Do antibodies to pneumococcal surface adhesin A prevent pneumococcal involvement in acute otitis media?

Antibodies to the pneumococcal (Pnc) surface protein PsaA are immunogenic a nd protective in experimental animal models, but their role in protection f rom Pnc disease in humans is not known. In the present study, the ability o f antibodies to PsaA to prevent the progression of Pnc carriage to Pnc acut e otitis media (Pnc AOM) was evaluated. Antibodies to PsaA were measured in acute-phase serum samples of children with AOM and with Streptococcus pneu moniae cultured from the nasopharynx. The risk of Pnc AOM was evaluated by a logistic regression model with anti-PsaA concentration as the predictive variable. Higher concentrations of antibodies to PsaA were associated with lower risk of the Pnc nasopharyngeal carriage progression to Pnc AOM. This was true in children 9-24 months old (odds ratio [OR], 0.49; 95% confidence interval [CI], 0.31-0.78) but not in children <9 months old (OR, 0.81; 95% CI, 0.48-1.35).