Role of TLR4 in the host response to Vibrio vulnificus, an emerging pathogen.

The incidence of infection with Vibrio vulnificus is increasing due to changing ecologic and demographic factors. Most fatal cases are caused by septic shock that results from dysregulation of proinflammatory cytokines such as tumor necrosis factor-alpha (TNFalpha), presumably due to interaction of V. vulnificus components with Toll-like receptors (TLRs). The goal of this study was to investigate the role of TLR4 in the host response to V. vulnificus. Results obtained using V. vulnificus type strain ATCC 27562 showed that (1) TLR4 signaling is myeloid differentiation factor 88 dependent and plays a key role in TNFalpha production by mouse blood and splenocytes stimulated ex vivo with inactivated V. vulnificus cells, (2) TLR4 signaling is deleterious in a mouse model of V. vulnificus infection, (3) signaling by TLR(s), exclusive of TLR4, is needed to eradicate infection, and (4) the TLR-mediated TNFalpha response plays a critical role in determining the outcome of infection. These results suggest that blockade of the harmful TLR4-mediated inflammatory response could be a useful adjunct to antibiotics for treatment of severe V. vulnificus infection.