Objective: To clarify the molecular mechanisms of HIV-induced apoptosis.
Design: The assessment of expression patterns for genes affecting the interrelated cell cycle and apoptosis processes in HIV-1LAI-infected T lymph oblastoid (CEM) cells, as well as CD4 and CD8 cells from HIV-infected individuals and controls.
Methods: The kinetics of HIV infection in CEM cells were defined by flow cytometry of green fluorescent protein expression from a reporter vector. Apoptosis of CEM cells was measured by propidium iodine staining and flow cytometry. Gene expression levels were determined by a multiprobe RNase protection assay.
Results: The infection and apoptosis of CEM cells were associated with enhanced expression of Bax, Bcl-2, Bcl-XL and caspase 1 (ICE). There was increased expression of Bcl-2 and caspase 1 and decreased expression of cyclin-dependent kinase inhibitor p21CIP1 in CD4 cells of HIV-infected individuals compared with uninfected controls. The CD8 cells of HIV-infected individuals exhibited increased expression of Bcl-2, Bcl-XL, Bax and caspase 1 but, in contrast to the CD4 subset, they showed elevated expression of p21CIP1 and p16INK4a compared with controls.
Conclusions: The Bax increase in CEM cells appears to be a direct effect associated with a high frequency of infection and apoptosis, because it was not found in the CD4 cells of patients. In contrast, the increase of Bax in the CD8 cells of patients seems to be an indirect effect. Increases in Bcl-2, Bcl-XL and caspase 1 in HIV-infected CEM cells may be caused by both direct and indirect mechanisms, because they also occurred in CD4 and CD8 cells of HIV-infected individuals. In addition, the low expression of p21CIP1 in the CD4 subset of HIV-infected individuals could promote apoptosis, whereas the high expression of p21CIP1 and p16INK4a in the CD8 subset may lead to a state of anergy, akin to replicative senescence.
From the The Scripps Research Institute, Department of Immunology, La Jolla, CA 92037, and *University of California at San Diego, Department of Medicine, La Jolla, CA 92093, USA. This is publication no. 11619-IMM from the Department of Immunology, The Scripps Research Institute, La Jolla, CA, USA
Sponsorship: This work was supported by NIH grants AI34215 (A.N.T.), CA67394, 5P30A136214 UCSD Center for AIDS Research (J.C.) and a fellowship from the Deutsche Forschungsgemeinschaft, Germany (U.J.S.).
Requests for reprints to: Professor Argyrios N. Theofilopoulos, Immunology Department, The Scripps Research Institute, 10550 North Torrey Pines Road/IMM3, La Jolla, CA 92037, USA.
Date of receipt: 8 May 1998; revised: 20 October 1998; accepted: 26 October 1998.