PHENOTYPIC ANALYSIS OF OUTER SURFACE PROTEIN-C (OSPC) OF BORRELIA-BURGDORFERI SENSU-LATO BY MONOCLONAL-ANTIBODIES - RELATIONSHIP TO GENOSPECIES AND OSPA SEROTYPE

Molecular analyses of the genes encoding OspC, a major immunodominant protein of Borrelia burgdorferi sensu late, revealed a considerable de gree of heterogeneity, In the present study, we investigated whether a similar heterogeneity of the OspC phenotype can be shown by analysis with monoclonal antibodies (MAbs). Thirteen OspC-specific MAbs (L22 MA bs) were produced by immunizing mice with either different combination s of whole-cell antigens or recombinantly expressed OspCs cloned from strains belonging to different Borrelia spp. Ten of them differed in t heir reactivities with various strains. Western blot (immunoblot) anal yses of 38 B. burgdorferi sensu late strains resulted in 13 different reactivity patterns. These 13 different patterns were observed among o nly six different OspA serotypes, indicating that OspC is more heterog eneous than OspA Patterns 1 to 4 were present only in B. burgdorferi s ensu stricto, patterns 5 to 7 were present only in Borrelia afzelii, a nd patterns 9 to 13 were present only in Borrelia garinii, Pattern 8 w as observed among B. afzelii and B. garinii strains but not among B. b urgdorferi sensu stricto strains. One L22 MAb (2B8) recognized a commo n OspC-specific epitope of all 38 B. burgdorferi sensu late strains an alyzed, and another one (22C11) recognized a common epitope of OspC fr om both B. afzelii and B. garinii and was not reactive with OspC from B. burgdorferi sensu stricto. Western blot and sequence analysis of tr uncated OspCs located the 22C11 epitope as well as a species-specific sequence motif between amino acids 20 and 35. Other broadly reactive L 22 MAbs were 10D3, 1F8, and 7G5. Some L22 MAbs (1C3, 1C3, 12E5, 1B11, 1F10, and 6C8) bound to epitopes present only in a few strains, Relaps ing fever borreliae (Borrelia hermsii, Borrelia turicatae, and Borreli a duttoni) were nonreactive, with the following exception: three L22 M Abs (2B8, 6C4, and 10C5) recognized an abundantly expressed 20-KDa-ran ge protein of B. turicatae. Because OspC is an immunodominant protein during the early immune response in Lyme borreliosis and has been show n to be effective as a vaccine in an animal model, our findings have i mportant implications for the development of diagnostic reagents as we ll as vaccine research.