Otitis media in children: local immune response to nontypeable Haemophilus influenzae

Twenty children experienced 30 episodes of otitis media with effusion due to nontypeable (NT) Haemophilus influenzae in the first 2 years of life. The local and systemic immune responses to homologous strains of NT H. influenzae were determined by an immunodot assay. Strain-specific immunoglobulin G (IgG) antibody predominated in the middle ear fluid (MEF). It was detected in 91% of the children, compared with IgM in 48% (P less than 0.005), IgA in 52% (P less than 0.005), and secretory IgA in 18% (P less than 0.005). The titer (log2) of NT H. influenzae-specific IgG antibody (mean +/- standard error, 8.2 +/- 0.1) exceeded the titers of IgM (3.4 +/- 0.1), IgA (3.7 +/- 0.1), and secretory IgA (1.2 +/- 0.3). NT H. influenzae-specific antibody was detected exclusively in MEFs of individuals who possessed homologous serum antibody. Although antibody titers in MEF declined over time, serum antibody titers remained stable. These data suggest that immunity to NT H. influenzae in the middle ear, in part, reflects systemic immunity. Whereas local antibody disappears after resolution of the infection, systemic antibody persists.