Molecular variation of meningococcal serotype 4 antigen genes
Changes in the frequency of serogroup B non serotypable (B[ratio]NT) meningococci isolated in England and Wales were investigated by T-track fingerprint analysis, DNA nucleotide sequence determination, and serotyping by whole cell ELISA and dot blot assay. Seventy-three per cent of the isolates designated as B[ratio]NT by the Meningococcal Reference Unit (MRU) dot blot assay during 1993–4, expressed variants of the serotyping antigen, PorB, that were serotype 4 by whole cell ELISA. T-track fingerprint patterns of these and other ‘serotype 4’ isolates revealed five distinct porB alleles which were shown by nucleotide sequence determination to encode different peptide sequences. Differential binding of the ‘serotype 4’ mAbs MN14G21 and 5DC4C8G8 in whole cell ELISA and dot blot assays was the result, (i) of differences in the peptide sequence of predicted surface loop I and (ii) an amino acid deletion in predicted loop VI of the PorB protein.(Accepted February 11 1998)
c1 Author for correspondence.
p1 Present address: Wellcome Trust Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS.