title: Exposure of the membrane-proximal external region of HIV-1 gp41 in the course of HIV-1 envelope glycoprotein-mediated fusion.
abstract: The membrane-proximal external region (MPER) of HIV-1 gp41 is highly conserved and critical for the fusogenic ability of the virus. However, little is known about the activity of this region in the context of viral fusion. In this study we investigate the temporal exposure of MPER during the course of HIV-1 Env-mediated fusion. We employed the broadly neutralizing monoclonal antibodies 2F5 and 4E10, whose epitopes localize to this region as indicators for accessibility to this region. Time of addition experiments indicated that escape of HIV-1 infection inhibition by 2F5 and 4E10 occurred concomitantly with that of C34, a peptide that blocks the six-helix bundle formation and fusion, which was about 20 min later than escape of inhibition by the mAb b12 that blocks CD4-gp120 attachment. We also probed accessibility of the MPER region on fusion intermediates by measuring the binding of the monoclonal antibodies at different time points during the fusion reaction. Immunofluorescence and in-cell Western assays showed that binding of 2F5 and 4E10 decreased upon triggering HIV-1 Env-expressing cells with appropriate target cells. Addition of C34 did not counteract the loss of antibody binding, suggesting that changes in exposure of MPER occur independently of six-helix bundle formation.
authors.affiliation: Center for Cancer Research Nanobiology Program, National Cancer Institute, National Institutes of Health, Frederick, Maryland 21702, USA.
authors.forename: Antony S
authors.initials: AS
authors.lastname: Dimitrov
authors.forename: Amy
authors.initials: A
authors.lastname: Jacobs
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Finnegan
authors.forename: Gabriela
authors.initials: G
authors.lastname: Stiegler
authors.forename: Hermann
authors.initials: H
authors.lastname: Katinger
authors.forename: Robert
authors.initials: R
authors.lastname: Blumenthal
mesh_terms: D000911:Antibodies, Monoclonal; D000937:Antigen-Antibody Reactions; D000956:Antigens, Viral; D015700:HIV Envelope Protein gp41 / Q000276:immunology / Q000502:physiology*; D015497:HIV-1 / Q000472:pathogenicity*; D008561:Membrane Fusion; D013997:Time Factors; D053585:Virus Attachment; D053586:Virus Internalization
chemical_list: D000911:Antibodies, Monoclonal; D000956:Antigens, Viral; D015700:HIV Envelope Protein gp41