Lack of clinical evidence for involvement of hepatitis C virus interferon-alpha sensitivity-determining region variability in RNA-dependent protein kinase-mediated cellular antiviral responses

The hepatitis C virus (HCV) interferon-alpha (IFN-alpha) sensitivity-determ ining region (ISDR) has been shown to suppress double-stranded RNA-dependen t protein kinase (PKR) activity in vitro in a yeast PKR expression system. Since variability of ISDR was shown to correlate with nonresponsiveness to IFN-alpha therapy in chronically HCV-infected patients, it has been suggest ed that prototype ISDR might be a viral inhibitor of cellular PKR. The pres ent study evaluates the biological significance of ISDR variability in situ , relating it to PKR-mediated cellular antiviral responses within the liver . ISDR variability was determined in patients chronically infected with HCV genotypes 1a, 1b, and 3a by direct sequencing using liver-derived RNA prep arations as starting material. As surrogate parameters for PKR-mediated cel lular responses, hepatic endogenous IFN-alpha gene expression as well as Mx A expression were analysed by a competitive, quantitative reverse transcrip tion-polymerase chain reaction technique. Irrespectively of intra- or inter genotypic ISDR amino acid substitutions, ISDR variability was found not to correlate with endogenous hepatic IFN-alpha or with hepatic MxA gene expres sion. The data suggest that at least two prominent PKR-mediated cellular re sponses might be largely unaffected by HCV ISDR variability. J. Med. Virol. 61:29-36, 2000. (C) 2000 Wiley-Liss, Inc.