Schneider, D. A. Bennett, P. L. De Jager, A TREM1
variant alters the accumulation of Alzheimer-related amyloid pathology. Ann. Neurol. 77,
469–477 (2015).
88. N. Bostanci, T. Thurnheer, J. Aduse-Opoku, M. A. Curtis, A. S. Zinkernagel, G. N. Belibasakis,
Porphyromonas gingivalis regulates TREM-1 in human polymorphonuclear neutrophils
via its gingipains. PLOS ONE 8, e75784 (2013).
89. F. Martinon, J. Tschopp, Inflammatory caspases: Linking an intracellular innate immune
system to autoinflammatory diseases. Cell 117, 561–574 (2004).
90. M. Saresella, F. La Rosa, F. Piancone, M. Zoppis, I. Marventano, E. Calabrese, V. Rainone,
R. Nemni, R. Mancuso, M. Clerici, The NLRP3 and NLRP1 inflammasomes are activated in
Alzheimer’s disease. Mol. Neurodegener. 11, 23 (2016).
91. I. Olsen, Ö. Yilmaz, Modulation of inflammasome activity by Porphyromonas gingivalis in
periodontitis and associated systemic diseases. J. Oral Microbiol. 8, 30385 (2016).
92. C. Venegas, S. Kumar, B. S. Franklin, T. Dierkes, R. Brinkschulte, D. Tejera, A. Vieira-Saecker,
S. Schwartz, F. Santarelli, M. P. Kummer, A. Griep, E. Gelpi, M. Beilharz, D. Riedel,
D. T. Golenbock, M. Geyer, J. Walter, E. Latz, M. T. Heneka, Microglia-derived ASC specks
cross-seed amyloid- in Alzheimer’s disease. Nature 552, 355–361 (2017).
93. M. T.-H. Huang, D. J. Taxman, E. A. Holley-Guthrie, C. B. Moore, S. B. Willingham,
V. Madden, R. K. Parsons, G. L. Featherstone, R. R. Arnold, B. P. O’Connor, J. P.-Y. Ting,
Critical role of apoptotic speck protein containing a caspase recruitment domain (ASC)
and NLRP3 in causing necrosis and ASC speck formation induced by Porphyromonas
gingivalis in human cells. J. Immunol. 182, 2395–2404 (2009).
94. S. Mariathasan, D. S. Weiss, V. M. Dixit, D. M. Monack, Innate immunity against
Francisella tularensis is dependent on the ASC/caspase-1 axis. J. Exp. Med. 202,
1043–1049 (2005).
95. T. N. Ellis, M. J. Kuehn, Virulence and immunomodulatory roles of bacterial outer
membrane vesicles. Microbiol. Mol. Biol. Rev. 74, 81–94 (2010).
96. J. D. Cecil, N. M. O’Brien-Simpson, J. C. Lenzo, J. A. Holden, W. Singleton, A. Perez-Gonzalez,
A. Mansell, E. C. Reynolds, Outer membrane vesicles prime and activate macrophage
inflammasomes and cytokine secretion in vitro and in vivo. Front. Immunol. 8, 1017
(2017).
97. A. J. Fleetwood, M. K. S. Lee, W. Singleton, A. Achuthan, M.-C. Lee, N. M. O’Brien-Simpson,
A. D. Cook, A. J. Murphy, S. G. Dashper, E. C. Reynolds, J. A. Hamilton, Metabolic
remodeling, inflammasome activation, and pyroptosis in macrophages stimulated by
Porphyromonas gingivalis and its outer membrane vesicles. Front. Cell. Infect. Microbiol. 7,
351 (2017).
98. Y. Zhao, F. Shao, Diverse mechanisms for inflammasome sensing of cytosolic bacteria
and bacterial virulence. Curr. Opin. Microbiol. 29, 37–42 (2016).
99. K. O. Bender, M. Garland, J. A. Ferreyra, A. J. Hryckowian, M. A. Child, A. W. Puri,
D. E. Solow-Cordero, S. K. Higginbottom, E. Segal, N. Banaei, A. Shen, J. L. Sonnenburg,
M. Bogyo, A small-molecule antivirulence agent for treating Clostridium difficile infection.
Sci. Transl. Med. 7, 306ra148 (2015).
100. Y. Shi, D. B. Ratnayake, K. Okamoto, N. Abe, K. Yamamoto, K. Nakayama, Genetic analyses
of proteolysis, hemoglobin binding, and hemagglutination of Porphyromonas gingivalis.
Construction of mutants with a combination of rgpA, rgpB, kgp, and hagA. J. Biol. Chem.
274, 17955–17960 (1999).
101. J. W. Smalley, A. J. Birss, B. Szmigielski, J. Potempa, Sequential action of R- and K-specific
gingipains of Porphyromonas gingivalis in the generation of the haem-containing
pigment from oxyhaemoglobin. Arch. Biochem. Biophys. 465, 44–49 (2007).
102. R. D. Pathirana, N. M. O’Brien-Simpson, G. C. Brammar, N. Slakeski, E. C. Reynolds, Kgp and
RgpB, but not RgpA, are important for Porphyromonas gingivalis virulence in the murine
periodontitis model. Infect. Immun. 75, 1436–1442 (2007).
103. C. L. Ventola, The antibiotic resistance crisis: Part 1: Causes and threats. P. T. 40, 277–283
(2015).
104. J. H. Kwon, M. A. Olsen, E. R. Dubberke, The morbidity, mortality, and costs associated
with Clostridium difficile infection. Infect. Dis. Clin. North Am. 29, 123–134 (2015).
105. P. J. Narayan, S.-L. Kim, C. Lill, S. Feng, R. L. M. Faull, M. A. Curtis, M. Dragunow, Assessing
fibrinogen extravasation into Alzheimer’s disease brain using high-content screening of
brain tissue microarrays. J. Neurosci. Methods 247, 41–49 (2015).
106. H. C. Kolb, M. G. Finn, K. B. Sharpless, Click chemistry: Diverse chemical function from a
few good reactions. Angew. Chem. Int. Ed. 40, 2004–2021 (2001).
107. J. L. Poirier, R. Čapek, Y. De Koninck, Differential progression of Dark Neuron and
Fluoro-Jade labelling in the rat hippocampus following pilocarpine-induced status
epilepticus. Neuroscience 97, 59–68 (2000).
108. J. M. Morillo, L. Lau, M. Sanz, D. Herrera, A. Silva, Quantitative real-time PCR based on
single copy gene sequence for detection of Actinobacillus actinomycetemcomitans and
Porphyromonas gingivalis. J. Periodontal Res. 38, 518–524 (2003).
Acknowledgments: We are enormously grateful to the brain tissue donors and their families.
We are also very grateful to N. Mehrabi, M. Singh-Bains, and S. Feng (Centre for Brain Research,
University of Auckland) for their expert assistance with TMA construction, IHC, and MetaMorph
analyses and to M. Eszes, the Human Brain Bank manager. Funding: P.M. was supported by
National Science Center 2016/23/B/NZ5/011469, Poland. J.P. was supported by NIH/NIDCR
grant R01DE022597. This work was funded by Cortexyme Inc. Author contributions: S.S.D.
and C.L. developed and coordinated the project, designed experiments, evaluated the data,
and drafted the manuscript. F.E. designed, performed, and analyzed IHC and
immunofluorescent experiments on human brain tissues; designed, performed, and analyzed
experiments on stereotactic injection of gingipains into mouse brain; designed, performed,
and analyzed experiments on the antibacterial effects of A on P. gingivalis; and analyzed brain
samples from all animal experiments. M.B. and A.M. designed, performed, and analyzed
experiments using a mouse model of P. gingivalis–induced periodontal disease
and brain infection. A.K. designed and oversaw the development of small-molecule gingipain
inhibitors. M.N. performed IP and WB of Kgp from human brain tissues. U.H. analyzed brain
samples from all animal experiments. D.R. designed, performed, and analyzed PCR
experiments of P. gingivalis DNA load in human CSF. C.G. performed in vitro digestion of
recombinant tau-441 by gingipains and developed the WB of tau proteolytic fragments. L.J.H.
and S.A.-K. designed and evaluated experiments and edited the manuscript. S.K. evaluated
experiments and edited the manuscript. A.L. assisted in biochemical aspects of the
experiments. M.I.R. evaluated experiments and edited the manuscript. B.P. provided purified
gingipains. P.M., A.H., and K.A. assisted in performing mouse experiments and analyzing
animal specimens. H.H. provided saliva and subgingival plaque samples from periodontal
subjects at The Forsyth Institute. G.D.W. and E.C.R. analyzed gingipain-IR in AD brain tissue at
the University of Melbourne and provided gingipain antibodies. R.L.M.F., M.A.C., and M.D.
coordinated experiments and analyzed brain TMAs using anti-gingipain antibodies at
NeuroValida, the University of Auckland. J.P. developed and coordinated the project, designed
experiments, evaluated the data, and helped draft the manuscript. Competing interests:
S.S.D. and C.L. are co-founders of Cortexyme, are employees of the company, and own
Cortexyme stock. F.E., M.N., U.H., D.R., C.G., L.J.H., S.A.-K., S.K., and A.L. are Cortexyme
employees with stock options. A.K. is a paid consultant of Cortexyme and owns Cortexyme
stock. M.I.R. and J.P. are scientific advisors to Cortexyme and have options to purchase
Cortexyme stock. A.K., S.S.D., and C.L. are inventors on two issued patents both entitled
“Inhibitors of lysine gingipain” (US/9,975,473 and US/9.988,375) as well as two pending
patent applications entitled “Inhibitors of arginine gingipain” (PCT/US2016/061197, filed on
9 November 2016) and “Ketone inhibitors of lysine gingipain” (PCT/US2017/051912, filed on
15 September 2017). S.S.D. and C.L. are inventors on a patent application entitled “Methods
of use for therapeutics targeting the pathogen P. gingivalis (US2017/ 0014468, filed on
29 April 2015). A.K. and L.J.H. are inventors on a patent application entitled “Gingipain activity
probes” (62/459,456; filed on 15 February 2017). Cortexyme is the assignee of these patents
and applications. The other authors declare that they have no competing interests. Data and
materials availability: All data needed to evaluate the conclusions in the paper are present in
the paper and/or the Supplementary Materials. Additional data related to this paper may be
requested from the authors.
Submitted 30 May 2018
Accepted 11 December 2018
Published 23 January 2019
10.1126/sciadv.aau3333
Citation: S. S. Dominy, C. Lynch, F. Ermini, M. Benedyk, A. Marczyk, A. Konradi, M. Nguyen,
U. Haditsch, D. Raha, C. Griffin, L. J. Holsinger, S. Arastu-Kapur, S. Kaba, A. Lee, M. I. Ryder,
B. Potempa, P. Mydel, A. Hellvard, K. Adamowicz, H. Hasturk, G. D. Walker, E. C. Reynolds,
R. L. M. Faull, M. A. Curtis, M. Dragunow, J. Potempa, Porphyromonas gingivalis in Alzheimer’s
disease brains: Evidence for disease causation and treatment with small-molecule inhibitors.
Sci. Adv. 5, eaau3333 (2019).
on January 17, 2020http://advances.sciencemag.org/Downloaded from
treatment with small-molecule inhibitors
in Alzheimer's disease brains: Evidence for disease causation andPorphyromonas gingivalis
Reynolds, Richard L. M. Faull, Maurice A. Curtis, Mike Dragunow and Jan Potempa
Ryder, Barbara Potempa, Piotr Mydel, Annelie Hellvard, Karina Adamowicz, Hatice Hasturk, Glenn D. Walker, Eric C.
Haditsch, Debasish Raha, Christina Griffin, Leslie J. Holsinger, Shirin Arastu-Kapur, Samer Kaba, Alexander Lee, Mark I.
Stephen S. Dominy, Casey Lynch, Florian Ermini, Malgorzata Benedyk, Agata Marczyk, Andrei Konradi, Mai Nguyen, Ursula
DOI: 10.1126/sciadv.aau3333
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Discussion

This was a multi-institution study, and the first authors are from the publicly traded company that has developed a small-molecule inhibitor for Alzheimers that is still going through clinical trials: Cortexyme (https://www.cortexyme.com/). Periodontal disease, is an infection of the tissues that hold your teeth in place that is caused by poor dental hygiene that allow plaque (which are a sticky film of bacteria) to accumulate on teeth and harden. For more about Periodontal disease: https://www.nidcr.nih.gov/health-info/gum-disease/more-info It is also important to note (as a limitation), that there is a difference between the permeability of the brain-blood barriers of individuals with and without Alzheimers, and individuals with the disease, are more susceptible to getting infections in their brains. Here is a video from the company leading this study, Cortexyme, discussing their small molecule inhibitor: https://vimeo.com/333736696 It is important to note the point that P. gingivalis is also found in individuals with no oral disease, and in individuals with oral disease but without Alzheimers disease. In this paper, the authors find evidence that the bacteria Porphyromonas gingivalis, which is associated with chronic gum diseases, is involved in the pathology of Alzheimers, and they introduce a potential treatment using small-molecule inhibitors. This study is groundbreaking for several reasons, not the least of which is the remarkable discovery of these pathogens in the brains of Alzheimer’s patients. Links between neurodegenerative diseases, brains and the microbiome, are bound to arise, and this paper has generated a lot of interest and funding in these directions. P. gingivalis has been previously shown to be significantly associated with cardiovascular disease, and knowledge of the link between plaques in teeth and plaques in arteries is well known by the cardiology community: https://www.health.harvard.edu/heart-health/gum-disease-and-heart-disease-the-common-thread Broad spectrum antibiotics cannot treat P. gingivalis, a motivation for the small molecule inhibitor in this study. Tau is one of the main biomarkers for AD. These key graphs demonstrate the presence of these P. gingivalis pathogens, and their correlation with Tau, and other Alzheimers biomarkers, in the brains of individuals with Alzheimers.