Effect of maternal antibody on IgA antibody response in nasopharyngeal secretion in infants and children during primary respiratory syncytial virus infection.

The IgA antibody response to respiratory syncytial virus (RSV) was determined in nasopharyngeal secretions (NPS) of 22 infants and children infected with RSV group A strains, employing an ELISA. The antibody activity observed during the convalescent phase against whole virus, fusion glycoprotein (F) and large glycoprotein (G) was examined in young infants (under 6 months) and compared with that of older individuals (6 to 16 months). Both groups showed similar degrees of IgA antibody activity to whole virus in NPS; however, older individuals showed a significantly higher activity of IgA F antibody than that of IgA G antibody in the NPS. On the other hand, in the NPS of young infants, IgA F antibody was somewhat suppressed and IgA G antibody activity predominated over that of IgA F. Pre-existing (maternal) serum IgG anti-RSV F antibody activity was higher than that of antibody to G. A significant reverse correlation was observed between the activity of pre-existing serum IgG F antibody and NPS IgA F antibody in the convalescent phase after primary infection with RSV. These observations suggest that maternally derived RSV IgG antibody, which contains abundant anti-F activity, may suppress the development of IgA F antibody response at infection sites in the respiratory tract in young infants during primary RSV infection. These changes may be related to the severity of acute infection and longer convalescence often observed in young infants during RSV infection.