HUMORAL IMMUNITY TO BORRELIA-BURGDORFERI N40 DECORIN BINDING-PROTEINSDURING INFECTION OF LABORATORY MICE

A Borrelia burgdorferi N40 genomic expression library was screened wit h serum from actively infected mice to identify gene products that eli cit protective immunity. A clone that contained a putative bicistronic operon containing two genes that encoded 20- and 22-kDa lipoproteins was identified and sequenced. These genes showed homology with the gen es encoding decorin binding proteins DbpB and DbpA, respectively, of B . burgdorferi 297 and B31. N40-dbpA DNA hybridized with B. burgdorferi N40 DNA on a single 48-kb linear plasmid. Homologous genes could be a mplified under various degrees of stringency by PCR or hybridized by S outhern blotting from B. burgdorferi sensu stricto N40 and B31, and fr om B. burgdorferi sensu late PBI and 25015, but not PKo. Recombinant N 40-DbpB and N40-DbpA were reactive with antibody in serum from infecte d mice, and serum was more reactive against N40-DbpA than against B. b urgdorferi N40 recombinant P39, OspC, or OspA. Sera from mice infected with B. burgdorferi sensu late strains PKo and PBi were weakly reacti ve against N40-DbpB and N40-DbpA, and sera from mice infected with 250 15 were moderately reactive, compared to sera from mice infected with B. burgdorferi N40. Hyperimmunization of mice with N40-DbpA, but not N 40-DbpB, induced protective immunity against Syringe challenge with cu ltured B. burgdorferi N40. DbpA may therefore be one of the antigens r esponsible for eliciting protective antibody known to exist in serum f rom infected mice. DNA amplification and serology suggest that DbpB an d DbpA are likely to have homologs throughout the B. burgdorferi sensu late family, but they are likely to be heterogeneous.