EFFECT OF VITAMIN-A SUPPLEMENTATION ON IMMUNOGLOBULIN-G SUBCLASS RESPONSES TO TETANUS TOXOID IN CHILDREN

Previously, we demonstrated that administering vitamin A supplements t o children resulted in a significant increase in the immunoglobulin G (IgG) response generated against a vaccine dose of tetanus toroid (TT) (R. D. Semba et al., J. Nutr. 122:101-107, 1991). However, from these analyses we could not determine whether there was an increase in leve ls of Ige of the subclass presumed to be important for protection agai nst challenge by the toxin or whether there was simply a general incre ase in the levels of all of the IgG subclasses expressing anti-TT acti vity. The goal of this study was to determine the profile of the anti- TT IgG subclasses in children receiving vitamin A supplementation or a placebo in order to assess the potential utility of the enhanced anti -TT response. In a randomized, double-masked, placebo-controlled clini cal trial, the levels of the different anti-TT IgG subclasses were mea sured in 139 Indonesian preschool children (3 to 6 years of age) 2 wee ks before and 3 weeks after immunization. Baseline anti-TT levels and immunization histories were used to separate those children who were r esponding to TT for the first time from those who responded in a secon dary fashion because of previous exposure to TT. Children who were giv en vitamin A prior to immunization had significant increases in IgG1 l evels regardless of,whether they were undergoing primary or memory rea ctions. In the group of individuals who underwent a secondary response to TT, vitamin A supplementation was also associated with a modest bu t significant change in the levels of anti-TT IgG3. There were only mi nor changes in the levels of anti-TT IgG2 and IgG4. Since IgG1 is the subclass associated with a protective response to TT immunization, the se results suggest that vitamin A supplementation may be a safe and ef fective intervention to enhance the relevant humoral response to TT an d other vaccine antigens.