IMMUNE RESPONSES TO NOVEL PNEUMOCOCCAL PROTEIN ANTIGENS (PNEUMOLYSIN, PSPA, PSAA AND CBPA) IN ADENOIDAL B CELLS FROM CHILDREN

A. Finn, E. Pettitt, S. Choo, Q. Zhang

Sheffield Institute for Vaccine Studies, UK

Studies in mice suggest that immunisation with pneumococcal proteins pneumolysin (PdB), pneumococcal surface protein A (PspA), pneumococcal surface adhesion A (PsaA) and choline-binding protein A (CbpA) can protect against infection and/or prevent nasopharyngeal carriage. Information on human mucosal responses to these proteins is lacking. We have investigated the immune responses to these proteins in adenoidal B cells from children. Adenoidal lymphocytes were isolated from 11 children and analysed for antigen-specific antibody secreting cells (ASCs) by ELISpot assay. IgG ASCs are predominant to the four antigens with geometric means of 4.5, 5.5, 23.1, 24.9 (ASCs per 10⁶ lymphocytes) for PspA, PdB, PsaA and CbpA respectively, with PsaA and CbpA-specific IgG ASCs significantly higher than PsaA and PdB IgG ASCs (p<0.01). The equivalent data for IgA ASCs are 1.9, 1.6, 2.9, 3.6 (NS), and for IgM ASCs 4.2, 8.4, 10.2 and 5.6 (NS). Preliminary experiments have shown that cells stimulated with pneumococcal culture supernatants show higher IgG ASC numbers than unstimulated controls for CbpA and PsaA antigens (p<0.01). CbpA and PsaA may be better mucosal antigens than PspA and pneumolysin. Significant increases in CbpA and PsaA-specific IgG ASCs after stimulation with antigens suggests IgG memory responses which may be important for elimination of nasopharyngeal carriage.