MOLECULAR VARIATION OF MENINGOCOCCAL SEROTYPE-4 ANTIGEN GENES

Changes in the frequency of serogroup B non serotypable (B:NT) meningo cocci isolated in England and Wales were investigated by T-track finge rprint 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:NT by the Meningococcal Reference Unit (MRU) dot blot assay during 1993-4, expressed variants of the serotyping an tigen, PorB, that were serotype 4 by whole cell ELISA. T-track fingerp rint patterns of these and other 'serotype 4' isolates revealed five d istinct porB alleles which were shown by nucleotide sequence determina tion to encode different peptide sequences. Differential binding of th e 'serotype 4' mAbs MN14G21 and 5DC4C8G8 in whole cell ELISA and dot b lot assays was the result, (i) of differences in the peptide sequence of predicted surface loop I and (ii) an amino acid deletion in predict ed loop VI of the PorB protein.