Detection and persistence of transduced CD4⁺ lymphocytes in the PB. Following each reinfusion of transduced lymphocytes, peripheral blood samples were isolated at regular intervals and used to isolate PBMC. Semiquantitative PCR for the Neo^R gene was performed on the genomic DNA isolated from the PBMC. The Neo^R PCR product was detected by Southern blotting and hybridization with a Neo^R-specific oligonucleotide. All samples were normalized to PCR reactions performed using the β-actin gene. The percent transduction was determined by comparison of the normalized Neo^R signal from the experimental samples to a Neo^R(+) standard curve prepared by isolating genomic DNA from predetermined percentages of G1N vector transduced SupT1 cells and nontransduced rhesus PBL. The percentage of Neo(+) cells in the standard curve were 10%, 1%, 0.1%, and 0.01%. The percentage of transduced cells in each animal following each reinfusion is plotted on a single graph per animal and the number of transduced PBL for each infusion is shown in the upper right corner of each plot.