Neisseria gonorrhoeae is an obligate human pathogen and the causative agent of the sexually transmitted infection gonorrhoea. There are over 106 million reported cases of gonorrhoea each year worldwide, and if left undiagnosed or untreated, infection can lead to severe sequelae that include pelvic inflammatory disease, infertility, neonatal complications, and an increased risk of HIV. N. gonorrhoeae is recognised by WHO and CDC as an urgent threat to global health due to the emergence of multi-drug resistant gonococcal strains. There is currently no vaccine, and no new antibiotics or new vaccine candidates in late-stage development. However, the outer membrane vesicle (OMV) meningococcal B vaccine MeNZB, that was developed to protect against the closely related pathogen Neisseria meningitidis, was recently reported to be associated with reduced rates of gonorrhoea following a mass vaccination campaign in New Zealand.
Our work is focused on identifying novel gonococcal vaccine target, as well as investigating the cross reactivity to N. gonorrhoeae of serum raised to the meningococcal B vaccine Bexsero, which contains the MeNZB OMV component plus three recombinant protein antigens. We have characterised several highly conserved and immunogenic gonococcal candidate vaccine antigens and shown that antibodies to these proteins are bactericidal and can block gonococcal infection of cervical and urethral epithelial cells. In addition, we have found that there is a high level of sequence identity between the MeNZB/Bexsero OMV antigens, and gonococcal proteins. NHBA is the only Bexsero recombinant antigen that is conserved and surfaced exposed in N. gonorrhoeae. Furthermore, we have found that Bexsero induces antibodies in humans that recognise and kill N. gonorrhoeae in vitro. Work is ongoing to identify the full set of gonococcal targets recognized by Bexsero-induced antibodies, and their functional activity against gonorrhoea.