title: Sequence variation in the outer-surface-protein genes of Borrelia burgdorferi.
abstract: Borrelia burgdorferi is a spirochete pathogen transmitted among warm-blooded hosts by ixodid ticks. Frequency-dependent selection for variant outer-surface proteins might be expected to arise in this species, since rare variants are more likely to avoid immune surveillance in previously infected hosts. We sequenced the OspA and OspB genes of nine North American strains and compared them with nine strains previously described. For each gene, the mean number of synonymous substitutions per synonymous site and the mean number of nonsynonymous substitutions per nonsynonymous site show only a twofold excess of silent mutations. Synonymous rates vary widely along the OspB protein. Some regions show a significant excess of silent substitutions, while divergence in other regions is constrained by biased base composition or selection. The presence, in antigenically important regions of the protein, of significant variation among strains, as well as evidence for recombination among strains, should be considered in attempts to develop vaccines against this disease.
authors.affiliation: Department of Zoology, University of New Hampshire, Durham 03824.
authors.forename: D A
authors.initials: DA
authors.lastname: Caporale
authors.forename: T D
authors.initials: TD
authors.lastname: Kocher
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial; D000954:Antigens, Surface / Q000235:genetics*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001428:Bacterial Vaccines; D001483:Base Sequence; D015748:Borrelia burgdorferi Group / Q000235:genetics* / Q000302:isolation & purification; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D014644:Genetic Variation; D006801:Humans; D008074:Lipoproteins; D008969:Molecular Sequence Data; D010802:Phylogeny; D012689:Sequence Homology, Nucleic Acid; D013987:Ticks / Q000382:microbiology
chemical_list: D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D001428:Bacterial Vaccines; D017931:DNA Primers; D004269:DNA, Bacterial; D008074:Lipoproteins; C072045:OspA protein; C077030:OspB protein, Borrelia burgdorferi