Identification and characterisation of vaccine candidate proteins in the Neisseria meningitidis surface proteome

Neisseria meningitidis is a major cause of meningitis and septicaemia in infants and children. Disease caused by serogroup A, C, W-135 and Y strains is prevented by vaccination using capsular polysaccharide preparations. For serogroup B strains for which the capsular polysaccharide is poorly immunogenic, antigenic proteins on the bacterial surface are under investigation as promising vaccine candidates. Due to the variability in sequence of antigenic proteins, vaccine formulations containing combinations of proteins and protein variants are tested for broad protection against serogroup B isolates. In search for new members for inclusion in multi-protein vaccines, the surface proteome of N. meningitidis from MC58 strain was investigated using treatment of whole meningococci with proteases followed by quantitative differential in-gel electrophoresis (DIGE) of the meningococcal proteome. The majority of proteins identified included known surface antigens and other uncharacterised predicted surface proteins. Quantitative analysis also allowed the assessment of the extent of protease cleavage on the protein population and suggested proteins were either completely or partially digested. Additionally, differences in the protein content of outer membrane vesicles (OMVs) from H44/76 meningococci grown in rich or minimal culture media were assessed by DIGE. Differentially expressed proteins were related to differences in bactericidal activity detected between immune sera from mice immunised with the different OMV preparations. Of the proteins detected on the surface and OMVs, those able to induce an immune response in mice were identified by immunoproteome analysis. Four of the previously uncharacterised proteins identified by the proteomic analyses were assessed in immunological assays for their potential as vaccine candidates. Recombinant forms of macrophage infectivity potentiator (NmMIP), type IV pili biogenesis proteins PilP and PilO and putative adhesin complex protein NMB2095 were produced in Escherichia coli, purified and used to immunise mice. Immune sera against NmMIP bound strongly to the surface of MC58 whilst exhibiting opsonophagocytic activity and facilitating deposition of complement factors on the surface of various meningococcal strains. The nucleotide sequence encoding NmMIP was assessed across a panel of 106 meningococcal isolates and found to be highly conserved and under negative selective pressure.EThOS - Electronic Theses Online ServiceGBUnited Kingdo