The bvg or vir locus in B. pertussis is responsible for coordinate regulation of the virulence associated factors. Using TnphoA mutagenesis several vir activated genes (vags) have been identified. Some of these fusions were deficient in previously characterized factors such as pertussis toxin, or filamentous hemagglutinin. However one of these TnphoA fusion strains was defective in a 95kDa outer membrane protein. This strain has been shown to be unable to cause lymphocytosis or to persist in a mouse aerosol model of pertussis. The TnphoA insertion mutant has been used to isolate the wild type gene, which is being sequenced. The 95 kDa protein has been purified from the triton insoluble outer membrane fraction of the wild type strain 18323 using a carboxy methyl cellulose column. Purified material has been used to make monoclonal antibodies and ascites fluid is currently being made. A further vag product has been characterized. Identified by TnphoA mutagenesis this vag product appears to be a 30 kDa major outer membrane protein. The gene has been cloned and sequenced and encodes a 60 kDa protein. However, there is a potential processing site at 30 kDa similar to that in pertactin. In addition, the C terminal portion of this protein is very homologous to that of pertactin. The mature protein contains an RGD sequence and we are currently investigating whether this protein may have a role in adhesion. The role of the C terminal portion of this protein in secretion, targeting or anchoring to the membrane is also being investigated.
