Efficacy of Newborn Vitamin A Supplementation in Improving Immune Function

Primary Outcome Measures:

• Thymus size measured by ultrasound [ Time Frame: through 15 wk of age ]
  Thymus size will be assessed sonographically using a validated method in which the transverse diameter of the thymus and the sagittal area of its largest lobe are multiplied to give a volume-related thymic index (TI). This index has been shown to correlate with thymus weight and has been used to show that the human thymus is sensitive to environmental influences during infancy.
  
  
• peripheral blood naive T-helper lymphocyte concentration [ Time Frame: through 15 wk of age ]
  Naive and memory CD4 T lymphocytes will be measured by flow cytometric analysis using the CD45RA and CD45RO markers to identify naive and memory CD4+ T-cells, respectively. Naive T cells develop in the thymus and their level in peripheral blood is an index of thymic function.
  
  
• T-cell receptor excision circle (TREC) level in peripheral blood mononuclear cells (PBMC) [ Time Frame: through 15 wk of age ]
  Thymic T-cell production can be assessed by measuring signal-joint T cell receptor excision circles (TRECs) as a traceable molecular marker in newly produced naive T-cells. Thus, the content of TRECs in peripheral blood is an indicator of thymopoiesis or newly synthesized and exported naive T-cells. TREC assessment will be conducted in the stored peripheral blood mononuclear cells (PBMC) isolated from infant's blood by standard Ficoll density gradient methods.
  
  
• T-cell response to BCG (Bacillus Calmette-Guérin; to protect against tuberculosis) and oral polio virus (OPV) immunization [ Time Frame: through 15 wk of age ]
  The Flow-cytometric Assay of Specific Cell-mediated Immune response in Activated whole blood (FASCIA) will be used on peripheral blood mononuclear cells to determine the percentage of CD4+ T cells that that are responsive to the BCG and OPV vaccines given at birth (OPV is given again at 6, 10 and 14 wk of age). The BCG response will be elicited using purified protein derivative of M. tuberculosis and the OPV response using formalin-inactivated polio virus antigen (types 1, 2 and 3).
  
  
• Antibody response to oral polio virus (OPV) immunization [ Time Frame: through 15 wk of age ]
  The antibody in lymphocyte supernatant (ALS) assay will be used to assess the production of polio-specific antibody by peripheral blood mononuclear cells (PBMC) at 15 wk of age and the secretory IgA response to OPV will be assessed at 6, 11 and 15 wk of age by measuring antibody in stool
  
  
• T-cell and antibody response to tetanus toxoid (TT) and hepatitis B virus (HBV) vaccinations given at 6, 10 and 14 wk of age [ Time Frame: through 15 wk of age ]
  The Flow-cytometric Assay of Specific Cell-mediated Immune response in Activated whole blood (FASCIA) will be used to measure the T-cell response to TT and HBV immunization using these vaccine antigens to stimulate a response at 6 and 15 wk of age. The antibody in lymphocyte supernatant assay (ALS) will be used to measure the antibody responses to these vaccines at 15 wk of age.
  
  
• bacterial translocation to blood [ Time Frame: through 15 wk of age ]
  Bacterial lipopolysaccharide (LPS) concentrations will be measured in plasma as a marker of bacterial translocation.
  
  

Secondary Outcome Measures:

• vitamin A status by modified, relative dose-response (MRDR) test [ Time Frame: through 15 wk of age ]
  vitamin A status will be measured using the MRDR in a subset of 30 subjects in each study arm.
  
  
• bulging fontanelle [ Time Frame: 48 h after vitamin A dosing ]
  The crainial fontanelle will be examined by study personnel to identify "bulging" as in indication of increased intracranial volume.
  
  

This project will examine the effect of vitamin A supplementation (50,000 IU) or placebo given with BCG and oral polio virus (OPV) immunization within 48 h of birth on immune function in 300 Bangladeshi infants (150 in each group) at risk of vitamin A deficiency recruited in a poor community of Dhaka, Bangladesh. Infants will be followed from birth through 15 wk of age. Current evidence from community-based mortality trials is not conclusive but suggests that such supplementation will decrease infant mortality from infectious disease through 6 m of age. The biological mechanism underlying this potential benefit is unclear but is presumed to include improving immune function. The investigators hypothesize that vitamin A supplementation at birth prevents vitamin A deficiency during a critical window of a few days to weeks when the immune system is first exposed to both normal, non-pathogenic organisms (e.g., commensal gut flora) and to potential pathogens. During this period the investigators propose that vitamin A supplementation will improve three aspects of immune function that will have sustained benefits throughout infancy: (1) normal thymus maturation and function; (2) development and mucosal targeting of adaptive immune responses, including regulatory T-cells (Treg), T-helper type 2 (Th2) cells, and IgA-secreting plasma cells and memory B-cells; and (3) mucosal barrier function. The three specific objectives of our project are: (1) Determine if vitamin A supplementation improves thymus maturation and function as indicated by ultrasonic analysis of thymus size and by analysis of thymic output of naïve T-cells using flow cytometric analysis of peripheral blood T-cells and by quantification of T-cell-receptor excision circles (TRECs) in peripheral blood. (2) Determine if vitamin A supplementation at birth alters (2.1) the T-cell response to BCG and OPV immunization assessed at 6 and 15 wk of age; (2.2) the T- and B-cell response to OPV immunization, assessed at 15 wk of age, and the secretory IgA response to OPV assessed at 6, 11 and 15 wk of age; and (2.3) the B-cell response to tetanus toxoid (TT) immunization, assessed at 15 wk of age. (3) Determine if vitamin A supplementation at birth will decrease bacterial lipopolysaccharide (LPS) concentrations in capillary blood, a marker of bacterial translocation.