Replication of the T20-dependent GIA-SKY mutant and the GIA-SKY-G431R revertant virus. Molecular clones were transfected in SupT1 cells that were cultured with (100 ng/ml) and without T20. Virus replication curves were made over a 7-day period. Closed circles represent the original GIA-SKY mutant virus and open circles the GIA-SKY-G431R revertant. This is a representative experiment, similar results were observed in 3 repeated experiments including results in figure 4, top.