Developing new models to predict treatment outcome in patients with chronic hepatitis C infection

Abstract

Chronic infection with hepatitis C virus (HCV) is a significant global health problem, with approximately 170 million individuals infected worldwide. Treatment is rapidly evolving to combinations of highly potent direct-acting antiviral drugs, although optimal combinations for individual patient groups are not yet clear. Treatment failure still occurs, and relapse may occur in as many as 10% of treated individuals. Whilst HCV replicates primarily in the liver, HCV RNA has been identified in extrahepatic sites, including monocytes, although extrahepatic replication is controversial. Our group recently developed a novel assay to study replication of patient-derived HCV by fusion of patient monocytes with cultured hepatoma cells. In this study, we extended the utility of this fusion model, by using cell culture monocytes to ‘capture’ HCV from patient serum prior to fusion with hepatoma cells. We studied whether this ‘capture-fusion’ model could be used to screen individual patient drug response and the mechanisms permitting viral replication in the hybrid cells. Using the capture-fusion assay, patient-derived HCV of all viral genotypes replicated to levels detectable by a sensitive PCR assay and could be inhibited by antiviral drugs in a genotype-specific manner. Isolates with genotypic and phenotypic drug resistance could be identified, and, in a blinded study, drug sensitivity in the assay correlated with clinical treatment response. Relapse after interferon and ribavirin treatment was associated with poor pre-treatment ribavirin sensitivity and also with viable HCV in patient-derived monocytes at the end of therapy. Uptake of HCV into monocytes appeared independent of classical HCV entry receptors, and our work implicated CD64 in HCV monocyte entry. Cell fusion appeared to permit transfer of HCV RNA to hepatocytes without triggering an intracellular antiviral innate immune response. Our data suggest that this novel ‘capture-fusion’ model represents a promising new technique which may help identify appropriate treatment strategies for patients with chronic HCV infection.