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Published online before print July 16, 2004

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© by The Society for Leukocyte Biology
Journal of Leukocyte Biology, doi:10.1189/jlb.0204100

Received for publication February 20, 2004.
Revised June 1, 2004.
Accepted for publication June 13, 2004.

Article

R5 HIV gp120-mediated cellular contacts induce the death of single CCR5-expressing CD4 T cells by a gp41-dependent mechanism

Retrovirology Laboratory, Fundació irsiCaixa, Hospital Universitari Germans Trias i Pujol, Universitat Autònoma de Barcelona, Catalonia, Spain

	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.

Key Words: coreceptors • cell death • fusion • caspases • envelope