Serum 25-hydroxyvitamin D is associated with enhanced pneumococcal antibody levels in individuals with asthma.

Recent studies suggest that vitamin D modulates innate immunity and reduces the risk of microbial infections. Little is known about the role of vitamin D in antipneumococcal immunity in individuals with asthma. We determined the correlation between serum 25-hydroxyvitamin D (25[OH]D) levels and pneumococcal antibody levels in individuals with asthma, atopic dermatitis, or allergic rhinitis, and atopic sensitization status. A cross-sectional study was conducted for 21 subjects with asthma and 23 subjects without asthma. Pearson's correlation coefficient between serum 25(OH)D concentrations and the number of positive serotype-specific antibody levels was calculated among individuals with and without asthma, atopic dermatitis, and/or allergic rhinitis and atopic sensitization status. The overall correlation between serum 25(OH)D concentrations and positive pneumococcal antibody levels in all subjects regardless of asthma was not significant (r = -0.14; p = 0.38). Stratified analysis results showed that there was a positive correlation between serum 25(OH)D concentrations and positive pneumococcal antibody levels in asthmatic patients (r = 0.45; p < 0.05) and an inverse correlation was observed in nonasthmatic patients (r = -0.53; p < 0.05). These trends were similar for subjects with and without atopic dermatitis and/or allergic rhinitis (r = 0.58 and p = 0.008 versus r = -0.63 and p = 0.001). Despite similar trends in the correlation between serum 25(OH)D and pneumococcal antibody concentrations among those with and without atopic sensitization status (r = 0.27 and p = 0.19 versus r = -0.41 and p = 0.08), they did not reach statistical significance. The 25(OH)D may enhance humoral immunity against Streptococcus pneumonia in subjects with atopic conditions but not without atopic conditions. Atopic conditions may have an important effect modifier in the relationship between serum 25(OH)D concentrations and immune function.