Peptide mimics of the group B meningococcal capsule induce bactericidal and protective antibodies after immunization

Neisseria meningitidis serogroup B (MenB) is a leading cause of sepsis and meningitis in children. No vaccine is available for the prevention of these infections because the group B capsular polysaccharide (CP) (MenB CP) is unable to stimulate an immune response, due to its similarity with human polysialic acid. Because the MenB CP bears both human cross-reactive and non-cross-reactive determinants, we developed immunogenic peptide mimics of the latter epitopes. Peptides were selected from phage display libraries for their ability to bind to a protective anti-MenB CP mAb. One of these peptides (designated 9M) induced marked elevations in serum bactericidal activity, but not polysialic acid cross-reacting Abs, after gene priming followed by carrier-conjugate boosting. Moreover, the occurrence of bacteremia was prevented in infant rats by administration of immune sera before MenB challenge. 9M is a promising lead candidate for the development of an effective and affordable anti-MenB vaccine.