TLR2 and TLR4 mediate the TNF[alpha] response to Vibrio vulnificus biotype 1

Vibrio vulnificus (Vv) is a pathogenic bacterium that can cause life-threatening infections in humans. Most fatal cases are due to septic shock that results from dysregulation of cytokines, particularly TNF[alpha], which plays a critical role in the outcome of Vv infection. The goal of this study was to investigate the Toll-like receptor (TLR)-mediated TNF[alpha] response to four Vv biotype 1 strains using mice deficient for TLR2, TLR4, and TLR2/TLR4. Ex vivo assays were performed with blood, splenocytes, and Kupffer cells (KC) from wild-type (WT) and TLR-knockout (KO) mice using formalin-inactivated Vv (f-Vv) as stimulant. All f-Vv biotype 1 strains elicited strong TNF[alpha] production by WT mouse blood and cells, which was TLR2 and TLR4 dependent. OxPAPC, an inhibitor of TLR2 and TLR4 signaling, effectively blunted the TLR-mediated TNF[alpha] response to f-Vv. Furthermore, TLR2 KO and TLR2/TLR4 KO mice were more resistant to lethal infection with VvATCC 27562 than WT mice, perhaps due to attenuation of the TNF[alpha] response. These data suggest that it may be possible to devise strategies to specifically target the harmful TLR-mediated TNF[alpha] response as an adjunct to antibiotic treatment of severe Vv infection.