However, we found no evidence of enhanced EGFP expression in cells infected with a constant level of EGFP viruses and increasing concentrations of mCherry viruses, suggesting that infection with a second provirus did not reactivate silenced promoters via production of Tat in trans. However, our experimental system differs from that used by Brégnard in key ways that likely account for these discrepant findings. This evidence concerns the gene TAT and infection.