Figure 7: IFN resistance associated with HCV-NS5A protein: NS5A induces IL-8, which leads to the fractional inhibition of IFN antiviral response. NS5A also contains ISDR (interferon sensitivity determining region), which is believed to inhibit PKR through its dimerization domain. Sustained virological response (SVR) is an efficacy measure of HCV therapy and mutations in ISDR increases SVR in various genotypes of HCV.