Salivary IgA antibody to oral streptococcal antigens in predentate infants

Salivary IgA antibodies to oral streptococci which colonize the infant oral cavity soon after birth were analyzed in 53 whole salivas of 17 infants who were between three and 27 weeks old. Antibody activities to Streptococcus mitis cells were detected by enzyme linked immunosorbent assay in 78% of the whole salivas by the twelfth week of age. This antibody activity was associated with polymeric IgA as determined after gel filtration of salivas on Superose 6, followed by ELISA. Western blot analyses were used to detect IgA antibodies to Streptococcus mitis and Streptococcus salivarius culture supernatants. Forty one, and 91% of saliva samples contained IgA antibody which reacted in Western blot analyses with S. salivarius and S. mitis culture supernatants, respectively. The youngest infant to show reactive IgA antibody with either oral streptococcal antigen preparation was five week old. Salivary IgA antibody to either bacterial culture supernatant was detected in Western blot only after the isolation of the respective streptococcal species from the oral cavity of these young infants. Some heterogeneity was observed among patterns developed with salivas from different infants. These results suggest that salivary IgA antibody responses may be induced by oral colonization (S. mitis, S. salivarius) by the end of the first month of life.