An Enterococcal Leucine-rich Repeats Containing Protein Involved in Virulence and Host Inflammatory Response

Unité des Bactéries Lactiques et pathogènes Opportunistes UR13888, INRA, Jouy-en-Josas, France, Institute of Microbiology, Catholic University of Sacred Heart, Roma, Italy; Unité des Interactions Bactéries-Cellules, Institut Pasteur, INSERM U604, INRA USC2020, Paris, France

^* To whom correspondence should be addressed. Email: pascale.serror{at}jouy.inra.fr.

	Abstract

Enterococcus faecalis is an important nosocomial pathogen associated with high morbidity and mortality for patients who are immunocompromised or who have severe underlying diseases. E. faecalis 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 elrA gene significantly attenuates bacterial virulence in a mouse peritonitis model. The elrA deletion mutant also displays a defect in infection of host macrophages and a decreased IL-6 response in vivo. Finally, elrA expression is induced in vivo. Altogether, these results demonstrate a role for ElrA in the E. faecalis infectious process in vivo and suggest that this surface protein may contribute to the E. faecalis virulence by stimulating the host inflammatory response.