Hepatitis C virus (HCV) infection is endemic in numerous countries and is a global health issue, placing a huge burden on health care systems and society. The high prevalence of people who are chronically infected with HCV, the disease burden and the absence of an effective vaccine reinforce the importance of HCV treatment in controlling this disease. Direct acting antivirals (DAAs), have revolutionised HCV treatment over the last few years. However, people failing DAAs typically develop antiviral resistance, so new treatments may still be needed in future.
To identify novel host factors involved in HCV infection, a mass spectrometry based Stable Isotope Labelling of Amino acids in Cell culture (SILAC) screen was performed, to identify proteins that are enriched in the Endoplasmic Reticulum (ER) of HCV infected hepatocytes. This showed significant upregulation of Coatomer Protein Complex-I (COPI). Next, we examined the effect of Phosphatidylinositol 4-phosphate (PI4P) depletion on tafficking of COPI to the ER and on HCV replication, by over-expressing the PI4P phosphatase Sac1. However, due to the limitations of the model, we could neither prove or disprove this hypothesis, as we could not achieve sustained overexpression of Sac1.
Next, we evaluated the consequence of silencing heterogeneous nuclear ribonucleoproteins C1/C2 (hnRNPC1/C2) and transmembrane 6 superfamily member 2 (TM6SF2) on HCV replication. We found that hnRNPC1/C2 inhibition has no effect on HCV replication, while TM6SF2 is required for HCV replication. In summary, these findings identify a range of essential host proteins that could be targeted by novel host-targeting antiviral drugs. Finally, our findings provide potential insights into the life cycle of other related viruses, which have far fewer treatments available.