NASOPHARYNGEAL ANTIBODIES TO PNEUMOCOCCAL PNEUMOLYSIN IN CHILDREN WITH ACUTE OTITIS-MEDIA

Pneumolysin, an intracellular protein toxin of all clinically relevant pneumococcal serotypes, is released in vivo during the autolysis of p neumococci and is believed to pave the way for intact pneumococci to i nvade and cause disease. Therefore, antibodies to pneumolysin should p revent its destructive function. We measured antibodies to pneumococca l pneumolysin in acute- and convalescent-phase nasopharyngeal aspirate samples of 120 children (median age, 2.5 years) with acute otitis med ia by enzyme immunoassay. Nasopharyngeal immunoglobulin M (IgM) and Ig G class antibodies to pneumolysin were rarely detectable, whereas IgA class antibody was detected often, occurred independently of serum IgA antibody in serum, and correlated with the presence of the secretory component in pneumococcal antibody, indicating local production of IgA antibodies. Nasopharyngeal IgA antibody to pneumolysin was detected i n 93% of the children already in the acute phase of otitis. Twenty per cent of the children developed at least a threefold rise in the pneumo lysin-specific IgA antibody concentration by the convalescent phase of otitis, with the youngest at 6 months of age, regardless of the pneum ococcal findings in the nasopharynx or middle ear fluid. We suggest th at nasopharyngeal IgA antibody to pneumolysin can be produced early in life by pneumococcal colonization.