FIG. 4.

Vpu modulates HIV-1 infectivity with MLV/GaLV Env. Infectivity of MLV Env, MLV/GaLV Env, or an empty DNA vector (control) pseudotyped with HIV-1 was determined in the absence (▪) or presence (□) of Vpu. Infectivity was measured as infectious units (I.U.) per ml of viral supernatant transferred from transfected 293FT cells to 293T mCAT-1 cells 48 h posttransfection. The averages and standard deviations of infectious units per milliliter of seven independent experiments with the same combinations are shown. Significant differences (*, P < 0.05) and nonsignificant differences (NS) were determined by two-tailed Student's t test for each envelope type in the presence or absence of Vpu.