Hepatitis C virus (HCV) is a major cause of liver disease. Therapeutic options are limited and preventive strategies are absent. Entry is the first step of infection and requires the cooperative interaction of several host cell factors. Using a functional RNAi kinase screen we identified epidermal growth factor receptor and ephrin receptor A2 as host co-factors for HCV entry. Blocking of kinase function by approved inhibitors broadly inhibited HCV infection of all major HCV genotypes and viral escape variants in cell culture and an animal model in vivo. Receptor tyrosine kinases (RTKs) mediate HCV entry by regulating CD81-claudin-1 co-receptor associations and membrane fusion. These results identify RTKs as novel HCV entry co-factors and uncover that kinase inhibitors have significant antiviral activity. Inhibition of RTK function may constitute a novel approach for prevention and treatment of HCV infection.

Recent evidence indicates there is a role for small membrane vesicles, including exosomes, as vehicles for intercellular communication. Exosomes secreted by most cell types can mediate transfer of proteins, mRNAs, and microRNAs, but their role in the transmission of infectious agents is less established. Recent studies have shown that hepatocyte-derived exosomes containing hepatitis C virus (HCV) RNA can activate innate immune cells, but the role of exosomes in the transmission of HCV between hepatocytes remains unknown. In this study, we investigated whether exosomes transfer HCV in the presence of neutralizing antibodies. Purified exosomes isolated from HCV-infected human hepatoma Huh7.5.1 cells were shown to contain full-length viral RNA, viral protein, and particles, as determined by RT-PCR, mass spectrometry, and transmission electron microscopy. Exosomes from HCV-infected cells were capable of transmitting infection to naive human hepatoma Huh7.5.1 cells and establishing a productive infection. Even with subgenomic replicons, lacking structural viral proteins, exosome-mediated transmission of HCV RNA was observed. Treatment with patient-derived IgGs showed a variable degree of neutralization of exosome-mediated infection compared with free virus. In conclusion, this study showed that hepatic exosomes can transmit productive HCV infection in vitro and are partially resistant to antibody neutralization. This discovery sheds light on neutralizing antibodies resistant to HCV transmission by exosomes as a potential immune evasion mechanism.