CHRONICALLY HIV-1-INFECTED MONOCYTIC CELLS INDUCE APOPTOSIS IN COCULTURED T-CELLS

We have previously developed a human macrophage hybridoma model system to study the effect of HIV-1 infection on monocytic function. Upon co culture of one chronically (35 days postinfection) HIV-1-infected huma n macrophage hybridoma cell line, 43(HIV), there was a dose-dependent decrease in the viability of cocultured Ag-stimulated T cells associat ed with an increase in DNA strand breaks. Enhanced apoptosis was deter mined by labeling with biotinylated dUTP and propidium iodide, increas ed staining with annexin V, increased side light scatter and expressio n of CD95, and decreased forward light scatter and expression of Bcl-2 , There was also increased DNA strand breaks as determined by propidiu m iodide staining in unstimulated T cells cocultured with 43, and in T cells stimulated with anti-CD3 mAb and PHA, Pretreatment with 5145, a human polyclonal anti-gp120 Ab that recognizes the CD4 binding region , as well as with an anti-Fas ligand mAb blocked apoptosis in CD4(+) T cells but not in CD8(+) T cells. A soluble factor with a M-r below 10 ,000 Da was defined that induced apoptosis in CD4(+) and CD8(+) T cell s and B cells. SDS-PAGE analysis of the active fractions revealed a ba nd of 6000 Da that, after electroelution, had proapoptotic activity. T he pI of the activity was estimated to be between 6.5 and 7.0, In conc lusion, chronically HIV-1-infected monocytic cells induce apoptosis in bystander-, Ag-, anti-CD3-, and mitogen-stimulated T cells by multipl e factors, which may contribute to the depletion of lymphocytes induce d by HIV-1.