co-incubation enhances virulence and increases migration of infected human oral keratinocytes.

BACKGROUND

is part of the subgingival biofilm and a keystone species in the development of periodontitis. Interactions between and other bacteria in biofilms have been shown to affect bacterial virulence. also inhabits the subgingival biofilm, but the consequences of interactions there with remain unknown. Here, we investigated how the pre-incubation of with affects virulence.

METHODS

We assayed internalization by oral keratinocytes (OKs), hemagglutination and biofilm formation to identify alterations in virulence after pre-incubation with . Also, we evaluated viability and migration of OKs infected with as well as the role of toll-like receptor 4 (TLR4).   In addition, we quantified the mRNA of genes associated with virulence.

RESULTS

Pre-incubation of with enhanced biofilm formation, bacterial internalization into OKs and hemagglutination. Infection with pre-incubated 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 no longer stimulated OK migration.

DISCUSSION

We provide here for the first time insight to the consequences of direct interaction between and In doing so, we shed light on the mechanism by which presence in the oral cavity increases the severity or progression of periodontitis.