S12.1 Progress towards a Gonorrhoea vaccine

Introduction Gonorrhoea is becoming increasingly difficult to control due to antibiotic resistance and the absence of a vaccine. However, a vaccine to the closely related bacteria Neisseria meningitidis, the outer membrane vesicle (OMV) vaccine MeNZB, was reported to be associated with reduced rates of gonorrhoea. To investigate this possible cross-protection we assessed serum raised to the meningococcal vaccine Bexsero, which contains the MeNZB OMV component plus three recombinant antigens (NadA, fHbp-GNA2091, NHBA-GNA1030), in terms of its cross reactivity and functional activity against Neisseria gonorrhoeae. Methods The similarity of MeNZB and Bexsero antigens to gonococcal proteins was assessed bioinformatically. Sera from rabbits immunised with the OMV component or the three recombinant antigens of Bexsero, and sera from humans immunised with Bexsero were tested in Western blot, ELISA, serum bactericidal activity (SBA) and neutrophil opsonophagocytic (OPA) assays to assess the level and functional activity of antibodies recognising N. gonorrhoeae. Results There is a high level of sequence identity between MeNZB/Bexsero OMV antigens and gonococcal proteins. NHBA is the only Bexsero recombinant antigen that is conserved and surfaced exposed in N. gonorrhoeae. Rabbit antibodies to the OMV component or to the three recombinant antigens of Bexsero recognise gonococcal proteins and mediate SBA and OPA killing of N. gonorrhoeae. Furthermore, Bexsero induces antibodies in humans that recognise gonococcal proteins. Analysis of the functional activity of Bexsero-induced human antibodies against N. gonorrhoeae is ongoing. Conclusions The ability of antibodies induced by MeNZB OMV proteins to recognise and kill N. gonorrhoeae could explain the decrease in gonococcal cases associated with MeNZB vaccination. The presence of antibodies to OMV proteins plus NHBA following Bexsero vaccination may result in additional protection against gonorrhoea. Analysis of Bexsero-vaccinate human sera may also facilitate the identification of a correlate of protection to guide future development of a gonococcal vaccine. Disclosure No significant relationships.