Journal of Biological Chemistry
Volume 270, Issue 50, 15 December 1995, Pages 29690-29697
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Cell Biology and Metabolism
T-lymphocytes from AIDS Patients Are Unable to Synthesize Ribonucleotides de Novo in Response to Mitogenic Stimulation: IMPAIRED PYRIMIDINE RESPONSES ARE ALREADY EVIDENT AT EARLY STAGES OF HIV-1 INFECTION(∗)

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Proliferative defects have been reported at the level of DNA synthesis, even in T-lymphocytes from asymptomatic human immunodeficiency virus type-1+ (HIV-1+) patients. Since purine and pyrimidine ribonucleotide availability is crucial for proliferation, we compared the ability of HIV-1 and HIV-1+ T-lymphocytes (>95% CD4+ and CD8+) to activate de novo biosynthetic and salvage pathways following phytohemagglutinin stimulation using 14C-labeled precursors.

The striking abnormality already detectable in asymptomatic patients' cells was the impaired ability of CTP, UDP-Glc, and UTP pools to expand over 72 h (44-70% of control), although ATP and GTP pools and responses were normal. In symptomatic patients, resting T-cells showed markedly reduced pyrimidine pools (53-74% of control) with no change following activation. Relatively normal ATP, GTP, and NAD pools masked the same impaired response of de novo synthesis to activation, with ATP and GTP being reduced by 50% at 48 h. Purine salvage was more active than the control in unstimulated HIV-1+ cells.

This impaired de novo synthesis in HIV-1+ T-lymphocytes severely restricts the availability of ribonucleotides for vital growth-related activities such as membrane expansion and strand break repair as well as DNA and RNA synthesis. The data indicate that resting T-lymphocytes from symptomatic patients survive through enhanced salvage, but that stimulation induces metabolic cell death, and provide an explanation for the activation-associated lymphocyte death seen in HIV-1+ T-lymphocytes.

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This work was supported by the Medical Research Council (to H. A. S.) and by NATO Grant CRG.921365 (to K. R.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.