Enterococcal leucine-rich repeat-containing protein involved in virulence and host inflammatory response

Enterococcus faecalis is an important nosocomial pathogen associated with high morbidity and mortality for patients who are immuntocompromised or who have severe underlying diseases. TheE.faecalis genome encodes numerous surface-exposed proteins that may be involved in virulence. This work describes the characterization of the first internalin-like protein in E.faecalis, ElrA, belonging to the recently identified WxL family of surface proteins. ElrA contains an N-terminal signal peptide for export, a leucine-rich repeat domain that may interact with host cells, and a C-terminal WxL domain that interacts with the peptidoglycan. Disruption of the e1rA gene significantly attenuates bacterial virulence in a mouse peritonitis model. The e1rA deletion mutant also displays a defect in infection of host macrophages and a decreased interieukin-6 response in vivo. Finally, e1rA expression is induced in vivo. Altogether, these results demonstrate a role for EIrA in the E. faecalis infectious process in vivo and suggest that this surface protein may contribute to E. faecalis virulence by stimulating the host inflammatory response.