Persistence of viral DNA in transduced cells during a 14 day time period. 293T cells were transduced at MOI 1 (relative DNA titer) with the four vectors utilizing the CMV-promoter. After 3, 6, 14 and 27 days cells were harvested and the proviral load determined by qPCR using primers LV2 and ALB. The vectors containing two separated copies of the insulator (d2 × 250 bp.CMV and 1.2 kb.CMV) elicit a significant (*, p < 0.05) drop in proviral load within the first 6 days after transduction compared to control vectors, CMV.SIN and s2 × 250 bp.CMV. The experiment was continued for 27 days with no change in proviral load compared to the 14 days time point. Error bars denote standard error of the mean.