VDR and hepatitis C virus infection: Conversely, another study showed that the effect of vitamin D3 is not mediated by its metabolic conversion to calcitriol, but may be due to its primary metabolite 25(OH)D3 [75]; it was shown that the antiviral activity of vitamin D3 and 25(OH)D3 was not impaired in a VDR knockout animal model, suggesting that the anti-hepatitis C effect of 25(OH)D3 is VDR-independent [75] (Figure 2).