title: Modulation of the virus-receptor interaction by mutations in the V5 loop of feline immunodeficiency virus (FIV) following in vivo escape from neutralising antibody.
abstract: BACKGROUND
  In the acute phase of infection with feline immunodeficiency virus (FIV), the virus targets activated CD4+ T cells by utilising CD134 (OX40) as a primary attachment receptor and CXCR4 as a co-receptor. The nature of the virus-receptor interaction varies between isolates; strains such as GL8 and CPGammer recognise a "complex" determinant on CD134 formed by cysteine-rich domains (CRDs) 1 and 2 of the molecule while strains such as PPR and B2542 require a more "simple" determinant comprising CRD1 only for infection. These differences in receptor recognition manifest as variations in sensitivity to receptor antagonists. In this study, we ask whether the nature of the virus-receptor interaction evolves in vivo.
  
  
  RESULTS
  Following infection with a homogeneous viral population derived from a pathogenic molecular clone, a quasispecies emerged comprising variants with distinct sensitivities to neutralising antibody and displaying evidence of conversion from a "complex" to a "simple" interaction with CD134. Escape from neutralising antibody was mediated primarily by length and sequence polymorphisms in the V5 region of Env, and these alterations in V5 modulated the virus-receptor interaction as indicated by altered sensitivities to antagonism by both anti-CD134 antibody and soluble CD134.
  
  
  CONCLUSIONS
  The FIV-receptor interaction evolves under the selective pressure of the host humoral immune response, and the V5 loop contributes to the virus-receptor interaction. Our data are consistent with a model whereby viruses with distinct biological properties are present in early versus late infection and with a shift from a "complex" to a "simple" interaction with CD134 with time post-infection.
authors.affiliation: Retrovirus Research Laboratory, Institute of Comparative Medicine, Faculty of Veterinary Medicine, University of Glasgow, Bearsden Road, Glasgow, UK. b.willett@vet.gla.ac.uk
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Willett
authors.forename: Martin
authors.initials: M
authors.lastname: Kraase
authors.forename: Nicola
authors.initials: N
authors.lastname: Logan
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: McMonagle
authors.forename: Ayman
authors.initials: A
authors.lastname: Samman
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Hosie
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000276:immunology*; D000914:Antibodies, Viral / Q000276:immunology*; D002415:Cats; D016181:Feline Acquired Immunodeficiency Syndrome / Q000276:immunology / Q000821:virology*; D016089:Immunodeficiency Virus, Feline / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification / Q000502:physiology; D008958:Models, Molecular; D020125:Mutation, Missense / Q000276:immunology*; D011487:Protein Conformation; D011991:Receptors, Virus / Q000378:metabolism; D012641:Selection, Genetic; D014759:Viral Envelope Proteins / Q000235:genetics / Q000276:immunology*; D053585:Virus Attachment
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D011991:Receptors, Virus; D014759:Viral Envelope Proteins