title: Depletion of interfering antibodies in chronic hepatitis C patients and vaccinated chimpanzees reveals broad cross-genotype neutralizing activity.
abstract: Using human immune globulins made from antihepatitis C virus (HCV)-positive plasma, we recently identified two antibody epitopes in the E2 protein at residues 412-426 (epitope I) and 434-446 (epitope II). Whereas epitope I is highly conserved among genotypes, epitope II varies. We discovered that epitope I was implicated in HCV neutralization whereas the binding of non-neutralizing antibody to epitope II disrupted virus neutralization mediated by antibody binding at epitope I. These findings suggested that, if this interfering mechanism operates in vivo during HCV infection, a neutralizing antibody against epitope I can be restrained by an interfering antibody, which may account for the persistence of HCV even in the presence of an abundance of neutralizing antibodies. We tested this hypothesis by affinity depletion and peptide-blocking of epitope-II-specific antibodies in plasma of a chronically HCV-infected patient and recombinant E1E2 vaccinated chimpanzees. We demonstrate that, by removing the restraints imposed by the interfering antibodies to epitope-II, neutralizing activity can be revealed in plasma that previously failed to neutralize viral stock in cell culture. Further, cross-genotype neutralization could be generated from monospecific plasma. Our studies contribute to understanding the mechanisms of antibody-mediated neutralization and interference and provide a practical approach to the development of more potent and broadly reactive hepatitis C immune globulins.
authors.affiliation: Division of Hematology and Center for Biologics Evaluation and Research, United States Food and Drug Administration, Bethesda, MD 20892, USA. pei.zhang@fda.hhs.gov
authors.forename: Pei
authors.initials: P
authors.lastname: Zhang
authors.forename: Lilin
authors.initials: L
authors.lastname: Zhong
authors.forename: Evi Budo
authors.initials: EB
authors.lastname: Struble
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Watanabe
authors.forename: Alla
authors.initials: A
authors.lastname: Kachko
authors.forename: Kathleen
authors.initials: K
authors.lastname: Mihalik
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Virata
authors.forename: Harvey J
authors.initials: HJ
authors.lastname: Alter
authors.forename: Stephen
authors.initials: S
authors.lastname: Feinstone
authors.forename: Marian
authors.initials: M
authors.lastname: Major
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000939:Epitopes / Q000276:immunology*; D005838:Genotype; D018937:Hepatitis C Antibodies / Q000097:blood / Q000235:genetics / Q000276:immunology*; D019698:Hepatitis C, Chronic / Q000276:immunology*; D006801:Humans; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D002679:Pan troglodytes / Q000235:genetics / Q000276:immunology*; D014611:Vaccination; D014759:Viral Envelope Proteins / Q000276:immunology*; D014761:Viral Hepatitis Vaccines / Q000276:immunology
chemical_list: D000939:Epitopes; D018937:Hepatitis C Antibodies; D014759:Viral Envelope Proteins; D014761:Viral Hepatitis Vaccines; C091015:glycoprotein E2, Hepatitis C virus