25-hydroxyvitamin D3 suppresses hepatitis C virus production

Because the current interferon (IFN)-based treatment for hepatitis C virus (HCV) infection has a therapeutic limitation and side effects, a more efficient therapeutic strategy is desired. Recent studies show that supplementation of vitamin D significantly improves sustained viral response via IFN-based therapy. However, mechanisms and an active molecular form of vitamin D for its anti-HCV effects have not been fully clarified. To address these questions, we infected HuH-7 cells with cell culture-generated HCV in the presence or absence of vitamin D3 or its metabolites. To our surprise, 25-hydroxyvitamin D3 [25(OH)D3], but not vitamin D3 or 1,25-dihydroxyvitamin D3, reduced the extra- and intracellular levels of HCV core antigen in a concentration-dependent manner. Single-cycle virus production assay with a CD81-negative cell line reveals that the inhibitory effect of 25(OH)D3 is at the level of infectious virus assembly but not entry or replication. Long-term 25(OH)D3 treatment generates a HCV mutant with acquired resistance to 25(OH)D3, and this mutation resulting in a N1279Y substitution in the nonstructural region 3 helicase domain is responsible for the resistance. Conclusion: 25(OH)D3 is a novel anti-HCV agent that targets an infectious viral particle assembly step. This finding provides insight into the improved efficacy of anti-HCV treatment via the combination of vitamin D3 and IFN. Our results also suggest that 25(OH)D3, not vitamin D3, is a better therapeutic option in patients with hepatic dysfunction and reduced enzymatic activity for generation of 25(OH)D3. (HEPATOLOGY 2012)