Apoptotic Killing of HIV-1–Infected Macrophages Is Subverted by the Viral Envelope Glycoprotein
Figure 2
Death Receptor Expression on Macrophages Infected with Wild-Type or Envelope-Minus HIV-1 Variants
(A) Macrophages were infected with VSV-pseudotyped wild-type HIV-1 (HIV-1HSAWT) or envelope-minus (HIV-1HSAΔenv) variants expressing HSA in place of Vpr. Levels of TRAIL-R1, Fas, and TWEAK-R expression on infected (HSA positive) cells was determined by flow cytometry.
(B) Statistical analysis of mean TRAIL-R1 expression from macrophages from seven donors infected with pseudotyped HIV-1HSA wild-type or envelope-minus viruses relative to mock-infected (ANOVA; error bars, SEM).
(C) The HIV-1 envelope negates macrophage susceptibility to apoptosis by TRAIL. Macrophages were infected with pseudotyped wild-type or Δenv minus HIV-1LAI variants. At 8 d post-infection, cultures were incubated with soluble TRAIL (100 ng/ml−1). Apoptosis was determined by ELISA for active (cleaved) caspase 3. The viral envelope increases macrophage survival in the presence of TRAIL. Eight days after infection with pseudotyped HIV-1LAI wild-type or Δenv viruses, macrophages were maintained with (D) or without (E) soluble TRAIL (100 ng/ml−1), and the percentage of viable cells (cell death ELISA) remaining over time was determined. Macrophage half-life was calculated from the linear regression slope over 24 h, compared by ANOVA, and expressed as mean value in days ± SEM. Concentrations of TRAIL required to impact viability and virus output in macrophages infected with wild-type and Δenv HIV-1 variants. Macrophages infected with HIV-1LAI wild-type or Δenv viruses were incubated with increasing concentrations of soluble TRAIL and cell viability (F) and virus production (G) were determined after 16 h.
(H) Activated CD8+ T cells selectively suppress virus production by HIV-1 Δenv-infected macrophages. Wild-type and Δenv HIV-1–infected macrophages were incubated with anti-CD3/CD28 stimulated autologous CD8+ TRAIL+ T lymphocytes for 4 h. Virus production was determined after an additional 24 h. T cells were pre-incubated with recombinant TRAIL-R1 or control receptor (5 μg/ml−1) for 1 h prior to co-culture.