HOMOLOGY BETWEEN BORRELIA-BURGDORFERI OSPC AND MEMBERS OF THE FAMILY OF BORRELIA-HERMSII VARIABLE MAJOR PROTEINS

Synthesis of the Borrelia burgdorferi outer surface protein C (OspC) i s quite variable. We have cloned and sequenced the ospC gene from B. b urdorferi isolate CA-11.2A, a clone in which ospC expression varies. T he 5' flanking region of the gene contains at least two consensus prom oter regions, as well as two large overlapping inverted repeats. Seque nce comparison to other OspC proteins indicated that the CA-11.2A OspC is as closely related to OspC from two different genospecies of Lyme disease spirochetes as it is to OspC from the prototype B. burdorferi strain, B31. Comparisons of the OspC amino acid (aa) sequence with tho se in aa sequence databases revealed partial identity with the variabl e major proteins Vmp3 and Vmp24 of B. hermsii, a causative agent of ti ck-borne relapsing fever. An ospC probe hybridized to B. hermsii restr iction fragments and linear plasmids that also were recognized by the vmp3 and vmp24 probes. OspC and these Vmp appear to be related, but th eir synthesis is regulated differently in the two species of spirochet es. This represents a fascinating example of the evolution of the numb er, position, regulation and perhaps function of homologous genes in t wo related pathogens. These parameters may relate to characteristic pr operties of the pathogens and their separate tick vectors.