AEGiS-11IAC: Human immunodeficiency virus-mediated programmed cell death: discrimination of different pathways by the use of BCL-2.

11th International AIDS Conference

Vancouver, British Columbia — July 7-12, 1996

Human immunodeficiency virus-mediated programmed cell death: discrimination of different pathways by the use of BCL-2.

Int Conf AIDS 1996 Jul 7-12; 11:8 (abstract no. We.A.261)
Kolesnitchenko V, King L, Korsmeyer SJ, Cohen DI; LTCB, NCI, NIH, Bethesda, MD, USA. Fax: 301-496-8394. E-mail: vk5q@nih.gov.

OBJECTIVE: To better understand the HIV-initiated cell death process, we have studied T cell lines transfected to stably overexpress the bcl-2 oncoprotein, which functions to inhibit multiple forms of PCD.

METHODS: Bcl-2 overexpression was engineered into Jurkat CD4+ T-cell lines and Jurkat HIVenv (Jurkat T-cell lines also stably expressing HIV-1 envelope glycoproteins gp120 and gp41, Tat protein, and Rev protein) T cell lines. Cell death was then initiated either by infection with HIV-1, or by coculture between CD4+ cells and Jurkat HIVenv cells.

RESULTS: In all cases cell killing persisted, and was substantially unaltered by bcl-2 overexpression. Cell viability was slightly (10%) higher in bcl-2 overexpressing cells than in controls and cell death was delayed approximately 48 hours. In contrast, apoptotis induced by sodium butyrate was completely (80%-90%) inhibited in all bcl-2 overexpressing cell lines, establishing that the overexpression of bcl-2 protein functioned to suppress apoptosis in these T cells. To test Fas killing in HIV-mediated cell death, infections were performed in the presence of blocking soluble IgG-Fas (10 micrograms/ml) and in Molt-4 cells which are insensitive to Fas-triggered cell death. HIV-1 killed Fas resistant Molt-4 and Fas sensitive Jurkat cells equally and was blocked only 5%-10% by IgG-Fas. Following reports from other laboratories that Tat could enhance Fas-triggered apoptosis, we generated Jurkat cell lines exclusively expressing the HIV Tat protein to further study the Fas-dependent component of HIV-mediated cell death. When these Tat-expressing cell lines were stimulated to undergo apoptosis with anti-human Fas antibody, CH-11, they were much more susceptible to Fas-induced cell death (15%-30%) than controls, and bcl-2 overexpression strongly (75%) inhibited this cell death.

CONCLUSION: Our results that bcl-2 can inhibit Tat-induced cell death, but does not block the majority of HIVenv-mediated PCD, establish that an important form of HIV-mediated killing proceeds by a bcl-2 and Fas-independent pathway. Our observations support the conclusion that several death pathways, and at least two HIV genes (env and tat), are involved in triggering distinct cell death pathways that can be discriminated by their sensitivity to bcl-2.

Keywords: AEGIS, Antigens, CD95, Apoptosis, Jurkat Cells, Gene Products, tat, HIV-1, Genes, bcl-2, T-Lymphocytes, Antigens, CD4, Butyric Acid, Oncogenes, T-Lymphocytes, Cytotoxic, Human, genetics, ICA11

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