Immunological responses to the relapsing fever spirochete Borrelia turicatae in infected Rhesus macaques: implications for pathogenesis and diagnosis.

The global public health impact of relapsing fever (RF) spirochetosis is significant, as the pathogens exist on five of seven continents. The hallmark sign of infection is episodic fever and the greatest threat is to the unborn. With the goal of better understanding the specificity of B cell responses and the role of immune responses in pathogenicity, we infected Rhesus macaques with Borrelia turicatae (a new world RF spirochete species) by tick bite and monitored the immune responses generated in response to the pathogen. Specifically, we evaluated inflammatory mediator induction by the pathogen, host antibody responses to specific antigens, and peripheral lymphocyte population dynamics. Our results indicate that B. turicatae elicits from peripheral blood cells key inflammatory response mediators (IL-1{beta} and TNF-) which are associated with pre-term abortion. Moreover, a global decline in peripheral B cell populations was observed in all animals at 14 days post-infection. Serological responses were also evaluated to assess the antigenicity of three surface proteins, BipA, BrpA and Bta112. Interestingly, a distinction was observed between antibodies generated in non-human primates (NHPs) and mice. Our results provide support for the nonhuman primate model not only in studies of prenatal pathogenesis, but for diagnostic and vaccine antigen identification and testing.