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Clinical and Diagnostic Laboratory Immunology, Sep 1997, 522-529, Vol 4, No. 5
B Rokbi, M Mignon, DA Caugant and MJ Quentin-Millet
ET-5 complex strains of Neisseria meningitidis were traced
intercontinentally and have been causing hyperendemic meningitis on a
worldwide scale. In an attempt to develop a fully broad cross-reactive
transferrin-binding protein B (TbpB)-based vaccine, we undertook to assess
the extent of variability of TbpB proteins among strains of this
epidemiological complex. For this purpose, a PCR-based method was developed
to study the heterogeneity of the tbpB genes from 31 serogroup B N.
meningitidis strains belonging to the ET-5 complex. To define adequate
primers, the tbpB gene from an ET-5 complex strain, 8680 (B:15:P1.3;
isolated in Chile in 1987), was cloned and the nucleotide sequence was
determined and compared to two other previously published tbpB sequences. A
tbpB fragment was amplified from genomic DNA from each of the 31 strains.
By this method, heterogeneity in size was observed and further
characterized by restriction pattern analysis with four restriction enzymes
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 strain 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 1987), was found to harbor a tbpB
gene different from all the others. These results demonstrated a pronounced
variability among tbpB alleles within a limited number of ET-5 complex
strains collected over a 19-year period. Despite the genetic heterogeneity
observed, specific antisera raised to purified Tbps from ET-5 complex
strains showed broad cross-reactivity between different TbpBs both by
Western blot analysis and bactericidal assay, confirming that a limited
number of TbpB molecules included in a vaccine are likely to induce broadly
cross-reactive antibodies against the different strains.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Heterogeneity of tbpB, the transferrin-binding protein B gene, among serogroup B Neisseria meningitidis strains of the ET-5 complex
Pasteur Merieux Connaught, Marcy-l'Etoile, France.
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