Schematic of vector systems to express CAR transgenes used in clinical trials. (A) Two SB DNA plasmids expressing a (CAR) transposon and a hyperactive transposase (eg, SB11). Transposition occurs at a TA dinucleotide sequence when the transposase enzymatically acts on the internal repeat flanking the transposon. (B) A recombinant retroviral vector showing the long terminal repeats (LTR) containing the promoter flanking the CAR. SD and SA are the splice donor and splice acceptor sites, respectively, and ψ is the viral packaging signal. (C) A self-inactivating recombinant lentiviral vector construct containing the LTR, ψ, SD and SA sites, HIV Rev response element (RRE), HIV central polypurine tract (cPPT), CAR under control of an internal promoter, and the wood-chuck hepatitis virus posttranscriptional regulatory element (WPRE).