Results of an unrelated transplant search strategy using partially HLA-mismatched cord blood as an immediate alternative to HLA-matched bone marrow

Expression analysis of genes involved in the expansion of hematopoietic stem cells (SCF, Flt3-L, TPO, IL-3, and IL-6) in unrestricted somatic stem cells cultured on fibrin

Umbilical cord blood (UCB) transplantation is a promising therapeutic approach for patients lacking HLA-matched donors. A main limitation to the use of UCB-derived HSCs (UCB-HSCs) is the low number of transplantable cells. Novel culture strategies are being developed to increase the number of HSCs. Unrestricted somatic stem cells (USSCs) have been identified as promising stromal cells for supporting HSC expansion. The current study aimed to explore the effect of fibrin on the expression of hematopoiesis-related genes (SCF, Flt3-L, TPO, IL-3, and IL-6) in USSCs. USSCs were isolated from UCB and characterized by flow cytometry and in vitro multilineage differentiation ability. DAPI staining and the MTT assay were used to assess the effect of fibrin on USSC viability. The cell attachment was evaluated using SEM. qRT-PCR was performed to evaluate the expression of SCF, Flt3-L, TPO, IL-3, and IL-6 in USSCs cultured on 3D fibrin scaffolds. USSCs were positive for CD73, CD105, and CD166 and negative for CD45. Alizarin red and Oil red O stains confirmed calcium deposition and lipid vacuoles in USSCs. Results obtained from DAPI and MTT assays revealed a positive effect of fibrin on USSC viability. Cells cultured on fibrin express significantly higher levels of SCF and TPO compared to those grown in a 2D environment. The positive effect of fibrin on IL-6 levels was reversed. Fibrin did not affect Flt3-L expression and IL-3 mRNA expression was not detected in either group. The results of this study provide the basis for developing further research on the ex vivo expansion of HSCs with USSCs.

Therapeutic Perspectives for the Clinical Application of Umbilical Cord Hematopoietic and Mesenchymal Stem Cells: Overcoming Complications Arising After Allogeneic Hematopoietic Stem Cell Transplantation

This review focuses on the therapeutic features of umbilical cord blood (UCB) cells as a source for allogeneic hematopoietic stem cell transplantation (aHSCT) in adult and child populations to treat malignant and nonmalignant hematologic diseases, genetic disorders, or pathologies of the immune system, when standard treatment (e.g., chemotherapy) is not effective or clinically contraindicated. In this article, we summarize the immunological properties and the advantages and disadvantages of using UCB stem cells and discuss a variety of treatment outcomes using different sources of stem cells from different donors both in adults and pediatric population. We also highlight the critical properties (total nucleated cell dose depending on HLA compatibility) of UCB cells that reach better survival rates, reveal the advantages of double versus single cord blood unit transplantation, and present recommendations from the most recent studies. Moreover, we summarize the mechanism of action and potential benefit of mesenchymal umbilical cord cells and indicate the most common posttransplantation complications.

Cord blood transplantation for acute leukemia

INTRODUCTION

Umbilical cord blood transplantation (UCBT) is a suitable alternative for patients with acute leukemia (AL) in need of an allograft and who lack an HLA-matched donor. Single-institution and registry studies have shown that, in both children and adults with AL, the outcome of UCBT is comparable to that of matched unrelated donor. At the same time, these studies have highlighted some limitations of UCBT, such as increased early mortality and delayed recovery of both hematopoietic and immune compartment, which hamper a more widespread adoption of this approach.

AREAS COVERED

In this review, we will analyze the current results of UCBT in children and adults with AL, including comparisons with other hematopoietic stem cell sources and transplant strategies. We will also discuss important factors to be considered when selecting UCB units, as well as future strategies to further improve the outcome of UCBT recipients.

EXPERT OPINION

The utilization of UCBT for the treatment of AL patients has decreased in recent years. However, recent clinical data suggesting that UCBT might offer better results in patients with minimal residual disease, as well as innovative strategies to facilitate engraftment, reduce transplant-related mortality, and optimize anti-leukemic activity, may pave the way toward a second youth for use of UCB cells.

Determining the extent of maternal-foetal chimerism in cord blood

During pregnancy, maternal T cells can enter the foetus, leading to maternal-foetal chimerism. This phenomenon may affect how leukaemia patients respond to transplantation therapy using stem cells from cord blood (CB). It has been proposed that maternal T cells, primed to inherited paternal HLAs, are present in CB transplants and help to suppress leukaemic relapse. Several studies have reported evidence for the presence of maternal T cells in most CBs at sufficiently high numbers to lend credence to this idea. We here aimed to functionally characterise maternal T cells from CB. To our surprise, we could not isolate viable maternal cells from CB even after using state-of-the-art enrichment techniques that allow detection of viable cells in heterologous populations at frequencies that were several orders of magnitude lower than reported frequencies of maternal T cells in CB. In support of these results, we could only detect maternal DNA in a minority of samples and at insufficient amounts for reliable quantification through a sensitive PCR-based assay to measure In/Del polymorphisms. We conclude that maternal microchimerism is far less prominent than reported, at least in our cohort of CBs, and discuss possible explanations and implications.

Recommendations for a standard UK approach to incorporating umbilical cord blood into clinical transplantation practice: an update on cord blood unit selection, donor selection algorithms and conditioning protocols

Allogeneic haemopoietic stem cell transplantation offers a potentially curative treatment option for a wide range of life-threatening malignant and non-malignant disorders of the bone marrow and immune system in patients of all ages. With rapidly emerging advances in the use of alternative donors, such as mismatched unrelated, cord blood and haploidentical donors, it is now possible to find a potential donor for almost all patients in whom an allograft is indicated. Therefore, for any specific patient, the transplant physician may be faced with a myriad of potential choices, including decisions concerning which donor to prioritize where there is more than one, the optimal selection of specific umbilical cord blood units and which conditioning and graft-versus-host disease prophylactic schedule to use. Donor choice may be further complicated by other important factors, such as urgency of transplant, the presence of alloantibodies, the disease status (homozygosity or heterozygosity) of sibling donors affected by inherited disorders and the cytomegalovirus serostatus of patient and donor. We report UK consensus guidelines on the selection of umbilical cord blood units, the hierarchy of donor selection and the preferred conditioning regimens for umbilical cord blood transplantation, with a summary of rationale supporting these recommendations.

Impaired interferon-alpha production by plasmacytoid dendritic cells after cord blood transplantation in children: implication for post-transplantation toll-like receptor ligand-based immunotherapy

Plasmacytoid dendritic cells (pDCs) initiate both innate and adaptive immune responses, making them attractive targets for post-transplantation immunotherapy, particularly after cord blood transplantation (CBT). Toll-like receptor (TLR) agonists are currently studied for pDC stimulation in various clinical settings. Their efficacy depends on pDC number and functionality, which are unknown after CBT. We performed a longitudinal study of pDC reconstitution in children who underwent bone marrow transplantation (BMT) and single-unit CBT. Both CBT and unrelated BMT patients received antithymocyte globulin as part of their graft-versus-host disease prophylaxis regimen. pDC blood counts were higher in CBT patients than in healthy volunteers from 2 to 9 months after transplantation, whereas they remained lower in BMT patients. We showed that cord blood progenitors gave rise in vitro to a 500-fold increase in functional pDCs over bone marrow counterparts. Upon stimulation with a TLR agonist, pDCs from both CBT and BMT recipients upregulated T cell costimulatory molecules, whereas interferon-alpha (IFN-α) production was impaired for 9 months after CBT. TLR agonist treatment is thus not expected to induce IFN-α production by pDCs after CBT, limiting its immunotherapeutic potential. Fortunately, in vitro production of large amounts of functional pDCs from cord blood progenitors paves the way for the post-transplantation adoptive transfer of pDCs.

Optimal stem cell source for allogeneic stem cell transplantation for hematological malignancies

Hematopoietic stem cell transplant (HSCT) is a standard treatment for many hematological malignancies. Three different sources of stem cells, namely bone marrow (BM), peripheral blood stem cells (PBSC) and cord blood (CB) can be used for HSCT, and each has its own advantages and disadvantages. Randomized controlled trials (RCTs) suggest that there is no significant survival advantage of PBSC over BM in Human Leukocyte Antigen-matched sibling transplant for adult patients with hematological malignancies. PBSC transplant probably results in lower risk of relapse and hence better disease-free survival, especially in patients with high risk disease at the expense of higher risks of both severe acute and chronic graft-versus-host disease (GVHD). In the unrelated donor setting, the only RCT available suggests that PBSC and BM result in comparable overall and disease-free survivals in patients with hematological malignancies; and PBSC transplant results in lower risk of graft failure and higher risk of chronic GVHD. High level evidence is not available for CB in comparison to BM or PBSC. The risks and benefits of different sources of stem cells likely change with different conditioning regimen, strategies for prophylaxis and treatment of GVHD and manipulation of grafts. The recent success and rapid advance of double CB transplant and haploidentical BM and PBSC transplants further complicate the selection of stem cell source. Optimal selection requires careful weighing of the risks and benefits of different stem cell source for each individual recipient and donor. Detailed counseling of patient and donor regarding risks and benefits in the specific context of the patient and transplant method is essential for informed decision making.

T cell depletion in paediatric stem cell transplantation

Haematopoietic stem cell transplantation (HSCT) can be a curative procedure for a growing number of paediatric diseases, but as the indications for HSCT grow, so does the need to find suitable stem cell donors. When the preferred option of a genoidentical sibling donor is not available alternative donors, including unrelated adult or umbilical cord blood donors, or haploidentical related donors may be considered. Outcome following alternative donor HSCT has improved over the past 20 years but graft-versus-host disease (GvHD) remains a significant obstacle. T cell depletion (TCD) for non-genoidentical grafts aims to reduce the morbidity and mortality associated with GvHD, but this intervention has not led directly to improved survival due to delayed immune reconstitution and increased infections, graft rejection and increased rates of disease relapse. Limited data from the paediatric population, however, suggest some encouraging results for children undergoing haploidentical HSCT: a move from positive selection of CD34(+) haematopoietic stem cells towards negative depletion of specific cell subsets in order to retain useful accessory cells within the graft appears to enhance immune reconstitution and improve disease-free survival. Here we review recent paediatric outcome data for T cell-depleted HSCT, explore the role of serotherapy in conditioning regimens and look at future possibilities to improve outcome, including novel allodepletion techniques, suicide gene therapy and pathogen-specific immunotherapy.

Reconstitution of maturating and regulatory lymphocyte subsets after cord blood and BMT in children

Some clinical characteristics of cord blood transplantation (CBT) might be explained by specificities in the reconstitution of immune subsets differing by their maturation stage or their implication in GVHD, tolerance or immune responses against tumor or infectious agents. Here, we compare the immune reconstitution of several of these subsets after CBT and BMT. B-cell count recovery was faster after CBT. There was no difference in the recovery of CD4(+) and CD8(+) cell counts. There was no difference either in the frequency of several subsets: CD45RO(+) memory, and CD45RA(+) naïve cells within the CD4(+) T-cell compartment, CD27(+) among B cells, CD56(bright), NKG2A(+), and KIR(+) cells among natural killer (NK) cells, CD25(+)FOXP3(+) regulatory T cells and invariant NKT cells. The proportion of the thymic naïve CD31(+)CD45RA(+)CD4(+) T cells was lower after CBT at 6 months post-transplant, and was still below normal at 1 year in both groups. NK-cell expansion was more sustained after CBT, with fewer double-negative NKG2A(-)KIR(-) hyporesponsive cells and more double-positive NKG2A(+)KIR(+) hyper-responsive NK cells. These results, therefore, indicate that further research to improve CBT outcome should try to improve thymopoieisis and take advantage of the sustained NK-cell reconstitution.

Reconstitution of protective immune responses against cytomegalovirus and varicella zoster virus does not require disease development in pediatric recipients of umbilical cord blood transplantation

CMV and varicella zoster virus (VZV) are significant causes of morbidity and mortality following umbilical cord blood transplantation (UCBT). However, the kinetics of reconstitution and protective potential of antiviral cell-mediated immune responses following UCBT remain poorly characterized. In this study, the reconstitution of CMV- and VZV-specific T cell responses was assessed using IFN-γ ELISPOT in 28 children who underwent UCBT to treat hematological or inherited disorders. Barely detectable in the first 3 mo posttransplantation, CMV- and VZV-specific T cell responses were observed in 30.4% and 40.3% of study subjects after 36 mo of follow-up. Four of five CMV-seropositive subjects developed detectable levels of circulating CMV DNA (DNAemia), and 5 of 17 VZV-seropositive patients experienced herpes zoster during the posttransplant period. Four CMV-seronegative subjects developed IFN-γ responses against CMV, and four subjects developed a VZV-specific IFN-γ response without clinical signs of infection. No CMV- or VZV-related events were observed in study subjects following the development of CMV- or VZV-specific responses > 150 spot-forming units/10(6) PBMCs, consistent with T cell-mediated protection. Finally, famciclovir prophylaxis did not strictly prevent the reconstitution of the VZV-specific T cell repertoire, because the frequency of T cells producing IFN-γ in response to VZV Ags reached levels consistent with protection in two nonzoster subjects. Monitoring of CMV- and VZV-specific cell-mediated immunity could inform immunocompetence and guide the initiation and cessation of antiherpetic prophylaxis in UCBT recipients.

Post-transcriptional down-regulation of Toll-like receptor signaling pathway in umbilical cord blood plasmacytoid dendritic cells

Plasmacytoid dendritic cells (PDCs) from human umbilical cord blood (UCB) produce lower amounts of IFN-α upon TLR stimulation compared with adult counterparts. This difference may play a role in the low graft-versus-host disease rate after UCB transplantation and in the impaired immune response of the neonate to pathogens. Comparing UCB PDC to their adults counterparts, we found that they exhibited a mature surface phenotype and a normal antigen uptake. They upregulated costimulatory molecules upon activation, although with delayed kinetics. Protein, but not ARN, levels of TLR-9, MyD88, IRAK1 and IRF-7, involved in the TLR-9 signaling pathway were reduced. The expression levels of miR-146a and miR-155, known to be involved in the post-transcriptional down-regulation of immune responses, were higher. These data point out a post-transcriptional down-regulation of the TLR-9/IRF-7 signaling pathway in UCB PDC.

Hematopoietic stem cell transplantation in children with leukemia: a single institution experience with respect to donors

Aim of this study was to compare the outcomes of transplantation by donor source and to help select the best alternative donor in children with leukemia. Donor sources included matched related donor (MRD, n = 35), allele-matched unrelated donor (M-UD, n = 10) or -mismatched (MM)-UD (n = 13) or unrelated umbilical cord blood (UCB, n = 11). UCB group had a significantly higher incidence of grade II-IV acute graft versus host disease (MRD, 11.8%; M-UD, 30.0%; MM-UD, 15.4%, UCB, 54.4%, P = 0.004) but there was no difference in incidence of chronic graft versus host disease between 4 groups. The 5-yr leukemia-free survival (LFS) was 76.7%, 60.0%, 69.2%, and 45.5%, respectively (P = 0.128). MRD group showed higher LFS rate than UCB group (P = 0.022). However, LFS of M-UD and MM-UD together (65.2%) was not different from that of MRD group (76.7%, P = 0.325), or from that of UCB (45.5%, P = 0.190). The relapse incidence at 5 yr was 17.1%, 20.0%, 15.4%, and 0%, respectively (P = 0.460). The 100-day treatment-related mortality was 2.9%, 20.0%, 7.7%, and 36.4%, respectively (P = 0.011). Despite the limitations of small number of patients, unrelated donor transplants including even allele-mismatched ones, seem to be as effective in children with leukemia lacking suitable relative donors. Also, UCB transplant may serve as another possible option in urgent transplants.

CD8+ T-cell reconstitution in recipients of umbilical cord blood transplantation and characteristics associated with leukemic relapse

Recipients of umbilical cord blood (UCB) transplantation (UCBT) face a high risk of morbidity and mortality related to opportunistic infections (OI) and leukemic relapse. To understand the molecular basis of these UCBT-related complications, the characteristics of UCB-derived antigen-specific CD8+ T cells were examined in a group of pediatric UCBT recipients. Compared with the UCB graft inoculum and the late post-UCBT period (12-36 months), declining clonal diversity of UCB-derived CD8+ T cells specific for the Melan-A26-35 A27L peptide and high frequencies of PD-1-expressing CD8+ T cells were observed in the first 3 months after UCBT, a period during which OIs are most frequent. The CD8+ T-cell compartment predominantly comprised CD45RA+ CCR7− terminally differentiated effector-memory T cells until 6 months after UCBT, at which time the polyfunctionality of antigen-specific CD8+ T cells was reestablished. Finally, the frequency of PD-1+ CD8+ T cells was significantly higher in subjects who subsequently experienced leukemic relapse. This study informs the biologic properties of UCB-derived CD8+ T cells and provides a rationale for the characteristics of UCBT in terms of immune reconstitution and OI. These results also suggest that the elevated frequency of PD-1+ CD8+ T cells could be associated with leukemic relapse in pediatric UCBT recipients.

Improving clinical outcomes using adoptively transferred immune cells from umbilical cord blood

Because of the necessary immunodepletion prior to cord blood transplantation as well as the immaturity of cord blood immune cells, recipients experience a high incidence of viral infection in addition to complications observed after hematopoietic stem cell transplantation, such as relapse and graft-versus-host disease. We describe current immunotherapeutic approaches to treating these complications, including the generation of antigen-specific T cells from cord blood, redirecting cord blood T cells using chimeric antigen receptors, and generating cord blood-derived natural killer cells and regulatory T cells.

Engraftment of unrelated cord blood after reduced-intensity conditioning regimen in children with refractory neuroblastoma: a feasibility trial

Relapsed or refractory neuroblastoma is uniformly fatal. We hypothesized that allogeneic response could provide a platform for immunotherapy in neuroblastoma. We therefore undertook a pilot trial of unrelated cord blood transplantation after reduced intensity conditioning regimen (RIC) in children with relapsed neuroblastoma to assess engraftment and tolerability in this heavily pretreated population. The RIC included CY (50 mg/kg, day -6), fludarabine (40 mg/m(2), days -6 to -2), total body irradiation (200 cGy, day -1), and rabbit anti-thymocyte globulin (2.5 mg/kg, days -3 to -1). Six patients were enrolled: four were in partial responsive relapse, one with a mixed response and one in refractory relapse. All patients tolerated the regimen well and had donor engraftment with full neutrophil and plt recovery (median time 12 and 35 days, respectively). One patient never experienced neutropenia and another did not need plt transfusions. All patients progressed after transplant (median time 55 days, 26-180 days). Natural killer (NK) cell counts were normal within 2 months, whereas T-cell recovery was slower. In conclusion, unrelated cord blood engrafts after RIC in children with refractory neuroblastoma. Future research should be aimed at transplanting patients with minimal residual disease, using less intensive immunosuppression and adding NK-cell based post transplant immunotherapy.

Influence of infused cell dose and HLA match on engraftment after double-unit cord blood allografts

The influence of cell dose and human leukocyte antigen (HLA) match on double-unit cord blood (CB) engraftment is not established. Therefore, we analyzed the impact of cell dose and high-resolution HLA match on neutrophil engraftment in 84 double-unit CB transplant recipients. The 94% sustained engraftment rate was accounted for by 1 unit in nearly all patients. Higher CD3(+) cell doses (P = .04) and percentage of CD34(+) cell viability (P = .008) were associated with unit dominance. After myeloablative conditioning, higher dominant unit total nucleated cell (TNC), CD34(+) cell, and colony-forming unit doses were associated with higher sustained engraftment and faster neutrophil recovery (P = .07, P = .0008, and P < .0001, respectively). Total infused TNC (P = .0007) and CD3(+) cell doses (P = .001) also significantly influenced engraftment. At high-resolution extensive donor-recipient HLA disparity was frequent, but had no influence on engraftment (P = .66), or unit dominance (P = .13). Although the unit-unit HLA match also did not affect sustained engraftment (P = 1.0), recipients of units closely (7-10 to 10-10) HLA-matched to each other were more likely to demonstrate initial engraftment of both units (P < .0001). Our findings have important implications for unit selection and provide further insight into double-unit biology.

Role of HLA-G and NCR in protection of umbilical cord blood haematopoietic stem cells from NK cell mediated cytotoxicity

Allogeneic umbilical cord blood haematopoietic stem cells (UCB-HSCs) can be transplanted into a host with the intact innate immunity with limited immuno-reaction, although the mechanisms remain unclear. The present studies aimed at investigating potential mechanisms of allogeneic UCB-HSCs escape from the cytolysis of natural killer (NK) cells. We compared UCB-HSCs ability to protect from NK-mediated cytotoxicity with peripheral blood or bone marrow haematopoietic stem cells (PB-HSCs and BM-HSCs). HSCs expressed lower levels of natural cytotoxicity receptor ligands including NKp30L, NKp44L and NKp46L than monocytes. Blocking these ligands respectively or in combination could increase the resistance of HSCs against NK cell mediated cytotoxicity. High expression of HLA-G was noticed on UCB-HSCs, rather than PB-HSCs or BM-HSCs, whereas blockade of HLA-G significantly elevated NK cell mediated cytolysis to UCB-HSCs. Thus, we conclude that natural cytotoxicity receptors and HLA-G on HSCs may contribute to the escape from NK cells, and activate and inhibitory NK cell receptors and their ligands can be novel therapeutic targets in cell transplantation.

GVHD after unrelated cord blood transplant in children: characteristics, severity, risk factors and influence on outcome

We reviewed our experience in 79 children who had unrelated cord blood transplant (UCBT) between 1996 and 2007 with a major focus on GVHD, comparing both traditional and National Institute of Health (NIH) criteria. The cumulative incidence (CI) of acute GVHD (aGVHD, by day +100) was 0.42 for grade II-IV and 0.22 for grade III-IV. The CI of all aGVHD (NIH, that is, no time limit) at 1 year was 0.45 for grade II-IV and 0.32 for grade III-IV. Infused CD34 cell dose (>1 × 10(5)/kg), pretransplant bacterial infection and nonmalignant disorders were risk factors for grade II-IV aGVHD on univariate analysis. Infused CD34 cell dose remained significant on multivariate analysis. At 1 year, the CI of chronic GVHD (cGVHD) using the Seattle criteria was 0.27, whereas that for cGVHD (NIH) was 0.08. By NIH criteria, the classic form of cGVHD was uncommon (5%) after UCBT. Instead, the acute (71%) and overlap (24%) GVHD variants predominated. Grade II-IV aGVHD was a significant risk factor for cGVHD by both Seattle and NIH criteria. We conclude that GVHD after day +100 after UCBT typically carries features of aGVHD. Moreover, and in marked contrast to adult unrelated donor hematopoietic stem cell transplantation, the GVHD observed in this series did not adversely affect survival.

Transplant outcomes in acute leukemia. II

Currently, it is possible to find a hematopoietic stem cell (HSC) donor for virtually all patients with acute leukemia who have an indication to receive an allogeneic hematopoietic stem cell transplant (HSCT) and lack a human leukocyte antigen (HLA)-identical sibling or a well-matched HLA unrelated donor (URD). According to the ethnicity of the patients and the donor registry, approximately 25% to 60% of patients will not find an 8/8 HLA-matched unrelated donor. Other alternative donors, such as HLA-mismatched related donor or unrelated donor umbilical cord blood (UCB), have emerged to solve the lack of a sibling or well-matched URD. In the haploidentical HSCT setting, new techniques of T-cell depletion, new approaches using combinations of immunosuppressive drugs or different conditioning regimens, and developments on immunotherapy have focused attention on this option. Therefore, any physician has to carefully evaluate, for each patient in need of an allograft, all of the possible alternatives in order to choose the best HSC donor, taking into account type of disease to be transplanted, urgency of transplantation, donor characteristics, and center experience. This review evaluates the current status of haploidentical HSCT in acute leukemia, its advantages and remaining limitations compared to other stem cell sources, and how these data may be used in the development of donor selection algorithms.

Stem cell source and outcome after hematopoietic stem cell transplantation (HSCT) in children and adolescents with acute leukemia

Allogeneic hematopoietic stem cell transplantation from siblings, unrelated donors or HLA mismatched family members has become an important procedure to offer a chance of cure to children and adolescents with acute leukemia at high risk of relapse and those with certain genetic diseases. Bone marrow (BM) was the only stem cell source for many years. During the past 15 years, peripheral blood stem cells from granulocyte colony-stimulating factor (G-CSF) mobilized healthy donors, or umbilical cord blood from related or unrelated donors, have become available. Each stem cell source has different risks/benefits for patients and donors, the choice depending not only on availability, but also on HLA compatibility and urgency of the HSCT. This review will analyze the advantages and limitations of each of these options, and the main criteria which can be applied when choosing the appropriate stem cell source for pediatric transplant recipients with acute leukemia.

Unrelated donor umbilical cord blood transplantation versus unrelated donor bone marrow transplantation in adult and pediatric patients: A meta-analysis

The effect of unrelated donor bone marrow transplantation (UBMT) and unrelated donor cord blood transplantation (UCBT) on the outcome of patients with hematological diseases remains controversial. We conducted a meta-analysis using data from controlled clinical trials comparing UCBT to UBMT in patients undergoing hematopoietic stem cell transplantation. Pooled comparisons of studies of UCBT and UBMT in children found that the incidence of chronic graft-versus-host disease (GVHD) was lower with UCBT (relative risk [RR]=0.41; 95% confidence interval [CI] (0.25, 0.68)), and the incidence of grades II-IV aGVHD was also significantly different (RR=0.69; 95% CI (0.55, 0.86)). The incidence of relapse was also lower with UCBT (RR=0.72; 95% CI (0.59, 0.87)). There was no difference in OS in children when studies were pooled (Hazard ratio [HR]=1.25; 95% CI (0.87, 1.78)). For adults, OS (HR=1.26; 95% CI (1.13, 1.40)) was statistically different. Thus, UCBT led to inferior outcomes than UBMT in adults.

[Allogeneic cord blood transplantation for adults: current results and future development]

Hematopoietic stem cell transplantation is the choice treatment of many hematopoietic disorders. However, there is still no related or HLA-matched unrelated donor for one-third of the patients. Cord blood, which contains a lot of hematopoietic progenitors immunologically naive, represents not only an interesting alternative as hematopoietic stem cell source but also allows more HLA incompatibilities than the other sources. Promising results in children lead to develop cord blood transplantation in adults first of all in hematopoietic malignancies (acute leukemias and lymphoid diseases) and in a second time, in non-malignant diseases such as aplastic anaemia. The main problems for the development of this new strategy in adults are the poor number of cells per unit, the delay for hematopoietic recovery in comparison with other hematopoietic stem cell sources and, consequently higher transplant related mortality. In order to improve the results in adults, new strategies emerged. Double cord blood transplantation, expansion methods and intra-bone injection of the graft will be reviewed here, as well as alternative transplantation strategies such as non-myeloablative conditioning.

Outcomes of unrelated cord blood transplants and allogeneic-related hematopoietic stem cell transplants in children with high-risk acute lymphocytic leukemia

Acute lymphocytic leukemia (ALL) is a common indication for hematopoietic stem cell transplantation (HSCT) in children. Use of unrelated cord blood (UCB) has become increasingly popular as a stem cell source, given the rapid availability and decreased GVHD potential. Publications describing outcomes of children with leukemia who underwent UCB transplants have compared them to those having received unrelated donor marrow transplants. Results are similar. We compared our outcomes using UCB vs allogeneic-related hematopoietic stem cells in pediatric ALL patients since 1992. A total of 49 patients were analyzed. All patients were either in CR1 with high-risk features (n=21) or in CR2 (n=28) with initial remission less than 36 months. Patients received myeloablation with fractionated total body irradiation, cyclophosphamide, and etoposide and GVHD prophylaxis with cyclosporine and methotrexate. Antithymocyte globulin was added for UCB recipients to address the HLA differences. In all, 23 patients underwent allogeneic -related HSCT and 26 underwent UCB transplantation. Other than increased time to engraftment for UCB recipients, results are equivalent. The 3-year overall survival is 64% and 3-year event-free survival is 60% for both groups. Rates of GVHD and transplant-related mortality are also equivalent. UCB is a reasonable option for children with ALL who are referred for HSCT.

Allogeneic haemopoietic stem cell transplantation in children: what alternative donor should we choose when no matched sibling is available?

Allogeneic haemopoietic stem cell transplantation has provided curative therapy for life-threatening malignant and non-malignant diseases in children for over 40 years. Only 25% of children in whom an allograft is indicated have the ideal option of a human leucocyte antigen-identical sibling donor. Substantial advances in the use of alternative donors (unrelated volunteer donors, haploidentical family donors and unrelated umbilical cord blood donors) now make it possible for almost all children to benefit from this life-saving treatment. Each donor choice is associated with distinct advantages and disadvantages, which have greater or lesser importance in different diseases. We review the current status of alternative donor transplantation for haematological malignancies, primary immunodeficiencies, inherited metabolic disorders and bone marrow failure syndromes and outline the current UK consensus donor selection algorithms for these disease groups.

Allogeneic cord blood transplantation in children with hematological malignancies: a long-term follow-up single-center study

Forty-two consecutive pediatric patients with high-risk leukemia who received cord blood (CB) transplantation at the authors' institution from January 1996 and December 2007 were included in this study. Age ranged from 6 months to 18 years and body weight from 7 to 73 kg. Twenty-nine patients had ALL and 13 AML. Twenty-seven out of 42 patients were transplanted in advanced phase of disease (beyond 2nd CR). For 13 patients the CB transplantation was their second transplant. The median follow-up for survivors was 60 months (range, 6-120 months). The probability of myeloid engraftment was 95 +/- 5% and the median time to neutrophil >500/microL was 20 days (range, 12-54). The median time to platelet engraftment was 60 days (range, 37-200). The probability of relapse was 33 +/- 9%. The nonrelapse mortality at day +100 after transplantation was 30 +/- 7%. The probability of disease-free survival was 34 +/- 7%. The CD34(+) cell dose had a significant impact on DFS (HR, 3.28; 95% CI: 1.49-7.23; p = .003). The results from a long-term follow-up study suggest that cord blood transplantation should be performed in the early phase of disease whenever possible. The cord blood unit for transplantation in pediatric patients with hematological malignancies should be chosen based on cell dose, especially a CD34(+) cell dose.

Unrelated umbilical cord blood transplantation and unrelated bone marrow transplantation in children with hematological disease: a meta-analysis

UCB has been used as an alternative source of HSC. Both unrelated donor BM and UCB are available as potential options for transplantation. However, there have been limited comparisons of the outcomes of unrelated donor UCBT vs. UBMT in the unrelated setting. Our aim is to observe the therapeutic efficacy of UCBT and UBMT for treatment of pediatric hematological diseases. We electronically searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and critically appraised all relevant articles (1989.1-2008.5). Comparative studies were carried out on clinical therapeutic effect of UCBT and UBMT with research on stem cells engraftment, complications, earlier mortality, and survival rate. We performed a meta-analysis using review manager 5.0 software (RevMan, The Nordic Cochrane Center, The Cochrane Collaboration) and adopted funnel plot regression to assess the publication bias. We obtained 324 records. Seven trials totaling 1453 patients have been assessed. Pooled comparisons of studies of UCBT and UBMT in children found that the incidence of engraftment failure and earlier transplantation-related mortality were higher with UCBT because of its delay of hematological recovery [OR = 4.96, 95% CI (3.25, 7.59), p < 0.00001 and OR = 2.36, 95% CI (1.79, 3.11), p < 0.00001 respectively], but CMV infection didn't increase obviously. There was no difference in long disease-free survival rate [OR = 0.85, 95% CI (0.65, 1.01), p = 0.06] between UCBT and UBMT due to the decrease of GVHD in UCBT [OR = 0.45, 95% CI (0.34, 0.60), p < 0.0001]. Our meta-analysis confirmed that UCBT in children is also an effective way to treat children with hematological disease and has equivalent survival outcomes compared with UBMT.

Umbilical cord blood transplantation: basic biology and clinical challenges to immune reconstitution

Allogeneic stem cell transplantation has continued to evolve as a common procedure for the treatment of hematological malignancies and bone marrow failure. Donor bone marrow and mobilized peripheral stem cells are routinely employed for the reconstitution of immune function in leukemia and lymphoma patients following radiation and/or chemotherapy. Unfortunately, only 30% of patients have an HLA-identical sibling donor and the identification of matched unrelated donors, particularly for minorities, can present an exceptional challenge. The transplantation of umbilical cord blood (UCB) represents the most recent strategy to expand the potential donor pool while maintaining an acceptable level of treatment-related complications. First utilized in children, UCB transplantation permits a higher degree of HLA disparity while demonstrating a reduction in the incidence and severity of graft-versus-host disease (GvHD) compared to previous transplantation modalities. Despite the apparent decrease in GvHD, relapse rates remain comparable to transplantation with bone marrow or mobilized peripheral blood suggesting a strong graft-versus-leukemia/lymphoma (GvL) effect. However, several issues complicate the use of UCB transplantation and its extension to the treatment of adults. Many infections that afflict transplant patients are particularly frequent and more severe in the context of UCB transplantation. UCB T-cells are naive and therefore display less proliferation and IFN-gamma production in response to cognate antigen and also appear to demonstrate defects in signal transduction mechanisms. In addition, UCB contains T regulatory cells (Treg) with more potent suppressor function than adult Treg. Furthermore, adult patients often require more total cells and CD34+ progenitors for transplantation than a single UCB unit can provide. Thus, strategies to expand selected subpopulations from UCB and the use of multi-unit transplantation are areas of active research. This review will provide a condensed summary of the clinical history of UCB transplantation and emphasize the advantages and disadvantages of this approach to hematological malignancies in comparison to other methods of hematopoietic stem cell transplantation. Subsequently, it will mainly focus on the current challenges to immune reconstitution presented by UCB transplantation, recent research into their cellular and molecular mechanisms, and experimental approaches to overcome them.

A strategy of splitting individual high volume cord blood units into two half subunits prior to processing increases the recovery of cells and facilitates ex vivo expansion of the infused haematopoietic progenitor cells in adults

This study was designed to maximize the recovery of the desirable cell populations contained in the cord blood (CB) freezing bag, in order to optimize donor selection for adolescents and adults. To evaluate this hypothesis, high volume CB units (CBUs) were categorized into three volume collection groups (120-139, 140-159 and >or=160 ml) and were randomly split before volume reduction into two half low volume CBUs; (a) and (b). Using the SEPAX Cell Processing System, all CBUs were standardized to 26 ml. In 128 high volume split CBUs, the WBC, mononuclear cell and CD34+ cell recoveries were significantly higher (P Collapse

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MESH Headings

• Blood Banking/methods
• Blood Cell Count
• Blood Preservation/methods
• Cell Separation/methods
• Cell Survival
• Cord Blood Stem Cell Transplantation/methods
• Female
• Fetal Blood
• Hematopoietic Stem Cells
• Humans

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Grants Collapse

Affiliation(s)

A C Papassavas Hellenic Cord Blood Bank, Foundation for Biomedical Research, Academy of Athens, Athens, Greece.
V Gioka
T Chatzistamatiou
T Kokkinos
I Anagnostakis
G Gecka
I Redoukas
G Paterakis
C Stavropoulos-Giokas

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Searching for alternative hematopoietic stem cell donors for pediatric patients

The use of alternative hematopoietic stem cell (HSC) donors has been witnessing important progress, mainly due to: (i) better HLA matching at the allelic level between donor and recipient in unrelated HSC transplantation (HSCT) translating into better patient outcome; (ii) better donor choice and patient selection in unrelated, often HLA-mismatched, cord blood transplantation and (iii) new strategies of adoptive cell therapy aimed at improving the results of T-cell-depleted haploidentical HSCT from a relative. Currently, it is possible to find an HSC donor for virtually almost all children with an indication to receive allogeneic HSCT and lacking an HLA-identical sibling. Each of the three options of HSCT from alternative donors has advantages and limitations. Therefore, any physician has to carefully evaluate, for each single pediatric patient in need of an allograft, all the possible alternatives to choose the best HSC donor, taking into account type of disease to be treated, urgency of transplantation, donor characteristics and center's experience. This review will analyze in detail the advantages and limitations of each of the three options of alternative donor HSCT and the main criteria to be used for choosing the most suitable donor for pediatric patients lacking an HLA-identical sibling.

Early proliferation of umbilical cord blood cells from premature neonates

BACKGROUND AND OBJECTIVE

Human umbilical cord blood (UCB) is an important source of haematopoietic stem cells; however, the behaviour of progenitor cells obtained from premature and full-term neonates is still a controversy subject. Thus, the aim of this study was to evaluate cell cycle parameters and the proliferative capacity of UCB progenitor cells from premature and full-term neonates.

MATERIAL AND METHODS

Clonogenic assays were performed with methylcellulose, medium supplemented with recombinant stimulating growth factors and the colonies were scored on the seventh day and the 14th day of culture. A cell cycle study was carried out by DNA analysis using flow cytometry and 30 000 events were acquired; p107 and p130 expressions were analysed by Western blotting.

RESULTS

Cultures obtained from UCB of premature neonates showed an early growth of colony-forming unit (CFU)-burst forming unit erythroid/CFU-granulocyte, erythrocyte, macrophage and megakaryocyte (BFU-E/GEMM), and CFU-granulocyte, macrophage (GM) by the seventh day of culture (P < 0.001). Therefore, the number and morphological characteristics of these colonies were comparable with those obtained from full-term neonates, on the 14th day of culture. At the 14th day, a large amount of CFU-GM was detected in the premature group (P < 0.0032). The premature culture on the 14th day showed fibroblasts and was comparable to those of full-term neonates on the 21st day in terms of number and morphology of the colonies. DNA analysis showed that the number of cells in S-phase was also higher in premature samples when compared to full-term neonates, P < 0.0021 (0 h = 12.8 vs. 2.5%; 16 h = 10.5 vs. 5.9%; 20 h = 13.5 vs. 10.3%; 24 h = 13.8 vs. 9.1%; 48 h = 14.0 vs. 5.4%; 72 h = 20.5 vs. 8.9%; 96 h = 13.8 vs. 7.7%). The Western blotting results demonstrated that p107 and p130 cell cycle protein expressions were higher in premature cells than in full-term cells.

CONCLUSION

These results suggest that the higher capacity of proliferation and early differentiation of premature UCB might not be related only to the amount of stem/progenitor cells but also to a different timing of cell cycle entry.

A Meta-Analysis of Unrelated Donor Umbilical Cord Blood Transplantation versus Unrelated Donor Bone Marrow Transplantation in Adult and Pediatric Patients

Several studies have compared the results of unrelated donor bone marrow transplantation (UBMT) and unrelated donor cord blood transplantation (UCBT). To objectively analyze these data, we performed a systematic review and meta-analysis of pooled data on comparative studies of UCBT and UBMT in patients requiring hematopoietic stem cell transplantation. Combining the studies, 161 children and 316 adults undergoing UCBT (mostly 1 or 2 antigen-mismatched), along with 316 children and 996 adults undergoing UBMT (almost entirely fully matched with the recipient), were analyzed. T-cell-depleted UBMT was excluded; where data were available, only fully matched UBMT was used in the analysis. Pooled comparisons of studies of UCBT and UBMT in children found that the incidence of chronic graft-versus-host disease (GVHD) was lower with UCBT (relative risk [RR] = 0.26; 95% confidence interval [CI] = 0.12-0.57; P = .16), but the incidence of grade III-IV acute GVHD did not differ (RR = 1.46; 95% CI = 0.42-5.03; P = .55). There was no difference in 2-year OS in children when studies were pooled (RR = 0.76; 95% CI = 0.31-1.87; P = .55). For adults, transplantation-related mortality (pooled estimate, 1.04; 95% CI = 0.52-2.08; P = .91) and disease-free survival (DFS) (pooled estimate, 0.59; 95% CI = 0.18-1.96; P = .39) were not statistically different. Because of the unavailability of randomized controlled trials, pooled analysis of nonrandomized comparative studies was performed. Thus, our meta-analysis confirmed that UCBT in children and adults had consistently equivalent survival outcomes compared with UBMT despite greater donor-recipient HLA disparity with UCBT.

Double cord blood transplants: filling a niche?

Over the last decade, umbilical cord blood (CB) has become a viable option for hematopoietic stem cell transplants. A limiting factor has been the 10-fold lower cell dose in a CB unit compared with harvested bone marrow or peripheral blood stem cells. The low cell dose leads to delayed engraftment and an increase in graft failure. Double cord blood transplants represent a novel strategy to overcome this limitation. This review will cover the rationale behind and clinical results of double cord blood transplant studies. The chimerism data from these studies reveal that typically only one CB "wins the battle" for engraftment. These results may have important scientific implications in terms of understanding the nature of the hematopoietic stem cell niche and how modulation of this niche may impact transplant outcomes.

Umbilical Cord Blood (UCB) Transplantation: An Alternative to the Use of Unrelated Volunteer Donors?

Cryopreserved umbilical cord blood (UCB) from 4-6/6 HLA-A,B antigen and DRB1 allele matched unrelated neonatal donors contains sufficient numbers of hematopoietic stem cells (HSC) to engraft most younger pediatric patients with leukemia. Recent data demonstrate promising results in larger children and adults, as well as in patients with nonmalignant disorders. As a result, the number of UCB transplantations (UCBT) being performed is increasing dramatically. UCB has the clear benefits of rapid availability and a reduced stringency of requirement for HLA match. The latter attribute has the potential to extend the donor pool, which is of great importance for racial and ethnic minorities. Furthermore, new preparative regimens combined with double-unit grafts have been associated with improved engraftment and survival in larger children and adults, making UCBT a viable potential alternative to unrelated volunteer donor transplantation, especially in preference to transplantation using mismatched volunteers. This review summarizes the current status of unrelated donor UCBT and describes both the challenges and current areas of research associated with this HSC source.

Umbilical cord blood transplantation

Over the past decade umbilical cord blood has been established as a viable source of hematopoietic stem cells for allogeneic transplantation. Early experience with umbilical cord blood transplantation (CBT) demonstrated a lower incidence of graft-versus-host disease even though the procedure was performed with HLA-disparate grafts. The overall outcome of CBT appears similar to that of allogeneic bone marrow transplantation. The expansion of the donor selection is particularly beneficial to ethnic minorities, whose representation in the marrow registries is relatively small. The major drawbacks of CBT are slow hematopoietic recovery and a high incidence of graft failure, as a result of a lower number of progenitors infused. This paper reviews the current results of CBT and ongoing investigations to increase its availability to a larger number of recipients.

Donor selection for unrelated cord blood transplants

The number of unrelated cord blood transplants is increasing, with more than 8000 patients reported worldwide. Criteria of donor choice have been identified. Cell dose measured by number of nucleated cells is the most important factor, thus increases in cell dose can partially overcome the presence of HLA incompatibilities. Overall, increasing the number of HLA incompatibilities is associated with non-engraftment, but it also decreases the risk of relapse in patients with malignant disease, resulting in an absence of effect of HLA incompatibilities on event-free survival (survival without relapse or complications related to the transplant). However, in patients with non-malignant disorders, increasing the number of HLA incompatibilities decreases the overall survival. These results show that criteria of donor choice based on number of infused cells, number of HLA incompatibilities and diagnosis improve outcomes of unrelated cord blood transplants. Currently, owing to the possibility of using a non HLA identical donor, most patients can find a donor, increasing the need for the development of the inventory of cord blood banks. Methods of improving engraftment are currently under investigation.

Clinical use of umbilical cord blood hematopoietic stem cells

Umbilical cord blood hematopoietic stem cells coming from related or unrelated donors are an alternative source of hematopoietic stem cells for patients undergoing transplantation for a wide variety of diseases. In the unrelated donor transplant setting, shorter time to transplant, which is particularly relevant to patients requiring urgent transplantation, and tolerance of 1-2 human leukocyte antigen mismatch, which increases the chance of finding a suitable donor, are evident advantages over bone marrow transplantation. The speed of engraftment is slower after cord blood transplantation but it is counterbalanced by a lower incidence of severe graft-versus-host disease. Cell dose and human leukocyte antigen are major factors influencing outcome after umbilical cord blood transplantation. Retrospective comparisons of clinical outcomes between unrelated cord blood and unrelated bone transplantation in children and adults have shown similar results, showing the value of this source of hematopoietic stem cell for transplantation. This review describes the recent clinical results and discusses developing research strategies aimed at optimizing the results of cord blood transplantation.

Assessment of cord blood unit characteristics on the day of transplant: comparison with data issued by cord blood banks

BACKGROUND

Selection of a cord blood (CB) unit for allogeneic transplantation relies on graft characterization results provided by cord blood banks (CBBs). The goal was to compare the graft characterization results obtained upon thawing and washing to those provided by CBBs at selection.

STUDY DESIGN AND METHODS

With tests that assess CB graft characteristics known to impact engraftment, CB units have been analyzed after thaw and before infusion. Our results were compared to data provided by CBBs to determine the impact on engraftment and assess how CBB-supplied information can affect future CB unit selection.

RESULTS

Variability was noted as to the type of information provided by the different CBBs. Also, variability was found between the information provided by CBBs and the graft characterization results obtained upon thawing and washing. In some cases, CB measures known to be predictive of engraftment were found much lower than reported by CBBs. Only the total nucleated cell count, which is the main CB graft selection criterion besides HLA matching, correlated favorably.

CONCLUSIONS

Our data reveal a high degree of variability in graft characteristics provided by CBBs and often poor correlation with results obtained on thawed and washed CB units. We suggest that standardized laboratory procedures aimed at graft characterization should be used by both CBBs and transplant centers to avoid unacceptable discrepancies.

Reduced-intensity conditioning followed by unrelated umbilical cord blood transplantation for advanced hematologic malignancies: rapid engraftment in bone marrow

Reduced-intensity (RI) conditioning followed by cord blood transplantation (CBT) is a new treatment modality, but failure to engraft is a major concern. We describe 12 patients with advanced hematologic malignancies who underwent RI conditioning and CBT with a conditioning regimen consisting of 200 mg/m(2) fludarabine (Flu), 50 mg/kg cyclophosphamide (CY), and 3 Gy total body irradiation (TBI). Cyclosporin A and/or methotrexate were used for graft-versus-host disease prophylaxis. Cord blood grafts were not mismatched for more than 2 serologically defined HLA alleles but were later found by high-resolution DNA typing to be mismatched for 2 to 4 alleles in most cases. Short tandem repeat analysis of bone marrow cells at day 14 showed complete donor chimerism in 6 of the patients and mixed chimerism in 5, indicating rapid engraftment in the bone marrow, whereas the remaining patient experienced graft rejection. Neutrophil recovery was achieved at a median of day 17 (range, days 11-24) in 10 of the 11 patients with marrow chimerism at day 14. Of these 10 patients, however, transplantation-related mortality within 100 days occurred in 4 patients who showed failed platelet recovery and a lack of durable engraftment. Overall survival and disease-free survival rates were 41.7% and 33.3%, respectively. These results show that CB mismatched at 2 to 4 HLA alleles and transplanted with the Flu/CY/3 Gy TBI regimen is able to engraft in the bone marrow as early as day 14.