HUMAN-MILK SECRETORY IGA ANTIBODY TO NONTYPABLE HAEMOPHILUS-INFLUENZAE - POSSIBLE PROTECTIVE EFFECTS AGAINST NASOPHARYNGEAL COLONIZATION

Sixty-eight children fed human milk were followed prospectively from b irth to 12 months of age to assess the effect of milk antibody on naso pharyngeal colonization. Human milk secretory IgA antibody to P6, a hi ghly conserved outer membrane protein of nontypeable Haemophilus influ enzae, was measured with the use of an enzyme-linked immunosorbent ass ay. Nasopharyngeal colonization with nontypeable H. influenzae and the occurrence of otitis media were determined. Nasopharyngeal colonizati on was found in 22 children (32%), and 39 children (57%) had otitis me dia. Frequency of isolation of nontypeable H. influenzae was directly related to episodes of otitis media (r = 0.35; p = 0.001). The level o f human milk anti-P6 secretory IgA antibody was inversely related to f requency of isolation of the organism (r = -0.27; p = 0.026). The aver age antibody level, expressed as nanograms per 0.1 mg total secretory IgA, in human milk fed to children with no colonization of nontypeable H. influenzae was significantly higher than in milk fed to children i n whom colonization occurred on multiple occasions (156 +/- 120 vs 69 +/- 50; p = 0.013). Prevention of colonization was most evident during breast-feeding. These data suggest that the protective effects of hum an milk against otitis media may be due in part to inhibition of nasop haryngeal colonization with nontypeable H. influenzae by specific secr etory IgA antibody.