Characterization of a peptide vaccine candidate mimicking an oligosaccharide epitope of Neisseria gonorrhoeae and resultant immune responses and function

The 2C7 epitope is a conserved oligosaccharide structure, a part of lipooligosaccharide (LOS) on Neisseria gonorrhoeae, present in 95% of clinical gonococcal isolates. 2C7 may represent a potential candidate for an anti-gonococcal vaccine. To circumvent the limitations of saccharide immunogens in producing long lived immune responses, we identified a peptide that mimics the 2C7 epitope using a random peptide library, characterizing linear and cyclic forms and formulating a multiple antigenic peptide. The multiple antigenic peptide Octa-MAP1 was used for immunization, and elicited ≥4-fold increase in cross-reactive anti-LOS antibodies in 26 of 30 mice (87%). IgG anti-LOS antibody elicited by Octa-MAP1 immunization possessed dose-responsive direct complement (C)-dependent bactericidal activity against gonococcal strains that expressed the 2C7 epitope. These data indicate that a peptide can mimic an oligosaccharide epitope and may form the basis for the development of a vaccine candidate for human immunization against N. gonorrhoeae.