SURFACE EXPOSURE AND SPECIES-SPECIFICITY OF AN IMMUNOREACTIVE DOMAIN OF A 66-KILODALTON OUTER-MEMBRANE PROTEIN (P66) OF THE BORRELIA SPP THAT CAUSE LYME-DISEASE

A chromosomally encoded 66-kDa protein (P66) of Borrelia spp, that cau se Lyme disease has previously been shown to be associated with the sp irochetal outer membrane, A topological model of P66 predicts a surfac e-exposed fragment which links the N- and C-terminal intramembranous d omains of the protein (J, Bunikis, L. Noppa, and S. Bergstrom, FEMS Mi crobiol, Lett. 131:139-145, 1995), In the present study, an immunogeni c determinant of P66 was identified by a comparison of the immunoreact ivities of different fragments of P66 generated either by proteolytic treatment of intact spirochetes or as recombinant proteins expressed i n Escherichia coil, The immune response to P66 during natural infectio n was found to be directed against the predicted surface domain which comprises amino acids at positions 454 through 491, A sequence compari son revealed considerable polymorphism of the surface domains of P66 p roteins of different Lyme disease-causing Borrelia species, Five seque nce patterns of this domain were observed in the B. garinii strains st udied, In contrast, sequences of the relevant part of P66 of the B. af zelii and B. burgdorferi sensu stricto isolates studied were identical within the respective species, In immunoblotting, 5 of 17 (29.4%) ser a from North American patients with early disseminated or persistent L yme disease reacted against P66 of B. burgdorferi sensu stricto B31. T hese sera, however, failed to recognize P66 of B. afzelii and B. garin ii, as well as an analog of P66 in the relapsing fever agent, B. herms ii. In conclusion, the topological model of P66 is supported by the de monstration of an apparent surface localization of an immunoreactive d omain of this protein. Furthermore, analogous to the plasmid-encoded b orrelial Outer surface proteins, the predicted surface-exposed portion of chromosomally encoded P66 appears to be antigenically heterogenous .