Reduced serum IgG responses to pneumococcal antigens in otitis-prone children may be due to poor memory B-cell generation

Abstract

A low level of serum antibody to antigens expressed by Streptococcus pneumoniae has been proposed to explain the susceptibility of children to recurrent episodes of acute otitis media (hereafter, "otitis-prone children"). By use of enzyme-linked immunospot assays, the percentages of memory B cells to pneumococcal protein antigens PhtD, LytB, PcpA, PhtE, and Ply were compared between otitis-prone and non-otitis-prone children at the time of acute otitis media or nasopharyngeal colonization with S. pneumoniae. We found significantly lower percentages of memory B cells to 3 pneumococcal protein antigens (PhtD, PhtE, and Ply) and reduced antigen-specific immunoglobulin G concentrations in otitis-prone children, compared with non-otitis-prone children.

Figure 1.

A, Frequencies of antigen-specific memory B cells (MBCs). B, Serum immunoglobulin G (IgG) titers to 5 pneumococcal protein antigens. C, Correlation between PhtD-specific serum antibody titers and PhtD-specific percentages of antigen-specific MBCs. Data are for 10 otitis-prone children and 12 non–otitis-prone children. Open circles denote otitis prone and closed circles denote non–otitis prone. P values were calculated using the Mann–Whitney U test. ^*P < .05; ^** P< .005.