qPCR measurements of the average vector copy/cell in blood cell samples obtained after transplantation. Separate qPCR analyses were performed on granulocytes (Grans) and PBMC fractions with primer/probe sets specific for the MND-ADA vector or the GCsapM-ADA vector provirus. (A) Results from subjects not receiving busulfan conditioning and remaining on ERT (201-204) and (B) results from subjects having ERT withdrawn and receiving busulfan before transplantation (301-306).