title: Human immunodeficiency virus type 1 membrane fusion mediated by a laboratory-adapted strain and a primary isolate analyzed by resonance energy transfer.
abstract: Previous studies of human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein-mediated membrane fusion have focused on laboratory-adapted T-lymphotropic strains of the virus. The goal of this study was to characterize membrane fusion mediated by a primary HIV-1 isolate in comparison with a laboratory-adapted strain. To this end, a new fusion assay was developed on the basis of the principle of resonance energy transfer, using HeLa cells stably transfected with gp120/gp41 from the T-lymphotropic isolate HIV-1LA1 or the macrophage-tropic primary isolate HIV-1JR-FL. These cells fused with CD4+ target cell lines with a tropism mirroring that of infection by the two viruses. Of particular note, HeLa cells expressing HIV-1JR-FL gp120/gp41 fused only with PM1 cells, a clonal derivative of HUT 78, and not with other T-cell or macrophage cell lines. These results demonstrate that the envelope glycoproteins of these strains play a major role in mediating viral tropism. Despite significant differences exhibited by HIV-1JR-FL and HIV-1LAI in terms of tropism and sensitivity to neutralization by CD4-based proteins, the present study found that membrane fusion mediated by the envelope glycoproteins of these viruses had remarkably similar properties. In particular, the degree and kinetics of membrane fusion were similar, fusion occurred at neutral pH and was dependent on the presence of divalent cations. Inhibition of HIV-1JR-FL envelope glycoprotein-mediated membrane fusion by soluble CD4 and CD4-IgG2 occurred at concentrations similar to those required to neutralize this virus. Interestingly, higher concentrations of these agents were required to inhibit HIV-1LAI envelope glycoprotein-mediated membrane fusion, in contrast to the greater sensitivity of HIV-1LAI virions to neutralization by soluble CD4 and CD4-IgG2. This finding suggests that the mechanisms of fusion inhibition and neutralization of HIV-1 are distinct.
authors.affiliation: Progenics Pharmaceuticals, Inc., Tarrytown, New York 10591, USA.
authors.forename: V
authors.initials: V
authors.lastname: Litwin
authors.forename: K A
authors.initials: KA
authors.lastname: Nagashima
authors.forename: A M
authors.initials: AM
authors.lastname: Ryder
authors.forename: C H
authors.initials: CH
authors.lastname: Chang
authors.forename: J M
authors.initials: JM
authors.lastname: Carver
authors.forename: W C
authors.initials: WC
authors.lastname: Olson
authors.forename: M
authors.initials: M
authors.lastname: Alizon
authors.forename: K W
authors.initials: KW
authors.lastname: Hasel
authors.forename: P J
authors.initials: PJ
authors.lastname: Maddon
authors.forename: G P
authors.initials: GP
authors.lastname: Allaway
mesh_terms: D015703:Antigens, CD / Q000502:physiology; D015704:CD4 Antigens / Q000502:physiology*; D002460:Cell Line; D004735:Energy Transfer; D005434:Flow Cytometry / Q000379:methods; D015686:Gene Products, env / Q000502:physiology*; D015699:HIV Envelope Protein gp120 / Q000096:biosynthesis / Q000502:physiology*; D015700:HIV Envelope Protein gp41 / Q000096:biosynthesis / Q000502:physiology*; D015497:HIV-1 / Q000145:classification / Q000302:isolation & purification / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D007074:Immunoglobulin G; D008264:Macrophages / Q000821:virology; D008561:Membrane Fusion; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014162:Transfection
chemical_list: D015703:Antigens, CD; D015704:CD4 Antigens; D015686:Gene Products, env; D015699:HIV Envelope Protein gp120; D015700:HIV Envelope Protein gp41; D007074:Immunoglobulin G; D011993:Recombinant Fusion Proteins