Mouse T-cells do not support CMV-driven reporter gene expression following VSV-G-mediated virion entry. Fusion of the VSV-G pseudotyped lentiviral vector carrying BlaM-Vpr (VSV-G HIV-CMV-GFP BlaM-Vpr) and subsequent GFP reporter gene expression was analyzed in (A) human MT-4 and (B) mouse S1A.TB T-cell lines by flow cytometry 6 h and 3 d p.i., respectively. Cells were challenged with the VSV-G pseudotyped vector either in the presence of the neutralizing anti-VSV-G monoclonal antibody I1, the NNRTI efavirenz, or left untreated. Shown are representative FACS dot plots of viable T-cells (gate R1; left panels) for the detection of the cleaved CCF2 substrate (gate R2; blue color; upper panels in A and B), reflecting HIV-1 entry, or early CMV-driven GFP expression (gate R2, lower panels in A and B). The relative percentage of cells in R2 is given.