FIG. 4.
VSV-G-pseudotyped virions do not fuse efficiently to unstimulated CD4+ T cells. Unstimulated CD4+ T cells (A and B) or CD3/CD28 bead-stimulated CD4+ T cells (C and D) were spinoculated with BlaM-Vpr-containing pNL4-3Δenv pseudotyped with VSV-G [HIVΔenv(VSV-G)] (A and C) or BlaM-Vpr-containing pNL4-3 (wtHIV) (B and D). The viral inocula were matched to have equivalent fusion activity levels (50% fusion) in CEMss cells. After spinoculation and induction of fusion at 37°C, the cells were loaded with the dye CCF2-AM, incubated at 25°C for 12 h, and analyzed by flow cytometry. Gates were set both by using the corresponding uninfected control and by setting the gate that measures viral fusion at ∼1% background. The figure is representative of two experiments.