The significance of TLRs in Brucella mediated dendritic cell activation in vitro and pulmonary clearance in vivo (42.16)

Abstract

Abstract Brucellosis is a worldwide zoonoses affecting 500,000 people annually with no approved human vaccines available. Live attenuated B. abortus vaccine strain RB51 protects cattle through CD4 and CD8 T-cell mediated responses. However, there are concerns regarding its efficacy and use as a live vaccine in people. Therefore, identifying how Brucella vaccines stimulate innate and adaptive immunity is critical to enhancing vaccine efficacy. Brucella stimulate dendritic cells (DCs) through Toll-Like Receptors (TLRs) 2, 4 and 9. In this study, to identify how rough vaccine strains stimulate DC activation and function in vitro, we used vaccine strain RB51 versus pathogenic strain 2308 to stimulate bone marrow derived dendritic cells (BMDCs) from TLR2, 4 or 9 knockout (KO) and wild type BALB/c mice. Since inhalation of infected aerosols is one of the most common routes of exposure, in vivo clearance of strain RB51 compared to strain 2308 from intranasally (IN) infected TLR KO vs. control BALB/c mice was assessed. We determined that strain RB51 induced significant (p≤0.05) DC activation compared to strain 2308 which was TLR independent. However, strain RB51 induced TNF - α production was TLR2 and TLR9 dependent and IL-12 production was TLR2 and TLR4 dependent. TLR4 KO mice had significantly (p≤0.05) delayed pulmonary clearance of strain RB51 in vivo at day 14 post infection. Based on these data, future studies will focus on enhancing the protective ability of strain RB51.