The DISC-HSV β-GAL vector transduces CD34⁺ cells with high efficiency. The x-axis denotes the intensity of β-GAL staining 48 hours after transduction with the DISC-HSV vector at various pfu/cell. The myeloid and lymphoid subpopulations were first gated by forward-versus-side scatter (FSC v SSC) (inset fig), with β-GAL expression in the CD34⁺ subset displayed separately for each population. *pfu/cell:- for details of titering see Materials and Methods section.