The ability of TLR agonists to upregulate Brucella abortus strain RB51 mediated protection in a murine respiratory model
Brucella abortus is amongst the top 5 zoonotic diseases worldwide. The overall goal of this research is to generate a safe and effective vaccine for humans. Brucella abortus strain RB51, approved for use in cattle, provides protection by initiating a strong T-helper 1 (Th1) type response is a candidate vaccine. Based on a model for aerosol exposure mice were vaccinated intranasally (IN) with strain RB51 and challenged IN with B. abortus strain 2308, strain RB51 did not protect. Protection against Brucella is mediated through TLRs 2, 4 and 9. The addition of TLR 2 or TLR 4 and a trend with TLR9 agonists with intranasal RB51 vaccination significantly increased bacterial clearance in the lung after strain 2308 challenge. Therefore, we hypothesized that combining TLR agonists 2, 4, and 9 with strain RB51 IN would upregulate protection and clearance in the lung against strain 2308 challenge (IN), by upregulating the DC1 and CD4 Th1 and CD8 immune response. This study showed that protection is not upregulated by combining all TLR agonists. Overall the addition of TLR 2 and 4 vs. TLR 2, 4 and 9 agonists affects the immune response and impacts the level of clearance. Our data support the development of a DC1 Th1 CD8 response, based on serology, and both DC and T-cell activation and function by the group which received the TLR 2 and 4 agonists and to a lesser degree the group receiving TLR 2, 4, and 9 agonists. Additional studies are warranted to further define the differential mechanisms and endpoints of protection.