Fanconi Anemia (FA) is recessive DNA double strand repair disorder where due to the accumulation of DNA damage over time, a high propensity exists to develop malignancies. Spontaneously occurring natural reversions of inherited mutations in stem cells of FA patients that completely correct the FA-specific defect in the hematopoietic system by repopulation with corrected progeny suggest that FA would be an ideal model disorder for stem cell gene therapy approaches. However, all clinical trials for genetic therapy in FA failed so far without any persistance of long-term marked cells or any clinical benefit for the patients. In addition, in vitro manipulation of murine FA stem cells for 2 to 4 days, as required for oncoretroviral vectors to be able to transduce repopulating cells, leads to the development of MDS and AML in transplanted recipients independent of any insertional mutagenesis. Here, we propose to continue our successful initial studies from the first SPP1230 funding period with foamy virus (FV)- and lentivirus (LV)-based gene delivery systems, thereby avoiding any prolonged in vitro manipulation periods for genetic correction of Fang-/- stem cells. Utilizing these complex retroviral vectors pseudotyped with the same modified FV envelope in competitive repopulation studies as well as high through-put pyrosequencing for analyses of any potential insertional mutagenesis will allow to develop these ideally suited gene delivery systems further for somatic genetic therapy in FA.

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