Comparison of different suicide-gene strategies for the safety improvement of genetically manipulated T cells.

Use of adoptive T-cell therapy (ACT) is increasing; however, T-cell therapy can result in severe toxicity. Consequently, several suicide-gene strategies that allow selective destruction of the infused T cells have been described. We compared effectiveness of four such strategies in vitro in Epstein Barr virus (EBV)-cytotoxic T lymphocytes (CTLs). Herpes simplex virus thymidine kinase (HSV-TK), human inducible caspase 9 (iCasp9), mutant human thymidylate kinase (mTMPK), and human CD20 codon optimized genes were cloned in frame with 2A-truncated codon optimized CD34 (dCD34) in a retroviral vector. Codon-optimization considerably improved CD20 expression. EBV-CTLs could be efficiently transduced in all constructs, with transgene expression similar to the control vector containing dCD34 alone. Expression was maintained for prolonged cultures. Expression of the suicide genes was not associated with alterations in immunophenotype, proliferation, or function of CTLs. Activation of HSV-TK, iCasp9, and CD20 ultima...