The Hepatitis C Virus Non-structural NS5A Protein Impairs Both the Innate and Adaptive Hepatic Immune Response in Vivo

Tilmann Bürckstümmer,Malte Kriegs,Eberhard Hildt,Matti Sällberg,Kyoshi Himmelsbach,Lars Frelin,Michael Bruns,Gustaf Ahlén

doi:10.1074/jbc.m109.038877

Abstract

The role of hepatitis C virus (HCV) protein non-structural (NS) 5A in HCV-associated pathogenesis is still enigmatic. To investigate the in vivo role of NS5A for viral persistence and virus-associated pathogenesis a transgenic (Tg) mouse model was established. Mice with liver-targeted NS5A transgene expression were generated using the albumin promoter. Alterations in the hepatic immune response were determined by Western blot, infection by lymphocytic choriomeningitis virus (LCMV), and using transient NS3/4A Tg mice generated by hydrodynamic injection. Cytotoxic T lymphocyte (CTL) activity was investigated by the Cr-release assay. The stable NS5A Tg mice did not reveal signs of spontaneous liver disease. The intrahepatic immunity was disrupted in the NS5A Tg mice as determined by clearance of LCMV infection or transiently NS3/4A Tg hepatocytes in vivo. This impaired immunity was explained by a reduced induction of interferon beta, 2',5'-OAS, and PKR after LCMV infection and an impairment of the CTL-mediated elimination of NS3-expressing hepatocytes. In conclusion, these data indicate that in the present transgenic mouse model, NS5A does not cause spontaneous liver disease. However, we discovered that NS5A could impair both the innate and the adaptive immune response to promote chronic HCV infection.

Highlights

Medical Research, the Swedish Society of Medicine, the Royal Swedish Academy of Sciences, Goljes Memorial Fund, the Ruth and Richard Juhlin Foundation, and the Karolinska Institutet
Cell culture-based experiments have shown that NS5A interacts directly with the interferon-dependent induced protein kinase R (PKR), a key player in the cellular antiviral response and that this interaction results in an inhibition of PKR function [15]
As expected for an ER-attached protein, the immunofluorescence microscopy for NS5A showed an inhomogeneous cytoplasmic staining with a concentration in the perinuclear region, while the nucleus remains unstained (Fig. 1c)

Summary

Introduction

Medical Research, the Swedish Society of Medicine, the Royal Swedish Academy of Sciences, Goljes Memorial Fund, the Ruth and Richard Juhlin Foundation, and the Karolinska Institutet Infection of transgenic mice expressing the complete HCV polyprotein with lymphocytic choriomeningitis virus (LCMV) showed a reduced IFN response and a delayed viral elimination [14].

Results

Conclusion