ANALYSIS OF NEISSERIA-MENINGITIDIS CLASS-3 OUTER-MEMBRANE PROTEIN GENE VARIABLE REGIONS AND TYPE IDENTIFICATION USING GENETIC TECHNIQUES

The class 3 porin proteins of Neisseria meningitidis stimulate bacteri cidal antibodies and express serotype-specific antigenic epitopes. Seq uence analysis of porB genes for the class 3 proteins revealed regions of variability that map to surface-exposed loops, To evaluate the rel ationship between serotype and variable-region (VR) genotype, sequence s from the 11 class 3-expressing serotype strains and 3 additional ser otype 3 strains were analyzed by molecular techniques, Multiple-sequen ce alignment revealed a limited number of unique sequences at each of four VRs (VR1 to VR4), ranging from four unique sequences at VR1 to se ven sequence patterns at VR2 and VR4, Serotype-specific VR sequences w ere found in each of the four VRs, suggesting that each VR has immunol ogic importance, Five serotypes had at least one VR sequence that was unique. Three serotypes which had sequences in common with other serot ypes at each VR were distinguished by examining multiple VRs, Serotype 3 was identical to serotype 19 at each VR, and serotype 8 was identic al to serotype 18 at each VR, Serotypes 4 and 21 were identical at VR1 and significantly different at VR3 and VR4, A subpopulation of seroty pe 4 strains with a unique VR2 sequence was identified, The serotypes which were grouped with closely related or identical sequences at one VR were grouped with different serotypes at other VRs consistent with the pattern of genetic mosaicism described for the porA (class 1 prote in) gene. Hybridization assays demonstrated the ability to identify VR genotypes and distinguish serotypes using biotin-labelled oligonucleo tide probes, This information may be useful in strain selection for va ccine development, in epidemiologic studies to determine the prevalenc e of the individual VR genotype (especially among nonserotypeable stra ins) and, combined with PCR, in the identification of culture-negative suspected meningococcal cases.