SUBCLASSES OF IGA ANTIBODIES IN SERUM AND SALIVA SAMPLES OF NEWBORNS AND INFANTS IMMUNIZED AGAINST ROTAVIRUS

Little is known about subclass levels of IgA in serum or saliva of inf ants in the perinatal period. We have previously shown that very young infants are capable of responding to an experimental rotavirus vaccin e with both serum and salivary IgA, and that small amounts of IgA are already detectable in cord blood of these infants. In the present stud y, total IgA1 and IgA2 antibodies in serum and saliva samples of some of these infants at birth, at 6 weeks of age, and at 12 weeks of age, were determined by a quantitative ELISA. Also, subclass-specific IgA a ntibodies to the rotavirus group A common antigen were determined by E LISA. The ratio of average serum concentrations of IgA1 to IgA2 for 14 infants at 6 weeks of age was 19:1, while in saliva it was 5:1. Betwe en 6 and 12 weeks of age levels of serum IgA1 increased by 25%, while levels of IgA2 did not increase perceptibly. Concentrations of IgA1 we re higher in infant sera than in saliva, while concentrations of IgA2 were slightly higher in saliva than in serum. When calculated as speci fic ELISA units per mg IgA1, more salivary IgA1 was specific for rotav irus than serum IgA1. Further studies are needed to determine when inf ant IgA2 levels rise to values more characteristic of children and adu lts. This may be of significance for infant mucosal immunizations if s ecretory IgA2, more resistant to bacterial proteases than IgA1, is req uired for efficient defence of the respiratory and intestinal tracts.