Mechanisms of vascular damage by systemic dissemination of the oral pathogen Porphyromonas gingivalis

Several studies have shown a clear association between periodontal disease and increased risk of cardiovascular disease. Porphyromonas gingivalis (Pg), a key oral pathogen, and its cell surface-expressed gingipains, induce oedema in a zebrafish larvae infection model although the mechanism of these vascular effects is unknown. Here, we aimed to determine whether Pg-induced vascular damage is mediated by gingipains. In vitro, human endothelial cells from different vascular beds were invaded by wild-type (W83) but not gingipain-deficient (ΔK/R-ab) Pg. W83 infection resulted inincreased endothelial permeability as well as decreased cell surface abundance of endothelial adhesion molecules PECAM-1 and VE-cadherin compared to infection with ΔK/R-ab. In agreement, when transgenic zebrafish larvae expressing fluorescently labelled PECAM-1 or VE-cadherin were systemically infected with W83 or ΔK/R-ab, a significant reduction in adhesion molecule fluorescence was observed specifically in endothelium proximal to W83 bacteria through a gingipain-dependent mechanism. Furthermore, this was associated with increased vascular permeability in vivo when assessed by dextran leakage microangiography. These data are thefirst to show that Pg directly mediates vascular damage in vivo by degrading PECAM-1 and VE-cadherin. Our data provide a molecular mechanism by which Pg might contribute to cardiovascular disease

Structural and functional probing of PorZ, an essential bacterial surface component of the type-IX secretion system of human oral-microbiomic Porphyromonas gingivalis.

Porphyromonas gingivalis is a member of the human oral microbiome abundant in dysbiosis and implicated in the pathogenesis of periodontal (gum) disease. It employs a newly described type-IX secretion system (T9SS) for secretion of virulence factors. Cargo proteins destined for secretion through T9SS carry a recognition signal in the conserved C-terminal domain (CTD), which is removed by sortase PorU during translocation. Here, we identified a novel component of T9SS, PorZ, which is essential for surface exposure of PorU and posttranslational modification of T9SS cargo proteins. These include maturation of enzyme precursors, CTD removal and attachment of anionic lipopolysaccharide for anchorage in the outer membrane. The crystal structure of PorZ revealed two β-propeller domains and a C-terminal β-sandwich domain, which conforms to the canonical CTD architecture. We further documented that PorZ is itself transported to the cell surface via T9SS as a full-length protein with its CTD intact, independently of the presence or activity of PorU. Taken together, our results shed light on the architecture and possible function of a novel component of the T9SS. Knowledge of how T9SS operates will contribute to our understanding of protein secretion as part of host-microbiome interactions by dysbiotic members of the human oral cavity

Type I interferon-dependent response of zebrafish larvae during tilapia lake virus (TiLV) infection

International audienceTilapia lake virus (TiLV; genus: Tilapinevirus, family: Amnoonviridae) is a recently characterised enveloped virus with a linear, negative-sense single-stranded RNA genome, which causes high mortality in tilapia species. In the present study, we demonstrated that zebrafish (Danio rerio) larvae are susceptible to TiLV infection upon systemic injection. TiLV replicated in zebrafish larvae and caused their high mortality (of about 70%). Histopathological examination revealed that TiLV infection caused pathological abnormalities in zebrafish larvae that were well visible within the brain. Moreover, gene expression analysis revealed that TiLV infection induced up-regulation of the expression of the immune-related genes encoding pathogen recognition receptors involved in sensing of viral dsRNA (rig-I (ddx58), tlr3, tlr22), transcription factors (irf3, irf7), type I interferon (infϕ1), antiviral protein (mxa), and pro-inflammatory cytokine (il-1β). We also demonstrated the protective role of the recombinant zebrafish IFNϕ1 on the survival of zebrafish larvae during TiLV infection. Our results show the importance of type I IFN response during TiLV infection in zebrafish larvae and demonstrate that zebrafish is a good model organism to study interactions between TiLV - a newly emerging in aquaculture virus, and fish host