Single Chain Fragment Variable (scFv) corresponding to a novel epitope within HCV envelope protein restricts virus entry into hepatocytes

Hepatitis C virus (HCV) is a leading cause of chronic viral hepatitis. The use of neutralizing antibodies could be a more effective therapeutic option. Previously we reported the discovery of a novel epitope at the C terminus of HCV-E2 protein, that induced potent neutralizing antibodies in the infected patients. Furthermore, monoclonal antibodies generated against this epitope could also significantly reduce virus replication in a cell culture system. In this study, we have focused on the generation of single chain variable fragments of this unique neutralizing monoclonal antibody A8A11 raised against the conserved epitope. The nucleotide sequence of the neutralizing monoclonal antibody A8A11 was determined and the scFv gene was constructed followed by cloning into the expression plasmid for recombinant protein expression. The scFv mimicked the antibody in binding to the hepatitis C virus like particles (HCV-LP). As expected, the scFv inhibited HCV-LP binding to hepatocytes and could effectively reduce viral replication in the cell culture system. More importantly, scFv A8A11 could restrict serum HCV RNA levels in HCV-infected chimeric mice harboring human hepatocytes. Results provide a basis for developing a promising scFv-based entry inhibitor, which could be more effective against viruses refractory to drugs targeting viral enzymes.