The 293T cell line was used for transient lentiviral vector production. The lentiviral vector plasmid pRRL.sinCMV-TK/ eGFPpre (5 mg) or pRRL.sinCMVeGFPpre (5 mg), the HIV gagpol-REV expression plasmid pCMV-dR8.91(12.5 mg) [21] and 2 mg of the envelope expression plasmid pHCMV-LCMV-GP [14] or pCMV-G [23] were cotransfected into 293T cells and concentrated as described previously [18] . For the production of retroviral vectors, 293T cells were transfected with 7.5 mg of pMP71-eGFP-pre, 12.5 mg of pSV-Mo-MLVgagpol, and 2 mg of the envelope expression plasmid pHCMV-LCMV-GP [14] or pCMV-G [23] . Vectors were harvested and concentrated as described previously [24] .