Schematic representation of HIV-1–based EGFP expression vectors.

(A) pHR′CMV-EGFP, pHR′PGK-EGFP, and pHR′MPSV-EGFP are HIV-1–based gene transfer vectors generated from pHR'CMV-LacZ,8 in which the CMV promoter was replaced with either PGK or MPSV promoters, and the transgene LacZ was replaced with EGFP, as described in “Materials and methods.” (B) Efficacy of different promoters in driving long-term transgene expression in lymphoid cell lines and activated primary PBLs after HIV-1 vector-mediated gene transfer. Cells were transduced with VSV-G peudotyped, accessory proteins deleted pHR′ vectors carrying EGFP driven by 3 different promoters (CMV, PGK, and MPSV) at an MOI of 5 to 10. Transduced lymphoid cell lines and primary activated human PBLs were cultured in vitro for 4 months and 2 weeks, respectively, before FACS analysis. Fluorescence of untransduced cells is represented by open histograms, whereas the shaded gray areas represent EGFP fluorescence derived from transduced cells. Data shown are representative of similar results obtained from 2 independent experiments.