Pseudotyping human immunodeficiency virus type 1 (HIV-1) by the glycoprotein of vesicular stomatitis virus targets HIV-1 entry to an endocytic pathway and suppresses both the requirement for Nef and the sensitivity to cyclosporin A.
Human immunodeficiency virus type 1 (HIV-1) normally enters cells by direct fusion with the plasma membrane. In this report, HIV-1 particles capable of infecting cells through an endocytic pathway are described. Chimeric viruses composed of the HIV-1 core and the envelope glycoprotein of vesicular stomatitis virus (VSV-G) were constructed and are herein termed HIV-1(VSV) pseudotypes. HIV-1(VSV) pseudotypes were 20- to 130-fold more infectious than nonpseudotyped HIV-1. Infection by HIV-1(VSV) pseudotypes was markedly diminished by ammonium chloride and concanamycin A, a selective inhibitor of vacuolar H+ ATPases, demonstrating that these viruses require endosomal acidification to achieve productive infection. HIV-1 is thus capable of performing all of the viral functions necessary for infection when entry is targeted to an endocytic route. Maximal HIV-1 infectivity requires the presence of the viral Nef protein and the cellular protein cyclophilin A (CyPA) during virus assembly. Pseudotyping by VSV-G markedly suppressed the requirement for Nef. HIV-1(VSV) particles were also resistant to inhibition by cyclosporin A; however, the deleterious effect of a gag mutation inhibiting CyPA incorporation was not relieved by VSV-G. These results suggest that Nef acts at a step of the HIV-1 life cycle that is either circumvented or facilitated by targeting virus entry to an endocytic pathway. The findings also support the hypothesis that Nef and CyPA enhance HIV-1 infectivity through independent processes and demonstrate a mechanistic difference between reduction of HIV-1 infectivity by cyclosporin A and gag mutations that decrease HIV-1 incorporation of CyPA.
Aiken
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Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2363, USA. chris.aiken@mcmail.vanderbilt.edu
D000591:Amino Acid Isomerases / Q000502:physiology; D002352:Carrier Proteins / Q000502:physiology; D016572:Cyclosporine / Q000378:metabolism / Q000494:pharmacology*; D004705:Endocytosis; D015683:Gene Products, gag / Q000378:metabolism; D015693:Gene Products, nef / Q000502:physiology*; D015497:HIV-1 / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D008562:Membrane Glycoproteins; D019696:Peptidylprolyl Isomerase; D014759:Viral Envelope Proteins / Q000502:physiology*; D054311:nef Gene Products, Human Immunodeficiency Virus
D002352:Carrier Proteins; C028391:G protein, vesicular stomatitis virus; D015683:Gene Products, gag; D015693:Gene Products, nef; D007166:Immunosuppressive Agents; D008562:Membrane Glycoproteins; D014759:Viral Envelope Proteins; D054311:nef Gene Products, Human Immunodeficiency Virus; D016572:Cyclosporine; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase