Molecular diversity of the ospC gene in Borrelia. Impact on phylogeny, epidemiology and pathology.

Lyme borreliosis is a 2 steps disease: i) Localized erythema migrans ii) occasionally a disseminated disease. Three out of the 10 up to now described Borrelia species are pathogenic for man and each of them exhibits its own organotropism: joints for Borrelia burgdorferi sensu stricto (B.b. ss), nervous system for B. garinii, skin for B. afzelii, ospc gene is subject to lateral transfer leading to a huge diversity among corresponding encoded proteins. This allows the spirochete to develop a repertoire of epitopes to escape the host immune response. We noticed that the European endemic ospc repertoire is only a subset of the American one. This bottleneck situation transduces a "founder's event" suggesting B.b. ss has been imported from North America to Europe at historical times. Another valuable observation is the fact that isolates from disseminated forms (called "invasive") of the disease, all are distributed in only ten out of the 70 ospc genotypes. The conclusion is that in human, some OspC conformations are associated with the invasive potential of a given Borrelia isolate.