The gene encoding the 17-kDa antigen of Bartonella henselae is located within a cluster of genes homologous to the virB virulence operon

A Bartonella henselae genomic lambda library was screened with antiserum ge nerated in mice against live B. henselae. One of the immunoreactive clones expressed a 17-kDa antigen that was characterized previously as an immunodo minant protein of B. henselae. Sequence analysis of the recombinant clone, pBHIM-2, revealed that the open reading frame (ORF) encoding the 17-kDa ant igen was situated between homologs of virB4 and virB6, two genes that belon g to the virB operon. The virB operon has been associated with the transfer of oncogenic T-DNA in Agrobacterium tumefaciens and with secretion of the pertussis toxin in Bordetella pertussis. Downstream of the virB6 gene withi n pBHIM-2 was a partial open reading frame that was homologous to the virB8 gene. Rescreening of the library by plaque hybridization using probes spec ific to the 5' and 3' ends of the pBHIM-2 insert resulted in the isolation of recombinant clones containing additional virB genes. Assembly of the seq uences obtained from the recombinant clones revealed that eight of the open reading frames encode homologs of the VirB proteins. The homology and coli nearity with the virB genes suggest that the gene encoding the 17-kDa antig en is expressed within the virB locus of B. henselae.