GENE THERAPY OF FANCONI ANEMIA BY LENTIVIRAL VECTORS

Fanconi Anemia is a rare genetic disease, which impairs the ability of cells to repair their DNA. This mainly affects the stem cells in the bone marrow, where blood cells are made. Consequently, patients (usually children) become increasingly anemic, and sometimes develop leukemia. In principle, the genetic correction of the patient’s stem cells would be the solution for bone marrow failure in FA patients. The most straightforward approach toward this goal is the ex vivo correction of hematopoietic stem cells. Ex vivo means that the cells we want to treat are temporarily removed from the body of the patient, genetically corrected in a culture dish, and then re-infused. This apparently simple procedure has proven to be a formidable challenge in the case of Fanconi Anemia, due to the extreme fragility of FA cells. The initial attempts to introduce the corrected gene by means of retroviral vectors met with very limited success. Using a new generation of vectors derived from lentiviruses, we were recently able to deliver Fanconi genes with remarkable efficiency into quiescent stem cells obtained from FA knock-out mice. The next step is testing their ability to correct the genetic defect of stem cells obtained from real Fanconi patients. Although the results on animal models are very promising, experiments on human samples are necessary before the procedure can be considered for clinical use. This project proposes to use our vectors for the correction of the Fanconi gene defect in stem cells derived from FA patients. We will purify hematopoietic stem cells from bone marrow samples, and correct their gene defect. We will then analyze the growth capability of the treated cells using a particular strain of immune-deficient mice, called NOD/scid, whose hematopoietic system can be repopulated by human tissue. If the promising results obtained in mice are confirmed on human tissue, this will be a significant step toward successful FA gene therapy.