CD34+ selected cells in mismatched stem cell transplantation: a single centre experience of haploidentical peripheral blood stem cell transplantation

Haploidentical transplantation for acute lymphoblastic leukemia in childhood

Haploidentical transplantation in childhood acute lymphoblastic leukemia (ALL) is a promising option for children lacking a suitable donor. We have updated our series of patients with ALL and report the results. Additionally, we reviewed the literature and try to embed our own experiences in the published results. We performed HLA-mismatched stem cell transplantations with megadoses of purified positively selected mobilized peripheral blood CD34+ progenitor cells (PBPC) from adult donors in 27 children with acute lymphoblastic leukemia (ALL) in first (CR1 n = 7), second (CR2 n = 10), or third (CR3 n = 4) complete remission, and in refractory state (NR n = 6). The patients received a mean number of 19.1+/-11.3 x 10(6)/kg purified CD34+ and a mean number of 15.5+/-24.2 x 10(3)/kg CD3+ T-cells. No additional graft-versus-host disease (GVHD) prophylaxis was used, except as short-term CSA in the first 3 patients. The myeloablative treatment was based on busulfan in 12 and on TBI in 14 patients. One patient was grafted with a non-myeloablative approach. Engraftment was rapid in 26 patients, with two patients suffering from a rejection. These two and one patient with initial non-engraftment had been successfully regrafted. The probability of survival of the total group is 0.34+/-0.09; the 12 patients transplanted in remission showed a probability of survival of 0.44+/-0.11. None of the patients transplanted in non-remission survived. There was no statistical difference in survival for patients with a 1, 2 or 3 antigen mismatched donor (out of 6 HLA antigens) or for patients in 1st, 2nd or 3rd remission. Causes of death were relapses in 10 patients, veno-occlusive disease (VOD) in 1, multi-organ failure (MOF) in 2 and infections in 4 patients. 3/24 evaluable patients without any additional GVHD-prophylaxis developed grade 1 or 2 GVHD. Ten patients were treated with additional donor lymphocyte infusion (DLI), from which 4 developed a maximum grade 3 GVHD. We conclude that the HLA barrier can be overcome by transplantation of megadoses of highly purified CD34+ PBPC and GVHD can effectively be prevented. This approach offers a promising treatment option for patients with acute lymphoblastic leukemia needing urgently transplantation but lacking a suitable donor.

The role of haploidentical stem cell transplantation in the management of children with haematological disorders

The broader application of stem cell transplantation (SCT) for paediatric diseases has been limited by a lack of human leucocyte antigen (HLA)-matched donors. Virtually all children, however have at least one haploidentical parent who could serve as a donor. Such a donor is immediately available and the considerable costs of additional HLA typing, registry and banking expenditures that are necessary to procure an unrelated donor, could be reduced. Recent technological advances appear to have overcome the historical problems of graft rejection and severe graft versus host disease in the haploidentical setting, and in the latest studies the overall survival for children undergoing haploidentical SCT for leukaemia is now comparable with that following unrelated donor bone marrow or cord blood transplantation. Post-transplant infectious complications and leukaemia relapse remain the most important barriers yet to overcome, and new directions in the use of adoptive cellular immunity appear to be promising in this respect. Haploidentical SCT is now a viable option for those children who do not have an HLA compatible sibling or fully matched unrelated donor. The relative merits of a haploidentical family donor versus mismatched unrelated bone marrow or cord blood donation needs to be assessed in prospective, randomized clinical trials.

Partially matched related donor peripheral blood progenitor cell transplantation in paediatric patients adding fludarabine and anti-lymphocyte gamma-globulin

Twenty-one paediatric patients (11 males and 10 females) received a CD34-selected partially matched related donor transplant for malignant (16 cases) and non-malignant conditions (five cases). The average cell dose was 11.13 x 10(6)/kg. Fifteen of 16 patients with malignant conditions and one with non-malignant disease received total body irradiation plus cyclophosphamide. Three of 5 patients with non-malignant conditions and one with leukaemia, received busulphan plus cyclophosphamide. One patient with Fanconi anaemia received 100 mg/kg of cyclophosphamide. Fludarabine (25 mg/m(2)/day for 5 days) was administered prior to all these regimens. Additionally, anti-lymphocyte gamma-globulin (12.5 mg/kg/day) was administered from day -2 to day +2. Three (15%) patients failed to achieve complete chimaerism (CC). These patients received a second cell infusion. Two of them achieved CC. In the third patient, the percentage of donor cells was increased. The likelihood for engraftment was not related to the cell dose received. Acute graft-versus-host disease (GVHD) occurred in nine patients but only one developed GVHD >grade II. Eight patients developed active viral infections, which resolved after treatment. Patients receiving cell doses higher than our average had a significantly faster CD3 and CD4 cell recovery and experienced a lower incidence of viral infections. After 480 +/- 255 days of median follow-up, 16/21 patients are alive and well and have CC. Three patients died of leukaemic relapse and a fourth from progression of his disease (adreno-leuko-dystrophy). We conclude that partially matched related donors are a feasible source of haemopoietic progenitor cells for transplantation for patients without matched familial or unrelated donors.

Campath-1G causes rapid depletion of circulating host dendritic cells (DCs) before allogeneic transplantation but does not delay donor DC reconstitution

Graft-versus-host disease (GVHD), a major complication after allogeneic transplantation, can be abrogated by the Campath (anti-CD52) monoclonal antibody. The induction of acute GVHD requires host antigens to be presented to donor T cells by antigen-presenting cells (APCs). Recent evidence has suggested that only host APCs can interact with donor T cells in the induction of GVHD. Because CD52 has been reported to be expressed on DCs, we reasoned that pretransplant Campath-1G might have a direct effect on circulating DCs in addition to any effects on donor T cells. Using direct immunostaining, we demonstrated expression of CD52 on DCs and that Campath-1G killed purified DCs in vitro. In vivo Campath also depleted DCs. Twenty-four hours after the first dose of Campath-1G, circulating DCs were reduced by a mean of 79% (range, 44%-96%). By day 0 after 5 doses of Campath-1G and chemoradiotherapy conditioning, DCs became undetectable in 7 of 9 cases, whereas in 6 of 7 patients receiving conditioning therapy without Campath-1G, host DCs were still detectable. The reconstitution of circulating DCs after transplantation was not affected by Campath-1G and in both groups DC1 (CD11c(+)) recovered more rapidly than DC2 (CD11c(-)). Analysis of chimerism confirmed that the DCs recovering after transplantation in patients receiving Campath-1G were of donor origin. We conclude that in vivo Campath-1G causes a rapid depletion of host circulating DCs and that this may, in part, explain the low incidence of acute GVHD. The reconstitution of donor DCs was not delayed, which may be important in preserving immune reconstitution.

Genetically haploidentical stem cell transplantation for acute leukemia

Genetically haploidentical stem cell transplants have been performed for several decades, mostly for patients with advanced acute leukemia. Such transplants are an option for those patients who do not have a histocompatible sibling donor. The historical data have been disappointing due to graft-versus-host disease, engraftment failure and delayed immune reconstitution. Recent modifications and new technological developments have led to more encouraging clinical results. Haploidentical transplantation is immediately available to the majority of patients with acute leukemia and is an acceptable alternative to matched unrelated donor transplantation.