Subclasses of IgA antibodies in serum and saliva samples of newborns and infants immunized against rotavirus

Abstract

Little is known about subclass levels of IgA in serum or saliva of infants in the perinatal period. We have previously shown that very young infants are capable of responding to an experimental rotavirus vaccine with both serum and salivary IgA, and that small amounts of IgA are already detectable in cord blood of these infants. In the present study, 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 antibodies to the rotavirus group A common antigen were determined by ELISA. 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. Between 6 and 12 weeks of age levels of serum IgA1 increased by 25%, while levels of IgA2 did not increase perceptibly. Concentrations of IgA1 were higher in infant sera than in saliva, while concentrations of IgA2 were slightly higher in saliva than in serum. When calculated as specific ELISA units per mg IgA1, more salivary IgA1 was specific for rotavirus than serum IgA1. Further studies are needed to determine when infant IgA2 levels rise to values more characteristic of children and adults. This may be of significance for infant mucosal immunizations if secretory IgA2, more resistant to bacterial proteases than IgA1, is required for efficient defence of the respiratory and intestinal tracts.

Rotavirus‐specific subclass antibody and cytokine responses in Bangladeshi children with rotavirus diarrhoea

“…The rotavirus-specific subclass response documented in this study is similar to that shown for children in developed countries where little or no IgA2 responses were seen [Friedman et al, 1996] and IgG1 and IgG3 subclass responses predominated [Grauballe et al, 1986]. The reason for the predominance of IgA1 to IgA2 can be severalfold, but one factor influencing the IgA subclass response is the character of the antigen; thus, bacterial polysaccharides induce an IgA2 response, and protein antigens induce an IgA1 response [Mestecky et al, 1999].…”

Viral proteins VP2, VP6, and NSP2 are strongly precipitated by serum and fecal antibodies from children with rotavirus symptomatic infection

“…In addition, jacalin binds specifically to the human IgA1 subclass [Roque-Barreira et al, 1985;Kondoh et al, 1986]. Several studies have found that the IgA1 subclass is predominant in both infant sera and in saliva [Fitzsimmons et al, 1994;Friedman et al, 1996]. The IgA-RIP assay performed in this study included jacalin-agarose beads and high salt concentrations in the buffer instead of SDS in order to foster the detection of antibodies to conformation-dependent epitopes, as previously described [Johansen et al, 1994].…”

Determination of Secretory IgA and Albumin in Saliva of Newborn Infants

“…The high values of salivary sIgA have to be taken into account when evaluating the potential of the immune system of newborn infants not only against microbial invasion in general but also with respect to the role of sIgA in the immune response to vaccination, e.g. against rotavirus [25], as well as in effector functions during allergic inflammation [26].…”