Transcriptional response to hepatitis C virus infection and interferon alpha treatment in the human liver

Hepatitis C virus (HCV) is widely used to investigate host-virus interactions and cellular responses to infection have been extensively studied in vitro. In human liver, interferon (IFN) stimulated gene expression can mask direct transcriptional responses to virus infection. To better characterize the direct effects of HCV infection in vivo, we analyze the transcriptomes of HCV-infected patients lacking an activated endogenous IFN system. We show that the expression changes observed in these patients predominantly reflect immune cell infiltrates rather than changes in cell-intrinsic metabolic pathways. We also investigate the transcriptomes of patients with endogenous IFN activation, which paradoxically cannot eradicate viral infection. We find that most IFN-stimulated genes (ISGs) are induced by both the endogenous IFN system and by recombinant IFN therapy, but with significantly higher induction levels in the latter. We conclude that the innate host immune response in chronic hepatitis C is too weak to clear the virus. Overall design: In this study, we aimed to disentangle the direct and indirect effects of HCV infection on cellular transcriptional profiles, by performing a detailed characterization of the gene expression changes associated with HCV infection, endogenous IFN system activation and pegIFNa treatment in the human liver. With this objective, we generated and analyzed high-throughput transcriptome sequencing profiles from liver biopsies derived from different categories of HCV-infected and non-infected patients, prior to and during treatment. First, to unveil HCV-induced cell-autonomous effects and to separate them from IFN-induced changes in the transcriptome, we selected liver biopsies from patients with chronic hepatitis C (CHC) without hepatic ISG induction, and compared them with un-infected control biopsies. Second, we examined the transcriptomic changes associated with the endogenous activation of the IFN system. Finally, we analyzed the gene expression changes resulting from pegIFNa/ribavirin treatment, by comparing transcriptome data from liver biopsies obtained before treatment and at different time points during the first week of therapy.

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Boldanova T, Suslov A, Heim MH, Necsulea A