Meningococcal vaccine antigens may generate an immune response that recognizes gonococcal proteins, according to study findings published in Clinical Infectious Diseases. Researchers demonstrated that anti-gonococcal antibodies induced by MeNZB-like outer membrane vesicle proteins may explain the decrease in gonococcal cases observed following MeNZB vaccination.
Neisseria gonorrhoeae and Neisseria meningitidis are closely related bacteria. MeNZB was developed in response to a meningococcal epidemic in New Zealand and 1 million people in the country were vaccinated. A retrospective case-control study subsequently showed that vaccinated individuals were significantly less likely to contract gonorrhea. In the current study, researchers conducted bioinformatic analyses to assess the similarity to gonococcal proteins of MeNZB outer membrane vesicle and Bexsero, which contains the MeNZB outer membrane vesicle protein plus other recombinant proteins. Using serum obtained from adults vaccinated with Bexsero, protein antigens present in Bexsero were compared with gonococcal proteins from available N gonorrhoeae genomes.
Overall, a high level of sequence identity was observed between MeNZB outer membrane vesicle protein and Bexsero outer membrane vesicle antigens and gonococcal proteins. To investigate the ability of Bexsero-induced antibodies to recognize gonococcal proteins, Western blot and enzyme-linked immunosorbent assay test were performed using serum from vaccinated adults. Titers were significantly increased from before to after vaccination for whole-cell N gonorrhoeae (1.8-fold increased geometric mean enzyme-linked immunosorbent assay test titers vs a 5.7-fold increase against whole-cell N meningitidis), along with a 34-fold increase in gonococcal Neisserial Heparin Binding Antigen.
“These data provide experimental evidence for the concept that cross-reactive antibodies may be the mechanism that underlies the recent observation that the meningococcal serogroup B outer membrane vesicle protein vaccine MeNZB was associated with reduced rates of gonorrhea,” wrote the researchers.