title: Single Amino Acid Substitution N659D in HIV-2 Envelope Glycoprotein (Env) Impairs Viral Release and Hampers BST-2 Antagonism.
abstract: BST-2 or tetherin is a host cell restriction factor that prevents the budding of enveloped viruses at the cell surface, thus impairing the viral spread. Several countermeasures to evade this antiviral factor have been positively selected in retroviruses: the human immunodeficiency virus type 2 (HIV-2) relies on the envelope glycoprotein (Env) to overcome BST-2 restriction. The Env gp36 ectodomain seems involved in this anti-tetherin activity, however residues and regions interacting with BST-2 are not clearly defined. Among 32 HIV-2 ROD Env mutants tested, we demonstrated that the asparagine residue at position 659 located in the gp36 ectodomain is mandatory to exert the anti-tetherin function. Viral release assays in cell lines expressing BST-2 showed a loss of viral release ability for the HIV-2 N659D mutant virus compared to the HIV-2 wild type virus. Inbst-2inactivated H9 cells, those differences were lost. Subtilisin treatment of infected cells demonstrated that the N659D mutant was more tethered at the cell surface. Förster resonance energy transfer (FRET) experiments confirmed a direct molecular link between Env and BST-2 and highlighted an inability of the mutant to bind BST-2. We also tested a virus presenting a truncation of 109 amino acids at the C-terminal part of Env, a cytoplasmic tail partial deletion that is spontaneously selected in vitro. Interestingly, viral release assays and FRET experiments indicated that a full Env cytoplasmic tail was essential in BST-2 antagonism. In HIV-2 infected cells, an efficient Env-mediated antagonism of BST-2 is operated through an intermolecular link involving the asparagine 659 residue as well as the C-terminal part of the cytoplasmic tail.
authors.affiliation: AIDS Reference Laboratory, Medical Microbiology Unit (MBLG), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Avenue Hippocrate 54 B1.54.05, B-1200 Brussels, Belgium. francois.dufrasne@uclouvain.be.
authors.forename: François E
authors.initials: FE
authors.lastname: Dufrasne
authors.affiliation: Pôle de Pédiatrie (PEDI), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Avenue Mounier 52 B1.52.03, B-1200 Brussels, Belgium. catherine.lombard@uclouvain.be.
authors.forename: Catherine
authors.initials: C
authors.lastname: Lombard
authors.affiliation: AIDS Reference Laboratory, Medical Microbiology Unit (MBLG), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Avenue Hippocrate 54 B1.54.05, B-1200 Brussels, Belgium. patrick.goubau@uclouvain.be.
authors.forename: Patrick
authors.initials: P
authors.lastname: Goubau
authors.affiliation: AIDS Reference Laboratory, Medical Microbiology Unit (MBLG), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Avenue Hippocrate 54 B1.54.05, B-1200 Brussels, Belgium. jean.ruelle@uclouvain.be.
authors.forename: Jean
authors.initials: J
authors.lastname: Ruelle
mesh_terms: D019943:Amino Acid Substitution; D015703:Antigens, CD; D002460:Cell Line; D058851:GPI-Linked Proteins / Q000037:antagonists & inhibitors; D015498:HIV-2 / Q000235:genetics / Q000276:immunology* / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism*; D057074:Virus Release; D054299:env Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*; D000074010:Bone Marrow Stromal Antigen 2
chemical_list: D015703:Antigens, CD; D058851:GPI-Linked Proteins; D050505:Mutant Proteins; D054299:env Gene Products, Human Immunodeficiency Virus; C094572:BST2 protein, human; D000074010:Bone Marrow Stromal Antigen 2
keywords: BST-2; CRISPR/Cas9 knockout; Env; FRET; HIV-2; envelope glycoprotein; gp36; restriction factors; tetherin; viral antagonist