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Hematopoietic stem cell transplantation (HSCT) from haploidentical donors is a viable option for patients lacking HLA-matched donors. Here we report the results of a prospective multicenter phase I/II trial of transplantation of TCRαβ and CD19-depleted peripheral blood stem cells from haploidentical family donors after a reduced-intensity conditioning with fludarabine, thiotepa, and melphalan. Thirty pediatric and 30 adult patients with acute leukemia (n = 43), myelodysplastic or myeloproliferative syndrome (n = 6), multiple myeloma (n = 1), solid tumors (n = 6), and non-malignant disorders (n = 4) were enrolled. TCR αβ/CD19-depleted grafts prepared decentrally at six manufacturing sites contained a median of 12.1 × 10 6 CD34 + cells/kg and 14.2 × 10 3 TCRαβ + T-cells/kg. None of the patients developed grade lll/IV acute graft-versus-host disease (GVHD) and only six patients (10%) had grade II acute GVHD. With a median follow-up of 733 days 36/60 patients are alive. The cumulative incidence of non-relapse mortality at day 100, 1 and 2 years after HSCT was 5%, 15%, and 17% for all patients, respectively. Estimated probabilities of overall and disease-free survival at 2 years were 63% and 50%, respectively. Based on these promising results in a high-risk patient cohort, haploidentical HSCT using TCRαβ/CD19-depleted grafts represents a viable treatment option., (© 2021. The Author(s).)

Regulation of sensitivity or resistance for apoptosis by death receptor ligand systems is a key control mechanism in the hematopoietic system. Dysfunctional or deregulated apoptosis can potentially contribute to the development of immune deficiencies, autoimmune diseases, and leukemia. Control of homeostasis starts at the level of hematopoietic stem cells (HSC). To this end, we found that CD34+ hematopoietic progenitor cells are constitutively resistant to CD95-mediated apoptosis and cannot be sensitized during short-term culture to death receptor-mediated apoptosis by cytokines. Detailed analysis of the death machinery revealed that CD34+ cells do not express caspase-8a/b, a crucial constituent of the death-inducing signaling complex (DISC) of death receptors. Instead, we found a smaller splice variant termed caspase-8L to be present in HSC. Forced expression of caspase-8L using a recombinant lentiviral vector was able to protect hematopoietic cells from death receptor-induced apoptosis even in the presence of caspase-8a/b. Furthermore, we found that caspase-8L is recruited to the DISC after CD95 triggering, thereby preventing CD95 from connecting to the caspase cascade. These results demonstrate an antiapoptotic function of caspase-8L and suggest a critical role as apoptosis regulator in HSC. Similar to CD34+ HSC, stem cell-derived leukemic blasts from AML(M0) patients only expressed caspase-8L. Additionally we found, caspase-8L expression in several AML and ALL samples. Thus, caspase-8L expression might explain constitutive resistance to CD95-mediated apoptosis in CD34+ progenitor cells and might participate in the development of stem cell-derived and other leukemias by providing protection from regulatory apoptosis.

Graft-versus-host disease (GVHD) is a major cause of mortality and morbidity after allogeneic bone marrow transplantation, but can be avoided by removing T lymphocytes from the donor bone marrow. However, T cell depletion increases the risk of graft rejection. In this study, two strategies are used to overcome rejection: (1) use of high doses of stem cells obtained from peripheral blood (PBSC), (2) admixture with a CD52 monoclonal antibody in order to deplete both donor and residual recipient lymphocytes. Two antibodies are compared: CAMPATH-1G (rat IgG2b) and its humanized equivalent CAMPATH-1H (human IgG1). A total of 187 consecutive patients at six centers received PBSC transplants from HLA-matched siblings between 1997 and 1999. A wide spectrum of diseases, both malignant and non-malignant, was included. The recovery of CD34+ cells after antibody treatment was close to 100%. The risk of acute GVHD (grade 2 to 4) was 11% in the CAMPATH-1G group and 4% in the CAMPATH-1H group (P = NS). The risk of chronic GVHD (any grade) was 11% in the CAMPATH-1G group and 24% in the CAMPATH-1H group (P = 0.03) but the risk of extensive chronic GVHD was only 2%. The overall risk of graft failure/rejection was 2%, not significantly different between the two antibodies. Antibody treatment was equally effective at concentrations between 10 microg/ml and 120 microg/ml and it made no significant difference to the outcome whether the patients received post-transplant immunosuppression or not (87% did not). Transplant-related mortality in this heterogenous group of patients (including high-risk and advanced disease) was 22% at 12 months. It is proposed that treatment of peripheral blood stem cells with CAMPATH-1H is a simple and effective method for depleting T cells which may be applicable to both autologous and allogeneic transplants from related or unrelated donors. Special advantages of this approach are the simultaneous depletion of donor B cells (which reduces the risk of EBV-associated lymphoproliferative disease) and the concomitant infusion of CAMPATH-1H to deplete residual recipient T cells and thus prevent graft rejection.

Over the past 3 years we have performed 10 haploidentical peripheral blood stem cell transplants in patients with incurable haematological malignancies and no prospect of a matched unrelated donor within an adequate time period. Conditioning consisted of ATG, TBI, thiotepa, cyclophosphamide and additional radioimmunotherapy in five patients. All patients received G-CSF mobilized peripheral blood stem cell grafts. GVHD prophylaxis consisted of T cell depletion by CD34+ selection; no post-transplant immunosuppression was given in nine patients. Stable engraftment was achieved in nine patients; one case of acute graft rejection was observed. Seven patients developed grade I acute GVHD, and six patients have developed chronic GVHD. Infections were the most significant clinical problem post transplant. Two patients have suffered a relapse of their disease and two further patients have died of transplant-related complications. After a median follow-up of 13 months (range 5-37 months) six patients are surviving in remission. We conclude that haploidentical PBSCT is a reasonable alternative to a MUD transplant.

In the present study the in vitro growth of CFU-GM from PBPC of patients with AML (n = 11), purged with mafosfamide alone or a combination of mafosfamide and amifostine, was compared to historical controls of mafosfamide-purged bone marrow (AML CR1, n = 16). Two patients were transplanted with mafosfamide and mafosfamide/amifostine pretreated PBPC autografts. The in vitro experiments demonstrated a significantly higher resistance of peripheral blood derived CFU-GM to mafosfamide (median ID95 190 microg mafosfamide/ml) compared with bone marrow derived CFU-GM (median ID95130 microg/ml). Preincubation with amifostine significantly further increased the median ID95 to 245 microg/ml. The clinical results showed short recovery times for neutrophils >500/microl (9 and 13 days) and platelets >20 000/microl (12 and 21 days) and stable long-term engraftment with one relapse at day +118 and one patient in CR at day 760 after transplantation. The in vitro results show a significant advantage of PBPC over bone marrow-derived progenitors for purging with mafosfamide. Furthermore, a protective effect from mafosfamide of amifostine on normal progenitors could be demonstrated. The clinical results demonstrate the clinical feasibility of using mafosfamide-purged autologous PBPCT without impairing the short-term and long-term repopulating capacities of the autografts.

The aim of this study was to reduce the rate of graft failure after HLA non-identical stem cell transplantation by using G-CSF mobilized CD34+ peripheral blood progenitor cells (PBPC), either in combination with bone marrow or as single grafts. To prevent GVHD, PBPC were highly purified, resulting in a 5 to 6 log T cell depletion. In additon to T cell depletion no further GVHD prophylaxis was used. We transplanted 23 pediatric patients with life-threatening malignant or non-malignant hematological disorders, who had no available matched donor. Engraftment was obtained in 18 of 21 evaluable patients. Five patients developed acute GVHD of grade II and III, which became chronic in four cases and was fatal in four. The use of highly purified PBPC allowed the exact quantification of residual T cells in the grafts and a strict correlation between the residual T cell load and the development of GVHD was observed: patients with GVHD had received numbers of T cells between 8 and 20 x 104/kg, whereas patients without GVHD were grafted with T cell numbers ranging from 0.7 to 6.0 x 104/kg. We therefore clearly demonstrate that a residual T cell content of <5 x 104/kg is safe for prevention of GVHD after HLA non-identical PBPC transplantation in children.

A median dose of 11 (6-17) microg G-CSF per kg and day was given to 96 (49 female, 47 male) healthy family donors in order to mobilize and to collect peripheral blood progenitor cells (PBPC) for allogeneic transplantation. Donor age was 36 (17-76) years. The leukocytes of the donors increased to 46 (12-115) x 10(9)/l on days 4-6 of G-CSF treatment with a median of 71 (2-657) CD34+ cells per microl, respectively. Female and older donors seem to have a lower response to G-CSF. About 32% of the donors suffered from side-effects of G-CSF requiring analgetics. A total of 197 stem cell aphereses were performed using the COBE Spectra cell separator. Median apheresis time was 225 (118-300) min processing 11.8 (5.7-20) l blood, collecting 5.3 (1.7-14.9) x 10(10) nucleated cells and containing 0.7 (0.1-3.7)% CD34+ cells. Severe citrate toxicity occurred in 5% of the donors. Retransfusion of autologous platelets post apheresis was necessary in 16% of the donors because of a platelet count <80 x 10(9)/l. An insufficient number of stem cells was collected in four female donors due to a very poor response to G-CSF. In conclusion, the collection of allogeneic G-CSF-mobilized PBPC is safe and effective. One or two aphereses were sufficient in 91% of the donors to achieve >4 x 10(6) CD34+ cells per kg. In 4% of the donors an additional bone marrow harvest or the use of an alternative donor was necessary because of a poor mobilization.

Antibodies to IFN-alpha have been recognized as a novel type of autoantibody developing after allogeneic BMT. Ninety-six patients undergoing BMT for various hematologic disorders were followed for the presence of spontaneous IFN-alpha antibodies until 12 years after transplantation. Seven of them (7.3%) developed IFN-alpha antibodies occurred late after BMT (> or = 15 months), rose to very high titers in some patients, and persisted for years despite combined immunosuppressive treatment. They were oligo- or polyclonal in nature, predominantly IgG with a broad IgG subclass distribution, and neutralized the antiviral and antiproliferative activity of various natural and recombinant IFN-alpha types including the patients' endogenous IFN-alpha in vitro. All antibody-positive recipients suffered from chronic GVHD (n = 5) or chronic viral hepatitis (n = 2), but the only significant association was with prior severe aplastic anemia (3/9, 33%; P = 0.022). There was no discernible HLA association of IFN antibody development. Although the clinical relevance of the IFN-alpha antibodies is uncertain they may interfere with cellular defence mechanisms and immune regulation after BMT.

Six patients treated for relapsed chronic myeloid leukaemia after allogeneic bone marrow transplantation with donor buffy coat transfusions were investigated. In the 5 patients who achieved molecular remission high frequencies of host-reactive interleukin 2-secreting T helper cell precursors (Th-p) were detectable by limiting dilution analysis. In four of the patients the presence of Th-p was associated with a clinical syndrome similar to transfusion GVHD suggesting a T cell response to minor histocompatibility antigens (minor H) expressed by both malignant haemopoiesis and host tissues. In the fifth responding patient no GVHD or bone marrow hypoplasia was observed. The nature of the antigens recognised by these donor Th-p remains unknown. No host-reactive Th-p were detectable in the non-responder and host-reactive cytotoxic T cell precursors (CTL-p) were not consistently detectable in the responding patients.

We have performed a non-randomised GVHD prophylaxis trial comparing cyclosporin/methotrexate with in vivo/ex vivo T cell depletion with the monoclonal antibodies Campath 1G/1M in patients with acute leukaemias in first complete remission. We observed significantly less acute and chronic GVHD, neutropenic fever and severe mucositis in the T cell depletion group. The incidence of graft rejection and relapses was no higher than in the cyclosporin/methotrexate group. There is a trend in favour of improved disease-free survival in the in vivo/ex vivo T cell depletion group (80% vs. 62%).

Combined in vivo/ex vivo T cell depletion is effective in the prophylaxis of graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation (BMT), but influences the occurrence of active cytomegalovirus (CMV) infection and disease. Twenty nine patients receiving a T cell-depleted marrow graft (Campath-1M) after intravenous application of the monoclonal antibody Campath-1G prior to conditioning were monitored for virus shedding and antigenaemia from day -7 to day +100. In seropositive patients in this group active CMV infection occurred more frequently (10 of 16) and much earlier (nine of 10 until day +21) than in 27 seropositive patients (10 of 27, P < 0.02) receiving cyclosporin A and methotrexate (CsA/MTX). Early active CMV infection after in vivo/ex vivo T cell depletion correlated strictly with an early increase in blood lymphocyte counts (P < 0.01), with predominance of NK cells and/or CD8+ T cells. Three cases of very early interstitial pneumonitis (IP) occurred after in vivo/ex vivo T cell depletion compared with none in the CsA/MTX group. IP was fatal in the only patient with early active CMV infection, who remained lymphocytopenic till death on day +31. This may indicate that an early immune response against CMV is possible and essential for favourable clinical outcome.

In a patient undergoing allogeneic BMT for chronic phase CML, de novo chronic GVHD developed within 80 days after transplantation. Eighteen months post-BMT, high serum levels of neutralizing interferon-alpha (IFN-alpha) antibodies were detected, which persisted despite continuous immunosuppressive treatment. The antibodies were of oligoclonal or polyclonal origin, predominantly of the IgG1 type, and reacted broadly with various human IFN-alpha types, including the patients endogenous IFN-alpha, but failed to recognize natural IFN-beta and recombinant IFN-gamma. Pathogenesis and clinical impact of the IFN-alpha antibodies are unknown. Antibodies of cytokines are a novel class of autoantibodies that may develop after allogeneic BMT and interfere with cytokine homeostasis and immune regulation.

We investigated a case of graft rejection after in vivo/ex vivo T-depleted BMT in a patient who had received a HVG-matched, GVH one locus-mismatched, MLC-negative graft from his cousin. In vivo/ex vivo T cell depletion was performed with Campath 1G (CP1G) and Campath 1M (CP1M), respectively. We identified a failure of CP1G to eradicate a CDw52- (Campath-negative) host T cell population as the main cause of treatment failure. The analysis also suggests that significant host-versus-donor reactivity prior to transplant, as detected by limiting dilution analysis, also contributed to graft rejection. The rejecting T cells were bifunctional in that they showed cytotoxic activity and were capable of inhibiting haemopoietic progenitor growth by producing inhibitory lymphokines.

Transplant related mortality and relapse after bmt have a negative influence on the outcome of patients transplanted for acute leukaemia in first remission. Transplant related mortality includes graft-versus-host disease, infections and graft failure. To prevent gvhd and associated infections without increased graft rejection, a protocol of combined in vivo/ex vivo T-cell depletion (Campath IgG 20 mg i.v. for 5 days and Campath IgM T-cell depleted graft) with no further immunosuppression was initiated. Up to now 22 adult patients (median age 39 years, range 21 to 51) have been transplanted. One graft failure most probably due to persistent leukaemia, three acute gvhd (grade I) and no chronic gvhd occurred. Two patients relapsed after bmt and died. Two further patients died due to idiopathic interstitial pneumonitis and acute liver failure, respectively. Eighteen patients are alive in complete remission. With a median follow up of 13 months (1-30) the probability of survival is 78%, disease free survival is 80% and transplant related mortality is 10%. We compared these results with 3 historical control groups with different regimens of gvhd prophylaxis. 1. MTX group (n = 15): With a median follow up of 135 (115-147) months after bmt the probability of survival is 40%, disease free survival is 40% and transplant related mortality is 60% (mainly gvhd and infection). 2. Campath group (only ex vivo T-cell depletion n = 25): With a median follow up of 86 (62-102) months probability of survival is 52%, disease free survival is 43% and transplant related mortality is 36% (mainly rejection and infection).(ABSTRACT TRUNCATED AT 250 WORDS)

We have investigated the clinical and immunological features of 10 cases of graft failure after T cell-depleted marrow transplantation. In addition, the hypothesis that the process of graft failure can be reversed by immunosuppressive therapy with cyclosporin + steroids +/- monoclonal antibodies was tested in seven patients. Early graft failures (before day 50) presented a uniform clinical syndrome with a host T lymphocytosis preceding the loss of the graft. In the majority of cases of late graft failure (after day 50) a syndrome comprising delayed granulopoietic regeneration, fever of unknown origin and abdominal symptoms was observed. Surface marker analysis of peripheral blood and bone marrow lymphocytes implicated a population of CD3+, CD8+, DR+ host T lymphocytes with a frequent co-expression of the Leu7+ antigen in the pathogenesis of graft failure. Immunosuppressive therapy reversed graft failure in the three cases of incomplete graft failure (i.e. with residual reticulocytes) and failed in the four cases of complete graft failure (i.e. no residual reticulocytes).

The remission state of 13 Philadelphia positive chronic myeloid leukemia patients was studied after bone marrow transplantation (BMT) by cytogenetic and Southern blot analysis of the breakpoint cluster region (BCR) gene. Eight of 13 patients showed neither clinical nor genetic evidence of residual disease. In two patients hematological relapse was confirmed by cytogenetic and molecular analysis. Evidence for residual leukemic cells in otherwise complete remission was obtained genetically in three patients. One of the latter cases revealed BCR rearrangement despite negative cytogenetic findings, while in another patient cytogenetic relapse was observed without demonstrable rearrangement within the major BCR. Our results may indicate that cytogenetic and molecular genetic methods complement rather than replace each other for the detection of residual CML cells after BMT.