title: Cell-cell spread of human immunodeficiency virus type 1 overcomes tetherin/BST-2-mediated restriction in T cells.
abstract: Direct cell-to-cell spread of human immunodeficiency virus type 1 (HIV-1) between T cells at the virological synapse (VS) is an efficient mechanism of viral dissemination. Tetherin (BST-2/CD317) is an interferon-induced, antiretroviral restriction factor that inhibits nascent cell-free particle release. The HIV-1 Vpu protein antagonizes tetherin activity; however, whether tetherin also restricts cell-cell spread is unclear. We performed quantitative cell-to-cell transfer analysis of wild-type (WT) or Vpu-defective HIV-1 in Jurkat and primary CD4(+) T cells, both of which express endogenous levels of tetherin. We found that Vpu-defective HIV-1 appeared to disseminate more efficiently by cell-to-cell contact between Jurkat cells under conditions where tetherin restricted cell-free virion release. In T cells infected with Vpu-defective HIV-1, tetherin was enriched at the VS, and VS formation was increased compared to the WT, correlating with an accumulation of virus envelope proteins on the cell surface. Increasing tetherin expression with type I interferon had only minor effects on cell-to-cell transmission. Furthermore, small interfering RNA (siRNA)-mediated depletion of tetherin decreased VS formation and cell-to-cell transmission of both Vpu-defective and WT HIV-1. Taken together, these data demonstrate that tetherin does not restrict VS-mediated T cell-to-T cell transfer of Vpu-defective HIV-1 and suggest that under some circumstances tetherin might promote cell-to-cell transfer, either by mediating the accumulation of virions on the cell surface or by regulating integrity of the VS. If so, inhibition of tetherin activity by Vpu may balance requirements for efficient cell-free virion production and cell-to-cell transfer of HIV-1 in the face of antiviral immune responses.
authors.affiliation: MRC Centre for Medical Molecular Virology, Division of Infection and Immunity, University College London, Windeyer Building, London, United Kingdom. c.jolly@ucl.ac.uk
authors.forename: Clare
authors.initials: C
authors.lastname: Jolly
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Booth
authors.forename: Stuart J D
authors.initials: SJ
authors.lastname: Neil
mesh_terms: D015703:Antigens, CD / Q000378:metabolism*; D015153:Blotting, Western; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism / Q000821:virology*; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D058851:GPI-Linked Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D015497:HIV-1 / Q000502:physiology*; D054298:Human Immunodeficiency Virus Proteins / Q000378:metabolism; D006801:Humans; D007365:Intercellular Junctions / Q000648:ultrastructure / Q000821:virology*; D019169:Jurkat Cells; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D054334:Viral Regulatory and Accessory Proteins / Q000378:metabolism; D014771:Virion / Q000502:physiology*; D014779:Virus Replication / Q000502:physiology*; D000074010:Bone Marrow Stromal Antigen 2; D000086082:Viroporin Proteins
chemical_list: D015703:Antigens, CD; D058851:GPI-Linked Proteins; D054298:Human Immunodeficiency Virus Proteins; D054334:Viral Regulatory and Accessory Proteins; C094572:BST2 protein, human; D000074010:Bone Marrow Stromal Antigen 2; C514859:vpu protein, Human immunodeficiency virus 1; D000086082:Viroporin Proteins