Background
Porphyromonas gingivalis
is part of the subgingival biofilm and a keystone species in the development of periodontitis. Interactions between
P.gingivalis
and other bacteria in biofilms have been shown to affect bacterial virulence.
Helicobacter pylori
also inhabits the subgingival biofilm, but the consequences of interactions there with
P.gingivalis
remain unknown. Here, we investigated how the pre-incubation of
P.gingivalis
with
H.pylori
affects
P.gingivalis
virulence.
Methods
We assayed
P.gingivalis
internalization by oral keratinocytes (OKs), hemagglutination and biofilm formation to identify alterations in virulence after pre-incubation with
H. pylori
. Also, we evaluated viability and migration of OKs infected with
P. gingivalis,
as well as the role of toll-like receptor 4 (TLR4). In addition, we quantified the mRNA of genes associated with
P.gingivalis
virulence.
Results
Pre-incubation of
P.gingivalis
with
H.pylori
enhanced
P.gingivalis
biofilm formation, bacterial internalization into OKs and hemagglutination. Infection with pre-incubated
P.gingivalis
increased OK migration in a manner dependent on the O-antigen and linked to increased expression of the gingipain RgpB. Also, OK TLR4 participates in these events, because upon TLR4 knock-down, pre-incubated
P.gingivalis
no longer stimulated OK migration.
Discussion
We provide here for the first time insight to the consequences of direct interaction between
P.gingivalis
and
H.pylori.
In doing so, we shed light on the mechanism by which
H. pylori
presence in the oral cavity increases the severity or progression of periodontitis.