Immunomodulatory effect of 1, 25 dihydroxy vitamin D on the expression of RNA sensing pattern recognition receptor genes and cytokine response in dengue virus infected U937-DC-SIGN cells and THP-1 macrophages.

Dengue virus (DENV) infections are straining public health systems worldwide. Vitamin D, a secosteroid hormone, is currently being investigated for its immunomodulatory effects in DENV infections. The objectives of the present study was to study the effect of 1, 25 dihydroxy vitamin D3 (1,25(OH)D) on the expression of genes coding for RNA sensing pattern recognition receptors, downstream signaling components including oligoadenylate synthetases (OAS) and interferon stimulated gene 15 (ISG15) and T helper (Th)1, Th2 and Th17 cytokine response in DENV infected U937-DC-SIGN cells and THP-1 macrophages. U937-DC-SIGN RNA was investigated for the expression of TLR3, DDX58, IFIH1, OAS1, OAS2, OAS3, CAMP and ISG15 genes using gene expression assays. Interleukin (IL)-12p70, IL-10, IL-4 and IL-17A levels were assessed in the THP-1 macrophage culture supernatants. The results revealed that 1,25(OH)D increased the expression of DDX58, OAS1, OAS2 and OAS3 at 0.1 μM while higher concentration had diminishing effect. 1,25(OH)D enhanced the expression of ISG15 and CAMP genes. 1,25(OH)D suppressed the levels of IL-4 and IL-17A. Lower concentration of 1,25(OH)D suppressed IL-12p70 and IL-10 levels while a higher concentration enhanced the levels. The results suggest that 1,25(OH)D may have concentration dependent immunomodulatory effects. Higher dose of 1,25(OH)D might have an immunoregulatory role in ameliorating inflammation during dengue infections. Further studies are needed to evaluate the efficacy of different doses of 1,25(OH)D in preventing severe dengue.