Schematic illustrations of phage display screening method.

The hepatitis C virus (HCV) E2 protein derived from either strain TH (genotype 1b) or strain JFH-1 (genotype 2a) was allowed to bind to the surface of magnetic beads, and the single chain Fv (scFv) phage library then was added to the coated beads. Specifically bound phages were amplified by infection of E. coli. These steps were repeated for a total of 4 times to enrich for phages with specific binding to the HCV E2 protein. To confirm the specific binding of scFv phages to HCV E2 protein-bound magnetic beads, the gene encoding the corresponding IgG was constructed from phagemid scFv-encoding sequences by PCR cloning. Specific binding of these antibodies to HCV E2 protein was assessed by enzyme immune assay (EIA) recognition and neutralization of HCV pseudoparticle (HCVpp) infection. (TIF)