HIV-1 Tat protects CD4+ Jurkat T lymphoblastoid cells from apoptosis mediated by TNF-related apoptosis-inducing ligand

We have here investigated the effect of TNF-related apoptosis-inducing ligand (TRAIL), a new member of the TNF cytokine superfamily, on the survival of Jurkat lymphoblastoid cell lines stably transfected with plasmids expressing the wild-type or mutated (Cys22) human immunodeficiency virus type 1 (HIV-1) tat gene. Jurkat cells transfected with wild-type tat were resistant to TRAIL-mediated apoptosis, while Jurkat cells mock-transfected with the control plasmid or with a mutated nonfunctional tat cDNA were highly susceptible to TRAIL-mediated apoptosis. Also, pretreatment with low concentrations (10–100 ng/ml) of extracellular synthetic Tat protein partially protected Jurkat cells from TRAIL-mediated apoptosis. Taken together, these results demonstrated that endogenously expressed tat and, to a lesser extent, extracellular Tat block TRAIL-mediated apoptosis. Since it has been shown that primary lymphoid T cells purified from HIV-1-infected individuals are more susceptible than those purified from normal individuals to TRAILmediated apoptosis, our findings underscore a potentially important role of Tat in protecting HIV-1- infected cells from TRAIL-mediated apoptosis.