Local antibody response to P6 of nontypable Haemophilus influenzae in otitis-prone and normal children.

The local antibody response to the outer membrane protein, P6, of nontypable H. influenzae was measured in middle ear fluids of 30 children during 46 episodes of otitis media, and in nasopharyngeal secretions from 7 children evaluated on 18 occasions. Immunoglobulin G antibody to P6 was detected in 92% of middle ear fluid compared to 70% for IgM, 78% for IgA, and 45% for secretory IgA. Antibody levels ranged from a high of 249 ng/ml for IgG to a low of 11 ng/ml for IgM. Concentrations of P6 specific IgG in the middle ear fluid was directly related to the concentration in the serum, r = 0.89, p < 0.001, and inversely related to the number of bacteria present, r = -0.62, p < 0.05. In contrast, IgA and secretory IgA antibodies to P6 were common (96% and 95%, respectively) and in relatively high concentrations (33 ng/ml and 29 ng/ml, respectively) in nasopharyngeal secretions. There was no relationship between nasopharyngeal and serum levels of antibodies. These data suggest that antibody to P6 nontypable H. influenzae is common, diffuses into the middle ear spaces passively from the serum during otitis media, and is manufactured locally in the nasopharynx in response to colonization.