| Borrelia hermsii and other relapsing fever (RF) species are noted for their highly polymorphic surface proteins, or variable major proteins (VMPs), the switching of which confers antigenic variation. Less is known, however, about non-variable surface proteins. In Chapter 2 of this dissertation, we investigated the non-variable surface proteins of B. hermsii and identified a 14-kDa surface protein by raising antibodies against whole cells of a null mutant that did not express the VMPs. This 14-kDa protein is unique to RF Borrelia, and is preferentially expressed in the tick environment over the mammalian environment, which may make it a candidate for a transmission-blocking vaccine.;In Chapter 3, I followed-up on an unexpected finding regarding the variable tick protein (Vtp) of B. hermsii. Vtp, a member of the VMP family which comprises the variable small proteins (Vsp) and variable large proteins (Vlp), has been thought to be active at different times than Vsp and Vlp proteins: Vsp and Vlp are active during vertebrate infections, and Vtp was thought to be active only in the tick vector. However, we found that mice inoculated with the VMP null mutant and Vtp+ wildtype B. hermsii produced specific antibodies to Vtp. In addition, Vtp proteins differ substantially in sequence between strains. Both these findings suggest that Vtp is under selective pressure, such as pressure by the adaptive immune system. |
