Vitamin A, Stool Microbiota and Vaccine Response in Bangladeshi Infants

Hypotheses and Specific Aims The investigators will test the hypotheses that VAS at birth will (1) improve production of new T cells at 1-2 yr of age; (2) improve T-cell memory responses at 1-2 yr of age to vaccines given early in infancy (birth - 14 wk); and (3) alter intestinal colonization early in infancy (6, 11 and 15 wk) and at 1-2 yr of age to increase Bifidobacterium and other healthy bacteria and decrease Proteobacteria and other harmful bacteria. Because the "secretor status" of the mother affects the carbohydrate content of the breastmilk, which can in turn affect Bifidobacterium growth in the infant gut, the "secretor status" of the mother will be determined. Furthermore these differences in composition of the intestinal bacteria will be associated with greater immunologic responses to oral and systemic vaccines. Specific Aim 1: Determine if VAS or placebo at birth affect the blood concentration and thymic output of naïve T-cells at 1-2 yr of age. Specific Aim 2: Determine if VAS or placebo at birth affect T-cell mediated responses at 1-2 yr of age to vaccines given early in infancy, including serum and intestinal antibody levels, vaccine-specific proliferative responses by T cells and cytokine production by T cells. Specific Aim 3: Determine if VAS or placebo at birth affect the relative abundance of healthy intestinal bacteria and common harmful bacteria in the feces at 6, 11, and 15 wk of age and at 1-2 yr of age and determine if relative abundance of these bacteria correlates with vaccine responses shortly after vaccination (6, 11, 15 wk) and later in infancy (1-2 yr). As part of Aim 3 the "secretor status" genotype (FUT2 gene) of the mother will be determined from a cheek swab DNA sample.