title: Monoclonal Antibodies Directed toward the Hepatitis C Virus Glycoprotein E2 Detect Antigenic Differences Modulated by the N-Terminal Hypervariable Region 1 (HVR1), HVR2, and Intergenotypic Variable Region.
abstract: Hepatitis C virus (HCV) envelope glycoproteins E1 and E2 form a heterodimer and mediate receptor interactions and viral fusion. Both E1 and E2 are targets of the neutralizing antibody (NAb) response and are candidates for the production of vaccines that generate humoral immunity. Previous studies demonstrated that N-terminal hypervariable region 1 (HVR1) can modulate the neutralization potential of monoclonal antibodies (MAbs), but no information is available on the influence of HVR2 or the intergenotypic variable region (igVR) on antigenicity. In this study, we examined how the variable regions influence the antigenicity of the receptor binding domain of E2 spanning HCV polyprotein residues 384 to 661 (E2661) using a panel of MAbs raised against E2661 and E2661 lacking HVR1, HVR2, and the igVR (Δ123) and well-characterized MAbs isolated from infected humans. We show for a subset of both neutralizing and nonneutralizing MAbs that all three variable regions decrease the ability of MAbs to bind E2661 and reduce the ability of MAbs to inhibit E2-CD81 interactions. In addition, we describe a new MAb directed toward the region spanning residues 411 to 428 of E2 (MAb24) that demonstrates broad neutralization against all 7 genotypes of HCV. The ability of MAb24 to inhibit E2-CD81 interactions is strongly influenced by the three variable regions. Our data suggest that HVR1, HVR2, and the igVR modulate exposure of epitopes on the core domain of E2 and their ability to prevent E2-CD81 interactions. These studies suggest that the function of HVR2 and the igVR is to modulate antibody recognition of glycoprotein E2 and may contribute to immune evasion.
  
  
  OBJECTIVE
  This study reveals conformational and antigenic differences between the Δ123 and intact E2661 glycoproteins and provides new structural and functional data about the three variable regions and their role in occluding neutralizing and nonneutralizing epitopes on the E2 core domain. The variable regions may therefore function to reduce the ability of HCV to elicit NAbs directed toward the conserved core domain. Future studies aimed at generating a three-dimensional structure for intact E2 containing HVR1, and the adjoining NAb epitope at residues 412 to 428, together with HVR2, will reveal how the variable regions modulate antigenic structure.
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Australia Department of Microbiology, Monash University, Clayton, Australia.
authors.forename: Yousef
authors.initials: Y
authors.lastname: Alhammad
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Australia Department of Microbiology, Monash University, Clayton, Australia.
authors.forename: Jun
authors.initials: J
authors.lastname: Gu
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Australia.
authors.forename: Irene
authors.initials: I
authors.lastname: Boo
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Harrison
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Australia Infection and Immunity Program, Monash Biomedicine Discovery Institute, and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia.
authors.forename: Kathleen
authors.initials: K
authors.lastname: McCaffrey
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Australia Department of Microbiology, Monash University, Clayton, Australia.
authors.forename: Patricia T
authors.initials: PT
authors.lastname: Vietheer
authors.affiliation: CSL Limited Research and Development, Parkville, Australia.
authors.forename: Stirling
authors.initials: S
authors.lastname: Edwards
authors.affiliation: CSL Limited Research and Development, Parkville, Australia.
authors.forename: Charles
authors.initials: C
authors.lastname: Quinn
authors.affiliation: Infection and Immunity Program, Monash Biomedicine Discovery Institute, and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia.
authors.forename: Fásseli
authors.initials: F
authors.lastname: Coulibaly
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Australia Department of Microbiology, Monash University, Clayton, Australia.
authors.forename: Pantelis
authors.initials: P
authors.lastname: Poumbourios
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Australia Department of Microbiology, Monash University, Clayton, Australia Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia hdrummer@burnet.edu.au.
authors.forename: Heidi E
authors.initials: HE
authors.lastname: Drummer
mesh_terms: D000818:Animals; D058846:Antibodies, Monoclonal, Murine-Derived / Q000737:chemistry* / Q000276:immunology; D057134:Antibodies, Neutralizing / Q000737:chemistry* / Q000276:immunology; D002460:Cell Line; D016174:Hepacivirus / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D018937:Hepatitis C Antibodies / Q000737:chemistry* / Q000276:immunology; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D060225:Tetraspanin 28 / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology
chemical_list: D058846:Antibodies, Monoclonal, Murine-Derived; D057134:Antibodies, Neutralizing; C554798:CD81 protein, human; D018937:Hepatitis C Antibodies; D060225:Tetraspanin 28; D014759:Viral Envelope Proteins; C091015:glycoprotein E2, Hepatitis C virus