Antigenicity in mice of multiple antigen peptides containing B-cell/T-cell epitopes of the Neisseria gonorrhoeae MafA 2/3 protein

There are no prophylactic vaccines for the sexually transmitted disease gonorrhoea, caused by infection with the Gram-negative pathogen Neisseria gonorrhoeae . In this pilot study, we examined the antigenicity in mice of two synthetic multiple antigen peptides (MAP) containing B- and T-cell epitopes of the MafA 2/3 outer membrane protein. The B- and T-cell epitopes were identified in silico and synthetic MAP octamer peptides synthesized. The peptides were docked in silico with mouse and human MHC II complexes to examine binding properties. Mice were immunized with MafA 2/3-MAP-A and MafA 2/3-MAP-B peptides with different adjuvants. Antisera were tested in ELISA against homologous and heterologous MAP peptides, against recombinant MafA 2/3 protein and outer membranes (OM) from strain P9-17, and two other strains (FA1090 and 12CFX_T_039; AR205). Antisera were also examined by flow cytometry against whole bacteria, and for their ability to induce complement-mediated killing of gonococci. Our data generated showed that immunization with MafA 2/3 MAP-A and MAP-B in saline, on alum and in SAS and TitreMax emulsions induced antibodies that reacted with peptides and OM in ELISA but showed low levels of binding to whole bacteria in flow cytometry. Antibodies were of the IgG1 subclass and weak bactericidal activity was observed only with anti-MAP-A sera against strain P9-17 (50% titres of 4), and not against the two other strains. Thus, MafA 2/3 MAP peptides were antigenic in mice, and this synthetic approach joins a limited list of previous attempts to create experimental epitope-based gonococcal vaccines. The ability to induce functional, albeit weak antibody responses, merits their further development.