The Cell Death-Inducing Ability of Glycoprotein 120 from Different HIV Strains Correlates with Their Ability to Induce CD4 Lateral Association with CD95 on CD4+ T Cells

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Abstract
CD4 cross-linking by HIV gp120 triggers CD4(+) T cell death. Several authors have suggested that this effect is mediated by CD95, but this possibility is debated by other authors. In a previous work, we found by cocapping that gp120(451) and gp120(MN), but not gp120(IIIB), induce lateral association of CD4 with CD95 on the T cell surface. In this work, we used fluorescence resonance energy transfer to confirm that CD4/CD95 lateral association is induced by gp120(451), but not gp120(IIIB) Moreover, we found that gp120 ability to induce the CD4/CD95 association correlates with ability to induce cell death, since gp120(451) and gp120(MN) induced higher levels of cell death than did gp120(IIIB) in PHA-derived CD4(+) T cell lines. CD95 involvement in gp120-induced cell death was confirmed by showing that gp120(451) and gp120(MN) did not induce death in CD4(+) T cells derived from patients with autoimmune/lymphoproliferative disease (ALD) and decreased CD95 function, Cell death induced by gp120(MN) was inhibited by a recombinant CD95/IgG.Fc molecule blocking the CD95/CD95L interaction, However, inhibition was late and only partial, These data suggest that the gp120-induced CD4/CD95 association exerts a dual effect: an early effect that is independent of CD95L and may be due to direct triggering of CD95 by gp120, and a late effect that may be due to sensitization of CD95 to triggering by CD95L. In line with the former effect, cell treatment with gp120(MN) activated caspase 3 in the presence of Fas/IgG.Fc, which shows that cell death induced by gp120(MN) independently of CD95L uses the same pathway as CD95.