HETEROGENEITY OF TBPB, THE TRANSFERRIN-BINDING PROTEIN-B GENE, AMONG SEROGROUP-B NEISSERIA-MENINGITIDIS STRAINS OF THE ET-5 COMPLEX

ET-5 complex strains of Neisseria meningitidis weft traced intercontin entally and have been causing hyperendemic meningitis on a worldwide s cale. In an attempt to develop a fully broad cross-reactive transferri n-binding protein B (TbpB)-based vaccine, we undertook to assess the e xtent of variability of TbpB proteins among strains of this epidemiolo gical complex, For this purpose, a PCR-based method was developed to s tudy the heterogeneity of the tbpB genes from 31 serogroup B N. mening itidis strains belonging to the ET-5 complex, To define adequate prime rs, the tbpB gene from an ET-5 complex strain, 8680 (B:15:P1.3; isolat ed in Chile in 1987), was cloned and the nucleotide sequence was deter mined and compared to two other previously published tbpB sequences, A tbpB fragment was amplified from genomic DNA from each of the 31 stra ins, By this method, heterogeneity in size was observed and further ch aracterized by restriction pattern analysis with four restriction enzy mes and by sequencing tbpB genes from three other ET-5 complex strains . Four distinct tbpB gene types were identified, Fifty-five percent of the strains studied (17/31) harbored tbpB genes similar to that of st rain BZ83 (B:15:-) isolated in The Netherlands in 1984. Ten of the 31 strains (32.2%) had tbpB genes close to that of strain M982. Only 3 of the 31 (9.6%) were found to harbor tbpB genes close to that of strain 8680, and finally one strain, 8710 (B:15:P1.3; isolated in Chile in 1 987), was found to harbor a tbpB gene different from ail the others, T hese results demonstrated a pronounced variability among tbpB alleles within a limited number of ET-5 complex strains collected over a 19-ye ar period, Despite the genetic heterogeneity observed, specific antise ra raised to purified Tbps from ET-5 complex strains showed broad cros s-reactivity between different TbpBs both by Western blot analysis and bactericidal assay, confirming that a limited number of TbpB molecule s included in a vaccine are likely to induce broadly cross-reactive an tibodies against the different strains.