Pneumococcal carriage and otitis media induce salivary antibodies to pneumococcal capsular polysaccharides in children

Mucosal immunity likely plays an important role in the defense against Streptococcus pneumoniae. This study examined whether pneumococcal carriage and acute otitis media induce mucosal antibodies to pneumococcal capsular polysaccharides (Pnc-PSs) of types 1, 6B, 11A, 14, 19F, and 23F. Immunoglobulin (Ig) A, IgG, and secretory (S) Ig anti-Pnc-PS antibodies were measured by enzyme immunoassay in the saliva of children at ages 6, 12, 18, and 24 months and were analyzed in relation to the previous pneumococcal findings. A larger proportion of IgA-positive samples and higher concentrations of type-specific IgA antibodies were detected in samples of children with pneumococci of the given types cultured before sampling from nasopharyngeal samples or middle-ear fluid, compared with children who had cultures negative for pneumococci of the indicated types or of all types. The IgA and S-Ig concentrations correlated strongly, which suggests that the anti-Pnc-PS IgA was secretory. Salivary anti-Pnc-PS IgG was detected only rarely.