Efficient LV-mediated ADA2 transfer in HDs’ HSPCs. (A) Schematic representation of LV-ADA2 and LV-GFP used in the study. Percentage of transduction (B) and VCN per genome (C) were evaluated in colonies derived from CD34⁺ HSPCs from 3 independent HDs transduced with LV-ADA2 at increasing vector concentrations (MOI of 10, 50, and 100). The numbers in panel C indicate the median VCN for each condition. (D) The viability of HDs’ CD34⁺ HSPCs in BM was examined before prestimulation (day 0), postovernight transduction (Post-TR) with LV-ADA2 and LV-GFP, and after in vitro expansion for 14 days (Post-LC) in the presence of support cytokines. Numbers indicate the expansion rate between in vitro expanded cells (Post-LC) and cells recovered after transduction (Post-TR). (E) Total numbers and percentages of single colonies derived from myeloid (CFU-GM) and erythroid (BFU-E) progenitors in UT and ADA2- or GFP-transduced conditions. Data in (B,D-E) are mean ± standard deviation; data in (C) are shown as box-and-whisker plots. **P < .01, ***P < .001; Mann-Whitney U test.