Variation in a major surface protein of Lyme disease spirochetes

Two monoclonal antibodies (H6831 and H5TS) differed in their indirect immunofluorescence reactivity when tested against 14 strains of Lyme disease spirochetes. Strains were bound by both antibodies, by H6831 or H5TS alone, or by neither. Western blot and immunoprecipitation studies revealed that the determinants of both antibodies were associated with abundant proteins with apparent subunit molecular weights of ca. 34,000 (34K-range proteins). The following results indicated that the 34K-range proteins were exposed on the surface of the spirochetes. (i) Antibody H6831 agglutinated the spirochetes; (ii) immune electron microscopy showed that the H6831 determinant was associated with the outer membrane; (iii) radiolabeled H6831 bound to live organisms; and (iv) proteases effectively removed the 34K-range proteins from intact cells. With their demonstrated variability and exposure on the surface, the 34K-range proteins may contribute to the serotype specificity of Lyme disease spirochetes.