VARIABILITY OF OSP GENES AND GENE-PRODUCTS AMONG SPECIES OF LYME-DISEASE SPIROCHETES

A comparison of the osp operon in 24 Lyme disease isolates, including representatives from each of the three established species, Borrellia burgdorferi, Borrelia garinii, and group VS461, was conducted. Several properties were assessed to determine whether the variability observed in this operon was reflective of the species of the isolate. At the transcriptional level, start site and Northern (RNA) blot analyses were conducted. B. garinii and VS461 group isolates were found to possess an untranslated leader sequence 6 nucleotides longer than that observed in B. burgdorferi isolates. By Northern blot analyses all Lyme disease isolates, except the B. garinii isolate VS102, were found to produce a polycistronic full-length ospAB message. Isolate VS102 produced a truncated message lacking the ospB portion of the transcript. Southern blot analyses suggest that the deletion occurred at the DNA level and was not due to a posttranscriptional event. Analysis of the outer surface proteins by two-dimensional gel electrophoresis demonstrated that the OspB isoelectric points were variable, with the OspB of B. garinii isolates exhibiting a pronounced acidic shift. The reactivity of different isolates to OspA and -B monoclonal antibodies and to a hyperimmune anti-ospAB serum was also variable. The results presented here demonstrate genotypic and phenotypic heterogeneity in the osp operon at both the inter- and intraspecies levels. The results have implications concerning the use of the osp genes or their gene products in the development of a Lyme disease vaccine, as diagnostic markers of Lyme disease, and in subtyping of Lyme disease isolates.