Efficient HPC transduction with use of high levels of vector. Transduction efficiencies in a NOD-SCID mouse 8 weeks after infusion with CD34⁺ progenitors transduced at approximately 500 TU/cell with high-speed centrifuged vector for 4 consecutive days. Cells isolated from the bone marrow were analyzed by flow cytometry. Percentages of eGFP-expressing human cells are shown in the upper right corner.