Effect of Hepatic Cirrhosis on the HCV Replication Cycle

 

Introduction: Worldwide an estimated 160 million people suffer from chronic hepatitis C (CHC). In about 20% of cases CHC progresses to severe liver disease, i.e. cirrhosis or hepatocellular carcinoma (HCC) within 20 years. Cirrhosis leads to alterations in the hepatic microenvironment as well as a number of metabolic and hormonal changes. The effects of these alterations on the HCV replication cycle have not yet been investigated.

Aim: The aim of the study is to determine whether the HCV replication cycle is affected by the metabolic changes due to the progression of cirrhosis.

Methods: The study included 48 serum samples from patients diagnosed with liver cirrhosis of the stages Child-Pugh A, B and C as well as healthy controls. All participants were HCV negative. We tested whether the addition of healthy and cirrhotic sera differentially affects the different steps of the HCV replication cycle in vitro. All experiments were performed in the presence of 10% human serum. For the analyses retroviral HCV pseudoparticles, HCV subgenomic replicons and fully infectious virions of the genotypes 1 and 2 carrying a luciferase reporter gene were used.

Results: The sera of Child B and C individuals showed a significant inhibitory effect on HCV infectivity using full length fully infectious HCV. Effects on viability and/or cell proliferation of the cells used were not detected so that a specific modulation of the HCV replication cycle was considered likely. Upon dissection of individual replication cycle step, we found that both cell entry and replication of HCV in vitro was impaired in the presence of sera from individuals with more advanced liver disease compared to sera of healthy controls and patients with Child A cirrhosis. However, cell entry effects appeared to be partially dependent on the cell line used. We hypothesized that lower levels of branched chain amino acids (BCAAs), activators of mTOR, in sera of patients with liver cirrhosis may be responsible for the observed effects. While we could confirm declining BCAA serum levels in advanced liver disease BCAA supplementation was unable to revert the inhibitory effect of Child C sera on HCV infectivity so that additional mechanisms appear to be involved.

Conclusion: Our results suggest that serum of patients with advanced liver disease includes anti-viral factors or lacks pro-viral factors resulting in impaired HCV replication. Reduced replication in end-stage liver disease may impair the ability of HCV to adapt to selective pressure exerted by anti-viral therapy and thus have an unexpected favourable effect on treatment outcome in this very sick subgroup CHC patients.