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The distribution of the hemoglobin receptor gene (hmbR) was investigated among disease and carriage Neisseria meningitidis isolates, revealing that the gene was detected at a significantly higher frequency among disease isolates than among carriage isolates. In isolates without hmbR, the locus was occupied by the cassettes exl2 or exl3 or by a "pseudo hmbR" gene, designated exl4. The hmbR locus exhibited characteristics of a pathogenicity island in published genomes of N. meningitidis, Neisseria gonorrhoeae, and Neisseria lactamica sequence type-640. These data are consistent with a role for the hmbR gene in meningococcal disease.

As an alternative approach towards the development of a meningococcal vaccine, the potential of peptide mimics of lipooligosaccharide (LOS) to elicit cross-reactive immune responses against LOS was investigated. The heptapeptides SMYGSYN and APARQLP were identified by enrichment from a coliphage display library with a LOS-specific monoclonal antibody. Mice immunised with these peptides conjugated to diphtheria toxoid elicited a total IgG response to LOS with geometric mean titres 2-4 times higher compared with non-immunised controls. There was an increase in LOS-specific IgG1 immunoglobulin, whereas specific IgG2a and IgG3 decreased slightly in response to immunisation. The data demonstrated that peptide mimics can elicit immune responses against meningococcal LOS.

A plasmid, pIF21, has been constructed that is able to donate transposons Tn1, Tn5 and Tn7. The transposons are located on a temperature-sensitive derivative of the incP1 plasmid pRP1, which is transferable to a wide range of Gram-negative genera.