FIG. 2.

Western blot analysis of viral proteins in viral particles produced by four-plasmid cotransfection. Eight micrograms of pNL4-3, 6 μg of pGP-RRE3, 7 μg of pH4Z, 4 μg of pRV67, and 3 μg of pCI-vpr were transfected, and the total amount of DNA was kept at 20 μg by addition of pCI-neo. At 48 h after transfection, viral pellets were collected from 1 ml of supernatant and separated on sodium dodecyl sulfate–10% (A) or –20% (B) polyacrylamide gels. Expression of viral proteins was visualized by using HIV-1-positive human serum (A) or rabbit anti-Vpr serum (B). Kb, kilodaltons.