Calcitriol reduces Newcastle disease virus replication by modulating galectin 3 and pro-inflammatory cytokines.

Calcitriol, or vitamin D (Vit D), is known for promoting strong bones and its ability to modulate inflammation and support the immune system. It has also been reported to be a potent antiviral agent, but the underlying mechanisms behind the mode of action are still unclear. Newcastle disease virus (NDV) belongs to the family Paramyxoviridae and causes infectious diseases in numerous avian species. In the present study, we explored the use of calcitriol as an antiviral agent against NDV infection. Post-treatment with calcitriol (the most active form of Vit D) was found to inhibit NDV replication in chicken embryo fibroblast cells (DF-1) in a time-of-addition- and concentration-dependent manner. The titer of NDV in allantoic fluid exhibited a substantial decrease after administration of cholecalciferol (the less active form of Vit D) to a 9-day-old chicken embryo. In addition, the results demonstrated a significant modulation of galectin 3 gene expression after NDV infection. Cytokine profiling of DF-1 cells treated with calcitriol and aloe-emodin, a known modulator of galectin 3, revealed significant upregulation of pro-inflammatory cytokines. The study indicates that calcitriol modulates host proteins, affecting NDV replication. These findings suggest that calcitriol or Vit D has the potential to be developed as an alternative antiviral drug against NDV, warranting further investigation.