Establishment of human clones producing neutralizing human monoclonal antibodies to the envelope E1/E2 protein of hepatitis C virus by EBV immortalization of immune CD22+ B cells

We aimed to establish Human cell lines producing human monoclonal antibodies to the envelope E1/E2 protein of hepatitis C virus (HCV). Two protocols for EBV immortalization of CD22 cells separated from HCV positive patients were used; 1) Immortalization with 100% EBV only, 2) immortalization by 30 % EBV and CPG2006. Immortalization was checked microscopically and verified by screening the culture supernatant for antibody production using dot blot and ELISA analysis. ELISA plates were coated by HCV E1/E2 derived from cell lysate transfected by plasmid expressed HCV E1/E2. Also we tested the reactivity of human antibodies based on ELISA plates coating with one linear peptides derived from HCV E1 (a.a 315–319) and two peptides derived from HCV E2 (a.a 412–419) and (a.a 517–530). Neutralization activity was measured using H77C HCV retroviral pseudoparticles (HCVpp). Fifteen clones secreting human immunoglobulin G against HCV E1/E2 protein were isolated. Results of ELISA plates coated with HCV peptides showed that one antibody was binding to E2 peptide (a.a 517–530), and two antibodies binding to HCV E2 peptide (a.a 412–419). The three generated antibodies showed extremely neutralization activity against HCV pp. The three human antibodies were IgG3 and IgG2. These antibodies may be useful for passive immunotherapy of HCV infection