title: An alpaca nanobody inhibits hepatitis C virus entry and cell-to-cell transmission.
abstract: Severe liver disease caused by chronic hepatitis C virus is the major indication for liver transplantation. Despite recent advances in antiviral therapy, drug toxicity and unwanted side effects render effective treatment in liver-transplanted patients a challenging task. Virus-specific therapeutic antibodies are generally safe and well-tolerated, but their potential in preventing and treating hepatitis C virus (HCV) infection has not yet been realized due to a variety of issues, not least high production costs and virus variability. Heavy-chain antibodies or nanobodies, produced by camelids, represent an exciting antiviral approach; they can target novel highly conserved epitopes that are inaccessible to normal antibodies, and they are also easy to manipulate and produce. We isolated four distinct nanobodies from a phage-display library generated from an alpaca immunized with HCV E2 glycoprotein. One of them, nanobody D03, recognized a novel epitope overlapping with the epitopes of several broadly neutralizing human monoclonal antibodies. Its crystal structure revealed a long complementarity determining region (CD3) folding over part of the framework that, in conventional antibodies, forms the interface between heavy and light chain. D03 neutralized a panel of retroviral particles pseudotyped with HCV glycoproteins from six genotypes and authentic cell culture-derived particles by interfering with the E2-CD81 interaction. In contrast to some of the most broadly neutralizing human anti-E2 monoclonal antibodies, D03 efficiently inhibited HCV cell-to-cell transmission.
  
  
  CONCLUSIONS
  This is the first description of a potent and broadly neutralizing HCV-specific nanobody representing a significant advance that will lead to future development of novel entry inhibitors for the treatment and prevention of HCV infection and help our understanding of HCV cell-to-cell transmission.
authors.affiliation: School of Molecular Medical Sciences, The University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom.
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Tarr
authors.forename: Pierre
authors.initials: P
authors.lastname: Lafaye
authors.forename: Luke
authors.initials: L
authors.lastname: Meredith
authors.forename: Laurence
authors.initials: L
authors.lastname: Damier-Piolle
authors.forename: Richard A
authors.initials: RA
authors.lastname: Urbanowicz
authors.forename: Annalisa
authors.initials: A
authors.lastname: Meola
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Jestin
authors.forename: Richard J P
authors.initials: RJ
authors.lastname: Brown
authors.forename: Jane A
authors.initials: JA
authors.lastname: McKeating
authors.forename: Felix A
authors.initials: FA
authors.lastname: Rey
authors.forename: Jonathan K
authors.initials: JK
authors.lastname: Ball
authors.forename: Thomas
authors.initials: T
authors.lastname: Krey
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002161:Camelids, New World / Q000276:immunology*; D002450:Cell Communication / Q000187:drug effects*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D018604:Epitope Mapping; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D005838:Genotype; D016174:Hepacivirus / Q000276:immunology* / Q000472:pathogenicity; D006526:Hepatitis C / Q000517:prevention & control / Q000635:transmission; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000473:pathology / Q000821:virology; D008969:Molecular Sequence Data; D061905:Single-Domain Antibodies / Q000737:chemistry / Q000276:immunology* / Q000494:pharmacology*; D014759:Viral Envelope Proteins / Q000276:immunology*; D053586:Virus Internalization / Q000187:drug effects*
chemical_list: D000939:Epitopes; D061905:Single-Domain Antibodies; D014759:Viral Envelope Proteins; C091015:glycoprotein E2, Hepatitis C virus