Presence of the intact, unrearranged vector genome in leukocyte DNA. Peripheral blood was obtained from animal CJ5B on day 183, from animal RQ2617 on day 135, and from animal RQ3556 on day 86 following infusion of autologous, transduced CD34⁺ cells. DNA was prepared, and a Southern blot was performed using standard techniques. For each reaction, 10 μg DNA was restricted with Bgl II, which cuts twice in the vector genome. The probe was a GFP fragment from the vector plasmid. Serial dilutions of control DNA were prepared by mixing DNA from a K562 erythroleukemia cell clone having a single copy of the vector genome with DNA from nontransduced K562 cells in the proportions indicated. Equivalency of loading of the DNA from lane to lane was verified by staining the gel with ethidium prior to DNA transfer (data not shown).