Studies on the por B gene of Neisseria Meningitidis

Abstract

Neisseria meningitidis is an obligate human pathogen responsible for endemic and epidemic disease world-wide.

Sequence variation in the class 1 outer membrane protein (OMP) has been shown to occur in regions not recognised by monoclonal antibodies representing a hidden source of epidemiological information. The variation of two additional OMPs, class 2/3 and Opc in a collection of strains from patients and close contacts following a disease outbreak was investigated. Comparison of the inferred amino acid sequences showed that three distinct variants within serotype 2a were present. Sequencing of the class 3 expressing strains allowed identification of two non-typeable strains.

The porB gene, which codes for the class 3 protein, was amplified by PCR and cloned into two expression systems. The highest levels of recombinant class 3 (rC13) protein expression were achieved in the Xpress^TM system in E. coli JM101. The rC13 protein was inserted into liposomes and Zwittergent 3-14 and NDSB-195 micelles in an attempt to refold the protein. The adjuvant MPLA was also included in some preparations to boost the immune response.

The various immunisation preparations all induced antibodies against the homologous class 3 protein as detected by ELISA and Western blotting. Cross-reactivity against a heterologous class 2 and class 3 protein was also seen in some sera. The highest levels of bactericidal activity were shown by sera raised against rC13 in Zwittergent 3-14 with MPLA and rC13 in NDSB-195 with MPLA. Thus, refolding the rC13 protein had been achieved and had resulted in significant bacterial activity.

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