title: Infectious HIV-1 assembles in late endosomes in primary macrophages.
abstract: Although human immunodeficiency virus type 1 (HIV-1) is generally thought to assemble at the plasma membrane of infected cells, virions have been observed in intracellular compartments in macrophages. Here, we investigated virus assembly in HIV-1-infected primary human monocyte-derived macrophages (MDM). Electron microscopy of cryosections showed virus particles, identified by their morphology and positive labeling with antibodies to the viral p17, p24, and envelope proteins, in intracellular vacuoles. Immunolabeling demonstrated that these compartments contained the late endosomal marker CD63, which was enriched on vesicles within these structures and incorporated into the envelope of budding virions. The virus-containing vacuoles were also labeled with antibodies against LAMP-1, CD81, and CD82, which were also incorporated into the viral envelope. To assess the cellular source of infectious viruses derived from MDM, virus-containing media from infected cells were precipitated with specific antibodies. Only antibodies against antigens found in late endosomes precipitated infectious virus, whereas antibodies against proteins located primarily on the cell surface did not. Our data indicate that most of the infectious HIV produced by primary macrophages is assembled on late endocytic membranes and acquires antigens characteristic of this compartment. This notion has significant implications for understanding the biology of HIV and its cell-cell transmission.
authors.affiliation: Cell Biology Unit, Medical Research (MRC) Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK.
authors.forename: Annegret
authors.initials: A
authors.lastname: Pelchen-Matthews
authors.forename: Beatrice
authors.initials: B
authors.lastname: Kramer
authors.forename: Mark
authors.initials: M
authors.lastname: Marsh
mesh_terms: D015703:Antigens, CD / Q000378:metabolism; D002451:Cell Compartmentation / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology*; D015683:Gene Products, gag / Q000378:metabolism; D015488:HIV Antigens / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism* / Q000472:pathogenicity / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D007425:Intracellular Membranes / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology*; D051861:Kangai-1 Protein; D051907:Lysosomal Membrane Proteins; D008264:Macrophages / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008854:Microscopy, Electron; D009000:Monocytes / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology; D011518:Proto-Oncogene Proteins; D011930:Reaction Time / Q000502:physiology; D015682:Retroviridae Proteins, Oncogenic / Q000378:metabolism; D060225:Tetraspanin 28; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology; D014759:Viral Envelope Proteins / Q000378:metabolism; D014764:Viral Proteins; D014779:Virus Replication / Q000502:physiology*; D017201:Virus Shedding / Q000502:physiology*; D054301:gag Gene Products, Human Immunodeficiency Virus
chemical_list: D015703:Antigens, CD; C554798:CD81 protein, human; C497688:CD82 protein, human; D015683:Gene Products, gag; D015488:HIV Antigens; D051861:Kangai-1 Protein; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D015682:Retroviridae Proteins, Oncogenic; D060225:Tetraspanin 28; D014759:Viral Envelope Proteins; D014764:Viral Proteins; D054301:gag Gene Products, Human Immunodeficiency Virus; C054858:p17 protein, Human Immunodeficiency Virus Type 1; C060954:p24 protein, Human T-lymphotropic virus 1