Strategies aimed at improving transduction of primate hemopoietic stem cells

The preferred larget cell in gene therapy for blood disorders is the plunpotent hemopoietic stem cell (PHSC) because of its capacity to contribute to the production of all blood cells over extended periods of time (probably lifelong). The relative success of retro viral-mediated gene transfer procedures into PHSC of rodents contrasts with the low frequency gene transfer currently achieved in the same target cell of primates. The clinical usefulness of these procedures is therefore still limited to those cases where selective advantage of the transduced stem cells can be expected such as in the case of ADA deficiency. The presentation will report on our efforts aimed at increasing the efficiency of PHSC gene transfer, which are focused towards a) the understanding of critical factors determining transducibtlily, including cell cycle behaviour and viral receptor availibility, b) the development of culture systems that permit stem cell maintenance and expansion ("self renewal"), and c) the employment of vectors carrying the multi-drug resistance gene useful for in vi'v" selection of transduced (stem) cells as well as in the treatment of cancer patients undergoing chemotherapy.