Mutation and recombination in the upstream homology box-flanked ospE-related genes of the lyme disease spirochetes result in the development of new antigenic variants during infection

The ospE gene family of the Lyme disease spirochetes encodes a polymorphic group of immunogenic lipoproteins. The ospE genes are one of several gene f amilies that are flanked by a highly conserved upstream sequence called the upstream homology box, or UHB, element. Earlier analyses in our lab demons trated that ospE-related genes are characterized by defined hypervariable d omains (domains 1 and 2) that are predicted to be hydrophilic, surface expo sed, and antigenic. The flanking of hypervariable domain 1 by DNA repeats m ay indicate that recombination contributes to ospE diversity and thus ultim ately to antigenic variation. Using an isogeneic clone of Borrelia burgdorf eri B31G (designated B31Gc1), we demonstrate that the ospE-related genes un dergo mutation and rearrangement during infection in mice. The mutations th at develop during infection resulted in the generation of OspE proteins wit h altered antigenic characteristics. The data support the hypothesized role of OspE-related proteins in immune system evasion.