Oral retinyl palmitate or retinoic acid corrects mucosal IgA responses toward an intranasal influenza virus vaccine in vitamin A deficient mice.

Vitamin A deficiency (VAD) is a leading cause of pediatric morbidity and mortality due to infectious diseases. Recent pre-clinical studies have revealed that VAD impairs mucosal IgA-producing antibody forming cell (AFC) responses toward a paramyxovirus vaccine in the upper respiratory tract (URT), thus impeding a first line of defense at the pathogen's point-of-entry. The studies described here tested the hypothesis that VAD may also impair immune responses after FluMist vaccinations. Results show that (i) IgA-producing antibody forming cells (AFCs) are significantly reduced following FluMist vaccination in VAD mice, and (ii) oral doses of either retinyl palmitate or retinoic acid administered on days 0, 3, and 7 relative to vaccination rescue the response. Data encourage the conduct of clinical studies to determine if there are FluMist vaccine weaknesses in human VAD populations and to test corrective supplementation strategies. Improvements in vaccine efficacy may ultimately reduce the morbidity and mortality caused by influenza virus worldwide.