title: Analysis of a highly flexible conformational immunogenic domain a in hepatitis C virus E2.
abstract: Hepatitis C (HCV) E2 glycoprotein is involved in virus attachment and entry, and its structural organization is largely unknown. Characterization of a panel of human monoclonal antibodies (HMAbs) to HCV by competition studies has led to an immunogenic organization model of E2 with three domains designated A, B, and C and epitopes in each domain having similar structural and functional properties. Domain A contains nonneutralizing epitopes, and domains B and C contain neutralizing epitopes. The isolation and characterization of three new HMAbs within domain A for a total of six provide support for this model. All six domain A HMAbs do not neutralize HCV retroviral pseudotype particle (HCVpp) infection on Huh-7 cells, and all six HMAbs have similar binding affinity and maximum binding, B(max), a relative indicator of epitope density, as other neutralizing HMAbs, suggesting that neutralization is epitope specific and not by binding to any surface epitope. The dose-dependent neutralizing activity of CBH-7, an HMAb to a domain C epitope in spatial proximity to domain A, and of CBH-5, a domain B HMAb to a more distant epitope, were tested in the presence and absence of each domain A HMAb. No enhancement or reduction in CBH-7 or CBH-5 neutralizing activity was observed, indicating that the potential induction of nonneutralizing antibodies should not be a central issue for HCV vaccine design. To assess whether domain A is involved in the structural changes as part of a pH-dependent virus envelope fusion process, changes in antibody binding patterns to normal pH and acid pH-treated HCVpp were measured. Antibody binding affinity of HMAbs to HCVpp was not affected by low pH. However, the B(max) values for low-pH-treated HCVpp with antibodies to domain A increased 46%, for domain C (CBH-7) they increased 23%, and for domain B (CBH-5) there was a decrease of 12%. Collectively, the organization and function of HCV E2 antigenic domains are roughly analogous to the large envelope glycoprotein E organizational structure for other flaviviruses with three distinct structural and functional domains.
authors.affiliation: Stanford Medical School Blood Center, 3373 Hillview Ave., Palo Alto, CA 94304, USA.
authors.forename: Zhen-Yong
authors.initials: ZY
authors.lastname: Keck
authors.forename: Ta-Kai
authors.initials: TK
authors.lastname: Li
authors.forename: Jinming
authors.initials: J
authors.lastname: Xia
authors.forename: Birke
authors.initials: B
authors.lastname: Bartosch
authors.forename: François-Loïc
authors.initials: FL
authors.lastname: Cosset
authors.forename: Jean
authors.initials: J
authors.lastname: Dubuisson
authors.forename: Steven K H
authors.initials: SK
authors.lastname: Foung
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology; D000914:Antibodies, Viral / Q000276:immunology; D000915:Antibody Affinity; D045744:Cell Line, Tumor; D018985:Epitopes, B-Lymphocyte; D016174:Hepacivirus / Q000276:immunology / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009500:Neutralization Tests; D011487:Protein Conformation; D017434:Protein Structure, Tertiary / Q000502:physiology*; D014759:Viral Envelope Proteins / Q000276:immunology* / Q000378:metabolism; D014779:Virus Replication
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D018985:Epitopes, B-Lymphocyte; D014759:Viral Envelope Proteins; C091015:glycoprotein E2, Hepatitis C virus