MOLECULAR CHARACTERIZATION OF THE 98-KILODALTON IRON-REGULATED OUTER-MEMBRANE PROTEIN OF NEISSERIA-MENINGITIDIS

When grown under iron limitation, Neisseria meningitidis expresses sev eral additional outer membrane proteins (OMPs), which were studied to assess their vaccine potential. Two monoclonal antibodies were obtaine d against a 98-kDa OMP of strain 2996 (B:2b:P1.2). Cross-reactivity st udies revealed that the two antibodies reacted with 44 and 42 of 74 me ningococcal strains, respectively. The antibodies did not block the bi nding of transferrin or lactoferrin to intact cells. The structural ge ne for the protein, tentatively designated iroA, was isolated and sequ enced. Computer analysis revealed homology to the ferric siderophore r eceptors in the outer membrane of Escherichia coli and to gonococcal t ransferrin-binding protein 1 (TbpA). The high degree of cross-reactivi ty and the results of Southern blot analyses, which showed that the ir oA gene is also present in strains that did not react with the monoclo nal antibodies, suggest that the 98-kDa OMP is well conserved among me ningococci and that it is a suitable vaccine candidate. However, the a ntibodies were not bactericidal in an in vitro assay with human comple ment.