Abstract

Title	The HCV NS3/4A-mediated impairment of the hepatic antiviral immune response is reversed by protease inhibition or ribavirin in vivo
Speaker:	Erwin Brenndörfer
Author:	E.D. Brenndörfer¹*, A. Brass¹, J. Söderholm², L. Frelin¹, J.G. Bode³, M. Sällberg¹
Affiliation:	¹Department of Laboratory Medicine, Division of Clinical Microbiology, Karolinska Institutet, Stockholm, ²Department of Infectious Diseases, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden, ³Department of Gastroenterology, Hepatology and Infectiology, University Hospital, Heinrich-Heine-University of Düsseldorf, Düsseldorf, Germany. *erwin.brenndorfer@ki.se
Background: Hepatitis C virus (HCV) has evolved mechanisms to evade elimination by both innate and adaptive immunity resulting in HCV persistence. The HCV NS3/4A protease/helicase is known to modulate signaling pathways in the infected hepatocyte by cleaving MAVS, TC-PTP and TRIF. However, the global effects exerted by NS3/4A in vivo still remain unclear. This is currently of a particular interest since new antiviral therapies are being introduced based on inhibitors blocking the NS3/4A protease. Thus, these therapies may exert effects beyond the viral replication. Objectives: We aimed to understand how NS3/4A affects intercellular signaling and immune cell function in vivo and to study the effects of ribavirin or NS3/4A protease inhibition on the NS3/4A-mediated modulation of the host's immune system. Methods: The intrahepatic immune response of naive and lipopolysaccharide (LPS)/D-galactosamine (D-galN) treated NS3/4A-transgenic (Tg) mice was determined by western blot, ELISA, Real Time PCR, Flow cytometry, ALT levels, and survival. Ribavirin pretreatment or NS3/4A protease inhibition was performed to analyze the influence of antivirals on the NS3/4A-mediated effects. Results: Hepatic IL10 expression is enhanced in NS3/4A-Tg mice both basally and after LPS/D-galN treatment, while IFNγ secretion is impaired. Furthermore, the chemokine profile (CCL2, CCL17, CXCL9) is altered towards an anti-inflammatory state. As result, the intrahepatic number of Th1 cells as well as IFNγ-positive CD4+ and CD8+ T cells in NS3/4A-Tg mice is decreased, while the amount of Th2 cells is increased. Interestingly, the NS3/4A-mediated effects could be reversed by both ribavirin treatment and inhibition of the NS3/4A protease. This is of particular importance since recent clinical trials suggest that ribavirin is essential for a functional therapy with only directly acting antiviral (DAAs) compounds. Conclusions: NS3/4A induces a shift of the intrahepatic immune response towards a non-antiviral Th2-dominated immunity. This may impair the host response to the infection and promote viral persistence. Importantly, both ribavirin treatment and the inhibition of the NS3/4A protease can block the effects mediated by NS3/4A.