Unrelated peripheral blood stem cell transplantation with 'megadoses' of purified CD34(+) cells in three children with refractory severe aplastic anemia

Three children with refractory severe aplastic anemia were transfused with high numbers of unrelated matched (n = 2) or C-locus haploidentical mismatc hed (n = 1) CD34-selected peripheral blood stem cells in the absence of an HLA-identical family donor. Two leukaphereses of the donors yielded a media n number of 10.1x10(10) nucleated cells (range 9.7-15.4) with a median numb er of 9.89 x 10(8) CD34(+) cells (range 7.46-26.1) and a median percentage of CD34(+) cells of 0.98% (range 0.77-1.7). After positive selection by mag netic cell sorting the patients received a median of 14.3 x 10(6) CD34(+) c ells/kg (range 11.7-24.3) and of 1.3 x 10(4) CD3(+) cells/kg (range 0.57-5. 8), Median time to ANC greater than or equal to 0.5 x 10(9)/l was 7 days (r ange 7-12) and to platelets greater than or equal to 20 x 10(9)/l 13 days ( range 13-27), Chimerism analysis of peripheral blood after transplantation revealed permanent 100% donor hematopoiesis in all patients. The patient wi th the C-locus haploidentical mismatch presented with acute GVHD (grade III -IV) of the skin, liver and lower gastrointestinal tract (onset day +40) an d died despite intensive immunosuppressive treatment on day +238, The two s urvivors developed lymphopoietic recovery of B and T lymphocytes within 3 m onths after transplantation. To our knowledge this experience represents th e first report of transplantation with unrelated CD34(+) enriched periphera l blood stem cell in children with refractory severe aplastic anemia.