Chemokine-receptor activation by env determines the mechanism of death in HIV-infected and uninfected T lymphocytes

There is considerable confusion concerning the mechanism of lymphocyte deat h during HIV infection. During the course of HIV infection, M-tropic viruse s (R5) that use CCR5 chemokine coreceptors frequently evolve to T-tropic vi ruses (X4) that use CXCR4 receptors. In this study we show that activation of the CD4 or CCR5 receptor by R5 HIVenv causes a caspase 8-dependent death of both uninfected and infected CD4 T cells. In contrast, CXCR4 activation by X4 HIVenv induces a caspase-independent death of both uninfected CD4 an d CD8 T cells and infected CD4 cells. These results suggest that activation of the chemokine receptor by HIVenv determines the mechanism of death for both infected and uninfected T lymphocytes.