Deciphering the role of Toll-like receptors in humoral responses to Borreliae.

The bacteria of the genus Borrelia are arthropod-borne spirochetes that cause relapsing fever and Lyme disease in humans. Like most arthropod-borne pathogens, Borreliae must survive in the periphery of their vertebrate hosts to allow for transmission to another arthropod vector. These spatial and temporal restrictions require that Borreliae evade the adaptive immune response. Borreliae have evolved genetic mechanisms that alter their surface protein expression, thereby altering the antigenic target presented to the host. To control Borreliae infection, the host relies on a rapid humoral response. While it is clear that B cell antigen receptor signaling is a critical requirement for the specific antibody responses, growing evidence suggests that additional signaling by innate immune receptors such as Toll-like receptors is necessary for optimal T cell-dependent and T cell-independent antibody responses. This review is focused on the role of Toll-like receptors in B cell responses to relapsing fever and Lyme disease Borreliae.