Background: Vaccines against pathogenic Neisseria face major challenges due to antigenic diversity and complex vaccine formulations. While effective vaccines exist for Neisseria meningitidis, they are serogroup-specific and require multicomponent designs, and no licensed vaccine is available for N. gonorrhoeae. The close genetic relationship between these species raises the possibility that conserved antigens could enable cross-species protective immunity. We previously identified highly conserved gonococcal cell-division antigens, included in the EVX-B2 vaccine candidate, that elicit complement-dependent bactericidal antibodies and reduce gonococcal colonization in vivo (Gulati et al., 2023). In the present ongoing study, we are evaluating whether these antigens can induce functional immune responses against N. meningitidis.
Aim/Methods: Lead antigens (NGO0265/Tpc and NGO1549/FtsN) in the EVX-B2 N. gonorrhoeae vaccine candidate were selected based on high conservation and demonstrated complement-dependent bactericidal activity. Sequence conservation across N. meningitidis serogroups (A, B, C, W, X, Y) was assessed. The two N. gonorrhoeae antigens were administered to mice, and the immune sera were analyzed for antigen-specific functionality in a serum bactericidal assay (SBA) against N. meningitidis strains.
Results: EVX-B2 N. gonorrhoeae antigens demonstrated >90% sequence conservation across major N. meningitidis serogroups. Immunization induced robust antigen-specific antibody responses. In the present ongoing study sera is being evaluated for complement-dependent bactericidal activity against N. meningitidis, demonstrating functional cross-species recognition.
Conclusions: This ongoing work will assess whether conserved gonococcal antigens can induce functional bactericidal immunity also against N. meningitidis. This cross-species antigen strategy represents a potential path toward simplified, broadly protective vaccines targeting multiple pathogenic Neisseria species.