Characterisation and Immunogenicity of outer membrane vesicles displaying NadA, NHBA and fHbp from serogroup B.

More affordable and effective vaccines against bacterial meningitis caused by serogroup B are still required for global prevention. We have previously shown that modified outer membrane vesicles (mOMVs) from commensal can be used as a platform to induce immune responses against meningococcal antigens. The aim of the present study was to use a combination of two genetically engineered mOMVs to express multiple antigens from known to be involved in protective immunity to meningococcal meningitis (different variants of factor H binding protein (fHbp), Heparin Binding Antigen (NHBA) and Adhesin A (NadA)). Antigen expression in the mOMVs was confirmed by Western blotting; detoxification of the lipooligosaccharide (LOS) was confirmed by measuring human Toll-like receptor 4 (hTLR4) activation using cell assays. Mice immunised with a combination of two mOMVs expressing fHbp, NHBA and NadA produced antibodies to all the antigens. Furthermore, serum bactericidal activity (SBA) was induced by the immunisation, with mOMVs expressing NadA displaying high SBA titres against a MenB strain. The work highlights the potential of mOMVs from to induce functional immune responses against multiple antigens involved in the protective immune response to meningococcal disease.