Pneumococcal antibodies and complement during and after periods of recurrent otitis

Streptococcus pneumoniae frequently accounts for acute purulent otitis media (AOM) episodes. Recurrences are common and are most often caused by pneumococci of groups 6, 19 and 23. In 15 two-year-old children with recurrent AOM (rAOM) complement (C) components and antibodies against various pneumococcal capsular polysaccharides were analyzed during the acute phase of an AOM episode and 6 years later. Comparison was made with findings in non-otitis-prone children of comparable age. In contrast to non-otitis-prone children, 60% of children with rAOM had no detectable IgG antibodies against the pneumococcal capsular polysaccharides 6A or 19F. Analysis of C1 subcomponent complexes together with the finding of relatively low C1q concentrations gave evidence of disturbed C1 function in the acute phase of rAOM. At the 6-year follow-up antibodies against all the investigated pneumococcal capsular polysaccharides had increased in most of the children, but low IgG antibodies to type 6A polysaccharide were still more frequently found in the former rAOM children than in non-otitis-prone children. The C profiles had normalized at follow-up. These findings indicate a reduced ability in rAOM children to respond adequately with IgG antibodies to pneumococcal types encountered in rAOM. The combination of low antibody concentrations and the interference with the complement system and efficient opsonization through classical pathway activation could possibly contribute to the development of rAOM.