title: R5 HIV gp120-mediated cellular contacts induce the death of single CCR5-expressing CD4 T cells by a gp41-dependent mechanism.
abstract: The use of CXC chemokine receptor 4 (CXCR4) and CC chemokine receptor 5 (CCR5) by X4 and R5 human immunodeficiency virus (HIV) envelopes (Env) influences HIV cytopathicity. Here, we have evaluated the role of CCR5 and gp41 in Env-induced cell death occurring during the contacts of uninfected, primary cells with MOLT cells infected with different R5 and X4 HIV isolates. As reported for X4-Env, R5 HIV-infected cells destroyed CD4 T cells expressing the appropriate coreceptor by inducing the formation of syncytia and the death of single target cells. Therefore, only the small (<10%) CCR5+ subset of primary CD4 T cells was sensitive to cellular presentation of R5-Env, and CCR5-CD4 T cells showed complete resistance to R5-Env-mediated cell death. X4- and R5-infected cells killed single primary cells by a common mechanism that was dependent on gp41 function and induced a rapid loss of mitochondrial membrane potential and plasma membrane integrity in target cells. Single-cell death was not affected by the blockade of HIV replication in target cells or G-protein signaling through CXCR4/CCR5. In contrast, caspase inhibition (Z-Val-Ala-Asp-fluoromethylketone) profoundly changed the outcome of cell-to-cell contacts by reducing the number of single dead CD4 T cells and increasing the rate of syncytium formation. In conclusion, X4 and R5 HIV Env share a common gp41-dependent mechanism to kill CD4 T cells during cellular contacts. Env tropism and coreceptor expression but not differential killing mechanisms seem to govern the extent of cytopathic effects induced by HIV infection.
authors.affiliation: Retrovirology Laboratory, Fundació irsiCaixa, Hospital Universitari Germans Trias i Pujol, Universitat Autònoma de Barcelona, Catalonia, Spain. jblanco@ns.hugtip.scs.es
authors.forename: Julià
authors.initials: J
authors.lastname: Blanco
authors.forename: Jordi
authors.initials: J
authors.lastname: Barretina
authors.forename: Bonaventura
authors.initials: B
authors.lastname: Clotet
authors.forename: José A
authors.initials: JA
authors.lastname: Esté
mesh_terms: D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D061945:Caspase Inhibitors; D016923:Cell Death; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015699:HIV Envelope Protein gp120 / Q000378:metabolism*; D015700:HIV Envelope Protein gp41 / Q000378:metabolism*; D015658:HIV Infections / Q000276:immunology / Q000378:metabolism / Q000821:virology; D015497:HIV-1 / Q000472:pathogenicity*; D006801:Humans; D019713:Receptors, CCR5 / Q000378:metabolism*; D019718:Receptors, CXCR4 / Q000378:metabolism; D014779:Virus Replication
chemical_list: D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D015699:HIV Envelope Protein gp120; D015700:HIV Envelope Protein gp41; D019713:Receptors, CCR5; D019718:Receptors, CXCR4