During the past year, we have collaborated Dr. John Tisdale in monitoring stem cell engraftment in children and young adults transplanted for amelioration of sickle cell anemia. Given the relatively benign clinical course in patients with sickle cell anemia in the absence of transplant, Dr. Tisdale elected to minimize the risk of potentially life-threatening graft versus host disease (GVHD) by using a very low intensity conditioning regimen (rapamycin and low intensity whole body irradiation). This regime is sufficent to assure myeloid stem cell engraftment while minimizing the engraftment of donor T cells in the recipient. Using this regimen, Dr. Tisdale has so far transplanted matched allogeneic stem cells into 5 patients. To date four of these patients have engrafted sufficient myeloid precursors to correct erythropoiesis. In one instance, a second stem cell infusion was required because of graft rejection, and in one patient the graft failed. The clinical course in patients successfully transplanted has been excellent, with minimal GVHD. We will continue our collaboration with Dr. Tisdale as he further perfects his engraftment conditions and extends his very promising studies.? Studies monitoring engraftment in Dr. Barretts patients receiving selectively T cell-depleted grafts continue. Of relevance, Dr. Barrett is in the process of initiating a new protocol using a new method (photodepletion) for selective depletion of alloreactive donor T cells. Clinical accrual into this protocol should begin during the coming year.
