Drosophila cells transfected with MHC I and a number of costimulatory molecules including CD54,CD58,CD70,and CD80 are potent artificial antigen presenting cells(APCs)for the generation of antigen-specific cytotoxic T lymphocytes(CTLs)in vitro.Using Drosophila APCs,CTLs specific for melanoma antigens have been generated in vitro and adoptively transferred to melanoma patients.However,the recent discovery that Drosophila cells can carry insect viruses raises the potential risk of Drosophila APCs transmitting xenogenic viruses to patient CTLs.In this study,we have investigated photo-reactive methods to inactivate insect viruses in APCs.A clinical grade psoralen compound,UVADEX in combination with UV-irradiation(5 joule/cm2)can sufficiently inactivate Drosophila cell viruses without an effect on expression of MHC I and costimulatory molecules on Drosophila APCs.In fact,UVADEX treatment prevents Drosophila APCs growth while maintains APC function.Furthermore,UVADEX-treated Drosophila APCs maintain or even have enhanced APC function as determined by enhancing T cell activation,proliferation and CTL generation.Thus,the use of UVADEX-treated Drosophila APCs may provide a valuable tool for immunotherapy to generate tumor antigen-specific CTLs.