Identification of Two Epitopes on the Outer Surface Protein A of the Lyme Disease Spirochete Borrelia burgdorferi

A murine IgM monoclonal antibody (MA-2C6) with κ-light chains directed against an antigenic determinant of outer surface protein A (OspA) of the Lyme disease spirochete, Borrelia burgdorferi, is produced. This antibody could bind specifically to OspA antigen of several isolates of B. burgdorferi, but not to the non-Lyme disease bacteria such as T. pallidum and B. hermsii. Antibody MA-2C6 was purified by ion-exchange chromatography and used for purification of OspA antigen from Borrelia burgdorferi cell lysate. This antibody together with an IgG1 monoclonal antibody specific for OspA, that was previously characterized, were used to test whether these antibodies recognize different epitopes on OspA antigen of Borrelia burgdorferi. For this test, ELISA double antibody binding was used. Two antibodies were added to the antigen either separately or simultaneously, and the amount of bound antibody was quantitatively measured by the use of rabbit anti-mouse IgG conjugated with alkaline phosphatase. Additivity of the bound enzymatic activity was observed when the monoclonal antibodies bind to distinct epitopes. With this test, two distinct epitopes were recognized on the OspA molecule. This antibody can be used not only for the purification and subtyping of OspA, but also for neutralization and immunotherapy.