BaEV-LV GPs allow efficient transduction of immature naive CB T cells. (A) Freshly isolated total CB CD4⁺ T cells were prestimulated with IL-7 for 48 hours and subsequently transduced in the presence of RetroNectin with VSV-G-, RD114TR-, BaEVTR-, BaEVRless-, and H/F-LV, encoding the GFP reporter at an MOI of 10. Three days after transduction, cells were stained for human surface markers CD45RA, CD62L, and CD31, and the percentage of GFP⁺ cells in recent thymocyte emigrants (CD45RA⁺, CD62L⁺, CD31⁺) and more mature naive CB CD4⁺ T cells (CD45RA⁺, CD62L⁺, CD31^–) was determined by FACS analysis (mean ± SD; n = 3; **P < .01). (B) Distribution of the recent thymocyte emigrants (CD45RA⁺, CD62L⁺, CD31⁺) and more mature naive CB (CD45RA⁺, CD62L⁺, CD31^–) CD4⁺ T cell subpopulations upon incubation of CB T cells with the different vector pseudotypes as in panel A compared with untransduced T cells (mean ± SD; n = 4).