Hepatic IFN-Induced Protein with Tetratricopeptide Repeats Regulation of HCV Infection.

Interferons (IFNs) suppress viral infection through the induction of >400 interferon-stimulated genes (ISGs). Among ISGs, IFN-induced protein with tetratricopeptide repeats (IFITs) is one of the most potent and well-characterized ISGs. IFIT family consists of 4 cluster genes. It has been suggested that the antiviral action of each IFIT employs distinct mechanisms. In addition, it has been shown that each IFIT exhibits its antiviral properties partially in a pathogen-specific manner. To date, the expression profile of IFITs in the liver, as well as the antiviral potency of the individual IFITs in the regulation of hepatitis C virus (HCV) infection, is not yet fully defined. Our previous study found that the expression of hepatic IFITs is well correlated with the outcome of IFN-based antiviral therapy. This study explored the significance of each IFIT in the suppression of HCV. Our in vitro and in vivo studies with humanized liver chimeric mouse system revealed that IFIT1, 2, and 3/4 play an important role in the suppression of HCV. In addition, our in vitro experiment found that all IFITs possess a comparable anti-HCV potency. Follow-up studies collectively indicated that IFITs suppress HCV likely through 2 distinct mechanisms: (1) inhibition of internal ribosome entry site-dependent viral protein translation initiation complex according to experiments with bicistronic reporter assay as well as confocal microscopic analyses and (2) sequestration of viral genome based on an experiment using replication defective viral genome. In conclusion, our study defined the importance of IFITs in the regulation of HCV and also suggested the multifaceted antiviral actions.