ASCIA‐P55: THE INFLUENCE OF VITAMIN D AND UV‐LIGHT EXPOSURE ON THE DEVELOPING IMMUNE PHENOTYPE IN INFANCY

Abstract

Background: Low levels of vitamin D have been linked to allergies in children, the potential result of lifestyle and reduced sunlight exposure. Vitamin D supplementation is already in use in many countries. This has not occurred in Australia, largely due to the belief that children are exposed to adequate sunlight. However, there is growing evidence of suboptimal vitamin D levels and a pressing need to understand if this is a contributing factor to the dramatic increase in infant allergy. Methodology: In this double-blind, placebo-controlled randomised trial, high risk infants are orally supplemented with either 400 IU vitamin D/day or placebo from birth to 6 months of age. Uniquely a UV-dosimeter is also worn. Blood samples are collected at birth, 3, 6 and 12 months of age to determine relationships between oral vitamin D supplementation and UVlight exposure with blood 25(OH)D concentration, immune cell function responses to allergens and on the development of allergic conditions in early childhood. Results: To date initial findings (n = 42) have found that vitamin D and UV exposure, both play a role in maintaining a suppressive Treg pool characterized by a greater expression of HLA-DR and CD45RA, and fewer CD69+ cells. Additionally a lower percentage of circulating mature dendritic cells (DC) was found. Beyond this we have found correlations between average daily UV exposure in the first 3 months and DC with reduced propensity for T cell activation at 6 months. Conclusion: Early preliminary results from this study demonstrate novel findings that vitamin D levels and UV exposure in infancy have important consequences for the developing immune phenotype in a population at hereditary risk of allergic disease. The findings offer insight into possible immunological mechanisms behind the reported inverse associations between vitamin D status and allergic disease.