Naturally Acquired Human Immunity to Pneumococcus Is Dependent on Antibody to Protein Antigens

• DOI: 10.1371/journal.ppat.1006137
• Publication Date: 2017-01-30T18:44:34Z
• Authors: Robert Wilson; Jonathan M. Cohen; Mark Reglinski; Ricardo J. Jose; Win Yan Chan; Helina Marshall; Corné de Vogel; Stephen Gordon; David Goldblatt; Fernanda C. Petersen; Helen Baxendale; Jeremy S. Brown
• Keywords: Pneumococcal infections; Humoral immunity

Naturally acquired immunity against invasive pneumococcal disease (IPD) is thought to be dependent on anti-capsular antibody. However nasopharyngeal colonisation by Streptococcus pneumoniae also induces antibody protein antigens that could protective. We have used human intravenous immunoglobulin preparation (IVIG), representing natural IgG responses S. pneumoniae, identify the classes of are functionally relevant for IPD. in IVIG recognised capsular antigen and multiple antigens, with highly conserved patterns between different geographical sources pooled IgG. Incubation resulted binding bacteria, formation bacterial aggregates, enhanced phagocytosis even unencapsulated strains, demonstrating capsule was unlikely dominant protective antigen. incubated reduced after partial chemical or genetic removal surface proteins, increased a mitis strain expressing PspC. In contrast, depletion type-specific from did not affect binding, opsonophagocytosis, protection passive vaccination IPD murine models. These results demonstrate naturally largely depends rather than capsule.