The weak interaction of LcrV and TLR2 does not contribute to the virulence of Yersinia pestis

Yersinia pestis and the enteropathogenic Yersinia pseudotuberculosis and Yersinia enterocolitica share the virulence-antigen LcrV. Previously, using reverse genetics we have proven that LcrV contributes to the virulence of Y. enterocolitica serotype O:8 by inducing IL-10 via Toll-like receptor 2 (TLR2). However, both the ability of Y. pestis LcrV to activate TLR2 and a possible role of TLR2-dependent IL-10 induction by LcrV in Y. pestis are not yet known. To eliminate interference from additional protein sequences, we produced LcrVs without affinity tags from Y. pestis and from Y. enterocolitica O:8 (LcrVO:8). LcrVO:8 was much more potent in TLR2-activity than Y. pestis LcrV. To analyse the role of TLR2 in plague, we infected both wild-type and TLR2-/- mice subcutaneously with Y. pestis GB. While TLR2-/- mice exhibited lower blood levels of IL-10 (day 2 post-infection) and of the pro-inflammatory cytokines TNF-alpha, IFN-gamma and MCP-1 (day 4) than wild-type mice, there was no significant difference in survival. The low TLR2-activity of Y. pestis LcrV and associated cytokine expression might explain why - in contrast to Y. enterocolitica O:8 infection - TLR2-deficient mice are not more resistant than wild-type mice in a bubonic plague model.