Effects of 1, 25-dihydroxy-vitamin D on the immune response in chicken embryo fibroblast cells infected by infectious bronchitis virus.

In addition to its nutritional role in regulating calcium and phosphorus metabolism, vitamin D also possesses immunoregulatory effects. Herein, we used chicken embryo fibroblast cells (CEFs) to study the effect of 1,25-dihydroxyvitamin D (1,25(OH)D) on the immune response induced by infectious bronchitis virus (IBV) infection. We observed the inhibition to virus proliferation in the cells by adding 10 nM 1,25(OH)D. In addition, treatment with 1,25(OH)D has significantly increased the mRNA expressions of toll-like receptor 15 (TLR15) (2.75-fold), avian beta-defensins 9 (AvBD9) (25.37-fold), and AvBD14 (2.28-fold) in the IBV-infected CEFs comparing with those of the control group. In contrast, the mRNA expression levels of TLR3 (0.98-fold), TLR4 (0.66-fold), TLR5 (0.44-fold), TLR7 (0.62-fold), and AvBD1 (0.57-fold), AvBD3 (0.54-fold), AvBD8 (0.60-fold), and AvBD12 (0.54-fold) were found to be decreased. In parallel with this results, the mRNA expression levels of the myeloid differentiation primary response protein 88 (MyD88) (0.69-fold), interleukin-8 (IL-8) (0.99-fold), IL-6 (0.98-fold), and IL-1β (0.93-fold) in 1,25(OH)D group were also significantly downregulated comparing with those of control group. Thus, the results suggest that adding of 1,25(OH)D is capable of inducing TLRs and AvBDs gene expressions, suppressing the inflammatory response and enhancing an antiviral defense, which might have a beneficial effect in controlling viral infections in poultry.