Correlation of vitamin D with Foxp3 induction and steroid-sparing effect of immunotherapy in asthmatic children

Abstract

Background: Vitamin D promotes different toleragenic processes of the immune system; however, its role in allergen specific immunotherapy (SIT) is still undefined.

Objective: To determine whether the immunologic and clinical effectiveness of allergen SIT depends on the serum level of 25-hydroxyvitamin D (25[OH]D) and its changes during SIT in asthmatic children.

Methods: This is a retrospective secondary analysis of pooled data obtained from our 2 recently published prospective, randomized, placebo-controlled trials on asthmatic children undergoing allergen immunotherapy. Both trials, which assessed the effect of different pharmacologic modulation of SIT effectiveness, were conducted according to the same study protocol. Children from the placebo arms in these trials were treated with immunotherapy only and were included in the present analysis. The study population consisted of 36 children. Data concerning clinical (asthma symptoms score and percent change in minimal daily inhaled corticosteroid dose) and immunologic parameters (including serum level of 25[OH]D) were analyzed in all patients.

Results: Patients with a higher serum level of 25(OH)D experienced more significant reduction in asthma symptoms score and steroid-sparing effect of SIT and had higher transforming growth factor â production and higher Foxp3 induction during SIT. Steroid-sparing effect correlated with 25(OH)D serum level at baseline, after 3 months of SIT, and with the changes in serum level of 25(OH)D during the build-up phase of SIT. Better response to SIT was observed among children with an 25(OH)D serum level higher than 30 ng/mL.

Conclusion: The efficacy of allergen SIT correlates with 25(OH)D serum concentration. It seems that a serum level of 25(OH)D higher than 30 ng/mL facilitates the optimal effect of allergen immunotherapy.