RDTR/SCFHA-displaying LVs preferentially transduce hCD34⁺ cells in whole CB–containing active human complement. (A) Outline of the experimental setup. Total hCB-containing active complement was incubated with RDTR- or VSV-G–LVs in the presence of rSCF (50 ng/mL) or with vectors co-displaying the RDTR or VSV-G together with SCFHA glycoprotein without the addition of exogenous cytokines. Vectors were used at MOI = 0.001 calculated for the total number of WBCs and RBCs present in the blood sample. After 6-8 hours of incubation with the LVs, the CD34⁺ cells were isolated by positive selection and were cultured in medium containing 50 ng/mL of recombinant rSCF. After removal of the CD34⁺ cells, the residual MCs were cultured in RPMI supplemented with anti-CD3, anti-CD28, and rhIL-2. After 3 days of culture, transduction of very early progenitors (CD34⁺GFP⁺ cells) and T cells (CD3⁺GFP⁺ cells) in the MC fraction was analyzed by FACS. The dot blots are represented in panel B. The percentages of CD34⁺GFP⁺ cells (left) and GFP⁺ T cells (right) are indicated. The data are representative of 5 experiments. (C) Comparison of the transduction efficiencies of early progenitors (CD34⁺ cells) and T cells (CD3⁺ cells) in the whole CB sample.