Antibodies to pneumolysin and pneumococcal capsular polysaccharides in middle ear fluid of children with acute otitis media.

Antibodies to pneumococcal pneumolysin and capsular polysaccharides were measured by enzyme immunoassay in 169 acute phase middle ear fluid samples of 116 children with acute otitis media. Antibodies to pneumococcal pneumolysin were detected in 84% and to capsular polysaccharides in 50% of the MEF samples. The Ig class detected most often was IgA to both types of pneumococcal antigens, and it was present in MEF even with non-detectable levels of serum IgA of the same specificity. 59% of the MEF samples positive for IgA to pneumolysin were also positive for secretory component of the same specificity, and 53% of IgA to capsular polysaccharide pool (containing serotypes 6B, 14, 19F, and 23F), respectively. This suggests both leakage of specific IgA from serum to the middle ear and local production of it. In contrast, specific IgG was detected in MEF only with concomitant IgG in serum. Antibodies to pneumolysin occurred in no relation to bacterial findings in MEF. On the contrary, IgG class antibodies to capsular polysaccharides, most likely serum-derived, were detected less often in MEF samples positive for pneumococcus than for other bacteria.