TR66-LV mediates efficient in vivo gene delivery into all T-cell subpopulations. (A) Experimental outline: NSG mice were transplanted with αCD3/αCD28-activated human PBMC by intraperitoneal (IP) injection followed by vector administration 1 day later and analyzed for transgene expression by flow cytometry 7 days after vector application. (B) Representative dot plots show transduced T cells gated from all viable single CD3⁺ cells harvested from the peritoneal cavity at 7 days after vector injection. (C-E) Scatter plots summarize the percentages of GFP⁺ cells gated from all viable single CD3⁺ cells for peritoneum (C), blood (D), and spleen (E). (F-H) Respective scatter plots of GFP⁺ cells gated from CD4⁺ and CD8⁺ T cells isolated from peritoneum (F), blood (G), and spleen (H) at the day of analysis. N = 3 mice per group, mean ± SD. **P < .01, ***P < .001, ****P < .0001 by 1-way analysis of variance with Sidak's or Dunnett's correction.