Reduced expression of Jak-1 and Tyk-2 proteins leads to interferon resistance in Hepatitis C virus replicon

Sidhartha Hazari,Frederic Regenstein,Srikanta Dash,Ronald Luftig,Lizeth Taylor,Robert F Garry,Salima Haque,Sander Florman

doi:10.1186/1743-422x-4-89

Abstract

BackgroundAlpha interferon in combination with ribavirin is the standard therapy for hepatitis C virus infection. Unfortunately, a significant number of patients fail to eradicate their infection with this regimen. The mechanisms of IFN-resistance are unclear. The aim of this study was to determine the contribution of host cell factors to the mechanisms of interferon resistance using replicon cell lines.ResultsHCV replicons with high and low activation of the IFN-promoter were cultured for a prolonged period of time in the presence of interferon-alpha (IFN-alpha2b). Stable replicon cell lines with resistant phenotype were isolated and characterized by their ability to continue viral replication in the presence of IFN-alpha. Interferon resistant cell colonies developed only in replicons having lower activation of the IFN promoter and no resistant colonies arose from replicons that exhibit higher activation of the IFN promoter. Individual cell clones were isolated and nine IFN resistant cell lines were established. HCV RNA and protein levels in these cells were not altered by IFN- alpha2b. Reduced signaling and IFN-resistant phenotype was found in all Huh-7 cell lines even after eliminating HCV, suggesting that cellular factors are involved. Resistant phenotype in the replicons is not due to lack of interferon receptor expression. All the cell lines show defect in the JAK-STAT signaling and phosphorylation of STAT 1 and STAT 2 proteins were strongly inhibited due to reduced expression of Tyk2 and Jak-1 protein.ConclusionThis in vitro study provides evidence that altered expression of the Jak-Stat signaling proteins can cause IFN resistance using HCV replicon cell clones.

Highlights

Alpha interferon in combination with ribavirin is the standard therapy for hepatitis C virus infection
Standard therapy for chronic Hepatitis C virus (HCV) infection is a combination of IFN-α and ribavirin, but the majority of chronic hepatitis C patients cannot clear their infection with this regimen
Isolation of interferon resistant HCV replicon cell lines Previously, we reported data suggesting that activation of this interferon stimulated response element (ISRE)-promoter is important for a successful antiviral action of IFN-α in replicon cells (37)

Summary

Introduction

Alpha interferon in combination with ribavirin is the standard therapy for hepatitis C virus infection. The majority of people exposed to HCV slowly develop into chronic infection. Long-standing chronic inflammation in the liver due to the virus infection leads to liver cirrhosis and carcinoma [1,2,3,4,5,6,7]. Standard therapy for chronic HCV infection is a combination of IFN-α and ribavirin, but the majority of chronic hepatitis C patients cannot clear their infection with this regimen. Patients infected with genotype 1 HCV in the United States are frequently resistant to IFN-α and ribavirin treatment [9,10,11,12,13]. The reason why some chronic hepatitis C patients do not respond to interferon therapy is unknown

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