In vitro Membrane Interaction and Liposome Fusion Assays Using Recombinant Hepatitis C Virus Envelope Protein E2

In order to study the mechanism underlying the Hepatitis C Virus (HCV) fusion process we have performed assays using phospholipid liposomes and a truncated form of E2 protein, E2(661) (amino acids 384-661 of the HCV polyprotein) lacking the transmembrane region. E2(661) has been previously generated by using the baculovirus expression system. This form has been used in lipid-protein interaction studies with different model vesicles at different pHs, and monitored using a variety of fluorescent assays. After the analysis of the results, we observed that E2(661) is able to insert into lipid bilayers and to induce vesicle aggregation, lipid mixing and liposome leakage, showing higher values of membrane destabilization for negatively charged phospholipids at acidic pH. This is indicative of the role of E2 glycoprotein in the HCV initial infective steps, interacting with the target membranes and producing their destabilization.