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Published on: December 1, 2017
Retinol Binding Protein, Sunlight Hours, and the Influenza Virus-Specific Immune Response
Nehali Patel1, Rhiannon R Penkert1, Robert E Sealy1
1Department of Infectious Diseases, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA.
Insights
Seasonal changes impact children's vitamin A and D levels, affecting immune responses. Lower vitamin A (retinol) and higher vitamin D (25(OH)D) were observed in winter, influencing antibody production and cytokine levels.
Area of Science:
- Pediatric immunology
- Nutritional science
- Environmental health
Background:
- Adequate vitamin A and D are crucial for pediatric immune function.
- The relationship between sunlight, vitamin A, and retinol-binding protein (RBP) in children is not well understood.
- Seasonal variations in sunlight exposure and diet may influence vitamin levels and immune readiness.
Purpose of the Study:
- To investigate the influence of season on vitamin A (retinol) and vitamin D (25(OH)D) levels in children.
- To explore the relationship between sunlight exposure, dietary intake, and serum levels of retinol and RBP.
- To examine the association between these vitamin levels and key immune markers, including antibodies and cytokines.
Main Methods:
- A pediatric clinical study involving 2-8-year-old children in Memphis, Tennessee, between September 2016 and March 2017.
- Serum samples were analyzed for vitamin A (retinol), RBP, and 25(OH)D levels.
- Food frequency questionnaires assessed dietary intake, and associations with sunlight hours, immune markers (immunoglobulins, antibodies, cytokines/chemokines) were examined.
Main Results:
- Retinol-binding protein (RBP) and RBP/retinol molar ratios decreased in winter months.
- RBP/retinol ratios positively correlated with average daily sunlight hours per month.
- Seasonal dietary shifts towards animal-based foods in spring increased retinol and zinc levels, potentially explaining RBP/retinol variations. RBP and retinol correlated positively with specific antibody levels and immunoglobulin ratios.
- Vitamin D (25(OH)D) showed a positive correlation with certain cytokines/chemokines, while retinol showed a negative correlation.
- Significant differences in 25(OH)D, immunoglobulin ratios, and cytokines/chemokines were noted between Black and White children.
Conclusions:
- Seasonal dietary changes, particularly increased intake of retinol and zinc in spring, may influence RBP levels in children.
- These seasonal variations in vitamin A and D levels appear to impact both innate and adaptive immune responses.
- Routine monitoring of season, RBP, and vitamin levels in pediatric studies is recommended to account for their effects on immune protection against infectious diseases.
Abstract:
Healthy pediatric immune responses depend on adequate vitamin A and D levels. Relationships between solar ultraviolet B (UVB) radiation and vitamin D are well understood, while relationships between sunlight, vitamin A, and its serum escort, retinol binding protein (RBP), are not. A pediatric clinical study enrolled 2-8-year-old children at various times between September 2016 and March 2017, inclusive, in Memphis, Tennessee. A serum sample from each child was then assayed to examine the influence of season on vitamin levels. We found that RBP and RBP/retinol molar ratios decreased in winter months and RBP/retinol ratios correlated positively with the average daily sunlight hours per month. A food frequency questionnaire given to parents/guardians indicated a shift in dietary intake from plant-based foods to animal-based foods by children between winter and spring months. This translated to higher retinol and zinc (integral to RBP-transthyretin-retinol complexes) in the spring, perhaps explaining the seasonal influence on RBP/retinol. RBP and retinol were associated positively with IgG/IgM and IgA/IgM ratios. RBP and retinol, but not 25(OH)D, also correlated positively with influenza virus-specific antibodies. Retinol correlated negatively, while 25(OH)D correlated positively, with certain serum cytokine/chemokine levels. Significant differences in 25(OH)D, immunoglobulin ratios, and cytokines/chemokines were observed between black and white children. In sum, seasonal changes in dietary foods rich in retinol and zinc may have influenced RBP levels, which in turn influenced innate and adaptive immune responses. Results encourage routine monitoring and reporting of season, RBP, and vitamin levels in future clinical studies, as seasons may affect sunlight exposures, diet, vitamin levels, and immune protection against infectious disease.
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