| Research Abstract |
Hepatitis C virus (HCV) is a major causative agent of hepatocellular carcinoma in Japan. About 60% of HCV infection becomes persistent, resulting in development of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. Neutralizing antibody against HCV is not clearly identified, because experimental systems of infection and proliferation of HCV are not yet established. Immune response analyzes in patients with acute and chronic hepatitis C suggest that neutralizing antibody is hardly induced in natural infection or a mutant of HCV escaping from neutralizing antibody generates by high mutation rate of HCV.In this work, neutralizing antibody is found out from animals such as mice and chimpanzee actively immunized with recombinant antigens, and is humanized by cDNA cloning of complimentarity-determining (CDR) of the neutralizing antibody.
We produced antibody against recombinant HCV envelope glycoproteins, E1 and E2, and synthesized hypervariable region (HVR) 1 peptides, as candidates for neutralizing antibody. Higher antibody response was induced in immunized mice and a chimpanzee, and immunoreactive peptides unique to animals were found in comparison with those of patients. Murine anti-E2 and anti-HVR1 antibodies but not anti-E1 antibody captured HCV.Chimpanzee antiserum against whole immunogens also captured HCV in vitro, and neutralized HCV infectivity in a chimpanzee. The immunized chimpanzee was also protected from HCV infection. Epitope analysis of capturing antibody showed that a reactive peptide exists in HVR1. Althogh HVR1 of HCV is isolate-specific, another HCV isolate was captured with these immunized sera. Now in order to clone cDNA of CDR of antibody, combinatorial antibody library is constructed from spleens of immunized mice and peripheral blood leukocytes of immunized chimpanzee.
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