Characterization of an anti-Borrelia burgdorferi OspA conformational epitope by limited proteolysis of monoclonal antibody-bound antigen and mass spectrometric peptide mapping

Lyme borreliosis is a multisystem disorder caused by the spirochete Borreli a burgdorferi that is transmitted to humans by the tick Ixodes dammini. The immune response against the 31 kDa OspA. which is one of the most abundant B. burgdorferi proteins, appears to be critical in preventing infection an d tissue inflammation. Detailed knowledge of the immunological and molecula r characteristics of the OspA protein is important for the development of r eliable diagnostic assays. In this study, we characterized a new conformati onal epitope present within the middle part of B. burgdorferi OspA. Our app roach used enzymatic proteolyses of the immune complex followed by mass spe ctrometric identification of the peptides bound to the antibody. It appears to be one of the first reports on the characterization of a discontinuous epitope using mass spectrometry.