title: An antibody directed against the fusion peptide of Junin virus envelope glycoprotein GPC inhibits pH-induced membrane fusion.
abstract: The arenavirus envelope glycoprotein (GPC) initiates infection in the host cell through pH-induced fusion of the viral and endosomal membranes. As in other class I viral fusion proteins, this process proceeds through a structural reorganization in GPC in which the ectodomain of the transmembrane fusion subunit (G2) engages the host cell membrane and subsequently refolds to form a highly stable six-helix bundle structure that brings the two membranes into apposition for fusion. Here, we describe a G2-directed monoclonal antibody, F100G5, that prevents membrane fusion by binding to an intermediate form of the protein on the fusion pathway. Inhibition of syncytium formation requires that F100G5 be present concomitant with exposure of GPC to acidic pH. We show that F100G5 recognizes neither the six-helix bundle nor the larger trimer-of-hairpins structure in the postfusion form of G2. Rather, Western blot analysis using recombinant proteins and a panel of alanine-scanning GPC mutants revealed that F100G5 binding is dependent on an invariant lysine residue (K283) near the N terminus of G2, in the so-called fusion peptide that inserts into the host cell membrane during the fusion process. The F100G5 epitope is located in the internal segment of the bipartite GPC fusion peptide, which also contains four conserved cysteine residues, raising the possibility that this fusion peptide may be highly structured. Collectively, our studies indicate that F100G5 identifies an on-path intermediate form of GPC. Binding to the transiently exposed fusion peptide may interfere with G2 insertion into the host cell membrane. Strategies to effectively target fusion peptide function in the endosome may lead to novel classes of antiviral agents.
authors.affiliation: Montana Biotechnology Center, Science Complex Room 221, The University of Montana, Missoula, MT 59812, USA.
authors.forename: Joanne
authors.initials: J
authors.lastname: York
authors.forename: Jody D
authors.initials: JD
authors.lastname: Berry
authors.forename: Ute
authors.initials: U
authors.lastname: Ströher
authors.forename: Qunnu
authors.initials: Q
authors.lastname: Li
authors.forename: Heinz
authors.initials: H
authors.lastname: Feldmann
authors.forename: Min
authors.initials: M
authors.lastname: Lu
authors.forename: Meg
authors.initials: M
authors.lastname: Trahey
authors.forename: Jack H
authors.initials: JH
authors.lastname: Nunberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000494:pharmacology*; D001117:Arenaviridae Infections / Q000276:immunology / Q000821:virology; D002522:Chlorocebus aethiops; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D006863:Hydrogen-Ion Concentration; D018051:Junin virus / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D008561:Membrane Fusion / Q000187:drug effects*; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D014709:Vero Cells; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*
chemical_list: D000906:Antibodies; D006023:Glycoproteins; D014760:Viral Fusion Proteins
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