Meningitis and sepsis caused by serogroup B meningococcus are two severe diseases that still cause significant mortality. To date there is no universal vaccine that prevents these diseases. In this work, five antigens discovered by reverse vaccinology were expressed in a form suitable for large-scale manufacturing and formulated with adjuvants suitable for human use. The vaccine adjuvanted by aluminum hydroxide induced bactericidal antibodies in mice against 78% of a panel of 85 meningococcal strains representative of the global population diversity. The strain coverage could be increased to 90% and above by the addition of CpG oligonucleotides or by using MF59 as adjuvant. The vaccine has the potential to conquer one of the most devastating diseases of childhood.meningococcus B ͉ reverse vaccinology

Oil-in-water emulsions have been successfully used to increase the efficacy, immunogenicity, and cross-protection of human vaccines; however, their mechanism of action is still largely unknown. Nlrp3 inflammasome has been previously associated to the activity of alum, another adjuvant broadly used in human vaccines, and MyD88 adaptor protein is required for the adjuvanticity of most Toll-like receptor agonists. We compared the contribution of Nlrp3 and MyD88 to the adjuvanticity of alum, the oil-in-water emulsion MF59, and complete Freund's adjuvant in mice using a threecomponent vaccine against serogroup B Neisseria meningitidis (rMenB). Although the basal antibody responses to the nonadjuvanted rMenB vaccine were largely dependent on Nlrp3, the highlevel antibody responses induced by alum, MF59, or complete Freund's adjuvant did not require Nlrp3. Surprisingly, we found that MF59 requires MyD88 to enhance bactericidal antibody responses to the rMenB vaccine. Because MF59 did not activate any of the Tolllike receptors in vitro, we propose that MF59 requires MyD88 for a Toll-like receptor-independent signaling pathway.

4CMenB is the first broad coverage vaccine for the prevention of invasive meningococcal disease caused by serogroup B strains. To gain a comprehensive picture of the antibody response induced upon 4CMenB vaccination and to obtain relevant translational information directly from human studies, we have isolated a panel of human monoclonal antibodies from adult vaccinees. Based on the Ig-gene sequence of the variable region, 37 antigen-specific monoclonal antibodies were identified and produced as recombinant Fab fragments, and a subset also produced as full length recombinant IgG1 and functionally characterized. We found that the monoclonal antibodies were cross-reactive against different antigen variants and recognized multiple epitopes on each of the antigens. Interestingly, synergy between antibodies targeting different epitopes enhanced the potency of the bactericidal response. This work represents the first extensive characterization of monoclonal antibodies generated in humans upon 4CMenB immunization and contributes to further unraveling the immunological and functional properties of the vaccine antigens. Moreover, understanding the mechanistic nature of protection induced by vaccination paves the way to more rational vaccine design and implementation.

Neisseria adhesin A (NadA) is one of the antigens of Bexsero, the recently licensed multicomponent vaccine against serogroup B Neisseria meningitidis (MenB). NadA belongs to the class of oligomeric coiled-coil adhesins and is able to mediate adhesion and invasion of human epithelial cells. As a vaccine antigen, NadA has been shown to induce high levels of bactericidal antibodies; however, the domains important for protective response are still unknown. In order to further investigate its immunogenic properties, we have characterized the murine IgG1 mAb (6E3) that was able to recognize the 2 main antigenic variants of NadA on the surface of MenB strains. The epitope targeted by mAb 6E3 was mapped by hydrogen-deuterium exchange mass spectrometry and shown to be located on the coiled-coil stalk region of NadA (aa 206-249). Although no serum bactericidal activity was observed for murine IgG1 mAb 6E3, functional activity was restored when using chimeric antibodies in which the variable regions of the murine mAb 6E3 were fused to human IgG3 constant regions, thus confirming the protective nature of the mAb 6E3 epitope. The use of chimeric antibody molecules will enable future investigations of complement-mediated antibody functionality independently of the Fc-mediated differences in complement activation.