AEGiS-11IAC: HIV-1 infection, apoptosis, and CD4 T cell depletion in vitro and in hu-PBL-SCID mice.

11th International AIDS Conference

Vancouver, British Columbia — July 7-12, 1996

HIV-1 infection, apoptosis, and CD4 T cell depletion in vitro and in hu-PBL-SCID mice.

Int Conf AIDS 1996 Jul 7-12; 11:9 (abstract no. We.A.265)
Mosier DE, Glynn JM, Ling Y, Gulizia R, Atencio I, McKinney D, McElligott DL; The Scripps Research Institute, La Jolla, CA, USA. Fax: 619 554-6627. E-mail: dmosier@scripps.edu.

OBJECTIVES: To determine the contribution and mechanism of apoptosis in acute HIV-1 infection in vitro and in hu-PBL-SCID mice.

METHODS: CD4-positive human T cell lines or primary cells were infected in vitro with HIV-1. Alternatively, hu-PBL-SCID mice were infected with wild type or nef-deleted HIV-1 isolates (supplied by D. Trono and R. Collman). The extent of apoptosis was determined by the TUNEL assay, which scores double-stranded DNA breaks. Survival of CD4-positive T cells was followed by flow cytometry, and HIV-1 replication was measured by p24 levels, quantitative proviral PCR, or competitive RNA PCR. Inhibitors of apoptosis added to cultures were tripeptide ICE-family protease inhibitors or antagonistic anti-Fas antibodies (provided by D. Lynch, Immunex).

RESULTS: HIV-1 infection led to the induction of apoptosis (TUNEL-positivity) in 15-50% of infected primary T cells or H9 T cells. This apoptosis was blocked efficiently by ICE-family protease inhibitors, but not by the M3 antagonistic anti-Fas antibody or by an inhibitor of HIV-1 protease. Apoptosis was observed at all phases of the cell cycle with no evidence of a G2 block. In hu-PBL-SCID mice, infection with HIV-1 led a rapid loss of CD4-positive cells with only minor evidence of increased apoptosis. Apoptotic bodies were observed in macrophages, suggesting a rapid and efficient clearance of dying cells. Nef-deleted virus caused a slower loss of CD4-positive T cells even at equivalent virus load, suggesting a role for nef in causing CD4-positive T cell death separate from its effect on viral infectivity.

CONCLUSIONS: Apoptosis is responsible for death of infected CD4-positive T cells in culture and is mediated by the activity of ICE-family proteases. Apoptosis in vitro is independent of a Fas-mediated pathway. The contribution of apoptosis to CD4-positive T cell depletion in the hu-PBL-SCID animal model is more difficult to determine, mainly because of the very rapid clearance of apoptotic cells. Deletion of nef may result in a failure to prime T cells for apoptosis, and result in the delayed loss of CD4-positive T cells observed in hu-PBL-SCID mice infected with nef-deleted HIV-1.

Keywords: AEGIS, HIV Infections, Mice, SCID, Antigens, CD4, HIV-1, Apoptosis, Lymphocyte Depletion, Antigens, CD95, T-Lymphocytes, Caspase 1, In Situ Nick-End Labeling, HIV Protease Inhibitors, Virus Replication, Protease Inhibitors, HIV Protease, Human, Mice, Animal, In Vitro, virology, ICA11

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