Hematopoietic stem cell transplantation donor sources in the 21st century: choosing the ideal donor when a perfect match does not exist

A fifty-year odyssey: prospects for a cytomegalovirus vaccine in transplant and congenital infection

INTRODUCTION

It has been almost fifty years since the Towne strain was used by Plotkin and collaborators as the first vaccine candidate for cytomegalovirus (CMV). While that approach showed partial efficacy, there have been a multitude of challenges to improve on the promise of a CMV vaccine. Efforts have been dichotomized into a therapeutic vaccine for patients with CMV-infected allografts, either stem cells or solid organ, and a prophylactic vaccine for congenital infection.

AREAS COVERED

This review will evaluate research prospects for a therapeutic vaccine for transplant recipients that recognizes CMV utilizing primarily T cell responses. Similarly, we will provide an extensive discussion on attempts to develop a vaccine to prevent the manifestations of congenital infection, based on eliciting a humoral anti-CMV protective response. The review will also describe newer developments that have upended the efforts toward such a vaccine through the discovery of a second pathway of CMV infection that utilizes an alternative receptor for entry using a series of antigens that have been determined to be important for prevention of infection.

EXPERT COMMENTARY

There is a concerted effort to unify separate therapeutic and prophylactic vaccine strategies into a single delivery agent that would be effective for both transplant-related and congenital infection.

The number of CD34+CD133+ hematopoietic stem cells residing in umbilical cord blood (UCB) units is not correlated with the numbers of total nucleated cells and CD34+ cells: a possible new indicator for quality evaluation of UCB units

Umbilical cord blood transplantation (UCBT) is often associated with delayed neutrophil and platelet recovery. Engraftment failure is another major obstacle. Several factors influence these serious complications, including the numbers of total nucleated cells (TNCs) and CD34⁺ cells which have been used as reliable factors for selecting UCB units for transplantation. However, whether both factors are reliable indices of the hematopoietic stem cell (HSC) activity of UCB units remains unknown. To evaluate the quality of UCB units, we quantified the actual number of transplantable CD34⁺CD133⁺ HSCs (tHSCs) residing in UCB units. The number of tHSCs was not correlated with the numbers of TNCs or CD34⁺ cells. These results strongly suggest that neither factor reflects the numbers of tHSCs residing in UCB units. To validate the significance of the number of tHSCs, further analysis is required to determine whether the number of tHSCs residing in UCB units is useful as a new indicator for the quality assessment of UCB units.

Favorable Outcome of Post-Transplantation Cyclophosphamide Haploidentical Peripheral Blood Stem Cell Transplantation with Targeted Busulfan-Based Myeloablative Conditioning Using Intensive Pharmacokinetic Monitoring in Pediatric Patients

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) with post-transplantation cyclophosphamide (PTCy) was performed previously in adults using a nonmyeloablative conditioning regimen and bone marrow as a graft source. In an effort to reduce relapse rates, myeloablative conditioning regimens with higher intensities are now used. We used an intensive daily pharmacokinetic monitoring method for busulfan dosing in children for effective myeloablation and to reduce toxicity. Here, we report the retrospective results of 34 patients (median age 11.1 years) who underwent haplo-HSCT with PTCy using a targeted busulfan-based myeloablative conditioning regimen and peripheral blood as a stem cell source. The donor-type neutrophil engraftment rate was 97.1%, and the cumulative incidence rates of grade II to IV and grade III to IV acute and extensive chronic graft-versus-host disease were 38.2%, 5.9%, and 9.1%, respectively. The overall survival and event-free survival rates, and treatment-related mortality were 85.0%, 79.4%, and 2.9%, respectively. Based on the subgroup analysis of patients with malignancies (n = 23), the relapse incidence rate was 21.7%. Haplo-HSCT using PTCy with targeted busulfan-based myeloablative conditioning and peripheral blood as a stem cell source was a safe and promising therapeutic option for children.

A revised road map for the commitment of human cord blood CD34-negative hematopoietic stem cells

We previously identified CD34-negative (CD34-) severe combined immunodeficiency (SCID)-repopulating cells as primitive hematopoietic stem cells (HSCs) in human cord blood. In this study, we develop a prospective ultra-high-resolution purification method by applying two positive markers, CD133 and GPI-80. Using this method, we succeed in purifying single long-term repopulating CD34- HSCs with self-renewing capability residing at the apex of the human HSC hierarchy from cord blood, as evidenced by a single-cell-initiated serial transplantation analysis. The gene expression profiles of individual CD34+ and CD34- HSCs and a global gene expression analysis demonstrate the unique molecular signature of CD34- HSCs. We find that the purified CD34- HSCs show a potent megakaryocyte/erythrocyte differentiation potential in vitro and in vivo. Megakaryocyte/erythrocyte progenitors may thus be generated directly via a bypass route from the CD34- HSCs. Based on these data, we propose a revised road map for the commitment of human CD34- HSCs in cord blood.

Frequency of Finding Family Donors: A Single Center Experience

OBJECTIVES

Allogeneic hematopoietic stem cell transplant is a curative treatment option for many hematologic diseases. The existence of a fully compatible donor for recipients is the first condition for minimized transplant-related mortality and morbidity. The best donor for hematopoietic stem cell transplant is an HLA-matched sibling donor. The possibility of finding an HLA-matched sibling is less than 30% worldwide. Hematopoietic stem cell transplant is needed for an increasing number of patients every year, but the ability to find a fully compatible donor has limited its use.

MATERIALS AND METHODS

From August 2012 to May 2017, we screened 412 adult patients who required AHSCT and their families for HLA tissue groups who were seen at our center (Baskent University Adana Dr. Turgut Noyan Research and Medical Center Hematology Unit). To screen tissue groups at our center, we perform lowresolution typing for HLA-A, -B, -C, -DRB1, and -DQB. If an HLA genotype cannot be identified, verification typing is done using highresolution testing.

RESULTS

We found matched family donors in 227 (55%) of 412 patients screened at our center. The ratio of HLAmatched related donors was 83% for 279 patients who received allogeneic stem cell transplant.

CONCLUSIONS

The likelihood of finding eligible unrelated donors has been gradually increasing, in part due to the development of the National Bone Marrow Bank. However, a careful screening for related donors is still important. Our findings indicate the importance of careful examination of family genealogy and of careful family screening in our region.

Cost-effectiveness analysis of haploidentical vs matched unrelated allogeneic hematopoietic stem cells transplantation in patients older than 55 years

Due to limited donor availability, high comorbidities, and cost issues, allogeneic hematopoietic stem cell transplant is not universally accessible. The aim of this study was to conduct a cost-effectiveness analysis of haploidentical vs matched unrelated transplant. This retrospective study included patients with hematological malignancies older than 55 years who underwent haploidentical or matched unrelated transplant between 2011 and 2013 in Marseille. The incremental cost-effectiveness ratio has been calculated using the mean overall survival and the mean transplant costs. Costs were calculated using a micro-costing strategy from the hospital perspective and a time horizon at 2 years. Haploidentical transplant was considered an innovative procedure and matched unrelated transplant as the reference. Probabilistic and sensitivity analyses were performed on the incremental cost-effectiveness ratio. During inclusion, 29 patients underwent haploidentical transplant and 63 matched unrelated transplant. In haploidentical and matched unrelated transplant, the mean overall survival was 19.4 (1.6) months and 15.1 (1.2) months (p = 0.06), respectively, and the mean cost was 98,304 (40,872) € and 151,373 (65,742) € (p < 0.01), respectively. The incremental cost-effectiveness ratio was assessed to -148,485 (-1,265,550; -64,368) € per life year gained. Among older patients suffering from hematological malignancies, haploidentical transplant seemed in our analysis to be cost-effective compared with matched unrelated transplant.

Network geometry of evidence from randomised controlled trials addressing donor selection and source of haematopoietic progenitor cells used in allogeneic transplantation: a systematic scoping review

BACKGROUND AND METHODS

A scoping review of randomised controlled trials (RCTs) addressing source of cells and choice of donor for allogeneic haematopoietic cell transplantation (HCT) was performed to create a network of best evidence that allows us to identify new potential indirect comparisons for the strategic development of future studies that connect to the existing evidence network.

RESULTS

A total of 19 eligible RCTs (2589 total patients) were identified. Nine studies (1566 patients) compared clinical outcomes following the use of peripheral blood progenitor cells (PBPCs) with bone marrow (BM) from matched related donors (eight studies) or matched unrelated donors (one study). The remaining studies compared BM or PBPCs with various methods of BM stimulation or manipulation (six studies), compared different methods of surface molecule-based selection and/or depletion of grafts (two studies) or compared the optimal number of units for paediatric cord blood transplantation (two studies). No published RCTs compared different types of donors. The geometry of the evidence network was analysed to identify opportunities for potential novel indirect comparisons and to identify opportunities to expand the network. Few indirect comparisons are currently feasible due to small sample size and heterogeneity in patient diagnoses and demographics between treatment nodes in the network.

CONCLUSION

More RCTs that enrol greater numbers of similar patients are needed to leverage the current evidence network concerning donor choice and source of cells used in allogeneic HCT.

[Non eligibility criteria for hematopoietic stem cell donors: Guidelines from the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

The evolution of HLA typing and transplantation techniques makes it easier to identify a donor for hematopoietic stem cell (HSC) transplantation. This activity, strongly regulated by regulatory or normative texts, implies in addition biological, medical, para-medical and sometimes psychological evaluations. The benefit/risk discussion is complicated because it must take into account the benefit/risk ratio for the recipient, and the donor risk. No Evidence-Based Medicine data is available and serious events are very rare situations. Biovigilance declarations and their analysis are of fundamental importance. Certain obvious and definite contraindications could be detected very early in the process. It is important to assess whether a risk factor or pathology contributes to increasing the risk associated with collection. In case of recipient risk, the situation should be discussed with the patient team. These recommendations focus on adult peripheral blood HSC donors. They refer to donor information, confidentiality of exchanges, the impact of moral or material pressures, declarations of biovigilance, collegiality and traceability of difficult decisions, desirable experience and training for doctors in charge, use of expert advice informed by an explicit exchange on the possible risks, parsimony of therapeutic interventions and minimization of risks for the donor. We also recommend creation, availability and use by the community of tools and documents (registries, questionnaires, synthetic recommendations, feedback, and collegial qualification meetings) useful for practice.

Anti-HLA Antibody Levels Are Associated With the Risk of Graft Failure After Allogeneic Hematopoietic Stem Cell Transplant

OBJECTIVES

Allogeneic hematopoietic stem cell transplant provides a curative treatment for a considerable amount of hematologic diseases, and it is widely used today. Successful allogeneic stem cell transplant can be compromised by treatment-related toxicity, graft-versus-host disease, infectious complications, disease relapse, and graft failure. Primary graft failure is an important cause of hematopoietic stem cell transplant failure. Primary graft failure correlates with the level of complement-binding, donor-specific anti-HLA antibodies prior to transplant.

MATERIALS AND METHODS

We evaluated 15 patients who underwent hematopoietic stem cell transplant using peripheral blood stem cells in terms of graft failure and anti-HLA antibody levels before transplant. All were treated between January 2015 and June 2016. Pretreatment serum anti-HLA class I and anti-HLA class II antibody levels were measured in all patients.

RESULTS

Anti-HLA class I antibodies were present in 7 patients (46.6%) and anti-HLA class II antibodies in 8 (53.3%). All three patients who developed primary graft failure were anti-HLA-positive.

CONCLUSIONS

Anti-HLA antibodies are a significant cause of graft failure. It is a situation that must be understood with caution. Our results support the considerations that allogeneic hematopoietic stem cell transplant, especially when a fully compatible sibling donor is not present, should include screening of donor-specific antibodies of alternative donors and desensitization therapy for allosensitized patients before transplant.

ABO incompatibility in mismatched unrelated donor allogeneic hematopoietic cell transplantation for acute myeloid leukemia: A report from the acute leukemia working party of the EBMT

ABO incompatibility is commonly observed in stem cell transplantation and its impact in this setting has been extensively investigated. HLA-mismatched unrelated donors (MMURD) are often used as an alternative stem cell source but are associated with increased transplant related complications. Whether ABO incompatibility affects outcome in MMURD transplantation for acute myeloid leukemia (AML) patients is unknown. We evaluated 1,013 AML patients who underwent MMURD transplantation between 2005 and 2014. Engraftment rates were comparable between ABO matched and mismatched patients, as were relapse incidence [34%; 95% confidence interval (CI), 28-39; for ABO matched vs. 36%; 95% CI, 32-40; for ABO mismatched; P = .32], and nonrelapse mortality (28%; 95% CI, 23-33; for ABO matched vs. 25%; 95% CI, 21-29; for ABO mismatched; P = .2). Three year survival was 40% for ABO matched and 43% for ABO mismatched patients (P = .35), Leukemia free survival rates were also comparable between groups (37%; 95% CI, 32-43; for ABO matched vs. 38%; 95% CI, 33-42; for ABO mismatched; P = .87). Incidence of grade II-IV acute graft versus host disease was marginally lower in patients with major ABO mismatching (Hazard ratio of 0.7, 95% CI, 0.5-1; P = .049]. ABO incompatibility probably has no significant clinical implications in MMURD transplantation.

Haploidentical peripheral blood stem cell transplantation without irradiation or busulfan after reduced-intensity conditioning for KMT2A(MLL)-rearranged infant B-cell precursor acute lymphoblastic leukemia: Report of two cases

We present two infants with KMT2A(MLL)-gene-R-associated BCP-ALL, who received HLA haploidentical PBSCT after RIC. The patients developed ALL at age 6 months and 3 months, respectively. Case 1 underwent PBSCT at the second CR with detectable KMT2A-AFF1(MLL-AF4) fusion gene transcript at 11 months of age, and Case 2 at the first CR without KMT2A-MLLT1(MLL-ENL) fusion gene transcript at 8 months of age. Both patients received G-CSF-mobilized unmanipulated peripheral blood mononuclear cells from their HLA haploidentical mothers after administration of FLU, MEL, and ATG. Tacrolimus, methotrexate, and mPSL were administered as prophylaxis against GVHD. Engraftment was rapidly obtained with complete chimerism in both patients. Acute adverse events included acute GVHD in Case 1 and bacterial sepsis in Case 2. At last clinical check at age 5 years and 4 years, respectively, both patients were recurrence-free and attained normal growth and development. We conclude that PBSCT from an HLA haploidentical mother with non-TBI and non-BU regimen seems feasible and efficacious, offering favorable life quality for infants.

Reprogramming MHC specificity by CRISPR-Cas9-assisted cassette exchange

The development of programmable nucleases has enabled the application of new genome engineering strategies for cellular immunotherapy. While targeted nucleases have mostly been used to knock-out or knock-in genes in immune cells, the scarless exchange of entire immunogenomic alleles would be of great interest. In particular, reprogramming the polymorphic MHC locus could enable the creation of matched donors for allogeneic cellular transplantation. Here we show a proof-of-concept for reprogramming MHC-specificity by performing CRISPR-Cas9-assisted cassette exchange. Using murine antigen presenting cell lines (RAW264.7 macrophages), we demonstrate that the generation of Cas9-induced double-stranded breaks flanking the native MHC-I H2-Kd locus led to exchange of an orthogonal H2-Kb allele. MHC surface expression allowed for easy selection of reprogrammed cells by flow cytometry, thus obviating the need for additional selection markers. MHC-reprogrammed cells were fully functional as they could present H2-Kd-restricted peptide and activate cognate T cells. Finally, we investigated the role of various donor template formats on exchange efficiency, discovering that templates that underwent in situ linearization resulted in the highest MHC-reprogramming efficiency. These findings highlight a potential new approach for the correcting of MHC mismatches in cellular transplantation.

Ocular progenitor cells and current applications in regenerative medicines - Review

The recent emerging field of regenerative medicine is to present solutions for chronic diseases which cannot be sufficiently repaired by the body's own mechanisms. Stem cells are undifferentiated biological cells and have the potential to develop into many different cell types in the body during early life and growth. Self renewal and totipotency are the characteristic features of stem cells and it holds a promising result for treating various diseases like diabetic foot ulcer, heart diseases, lung diseases, Autism, Skin diseases, arthritis including eye disease. Failure of complete recovery of eye diseases and complications that follow conventional treatments have shifted search to a new form of regenerative medicine using Stem cells. The ocular progenitor cells are remarkable in stem cell biology and replenishing degenerated cells despite being present in low quantity and quiescence in our body has a high therapeutic value. In this paper we have review the applications on ocular progenitor stem cells in treatment of human eye diseases and address the strategies that have been exploited in an effort to regain visual function in the advance treatment of stem cells without any side effects and also present the significance in advance stem cell research.

Pediatric Hematopoietic Stem Cell Transplantation in India: Status, Challenges and the Way Forward : Based on Dr. K. C. Chaudhuri Oration 2016

Hematopoietic stem cell transplantation (HSCT) refers to therapies that aim to eliminate a patient's hematopoietic and immune system and replace it with his own (autologous) or someone else's (allogenic) system. The applications of this therapy are vast and growing, and include several malignant and benign diseases incurable by any other existing modalities. Pediatric patients constitute a minority of HSCT recipients with unique concerns. Despite substantial progress in the last two decades, limitations due to financial, infrastructural, manpower and research constraints act as barriers to fulfilling the large need for pediatric HSCT services in our country. Limited availability of unrelated donors and cord blood units is another constraint. Here in this oration, we discuss the current issues pertaining to pediatric HSCT in India and describe our experience with the same.

Pharmacokinetics, Pharmacodynamics and Pharmacogenomics of Immunosuppressants in Allogeneic Haematopoietic Cell Transplantation: Part I

Although immunosuppressive treatments and target concentration intervention (TCI) have significantly contributed to the success of allogeneic haematopoietic cell transplantation (alloHCT), there is currently no consensus on the best immunosuppressive strategies. Compared with solid organ transplantation, alloHCT is unique because of the potential for bidirectional reactions (i.e. host-versus-graft and graft-versus-host). Postgraft immunosuppression typically includes a calcineurin inhibitor (cyclosporine or tacrolimus) and a short course of methotrexate after high-dose myeloablative conditioning, or a calcineurin inhibitor and mycophenolate mofetil after reduced-intensity conditioning. There are evolving roles for the antithymyocyte globulins (ATGs) and sirolimus as postgraft immunosuppression. A review of the pharmacokinetics and TCI of the main postgraft immunosuppressants is presented in this two-part review. All immunosuppressants are characterized by large intra- and interindividual pharmacokinetic variability and by narrow therapeutic indices. It is essential to understand immunosuppressants' pharmacokinetic properties and how to use them for individualized treatment incorporating TCI to improve outcomes. TCI, which is mandatory for the calcineurin inhibitors and sirolimus, has become an integral part of postgraft immunosuppression. TCI is usually based on trough concentration monitoring, but other approaches include measurement of the area under the concentration-time curve (AUC) over the dosing interval or limited sampling schedules with maximum a posteriori Bayesian personalization approaches. Interpretation of pharmacodynamic results is hindered by the prevalence of studies enrolling only a small number of patients, variability in the allogeneic graft source and variability in postgraft immunosuppression. Given the curative potential of alloHCT, the pharmacodynamics of these immunosuppressants deserves to be explored in depth. Development of sophisticated systems pharmacology models and improved TCI tools are needed to accurately evaluate patients' exposure to drugs in general and to immunosuppressants in particular. Sequential studies, first without and then with TCI, should be conducted to validate the clinical benefit of TCI in homogenous populations; randomized trials are not feasible, because there are higher-priority research questions in alloHCT. In Part I of this article, we review the alloHCT process to facilitate optimal design of pharmacokinetic and pharmacodynamics studies. We also review the pharmacokinetics and TCI of calcineurin inhibitors and methotrexate.

Emerging cellular and gene therapies for congenital anemias

Congenital anemias comprise a group of blood disorders characterized by a reduction in the number of peripherally circulating erythrocytes. Various genetic etiologies have been identified that affect diverse aspects of erythroid physiology and broadly fall into two main categories: impaired production or increased destruction of mature erythrocytes. Current therapies are largely focused on symptomatic treatment and are often based on transfusion of donor-derived erythrocytes and management of complications. Hematopoietic stem cell transplantation represents the only curative option currently available for the majority of congenital anemias. Recent advances in gene therapy and genome editing hold promise for the development of additional curative strategies for these blood disorders. The relative ease of access to the hematopoietic stem cell compartment, as well as the possibility of genetic manipulation ex vivo and subsequent transplantation in an autologous manner, make blood disorders among the most amenable to cellular therapies. Here we review cell-based and gene therapy approaches, and discuss the limitations and prospects of emerging avenues, including genome editing tools and the use of pluripotent stem cells, for the treatment of congenital forms of anemia. © 2016 Wiley Periodicals, Inc.

National Institutes of Health Hematopoietic Cell Transplantation Late Effects Initiative: The Research Methodology and Study Design Working Group Report

The increasing numbers of hematopoietic cell transplantations (HCTs) performed each year, the changing demographics of HCT recipients, the introduction of new transplantation strategies, incremental improvement in survival, and the growing population of HCT survivors demand a comprehensive approach to examining the health and well-being of patients throughout life after HCT. This report summarizes strategies for the conduct of research on late effects after transplantation, including consideration of the study design and analytic approaches; methodologic challenges in handling complex phenotype data; an appreciation of the changing trends in the practice of transplantation; and the availability of biospecimens to support laboratory-based research. It is hoped that these concepts will promote continued research and facilitate the development of new approaches to address fundamental questions in transplantation outcomes.

Impact of HLA-Mismatch in Unrelated Donor Hematopoietic Stem Cell Transplantation: A Meta-Analysis

The magnitude of risk associated with 9/10 mismatched unrelated donor (MMURD) hematopoietic stem cell transplantation and that of mismatches at the individual HLA loci remain unclear. We performed a meta-analysis to assess the difference in clinical outcomes between matched unrelated donor (MUD) and MMURD transplantation. A comprehensive search of Medline and Embase for manuscripts regarding transplantation outcomes in primarily adult patients with hematologic malignancies was performed. The pooled effect estimates were calculated using DerSimonian-Laird random effects models. A total of 13 studies were included, reporting on 13,446 transplants. 9/10 MMURD transplantation was associated with worse overall survival compared to 10/10 MUD transplantation (pooled HR: 1.27, 95% CI: 1.12-1.45; n = 7 studies). Mismatch at HLA-A, -B, or -C was associated with significantly worse overall survival compared to MUD transplantation, while there was no significant difference associated with -DQ or -DPB1 mismatch. Inferior survival associated with HLA-DRB1 mismatch could not be ruled out. Data on acute and chronic graft-versus-host disease were scarce but favored MUD transplantation. In summary, this meta-analysis of the available literature favored MUD over MMURD transplantation in hematologic malignancies and further quantifies the risks associated with specific HLA-allele mismatches. Am. J. Hematol. 91:551-555, 2016. © 2016 Wiley Periodicals, Inc.

Haploidentical hematopoietic stem cell transplantation without total body irradiation for pediatric acute leukemia: a single-center experience

Hematopoietic stem cell transplantation (HSCT) is a promising method for therapy of pediatric patients with acute leukemia. However, less availability of matched donors limited its wide application. Recently, haploidentical HSCT has become a great resource. Here, we have retrospectively reported our experience of 20 pediatric patients with acute leukemia who underwent haploidentical HSCT without total body irradiation (TBI) myeloablative regimen in our center from November 2007 to June 2014. All the patients attained successful HSCT engraftment in terms of myeloid and platelet recovery. Thirteen patients developed grade I–IV acute graft-versus-host disease (a-GVHD). The incidence of grade I–II a-GVHD, grade III–IV a-GVHD, and chronic GVHD (c-GVHD) was 45%, 20%, and 25%, respectively. The mean myeloid and platelet recovery time was 13.20±2.41 and 19.10±8.37 days. The median follow-up time was 43.95±29.26 months. During the follow-up, three patients died. The overall survival (OS) rate was 85%. The present study indicated that haploidentical HSCT without TBI myeloablative regimen significantly improved the OS rate of pediatric patients with acute leukemia.

Advances in haploidentical stem cell transplantation for hematologic malignancies

One of the most important advances in allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the use of alternative donors and cell sources, such as haploidentical transplants (haplo-HSCT) from family donors. Several approaches have been developed to overcome the challenging bidirectional alloreactivity. We discuss these approaches, including ex vivo T-cell-depleted grafts with megadose of CD34(+) cells, not requiring immunosuppression after allogeneic transplantation for graft-versus-host disease (GVHD) prophylaxis, and other strategies using unmanipulated T-cell-replete grafts with intensive immunosuppression or post-transplantation cyclophosphamide to minimize the GVHD. We also address the role of other strategies developed in the context of the haplo-HSCT platforms, such as ex vivo selective depletion of alloreactive donor T-cell subpopulations, infusion of antigen-specific T-cells against several pathogens, and infusion of regulatory T-cells, among other experimental approaches. Finally, some considerations about the selection of the most suitable donor, when more than one family member is available, are also addressed.

How do we choose the best donor for T-cell-replete, HLA-haploidentical transplantation?

In haploidentical stem cell transplantations (haplo-SCT), nearly all patients have more than one donor. A key issue in the haplo-SCT setting is the search for the best donor, because donor selection can significantly impact the incidences of acute and chronic graft-versus-host disease, transplant-related mortality, and relapse, in addition to overall survival. In this review, we focused on factors associated with transplant outcomes following unmanipulated haplo-SCT with anti-thymocyte globulin (ATG) or after T-cell-replete haplo-SCT with post-transplantation cyclophosphamide (PT/Cy). We summarized the effects of the primary factors, including donor-specific antibodies against human leukocyte antigens (HLA); donor age and gender; killer immunoglobulin-like receptor-ligand mismatches; and non-inherited maternal antigen mismatches. We also offered some expert recommendations and proposed an algorithm for selecting donors for unmanipulated haplo-SCT with ATG and for T-cell-replete haplo-SCT with PT/Cy.

HLA Haplotype Mismatch Transplants and Posttransplant Cyclophosphamide

The use of high dose posttransplant cyclophosphamide (PT-CY) introduced by the Baltimore group approximately 10 years ago has been rapidly adopted worldwide and is becoming a standard for patients undergoing unmanipulated haploidentical (HAPLO) transplants. PT-CY has been used following nonmyeloablative as well as myeloablative conditioning regimens, for bone marrow or peripheral blood grafts, for patients with malignant and nonmalignant disorders. Retrospective comparisons of HAPLO grafts with conventional sibling and unrelated donor grafts have been published and suggest comparable outcome. The current questions to be answered include the use of PT-CY for sibling and unrelated donors transplant, possibly in the context of prospective randomized trial.

Alloantigen presentation and graft-versus-host disease: fuel for the fire

Allogeneic stem cell transplantation (SCT) is a unique procedure, primarily in patients with hematopoietic malignancies, involving chemoradiotherapy followed by the introduction of donor hematopoietic and immune cells into an inflamed and lymphopenic environment. Interruption of the process by which recipient alloantigen is presented to donor T cells to generate graft-versus-host disease (GVHD) represents an attractive therapeutic strategy to prevent morbidity and mortality after SCT and has been increasingly studied in the last 15 years. However, the immune activation resulting in GVHD has no physiological equivalent in nature; alloantigen is ubiquitous, persists indefinitely, and can be presented by multiple cell types at numerous sites, often on incompatible major histocompatibility complex, and occurs in the context of intense inflammation early after SCT. The recognition that alloantigen presentation is also critical to the development of immunological tolerance via both deletional and regulatory mechanisms further adds to this complexity. Finally, GVHD itself appears capable of inhibiting the presentation of microbiological antigens by donor dendritic cells late after SCT that is mandatory for the establishment of effective pathogen-specific immunity. Here, we review our current understanding of alloantigen, its presentation by various antigen-presenting cells, subsequent recognition by donor T cells, and the potential of therapeutic strategies interrupting this disease-initiating process to modify transplant outcome.

Desensitization with plasma exchange in a patient with human leukocyte antigen donor-specific antibodies before T-cell-replete haploidentical transplantation

BACKGROUND

The presence of human leukocyte antigen donor-specific antibodies (DSAs) increases the risk of graft failure in T-cell-replete haploidentical hematopoietic stem cell transplantation (haplo-HSCT) CASE REPORT: A 49-year-old female with high-risk acute myeloid leukemia in first complete remission received a haplo-HSCT from her daughter. Pretransplant recipient screening examination showed high DSAs levels against unshared class I leukocyte antigens.

RESULTS

The patient underwent a desensitization program consisting of plasma exchange (PEX), polyvalent intravenous (IV) immunoglobulins, and IV tacrolimus and mycophenolate mofetil (MMF). This protocol resulted in the disappearance of the DSA anti HLA B41. Engraftment was prompt with stable full donor chimerism.

CONCLUSIONS

This case report suggests that the adopted scheme is safe for reducing DSA levels and facilitating donor engraftment in patients scheduled for haplo-HSCT.

Supportive care in alternative donor transplantation

Alternative donor hematopoietic cell transplantation (HCT) using umbilical cord blood, haploidentical or mismatched unrelated donors is a viable option for patients without human leukocyte antigen (HLA)-identical sibling or matched unrelated donors. The same principles of supportive care as conventional graft sources apply to alternative donor HCT recipients. However, there are some unique supportive care issues related to post-transplant complications, engraftment, graft-versus-host disease, immune reconstitution, and infections that are unique to each of the three alternative graft sources, both in the early and late post-transplant periods. This review discusses the supportive care issues relevant to this population and their management.

Expanding transplant options to patients over 50 years. Improved outcome after reduced intensity conditioning mismatched-unrelated donor transplantation for patients with acute myeloid leukemia: a report from the Acute Leukemia Working Party of the EBMT

The outcome of patients undergoing HLA-matched unrelated donor allogeneic hematopoietic cell transplantation following reduced-intensity conditioning or myeloablative regimens is reported to be equivalent; however, it is not known if the intensity of the conditioning impacts outcomes after mismatched unrelated donor transplantation for acute myeloid leukemia. Eight hundred and eighty three patients receiving reduced-intensity conditioning were compared with 1041 myeloablative conditioning regimen recipients in the setting of mismatched unrelated donor transplantation. The donor graft was HLA-matched at 9/10 in 872 (83.8%) and at 8/10 in 169 (16.2%) myeloablative conditioning recipients, while in the reduced-intensity conditioning cohort, 754 (85.4%) and 129 (14.6%) were matched at 9/10 and 8/10 loci, respectively. Myeloablative conditioning regimen recipients were younger, 70% being <50 years of age compared to only 30% in the reduced-intensity conditioning group (P=0.0001). Significantly, more patients had secondary acute myeloid leukemia (P=0.04) and Karnofsky Performance Status score <90% (P=0.02) in the reduced-intensity conditioning group. Patients <50 and ≥50 years were analyzed separately. On multivariate analysis and after adjusting for differences between the two groups, reduced-intensity conditioning in patients age ≥50 years was associated with higher overall survival (HR 0.78; P=0.01), leukemia-free survival (HR 0.82; P=0.05), and decreased non-relapse mortality (HR 0.73; P=0.03). Relapse incidence (HR 0.91; P=0.51) and chronic graft-versus-host disease (HR 1.31; P=0.11) were, however, not significantly different. In patients <50 years old, there were no statistically significant differences in overall survival, leukemia-free survival, relapse incidence, non-relapse mortality, and chronic graft-versus-host-disease between the groups. Our study shows no significant outcome differences in patients younger than 50 years receiving reduced-intensity vs myeloablative conditioning regimens after mismatched unrelated donor transplantation. Furthermore, the data support the superiority of reduced-intensity conditioning regimens in older adults receiving transplants from mismatched unrelated donors.

Haploidentical Donors: Can Faster Transplantation Be Life-Saving for Patients with Advanced Disease?

Haploidentical stem cell transplantation is a therapeutic option for patients without an HLA-matched donor. It is increasingly being used worldwide due to the application of posttransplantation cyclophosphamide and is associated with lower incidence of graft-versus-host disease and treatment-related mortality. Haploidentical donors are generally available for most patients and stem cells can be rapidly obtained. Delays in transplantation while waiting for unrelated donor cells can be potentially problematic for patients with advanced disease at risk for progression; thus, the use of haploidentical donors, especially in this setting, can be life-saving. Here we reviewed the literature on haploidentical stem cell transplantation performed with posttransplantation cyclophosphamide.

Genetic editing of HLA expression in hematopoietic stem cells to broaden their human application

Mismatch of human leukocyte antigens (HLA) adversely impacts the outcome of patients after allogeneic hematopoietic stem-cell transplantation (alloHSCT). This translates into the clinical requirement to timely identify suitable HLA-matched donors which in turn curtails the chances of recipients, especially those from a racial minority, to successfully undergo alloHSCT. We thus sought to broaden the existing pool of registered unrelated donors based on analysis that eliminating the expression of the HLA-A increases the chance for finding a donor matched at HLA-B, -C, and -DRB1 regardless of a patient’s race. Elimination of HLA-A expression in HSC was achieved using artificial zinc finger nucleases designed to target HLA-A alleles. Significantly, these engineered HSCs maintain their ability to engraft and reconstitute hematopoiesis in immunocompromised mice. This introduced loss of HLA-A expression decreases the need to recruit large number of donors to match with potential recipients and has particular importance for patients whose HLA repertoire is under-represented in the current donor pool. Furthermore, the genetic engineering of stem cells provides a translational approach to HLA-match a limited number of third-party donors with a wide number of recipients.

Hematopoietic stem cell transplantation activity worldwide in 2012 and a SWOT analysis of the Worldwide Network for Blood and Marrow Transplantation Group including the global survey

Data on 68 146 hematopoietic stem cell transplants (HSCTs) (53% autologous and 47% allogeneic) gathered by 1566 teams from 77 countries and reported through their regional transplant organizations were analyzed by main indication, donor type and stem cell source for the year 2012. With transplant rates ranging from 0.1 to 1001 per 10 million inhabitants, more HSCTs were registered from unrelated 16 433 donors than related 15 493 donors. Grafts were collected from peripheral blood (66%), bone marrow (24%; mainly non-malignant disorders) and cord blood (10%). Compared with 2006, an increase of 46% total (57% allogeneic and 38% autologous) was observed. Growth was due to an increase in reporting teams (18%) and median transplant activity/team (from 38 to 48 HSCTs/team). An increase of 167% was noted in mismatched/haploidentical family HSCT. A Strengths, Weaknesses, Opportunities, Threats (SWOT) analysis revealed the global perspective of WBMT to be its major strength and identified potential to be the key professional body for patients and authorities. The limited data collection remains its major weakness and threat. In conclusion, global HSCT grows over the years without plateauing (allogeneic>autologous) and at different rates in the four World Health Organization regions. Major increases were observed in allogeneic, haploidentical HSCT and, to a lesser extent, in cord blood transplantation.

Frequency and Risk Factors Associated with Cord Graft Failure after Transplant with Single-Unit Umbilical Cord Cells Supplemented by Haploidentical Cells with Reduced-Intensity Conditioning

Delayed engraftment and cord graft failure (CGF) are serious complications after unrelated cord blood (UCB) hematopoietic stem cell transplantation (HSCT), particularly when using low-cell-dose UCB units. The haplo-cord HSCT approach allows the use of a lower dose single UCB unit by co-infusion of a CD34(+) selected haploidentical graft, which provides early transient engraftment while awaiting durable UCB engraftment. We describe the frequency, complications, and risk factors of CGF after reduced-intensity conditioning haplo-cord HSCT. Among 107 patients who underwent haplo-cord HSCT, 94 were assessable for CGF, defined as <5% cord blood chimerism at day 60 in the myeloid and CD3 compartments, irrespective of neutrophil and platelet counts. CGF occurred in 14 of 94 assessable patients (15%). Median survival after CGF was 12.7 months with haploidentical or mixed haploidentical-autologous hematopoiesis persisting in the 7 surviving. Median progression-free survival after CGF was 7.7 months and was not statistically different from those without CGF (10.47 months; P = .18). In univariate analyses, no UCB factors were associated with CGF, including cell dose, cell viability, recipient major ABO mismatch against the UCB unit, or degree of HLA match. We also found no association of CGF with recipient cytomegalovirus serostatus, haploidentical donor age, or day 30 haploidentical chimerism. However, higher haploidentical total nucleated and CD34(+) cell doses and day 30 UCB chimerism < 5% in either the myeloid or CD3 compartments were associated with greater risk of CGF. We conclude that assessing chimerism at day 30 may foretell impending CGF, and avoidance of high haploidentical cell doses may reduce risk of CGF after haplo-cord HSCT. However, long-term survival is possible after CGF because of predominant haploidentical or mixed chimerism and hematopoietic function.

Update of hematopoietic cell transplantation for sickle cell disease

PURPOSE OF REVIEW

Hematopoietic cell transplantation (HCT) is a curative therapy for sickle cell disease (SCD) that is utilized very rarely because of limited allogeneic donor availability, limited healthcare resources needed to expand the treatment to regions in the world where most affected individuals reside, and by a view among SCD experts that HCT lacks the evidential rigor with short and long-term toxicity profiles that together might support its broader application.

RECENT FINDINGS

In this update, recent advances focused on donor selection, reduced toxicity preparation for HCT, and treatment of young adults will be presented. The current status of conventional bone marrow transplantation with a human leukocyte antigen-identical sibling donor is summarized.

SUMMARY

HCT for SCD is curative in almost all children who have a human leukocyte antigen-matched sibling donor. The future of this therapy will hinge on expanding the number of individuals who might be treated.

Sequential renal and bone marrow transplants in a child with Fanconi anemia

FA is an autosomal recessive disorder characterized by small stature and renal abnormalities. FA can lead to progressive bone marrow failure, myelodysplastic syndrome, or acute leukemia. Using a multidisciplinary team approach, we managed a 3-yr-old boy with FA who simultaneously developed renal and hematopoietic failure. Because renal function was insufficient to support the conditioning regimen for HCT, we performed a deceased donor renal transplant in December 2012 prior to HCT with the known risk of graft-versus-graft rejection of the donor kidney. Seven months later he underwent allogeneic HCT. He obtained myeloid engraftment on day +11 and peripheral blood chimerism demonstrated all donor by day +21. He developed asymptomatic CMV reactivation and despite antirejection medications, mild skin graft-versus-host disease. He has maintained excellent renal function and remains transfusion independent with full hematopoietic recovery. He has not experienced any renal rejection episodes nor developed donor-specific antibodies toward his renal donor. Peripheral blood chimerism remains completely HCT donor. He is clinically well, now greater than two and a half yr after renal transplant and two yr after HCT. The continuing close collaboration between the Pediatric Nephrology and Bone Marrow Transplant teams is a major factor in this successful outcome.

Stem cell transplantation in adults with acute myelogenous leukemia, normal cytogenetics, and the FLT3-ITD mutation

Following chemotherapy, patients with acute myelogenous leukemia (AML), normal cytogenetics, and the FLT3-ITD mutation have shorter survival compared to wild type (WT) patients. To determine the role of stem cell transplantation (SCT), we performed a retrospective review of adult patients with AML who underwent SCT at our center between January 1, 2007 and December 31, 2011. Of the 200 patients transplanted, 79 patients (40%) had normal cytogenetics; of these, 17 (22%) had the FLT3-ITD mutation, 35 were WT (44%), and 27 (34%) did not have FLT3 testing performed. Clinical characteristics were similar in each group. At four years, overall survival (OS) between FLT3 positive and WT groups was similar: 0.54 (95% CI 0.29-0.75) versus 0.73 (95% CI 0.53-0.99), p=0.18. Relapse rates were also similar, 0.09 (95% CI 0.02-0.21) versus 0.12 (95% CI: 0.02-0.32); p=0.67. We conclude that SCT can abrogate the poor prognosis in FLT3-ITD positive patients.

Hematopoietic Stem and Progenitor Cell Expansion in Contact with Mesenchymal Stromal Cells in a Hanging Drop Model Uncovers Disadvantages of 3D Culture

Efficient ex vivo expansion of hematopoietic stem cells with a concomitant preservation of stemness and self-renewal potential is still an unresolved ambition. Increased numbers of methods approaching this issue using three-dimensional (3D) cultures were reported. Here, we describe a simplified 3D hanging drop model for the coculture of cord blood-derived CD34⁺ hematopoietic stem and progenitor cells (HSPCs) with bone marrow-derived mesenchymal stromal cells (MSCs). When seeded as a mixed cell suspension, MSCs segregated into tight spheroids. Despite the high expression of niche-specific extracellular matrix components by spheroid-forming MSCs, HSPCs did not migrate into the spheroids in the initial phase of coculture, indicating strong homotypic interactions of MSCs. After one week, however, HSPC attachment increased considerably, leading to spheroid collapse as demonstrated by electron microscopy and immunofluorescence staining. In terms of HSPC proliferation, the conventional 2D coculture system was superior to the hanging drop model. Furthermore, expansion of primitive hematopoietic progenitors was more favored in 2D than in 3D, as analyzed in colony-forming assays. Conclusively, our data demonstrate that MSCs, when arranged with a spread (monolayer) shape, exhibit better HSPC supportive qualities than spheroid-forming MSCs. Therefore, 3D systems are not necessarily superior to traditional 2D culture in this regard.

Use of molecular markers to determine postremission treatment in acute myeloid leukemia with normal cytogenetics

Most patients with acute myeloid leukemia can be induced into complete remission, but postremission treatment is required for cure. The choice of postremission therapy in a majority of nonelderly patients, between intensive chemotherapy and allogeneic hematopoietic cell transplantation, is largely determined by the results of conventional cytogenetic analysis. In 45% of patients with a normal karyotype, the presence or absence of specific molecular mutations should be used to determine the prognosis and postremission treatment. In addition, the identification of mutations may indicate a role for targeted intervention, including following transplantation.

A Two-Step Haploidentical Versus a Two-Step Matched Related Allogeneic Myeloablative Peripheral Blood Stem Cell Transplantation

Haploidentical stem cell transplantation (SCT) offers a transplantation option to patients who lack an HLA-matched donor. We developed a 2-step approach to myeloablative allogeneic hematopoietic stem cell transplantation for patients with haploidentical or matched related (MR) donors. In this approach, the lymphoid and myeloid portions of the graft are administered in 2 separate steps to allow fixed T cell dosing. Cyclophosphamide is used for T cell tolerization. Given a uniform conditioning regimen, graft T cell dose, and graft-versus-host disease (GVHD) prophylaxis strategy, we compared immune reconstitution and clinical outcomes in patients undergoing 2-step haploidentical versus 2-step MR SCT. We retrospectively compared data on patients undergoing a 2-step haploidentical (n = 50) or MR (n = 27) peripheral blood SCT for high-risk hematological malignancies and aplastic anemia. Both groups received myeloablative total body irradiation conditioning. Immune reconstitution data included flow cytometric assessment of T cell subsets at day 28 and 90 after SCT. Both groups showed comparable early immune recovery in all assessed T cell subsets except for the median CD3/CD8 cell count, which was higher in the MR group at day 28 compared with that in the haploidentical group. The 3-year probability of overall survival was 70% in the haploidentical group and 71% in the MR group (P = .81), while the 3-year progression-free survival was 68% in the haploidentical group and 70% in the MR group (P = .97). The 3-year cumulative incidence of nonrelapse mortality was 10% in the haploidentical group and 4% in the MR group (P = .34). The 3-year cumulative incidence of relapse was 21% in the haploidentical group and 27% in the MR group (P = .93). The 100-day cumulative incidence of overall grades II to IV acute GVHD was higher in the haploidentical group compared with that in the MR group (40% versus 8%, P < .001), whereas the grades III and IV acute GVHD was not statistically different between both groups (haploidentical, 6%; MR, 4%; P = .49). The cumulative incidence of cytomegalovirus reactivation was also higher in the haploidentical group compared to the MR group (haploidentical, 68%; MR, 19%; P < .001). There were no deaths from GVHD in either group. Using an identical conditioning regimen, graft T cell dose, and GVHD prophylaxis strategy, comparable early immune recovery and clinical outcomes were observed in the 2-step haploidentical and MR SCT recipients.

The role of gamma delta T cells in haematopoietic stem cell transplantation

Although haematopoietic stem cell transplantation (HSCT) is a potential curative treatment for haematological malignancies, it is still a procedure associated with substantial morbidity and mortality due to toxicity, graft-versus-host disease (GVHD) and relapse. Recent attempts of developing safer transplantation modalities increasingly focuses on selective cell depletion and graft engineering with the aim of retaining beneficial immune donor cells for the graft-versus-leukaemia (GVL) effect. In this context, the adoptive and especially innate effector functions of γδ T cells together with clinical studies investigating the effect of γδ T cells in relation to HSCT are reviewed. In addition to phospho-antigen recognition by the γδ T cell receptor (TCR), γδ T cells express receptors of the natural killer (NK) and natural cytotoxicity (NCR) families enabling them to recognize and kill leukaemia cells. Antigen recognition independent from the major histocompatibility complex (MHC) allows for the theoretical possibility of mediating GVL without an allogeneic response in terms of GVHD. Early studies on the impact of γδ T cells in HSCT have reported conflicting results. Recent studies, however, do suggest an overall favourable effect of high γδ T cell immune reconstitution after HSCT; patients with elevated numbers of γδ T cells had a significantly higher overall survival rate and a decreased rate of acute GVHD compared to patients with low or normal γδ T cell counts. Further research in terms of effector mechanisms, subtypes and tissue distribution during the course of HSCT is needed to assess the potentially beneficial effects of γδ T cells in this setting.

Automated CD34+ cell isolation of peripheral blood stem cell apheresis product

BACKGROUND AIMS

Immunomagnetic enrichment of CD34+ hematopoietic "stem" cells (HSCs) using paramagnetic nanobead coupled CD34 antibody and immunomagnetic extraction with the CliniMACS plus system is the standard approach to generating T-cell-depleted stem cell grafts. Their clinical beneficence in selected indications is established. Even though CD34+ selected grafts are typically given in the context of a severely immunosuppressive conditioning with anti-thymocyte globulin or similar, the degree of T-cell depletion appears to affect clinical outcomes and thus in addition to CD34 cell recovery, the degree of T-cell depletion critically describes process quality. An automatic immunomagnetic cell processing system, CliniMACS Prodigy, including a protocol for fully automatic CD34+ cell selection from apheresis products, was recently developed. We performed a formal process validation to support submission of the protocol for CE release, a prerequisite for clinical use of Prodigy CD34+ products.

METHODS

Granulocyte-colony stimulating factor-mobilized healthy-donor apheresis products were subjected to CD34+ cell selection using Prodigy with clinical reagents and consumables and advanced beta versions of the CD34 selection software. Target and non-target cells were enumerated using sensitive flow cytometry platforms.

RESULTS

Nine successful clinical-scale CD34+ cell selections were performed. Beyond setup, no operator intervention was required. Prodigy recovered 74 ± 13% of target cells with a viability of 99.9 ± 0.05%. Per 5 × 10E6 CD34+ cells, which we consider a per-kilogram dose of HSCs, products contained 17 ± 3 × 10E3 T cells and 78 ± 22 × 10E3 B cells.

CONCLUSIONS

The process for CD34 selection with Prodigy is robust and labor-saving but not time-saving. Compared with clinical CD34+ selected products concurrently generated with the predecessor technology, product properties, importantly including CD34+ cell recovery and T-cell contents, were not significantly different. The automatic system is suitable for routine clinical application.