Immunoproteomic Analysis of the Development of Natural Immunity in Subjects Colonized by Neisseria meningitidis Reveals Potential Vaccine Candidates†

The potential protective effect of existing vaccines against serogroup B meningococci, based on outer membrane proteins, is limited by strain restriction and apparent short duration of immune responses. In contrast, meningo-coccal colonization is known to stimulate the production of cross-protective antibodies as defined by the develop-ment of serum bactericidal activity (SBA) against heterologous serogroup B strains. In the current study, a resource of human serum samples and meningococcal carriage strains from studies of longitudinal carriage has been subjected to immunoproteomic analysis to investigate the outer membrane protein antigens associated with the development of SBA to both homologous and heterologous meningococcal serogroup B strains. Proteins from outer membranes of homologous and heterologous strains were separated by two-dimensional electrophoresis and reacted with paired sera which showed an increase in SBA following colonization. Individuals showed differing patterns of reactivity upon colonization, with an increase in SBA being associated with increases in the number of spots detected before and after colonization and/or with increases in the intensity of individual spots. Analysis of immunoreactive spots by mass spectrometry resulted in the identification of 43 proteins potentially associated with the development of SBA against both homologous and heterologous strains. The list of protein immunogens generated included not only well-established antigens but also novel proteins that represent potentially new candidates for inclusion i