Impact of thymoglobulin prior to pediatric unrelated umbilical cord blood transplantation on immune reconstitution and clinical outcome

Unlicensed Umbilical Cord Blood Units Provide a Safe and Effective Graft Source for a Diverse Population: A Study of 2456 Umbilical Cord Blood Recipients

Umbilical cord blood (UCB) transplantation (UCBT) is a curative procedure for patients with hematologic malignancies and genetic disorders and expands access to transplantation for non-Caucasian patients unable to find a fully matched unrelated donor. In 2011, the US Food and Drug Administration required that unrelated UCBT be performed using either licensed UCB or unlicensed UCB under the Investigational New Drug (IND) program. The National Marrow Donor Program manages an IND under which 2456 patients (1499 adults and 957 children, 564 with malignant diseases and 393 with nonmalignant diseases) underwent single or double UCBT between October 2011 and December 2016. The median patient age was 31 years (range, <1 to 81 years), and 50% of children and 36% of adults were non-Caucasian. The median time to neutrophil engraftment (ie, absolute neutrophil count ≥500/mm³) was 22 days for adults, 20 days for pediatric patients with malignant diseases, and 19 days for pediatric patients with nonmalignant diseases, with corresponding rates of engraftment at 42 days of 89%, 88%, and 90%. In these 3 groups of patients, the incidence of acute graft-versus-host disease (GVHD) grade II-IV was 35%, 32%, and 24%; the incidence of chronic GVHD was 24%, 26%, and 24%; and 1-year overall survival (OS) was 57%, 71%, and 79%, respectively. In multivariate analysis, younger age, lower Hematopoietic Cell Transplantation-Specific Comorbidity Index, early-stage chemotherapy-sensitive disease, and higher performance score were predictive of improved OS for adults. In a subset analysis of children with malignancies undergoing single UCBT, the use of either licensed UCB (n = 48) or unlicensed UCB (n = 382) was associated with similar engraftment and survival. The use of unlicensed UCB units is safe and effective and provides an important graft source for a diverse population.

Reduced-Toxicity (BuFlu) Conditioning Is Better Tolerated but Has a Higher Second Transplantation Rate Compared to Myeloablative Conditioning (BuCy) in Children with Inherited Metabolic Disorders

Hematopoietic stem cell transplantation (HCT) is a primary treatment for various inherited metabolic disorders (IMDs). Achieving stable and sustained engraftment while minimizing transplantation-related morbidity and mortality is critical to optimizing outcomes for IMDs. Traditional regimens have used myeloablative approaches, primarily busulfan and cyclophosphamide (BuCy), which is associated with significant regimen-related toxicity. Alternatively, reduced-toxicity regimens, such as busulfan and fludarabine (BuFlu), have been proposed to offer similar efficacy with reduced toxicities. We compared transplantation-related outcomes with BuCy-based and BuFlu-based conditioning in patients with IMDs. We retrospectively analyzed the University of Minnesota's transplantation database for patients with IMDs who underwent HCT using a BuCy (with alemtuzumab) or BuFlu (with antithymocyte globulin) preparative regimen between March 2008 and September 2017. Overall survival (OS), event-free survival (EFS), and incidence of neutrophil and platelet recovery were determined using standard definitions. Complications such as graft failure, sinusoidal obstruction syndrome, hemorrhagic cystitis, and respiratory failure were compared. Graft failure includes primary and secondary aplastic graft failure with and without autologous recovery. The incidence of viral infections post-transplantation in the 2 regimens was also determined. A total of 99 patients underwent HCT for IMDs during the study period. Sixty-four patients received BuCy conditioning, and the other 35 received BuFlu. Hurler syndrome (46%) and adrenoleukodystrophy (43%) were the most common IMDs, and umbilical cord blood was the most common graft source (74%). One-year OS was similar in the 2 groups (81.2% in BuCy versus 85.5% in BuFlu; P = .8), with an EFS of 75% versus 63%, respectively. The 2 groups also had similar incidences of grade III-IV acute GVHD (9% versus 6%; P = .5) and chronic GVHD (9% versus 7%; P = .67). Neutrophil and platelet recovery were similar in the 2 groups, with a significantly shorter duration of hospital stay noted in the BuFlu cohort (median, 21 days versus 34 days; P = .002). The cumulative incidence of graft failure was significantly higher in the BuFlu group (29% versus 14%; P = .08), as was the rate of second HCT (27% versus 3%; P = .001). The incidences of adenoviral infection (14% versus 0%; P = .02) and hemorrhagic cystitis (23% versus 3%; P = .01) were higher in the BuCy group. T cell engraftment occurred significantly sooner with BuCy conditioning until 1-year post-transplantation, but donor myeloid engraftment was similar in the 2 groups. Our data indicate that reduced-toxicity conditioning is associated with lower rates of infection and other transplantation-related complications but is concerning for a higher rate of graft failure in patients with IMDs. Alternate immunosuppressive agents and novel techniques should be considered to minimize toxicities and reduce complications.

Clinical Relevance of Immunobiology in Umbilical Cord Blood Transplantation

Umbilical cord blood transplantation (UCBT) has been an important donor source for allogeneic hematopoietic stem cell transplantation, especially for patients who lack suitable matched donors. UCBT provides unique practical advantages, such as lower risks of graft-versus-host-disease (GVHD), permissive HLA mismatch, and ease of procurement. However, there are clinical challenges in UCBT, including high infection rates and treatment-related mortality in selected patient groups. These clinical advantages and challenges are tightly linked with cell-type specific immune reconstitution (IR). Here, we will review IR, focusing on T and NK cells, and the impact of IR on clinical outcomes. Better understanding of the immune biology in UCBT will allow us to further advance this field with improved clinical practice.

Delaying haematopoietic stem cell transplantation in children with viral respiratory infections reduces transplant-related mortality

Viral respiratory infections (VRIs) contribute to the morbidity and transplant‐related mortality (TRM) after allogeneic haematopoietic stem cell transplantation (HSCT) and strategies to prevent and treat VRIs are warranted. We monitored VRIs before and after transplant in children undergoing allogeneic HSCT with nasopharyngeal aspirates (NPA) and assessed the impact on clinical outcome. Between 2007 and 2017, 585 children underwent 620 allogeneic HSCT procedures. Out of 75 patients with a positive NPA screen (12%), transplant was delayed in 25 cases (33%), while 53 children started conditioning with a VRI. Patients undergoing HSCT with a positive NPA screen had a significantly lower overall survival (54% vs. 79%) and increased TRM (26% vs. 7%) compared to patients with a negative NPA. Patients with a positive NPA who delayed transplant and cleared the virus before conditioning had improved overall survival (90%) and lower TRM (5%). Pre‐HSCT positive NPA was the only significant risk factor for progression to a lower respiratory tract infection and was a major risk factor for TRM. Transplant delay, whenever feasible, in case of a positive NPA screen for VRIs can positively impact on survival of children undergoing HSCT.

Immune recovery after in vivo T-cell depletion myeloablative conditioning hematopoietic stem cell transplantation in severe beta-thalassemia children

BACKGROUND

The clinical outcome of hematopoietic stem cell transplantation (HSCT) in those with severe beta-thalassemia (β-TM) is closely related to post-transplantation immune reconstitution (IR). However, the data on the IR in these settings are scarce.

METHODS

A prospective analysis of the clinical outcome and IR in 47 children with severe β-TM who underwent in vivo T-cell depletion myeloablative conditioning and matched sibling donor HSCT was performed. Immune reconstitution, including immune cell subset counts, as well as the generation of new T and B cells assays after HSCT, was measured.

RESULTS

In the first year after HSCT, bacterial infections and cytomegalovirus (CMV) reactivation were observed in 70.2% and 36.2% of the patients, respectively. In the same period, poor CD4⁺ T-cell recovery was observed. The B cells recovered within 6 months. Natural killer (NK) cells recovered as early as 1 month, but their function was defective. Cord blood and bone marrow (CB + BM) group had slower T-cell recovery, and higher B cells and NK cells in comparison with peripheral blood and bone marrow (PB + BM) group.

CONCLUSIONS

The high incidence of infection within 1 year after in vivo T-cell depletion myeloablative conditioning HSCT in severe β-TM was consistent with poor IR.

Host and Graft Factors Impacting Infection Risk in Hematopoietic Cell Transplantation

Infection contributes significantly to morbidity and mortality in hematopoietic cell transplantation. A complex interplay of host, graft, and technical factors contributes to infectious risk in the recipient. Host factors such as age, underlying disease, and comorbidities; central venous access; and the preparative regimen contribute to mucosal disruption, organ dysfunction, and immunodeficiency before hematopoietic cell transplantation. Graft factors, including donor histocompatibility, cell source, and graft components, along with immunosuppression and graft-versus-host disease, contribute to the speed of immune reconstitution. Evaluation of these factors, plus previous and posttransplant exposure to pathogens, is necessary to best assess an individual recipient's infection risk.

Filgrastim enhances T-cell clearance by antithymocyte globulin exposure after unrelated cord blood transplantation

Residual antithymocyte globulin (ATG; Thymoglobulin) exposure after allogeneic hematopoietic (stem) cell transplantation (HCT) delays CD4⁺ T-cell immune reconstitution (CD4⁺ IR), subsequently increasing morbidity and mortality. This effect seems particularly present after cord blood transplantation (CBT) compared to bone marrow transplantation (BMT). The reason for this is currently unknown. We investigated the effect of active-ATG exposure on CD4⁺ IR after BMT and CBT in 275 patients (CBT n = 155, BMT n = 120; median age, 7.8 years; range, 0.16-19.2 years) receiving their first allogeneic HCT between January 2008 and September 2016. Multivariate log-rank tests (with correction for covariates) revealed that CD4⁺ IR was faster after CBT than after BMT with <10 active-ATG × day/mL (P = .018) residual exposure. In contrast, >10 active-ATG × day/mL exposure severely impaired CD4⁺ IR after CBT (P < .001), but not after BMT (P = .74). To decipher these differences, we performed ATG-binding and ATG-cytotoxicity experiments using cord blood- and bone marrow graft-derived T-cell subsets, B cells, natural killer cells, and monocytes. No differences were observed. Nevertheless, a major covariate in our cohort was Filgrastim treatment (only given after CBT). We found that Filgrastim (granulocyte colony-stimulating factor [G-CSF]) exposure highly increased neutrophil-mediated ATG cytotoxicity (by 40-fold [0.5 vs 20%; P = .002]), which explained the enhanced T-cell clearance after CBT. These findings imply revision of the use (and/or timing) of G-CSF in patients with residual ATG exposure.

Adoptive T Cell Therapy Strategies for Viral Infections in Patients Receiving Haematopoietic Stem Cell Transplantation

Adverse outcomes following virus-associated disease in patients receiving allogeneic haematopoietic stem cell transplantation (HSCT) have encouraged strategies to control viral reactivation in immunosuppressed patients. However, despite timely treatment with antiviral medication, some viral infections remain refractory to treatment, which hampers outcomes after HSCT, and are responsible for a high proportion of transplant-related morbidity and mortality. Adoptive transfer of donor-derived lymphocytes aims to improve cellular immunity and to prevent or treat viral diseases after HSCT. Early reports described the feasibility of transferring nonspecific lymphocytes from donors, which led to the development of cell therapy approaches based on virus-specific T cells, allowing a targeted treatment of infections, while limiting adverse events such as graft versus host disease (GvHD). Both expansion and direct selection techniques have yielded comparable results in terms of efficacy (around 70–80%), but efficacy is difficult to predict for individual cases. Generating bespoke products for each donor–recipient pair can be expensive, and there remains the major obstacle of generating products from seronegative or poorly responsive donors. More recent studies have focused on the feasibility of collecting and infusing partially matched third-party virus-specific T cells, reporting response rates of 60–70%. Future development of this approach will involve the broadening of applicability to multiple viruses, the optimization and cost-control of manufacturing, larger multicentred efficacy trials, and finally the creation of cell banks that can provide prompt access to virus-specific cellular product. The aim of this review is to summarise present knowledge on adoptive T cell manufacturing, efficacy and potential future developments.

Conditioning Perspectives for Primary Immunodeficiency Stem Cell Transplants

The majority of children undergoing Hematopoietic Stem cell Transplantation (HSCT) require conditioning therapy to make space and prevent rejection of the donor stem cells. The exception is certain children with Severe Combined immune deficiency, who have limited or no ability to reject the donor graft. Transplant conditioning is associated with significant morbidity and mortality from both direct toxic effects of chemotherapy as well as opportunistic infections associated with profound immunosuppression. The ultimate goal of transplant practice is to achieve sufficient engraftment of donor cells to correct the underlying disease with minimal short- and long-term toxicity to the recipient. Traditional combinations, such as busulfan and cyclophosphamide, achieve a high rate of full donor engraftment, but are associated with significant acute transplant-related-mortality and late effects such as infertility. Less "intensive" approaches, such as combinations of treosulfan or melphalan with fludarabine, are less toxic, but may be associated with rejection or low level chimerism requiring the need for re-transplantation. The major benefit of these novel approaches, however, which we hope will be realized in the decades to come, may be the preservation of fertility. Future approaches look to replace chemotherapy with non-toxic antibody conditioning. The lessons learnt in refining conditioning for HSCT are likely to be equally applicable to gene therapy protocols for the same diseases.

Pharmacotherapy in Pediatric Hematopoietic Cell Transplantation

Hematopoietic cell transplantation (HCT) is a curative treatment option for both malignant and nonmalignant diseases. Success of the procedure mainly depends on disease control and treatment-related complications. Pharmacotherapy plays a major role in HCT and significantly impacts the outcomes. Main drug use within HCT includes conditioning, GvHD prophylaxis, and prevention/treatment of infections.Increasing evidence suggests individualized dosing in (pediatric) HCT may improve outcome. Dose individualization may result in a better predictable drug treatment in terms of safety and efficacy, including timely immune reconstitution after HCT and optimal tumor or disease control, which may result in improved survival chances.

Impact of low-dose irradiation and in vivo T-cell depletion on hematopoietic stem cell transplantation for non-malignant diseases using fludarabine-based reduced-intensity conditioning

Reduced-intensity conditioning is widely used with hematopoietic stem cell transplantation for non-malignant diseases: however, the optimal conditioning to ensure stable engraftment has not been established. In this study, we retrospectively compared the impact of low-dose (1-6 Gy) irradiation and in vivo T-cell depletion on the clinical outcome of 523 patients with non-malignant disease who underwent a first allogeneic hematopoietic stem cell transplantation using fludarabine-based reduced-intensity conditioning. Use of low-dose irradiation, but not of anti-thymocyte globulin/anti-lymphocyte globulin, showed a beneficial effect on overall survival (adjusted hazard ratio: 0.56; 95% confidence interval: 0.35-0.91, P = 0.018). Furthermore, use of low-dose irradiation was strongly associated with lower transplant-related mortality (adjusted hazard ratio: 0.55; 95% confidence interval: 0.32-0.96, P = 0.034). The addition of low-dose irradiation to the conditioning regimen was beneficial, at least to the short-term clinical outcome. A large prospective study with long-term follow-up is now required to extend these findings and establish the optimal hematopoietic stem cell transplant conditioning for patients with at least some subgroups of non-malignant diseases.

Mechanisms That Contribute to a Profound Reduction of the HIV-1 Reservoir After Allogeneic Stem Cell Transplant

This article has been corrected. The original version (PDF) is appended to this article as a Supplement.

BACKGROUND

The multifactorial mechanisms associated with radical reductions in HIV-1 reservoirs after allogeneic hematopoietic stem cell transplant (allo-HSCT), including a case of HIV cure, are not fully understood.

OBJECTIVE

To investigate the mechanism of HIV-1 eradication associated with allo-HSCT.

DESIGN

Nested case series within the IciStem observational cohort.

SETTING

Multicenter European study.

PARTICIPANTS

6 HIV-infected, antiretroviral-treated participants who survived more than 2 years after allo-HSCT with CCR5 wild-type donor cells.

MEASUREMENTS

HIV DNA analysis, HIV RNA analysis, and quantitative viral outgrowth assay were performed in blood, and HIV DNA was also measured in lymph nodes, ilea, bone marrow, and cerebrospinal fluid. A humanized mouse model was used for in vivo detection of the replication-competent blood cell reservoir. HIV-specific antibodies were measured in plasma.

RESULTS

Analysis of the viral reservoir showed that 5 of 6 participants had full donor chimera in T cells within the first year after transplant, undetectable proviral HIV DNA in blood and tissue, and undetectable replication-competent virus (<0.006 infectious unit per million cells). The only participant with detectable virus received cord blood stem cells with an antithymocyte globulin-containing conditioning regimen, did not develop graft-versus-host disease, and had delayed complete standard chimerism in T cells (18 months) with mixed ultrasensitive chimera. Adoptive transfer of peripheral CD4+ T cells to immunosuppressed mice resulted in no viral rebound. HIV antibody levels decreased over time, with 1 case of seroreversion.

LIMITATION

Few participants.

CONCLUSION

Allo-HSCT resulted in a profound long-term reduction in the HIV reservoir. Such factors as stem cell source, conditioning, and a possible "graft-versus-HIV-reservoir" effect may have contributed. Understanding the mechanisms involved in HIV eradication after allo-HSCT can enable design of new curative strategies.

PRIMARY FUNDING SOURCE

The Foundation for AIDS Research (amfAR).

Innate Immune Recovery Predicts CD4+ T Cell Reconstitution after Hematopoietic Cell Transplantation

Innate immune cells are the first to recover after allogeneic hematopoietic cell transplantation (HCT). Nevertheless, reports of innate immune cell recovery and their relation to adaptive recovery after HCT are largely lacking. Especially predicting CD4⁺ T cell reconstitution is of clinical interest, because this parameter directly associates with survival chances after HCT. We evaluated whether innate recovery relates to CD4⁺ T cell reconstitution probability and investigated differences between innate recovery after cord blood transplantation (CBT) and bone marrow transplantation (BMT). We developed a multivariate, combined nonlinear mixed-effects model for monocytes, neutrophils, and natural killer (NK) cell recovery after transplantation. A total of 205 patients undergoing a first HCT (76 BMT, 129 CBT) between 2007 and 2016 were included. The median age was 7.3years (range, .16 to 23). Innate recovery was highly associated with CD4⁺ T cell reconstitution probability (P < .001) in multivariate analysis correcting for covariates. Monocyte (P < .001), neutrophil (P < .001), and NK cell (P < .001) recovery reached higher levels during the first 200days after CBT compared with BMT. The higher innate recovery after CBT may be explained by increased proliferation capacity (measured by Ki-67 expression) of innate cells in CB grafts compared with BM grafts (P = .041) and of innate cells in vivo after CBT compared with BMT (P = .048). At an individual level, patients with increased innate recovery after either CBT or BMT had received grafts with higher proliferating innate cells (CB; P = .004, BM; P = .01, respectively). Our findings implicate the use of early innate immune monitoring to predict the chance of CD4⁺ T cell reconstitution after HCT, with respect to higher innate recovery after CBT compared with BMT.

Immune Reconstitution and Infection Patterns after Early Alemtuzumab and Reduced Intensity Transplantation for Nonmalignant Disorders in Pediatric Patients

Hematopoietic stem cell transplantation (HSCT) is a therapeutic option for many nonmalignant disorders (NMD) and is curative or prevents disease progression. Reduced-intensity conditioning (RIC) in HSCT for NMD may reduce regimen-related acute toxicities and late complications. Myeloablation is often replaced by immune suppression in RIC regimens to support donor engraftment. The pace of immune reconstitution after immune suppression by RIC regimens is influenced by agents used, donor source, and graft-versus-host disease prophylaxis/treatment. In a multicenter trial (NCT 00920972) of HSCT for NMD, a RIC regimen consisting of alemtuzumab, fludarabine, and melphalan was substituted for myeloablation. Alemtuzumab was administered early (days -21 to -19) to mitigate major lymphodepletion of the incoming graft and the risk of graft rejection. Immune reconstitution and infectious complications were prospectively monitored for 1-year post-HSCT. Seventy-one patients met inclusion criteria for this report and received marrow or peripheral blood stem cell transplants. Immune reconstitution and infections are reported for related donor (RD) and unrelated donor (URD) transplants at 3 time-points (100days, 6 months, and 1 year post-HSCT). Natural killer cell recovery was rapid, and numbers normalized in both cohorts by day +100. Mean CD3, CD4, and CD8 T-lymphocyte numbers normalized by 6 months after RD HSCT and by 1 year in the URD group. CD4 and CD8 T-lymphocyte counts were significantly higher in patients who received RD HSCT at 6 months and at 1 year, respectively, post-HSCT compared with patients who received URD HSCT. The pace of CD19 B-cell recovery was markedly different between RD and URD cohorts. Mean B-cell numbers were normal by day 100 after RD HSCT but took 1 year post-HSCT to normalize in the URD cohort. Despite these differences in immune reconstitution, the timing and nature of infections did not differ between the groups, presumably because of comparable T-lymphocyte recovery. Immune reconstitution occurred at a faster pace than in prior reports using RIC with T-cell depletion. The incidence of infections was similar for both cohorts and occurred most frequently in the first 100days post-HSCT. Viral and fungal infections occurred at a lower incidence in this cohort, with "early" alemtuzumab compared with regimens administering serotherapy in the peritransplantation period. Patients were susceptible to bacterial infections primarily in the first 100days irrespective of donor source and had no increase in mortality from the same. The overall mortality rate from infections was 1.4% at 1 year. Close monitoring and prophylaxis against bacterial infections in the first 100days post-HSCT is necessary but is followed by robust immune reconstitution, especially in the T-cell compartment.

Intrabone transplant provides full stemness of cord blood stem cells with fast hematopoietic recovery and low GVHD rate: results from a prospective study

Umbilical Cord Blood (UCB) represents a valid option for patients with hematopoietic malignancies lacking an HLA matched donor. To overcome the limitation of the low stem cell dose of UCB, the intrabone (IB) route has been proposed. We report the results of a prospective study on a poor-prognosis cohort of 23 patients receiving intrabone single UCB transplant (Clinicaltrials.gov NCT00886522). Cumulative incidence of hematological recovery at day 90 was 82 ± 9% (ANC > 0.5 × 10⁹/L) and 70 ± 10% (platelet > 50 × 10⁹/L) and correlated with CD34 + cells in the graft. NRM was 20 ±  9%. No severe aGVHD and only one extensive cGVHD occurred, with fast immune reconstitution. To test the hypothesis that the direct IB injection could affect the expression of stem cells regulatory pathways, CD34 + cells from BM aspirates at day + 10, + 20, + 30, processed in hypoxic conditions mimicking the BM-microenvironment (7%pO₂), were studied for the expression of c-Mpl, Notch1 and CXCR4. We found that the expression of c-Mpl in CD34 + cells at day + 10 significantly correlated with hematological recovery. In conclusion, IB-UCB transplant success is associated with low incidence of GVHD and high-speed platelet recovery; intrabone route may preserve full hematopoietic stemness by direct delivery of UCB stem cells into the hypoxic HSC niche.

Cord blood transplantation recapitulates fetal ontogeny with a distinct molecular signature that supports CD4+ T-cell reconstitution

Omission of in vivo T-cell depletion promotes rapid, thymic-independent CD4⁺-biased T-cell recovery after cord blood transplant. This enhanced T-cell reconstitution differs from that seen after stem cell transplant from other stem cell sources, but the mechanism is not known. Here, we demonstrate that the transcription profile of naive CD4⁺ T cells from cord blood and that of lymphocytes reconstituting after cord blood transplantation is similar to the transcription profile of fetal CD4⁺ T cells. This profile is distinct to that of naive CD4⁺ T cells from peripheral blood and that of lymphocytes reconstituting after T-replete bone marrow transplantation. The transcription profile of reconstituting naive CD4⁺ T cells from cord blood transplant recipients was upregulated in the T-cell receptor (TCR) signaling pathway and its transcription factor activator protein-1 (AP-1). Furthermore, a small molecule inhibitor of AP-1 proportionally inhibited cord blood CD4⁺ T-cell proliferation (P < .05). Together, these findings suggest that reconstituting cord blood CD4⁺ T cells reflect the properties of fetal ontogenesis, and enhanced TCR signaling is responsible for the rapid restoration of the unique CD4⁺ T-cell biased adaptive immunity after cord blood transplantation.

Homeostatic γδ T Cell Contents Are Preserved by Granulocyte Colony-Stimulating Factor Priming and Correlate with the Early Recovery of γδ T Cell Subsets after Haploidentical Hematopoietic Stem Cell Transplantation

Emerging evidence from graft manipulations and immunotherapeutic treatments has highlighted a favorable effect of γδ T cells in the setting of allogeneic hematopoietic stem cell transplantation (alloHSCT). However, γδ T cell subsets and their distinct features in the allograft have not been characterized. Additionally, whether homeostatic γδ T cell fractions are influenced by treatment with granulocyte colony-stimulating factor (G-CSF) remains elusive. We initially compared the phenotypes of γδ T cell subsets, including CD27⁺, CD27^-, Vδ1⁺, Vδ2⁺, Vδ1⁺CD27⁺, Vδ1⁺CD27^-, Vδ2⁺CD27⁺, and Vδ2⁺CD27^- cells, in the peripheral blood of 20 healthy donors before and after G-CSF mobilization. The effects of G-CSF on the cytokine production capacities of γδ T cell subsets were also detected. Moreover, the correlation between donor homeostatic γδ T cell content and the early recoveries of γδ T cell subgroups after haploidentical HSCT was investigated in 40 pairs of donors and recipients. We found that both the proportions and IFN-γ secretion capacities of peripheral γδ T cell subsets were preserved in G-CSF-primed grafts. Homeostatic Vδ1 and Vδ2 proportions of donors significantly correlated with the early recoveries of Vδ1 and Vδ2 cells after haploidentical HSCT. Interestingly, a higher day 30 Vδ1 concentration was associated with a lower incidence of cytomegalovirus reactivation in recipients. These results not only clarify the preservation of γδ T cell phenotypes and functional features by G-CSF mobilization but also suggest the importance of homeostatic γδ T cell content for immune recovery after alloHSCT.

Predicting CD4 T-Cell Reconstitution Following Pediatric Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is an increasingly common treatment for children with a range of hematological disorders. Conditioning with cytotoxic chemotherapy and total body irradiation leaves patients severely immunocompromised. T-cell reconstitution can take several years due to delayed restoration of thymic output. Understanding T-cell reconstitution in children is complicated by normal immune system maturation, heterogeneous diagnoses, and sparse uneven sampling due to the long time spans involved. We describe here a mechanistic mathematical model for CD4 T-cell immune reconstitution following pediatric transplantation. Including relevant biology and using mixed-effects modeling allowed the factors affecting reconstitution to be identified. Bayesian predictions for the long-term reconstitution trajectories of individual children were then obtained using early post-transplant data. The model was developed using data from 288 children; its predictive ability validated on data from a further 75 children, with long-term reconstitution predicted accurately in 81% of the patients.

An Integrative Scoring System for Survival Prediction Following Umbilical Cord Blood Transplantation in Acute Leukemia

Purpose: Survival of acute leukemia (AL) patients following umbilical cord blood transplantation (UCBT) is dependent on an array of individual features. Integrative models for risk assessment are lacking. We sought to develop a scoring system for prediction of overall survival (OS) and leukemia-free survival (LFS) at 2 years following UCBT in AL patients.Experimental Design: The study cohort included 3,140 pediatric and adult AL UCBT patients from the European Society of Blood and Marrow Transplantation and Eurocord registries. Patients received single or double cord blood units. The dataset was geographically split into a derivation (n = 2,362, 65%) and validation set (n = 778, 35%). Top predictors of OS were identified using the Random Survival Forest algorithm and introduced into a Cox regression model, which served for the construction of the UCBT risk score.Results: The score includes nine variables: disease status, diagnosis, cell dose, age, center experience, cytomegalovirus serostatus, degree of HLA mismatch, previous autograft, and anti-thymocyte globulin administration. Over the validation set an increasing score was associated with decreasing probabilities for 2 years OS and LFS, ranging from 70.21% [68.89-70.71, 95% confidence interval (CI)] and 64.76% (64.33-65.86, 95% CI) to 14.78% (10.91-17.41) and 18.11% (14.40-22.30), respectively. It stratified patients into six distinct risk groups. The score's discrimination (AUC) over multiple imputations of the validation set was 68.76 (68.19-69.04, range) and 65.78 (65.20-66.28) for 2 years OS and LFS, respectively.Conclusions: The UCBT score is a simple tool for risk stratification of AL patients undergoing UCBT. Widespread application of the score will require further independent validation. Clin Cancer Res; 23(21); 6478-86. ©2017 AACR.

Efficacy of two different doses of rabbit anti-T-lymphocyte globulin to prevent graft-versus-host disease in children with haematological malignancies transplanted from an unrelated donor: a multicentre, randomised, open-label, phase 3 trial

BACKGROUND

Although rabbit anti-T-lymphocyte globulin (ATLG) is largely used for the prevention of immune-mediated complications in patients given allogeneic haemopoietic stem-cell transplantation (HSCT) from an unrelated donor, the optimum dose of this drug in children is still undefined. We aimed to test whether a higher dose of ATLG was superior to a lower dose for prevention of grade II-IV acute graft-versus-host disease (GVHD).

METHODS

We conducted a multicentre, randomised, open-label, phase 3 trial in seven Italian centres comparing two different doses of ATLG (30 mg/kg vs 15 mg/kg, given intravenously over 3 days, from day -4 to -2) in children (aged 0-18 years) with haematological malignancies transplanted from an unrelated donor, selected using high-resolution typing for HLA-class I/II loci. All patients received a myeloablative regimen and cyclosporine-A plus short-term methotrexate as post-transplantation GVHD prophylaxis. Patients were randomly assigned (1:1) to either of the two groups and were stratified by the degree of HLA-compatibility with their donor, the source of haemopoietic stem cells used (bone marrow vs peripheral blood stem cells), and the disease risk category. The randomisation was open label; all investigators were aware of the treatment allocation. The primary endpoint of the study was 100-day cumulative incidence of grade II-IV acute GVHD. Statistical analyses were done according to the per-protocol principle. Other outcomes included cumulative incidence of chronic GVHD, non-relapse mortality, disease recurrence, and probability of overall survival and event-free survival. This study was registered with ClinicalTrials.gov, number NCT00934557.

FINDINGS

Between Jan 15, 2008, and Sept 25, 2012, 89 patients were randomly assigned to the 30 mg/kg ATLG group and 91 to the 15 mg/kg ATLG group; 84 patients in the 30 mg/kg ATLG group and 88 in the 15 mg/kg ATLG group were included in the analysis. The median follow-up for the whole study population was 3·4 years (IQR 1·7-5·1). The 100-day cumulative incidence of grade II-IV acute GVHD was 36% (95% CI 28-48) in the 15 mg/kg ATLG group and 29% (20-40) in the 30 mg/kg ATLG group (hazard ratio [HR] 0·74, 95% CI 0·44-1·25; p=0·26). The cumulative incidence of non-relapse mortality was 9% (5-18) in the 15 mg/kg ATLG group and 19% (12-30) in the 30 mg/kg ATLG group (HR 2·08, 0·89-4·96; p=0·092). Cumulative incidence of disease recurrence was 15% (12-24): 14% (8-23) in the 15 mg/kg ATLG group versus 20% (13-31) in the 30 mg/kg ATLG group (HR 1·54, 0·74-3·21; p=0·25). The 5-year overall survival probability was 70% (62-77) for the whole study population: 78% (69-87) in the 15 mg/kg ATLG group versus 62% (50-73) in the 30 mg/kg ATLG group (HR 1·80, 1·01-3·20; p=0·045). The 5-year event-free survival was 77% for children in the 15 mg/kg ATLG group versus 61% in the 30 mg/kg ATLG group (HR 1·87, 1·07-3·28; p=0·028).

INTERPRETATION

Children with haematological malignancies transplanted from unrelated donors selected through high-resolution HLA-typing benefit from the use of a 15 mg/kg ATLG dose in comparison with a 30 mg/kg ATLG dose. ATLG at 15 mg/kg should thus be regarded as the standard serotherapy regimen for unrelated donor allogeneic HSCT in this patient population. Future randomised studies will continue to aim to optimise patient outcome and strategies to prevent acute GVHD occurrence.

FUNDING

Fresenius/Neovii Biotech.

Umbilical Cord Blood Transplantation in Children with Acute Leukemia: Impact of Conditioning on Transplantation Outcomes

The Blood and Marrow Transplant Clinical Trials Network (BMT CTN 0501) randomized children with hematologic malignancies to transplantation with 1 or 2 cord blood units (UCB) between 2006 and 2012. While the trial concluded that survival was similar regardless of number of units infused, survival was better than previously reported. This prompted a comparison of survival of trial versus nontrial patients to determine the generalizability of trial results and whether survival was better because of the trial treatment regimen. During the trial period, 396 recipients of a single UCB unit met trial eligibility but were not enrolled. Trial patients (n = 100) received total body irradiation (TBI) 1320 cGy, cyclophosphamide 120 mg/kg, and fludarabine 75 mg/m² (TCF). Nontrial patients either received the same regimen (n = 62; nontrial TCF) or alternative regimens (n = 334; nontrial regimens). Five-year survival between trial and nontrial patients conditioned with TCF was similar (70% versus 62%). However, 5-year survival was significantly lower with nontrial TBI-containing (47%; hazard ratio [HR], 1.97; P = .001) and chemotherapy-only regimens (49%; HR, 1.87; P = .007). The results of BMT CTN 0501 appear generalizable to the population of trial-eligible patients. The survival difference between the trial-specified regimen and other regimens indicate the importance of conditioning regimen for UCB transplantation.

Single umbilical cord blood with or without CD34+ cells from a third-party donor in adults with leukemia

We retrospectively compared the clinical outcomes of adults with acute leukemia who received single-unit umbilical cord blood (UCB) transplantation (sUCBT) (n = 135) or stem cell transplant using coinfusion of a UCB graft with CD34⁺ cells from a third-party donor (Haplo-Cord) (n = 72) at different institutions within the Grupo Español de Trasplante Hematopoyético. In multivariable analysis, patients in the Haplo-Cord group showed more rapid neutrophil (hazard ratio [HR], 2.3; 95% confidence interval [CI], 1.5-3.3; P < .001) and platelet recovery (HR, 1.6; 95% CI, 1.2-2.3; P = .015) and lower incidence of chronic graft-versus-host disease (GVHD) (relative risk, 0.5; 95% CI, 0.3-0.8; P = .01). Nonrelapse mortality, relapse, disease-free survival (DFS), and GVHD/relapse-free survival were similar in the 2 groups. Regarding disease-specific outcomes, DFS in both acute myeloid leukemia (AML) and acute lymphoblastic leukemia patients was not significantly different; however, a significantly higher relapse rate was found in patients with AML treated with Haplo-Cord (HR, 2.3; 95% CI, 1-5.4; P = .04). Our study confirms that Haplo-Cord was an effective strategy to accelerate neutrophil and platelet recovery and shows that, in the context of specific treatment platforms, sUCBT and Haplo-Cord offer similar long-term outcomes.

GvHD prophylaxis after single-unit reduced intensity conditioning cord blood transplantation in adults with acute leukemia

To investigate better GVHD prophylaxis in reduced intensity conditioning umbilical cord blood transplantation (RIC-UCBT), we compared transplant outcomes after UCBT among GvHD prophylaxes using the registry data. We selected patients transplanted for AML or ALL with a calcineurin inhibitor and methotrexate (MTX)/mycophenolate mofetil (MMF) combination. A total of 748 first RIC-UCBT between 2000 and 2012 (MTX+ group, 446, MMF+ group, 302) were included. The cumulative incidence of neutrophil and platelet counts higher than 50 000/μL was significantly better in the MMF+ group (relative risk (RR), 1.55; P<0.001: RR, 1.34; P=0.003, respectively). In multivariate analyses, the risk of grade II-IV and III-IV acute GvHD was significantly higher in the MMF+ group than in the MTX+ group (RR, 1.75; P<0.001: RR, 1.97; P=0.004, respectively). In disease-specific analyses of AML, the risk of relapse of high-risk disease was significantly lower in the MMF+ group (RR, 0.69; P=0.009), whereas no significant difference was observed in the risk of relapse-free and overall survival in high-risk disease. In patients with standard-risk disease, no significant differences were noted in the risk of relapse or survival between the MTX+ and MMF+ groups. Collectively, these results suggest that MMF-containing prophylaxis may be preferable in RIC-UCBT, particularly for high-risk disease.

Reconstitution of adaptive immunity after umbilical cord blood transplantation: impact on infectious complications

In comparison with allogeneic stem cell transplantation (alloHSCT) with other stem cell sources, umbilical cord blood transplantation (UCBT) was traditionally associated with increased risk of infections, particularly during the first 3 months after transplantation. Longitudinal studies of immune monitoring reported peculiar patterns of T- and B-cell recovery in the peripheral blood of UCB recipients during the first months post-transplantation. Overall, current data suggest delayed reconstitution of naive and memory CD4⁺ and CD8⁺ T-cell pools after UCBT. This is particularly true for adult recipients and for patients who received in vivo T-cell depleting approaches before the transplantation. Such delayed T-cell recovery may increase susceptibility of UCB recipients for developing opportunistic infections and viral reactivations. Regarding B-cell recovery, UCBT was associated with accelerated B-lymphopoiesis. Recent studies also reported evidence for faster functional memory B-cell recovery in UCB recipients. In this article, we briefly review T- and B-cell reconstitution after alloHSCT, with emphasis on peculiarities observed after UCBT. We further put these data in lines with risks of infections after UCBT.

Immune reconstitution and outcomes after conditioning with anti-thymocyte-globulin in unrelated cord blood transplantation; the good, the bad, and the ugly

Unrelated umbilical cord blood transplantation (UCBT) exhibits a low risk of graft-versus-host-disease (GvHD) and has unique potent anti-virus and anti-leukemia effects. Anti-thymocyte globulin (ATG) in the conditioning regimen for UCBT is successful in reducing graft rejection and GvHD. Nevertheless, this beneficial effect of ATG coincides with its detrimental effect on immune reconstitution. The latter directly relates to a high incidence of viral infections and leukemia relapses. ATG has been used in transplant patients for over 30 years. In recent years, the knowledge on the mechanisms of action of ATG and its implementation in the UCBT setting has increased dramatically. Important data became available showing the highly variable pharmacokinetics (PK) of ATG and its consequence on outcome measures. Here, we review the effects of ATG on immune reconstitution and subsequent outcomes after UCBT, and describe the mechanisms causing these effects. We highlight the importance of optimizing ATG exposure before and after UCBT and discuss strategies to maintain the 'good' and overcome the 'bad and ugly' effects of ATG on UCBT outcome.

Association between anti-thymocyte globulin exposure and survival outcomes in adult unrelated haemopoietic cell transplantation: a multicentre, retrospective, pharmacodynamic cohort analysis

BACKGROUND

Anti-thymocyte globulin (ATG) is used to prevent graft-versus-host disease (GvHD) after allogeneic haemopoietic cell transplantation (HCT). However, ATG can also cause delayed immune reconstitution of T cells, negatively affecting survival. We studied the relation between exposure to ATG and clinical outcomes in adult patients with acute leukaemia and myelodysplastic syndrome.

METHODS

We did a retrospective, pharmacokinetic-pharmacodynamic analysis of data from patients with acute lymphoid leukaemia, acute myeloid leukaemia, or myelodysplastic syndrome receiving their first T-cell repleted allogeneic peripheral blood stem cell HCT with ATG (thymoglobulin) as part of non-myeloablative conditioning from March 1, 2004, to June 1, 2015. Patients received a cumulative intravenous dose of 8 mg/kg divided over 4 days, starting on day -8 before HCT. Active ATG concentrations were measured using a validated bioassay and pharmacokinetic exposure measures (maximum concentration, concentration at time of infusion of the graft, time to reach a concentration of 1 arbitary unit [AU] per day/mL, area under the curve [AUC], and the AUC before and after HCT) were calculated with a validated population pharmacokinetic model. The main outcome of interest was 5-year overall survival, defined as days to death from any cause or last follow-up. Other outcomes were relapse-related mortality, non-relapse mortality, event-free survival, acute and chronic GvHD, and assessment of current and optimum dosing. We used Cox proportional hazard models and Fine-Gray competing risk models for the analyses.

FINDINGS

146 patients were included. ATG exposure after HCT was shown to be the best predictor for 5-year overall survival. Optimum exposure after transplantation was determined to be 60-95 AU per day/mL. Estimated 5-year overall survival in the group who had optimum exposure (69%, 95% CI 55-86) was significantly higher than in the group who had below optimum exposure (32%, 20-51, p=0·00037; hazard ratio [HR] 2·41, 95% CI 1·15-5·06, p=0·020) and above optimum exposure (48%, 37-62, p=0·030; HR 2·11, 95% CI 1·04-4·27, p=0·038). Patients in the optimum exposure group had a greater chance of event-free survival than those in the below optimum exposure group (HR 2·54, 95% CI 1·29-5·00, p=0·007; HR for the above optimum group: 1·83, 0·97-3·47, p=0·063). Above-optimum exposure led to higher relapse-related mortality compared with optimum exposure (HR 2·66, 95% CI 1·12-6·31; p=0·027). Below optimum exposure increased non-relapse mortality compared with optimum exposure (HR 4·36, 95% CI 1·60-11·88; p=0·0040), grade 3-4 acute GvHD (3·09, 1·12-8·53; p=0·029), but not chronic GvHD (2·38, 0·93-6·08; p=0·070). Modelled dosing based on absolute lymphocyte counts led to higher optimum target attainment than did weight-based dosing.

INTERPRETATION

Exposure to ATG affects survival after HCT in adults, stressing the importance of optimum ATG dosing. Individualised dosing of ATG, based on lymphocyte counts rather than bodyweight, might improve survival chances after HCT.

FUNDING

Netherlands Organization for Health Research and Development and Queen Wilhelma Fund for Cancer Research.

Antithymocyte globulin improves the survival of patients with myelodysplastic syndrome undergoing HLA-matched unrelated donor and haplo-identical donor transplants

Significant advances have been achieved in the outcomes of patients with myelodysplastic syndromes (MDS) after both HLA-matched sibling donor transplants (MSDT) and non-MSDT, the latter including HLA-matched unrelated donor (MUDT) and haplo-identical donor transplants (HIDT). In this retrospective study, we analyzed the data of 85 consecutive patients with MDS who received allogeneic HSCT between Dec 2007 and Apr 2014 in our center. These patients comprised 38 (44.7%) who received MSDT, 29 (34.1%) MUDT, and 18 (21.2%) HIDT. The median overall survival (OS) was 60.2 months, the probabilities of OS being 63%, 57%, and 48%, at the first, second, and fifth year, respectively. Median OS post-transplant (OSPT) was 57.2 months, the probabilities of OSPT being 58%, 55%, and 48% at the first, second, and fifth year, respectively. The survival of patients receiving non-MSDT was superior to that of MSDT, median OSPT being 84.0 months and 23.6 months, respectively (P = 0.042); the findings for OS were similar (P = 0.028). We also found that using ATG in conditioning regimens significantly improved survival after non-MSDT, with better OS and OSPT (P = 0.016 and P = 0.025). These data suggest that using ATG in conditioning regimens may improve the survival of MDS patients after non-MSDT.

GvHD after umbilical cord blood transplantation for acute leukemia: an analysis of risk factors and effect on outcomes

Using the Center for International Blood and Marrow Transplant Research (CIBMTR) registry, we analyzed 1404 umbilical cord blood transplantation (UCBT) patients (single (<18 years)=810, double (⩾18 years)=594) with acute leukemia to define the incidence of acute GvHD (aGvHD) and chronic GvHD (cGvHD), analyze clinical risk factors and investigate outcomes. After single UCBT, 100-day incidence of grade II-IV aGvHD was 39% (95% confidence interval (CI), 36-43%), grade III-IV aGvHD was 18% (95% CI, 15-20%) and 1-year cGvHD was 27% (95% CI, 24-30%). After double UCBT, 100-day incidence of grade II-IV aGvHD was 45% (95% CI, 41-49%), grade III-IV aGvHD was 22% (95% CI, 19-26%) and 1-year cGvHD was 26% (95% CI, 22-29%). For single UCBT, multivariate analysis showed that absence of antithymocyte globulin (ATG) was associated with aGvHD, whereas prior aGvHD was associated with cGvHD. For double UCBT, absence of ATG and myeloablative conditioning were associated with aGvHD, whereas prior aGvHD predicted for cGvHD. Grade III-IV aGvHD led to worse survival, whereas cGvHD had no significant effect on disease-free or overall survival. GvHD is prevalent after UCBT with severe aGvHD leading to higher mortality. Future research in UCBT should prioritize prevention of GvHD.

Pharmacokinetics, Pharmacodynamics, and Pharmacogenomics of Immunosuppressants in Allogeneic Hematopoietic Cell Transplantation: Part II

Part I of this article included a pertinent review of allogeneic hematopoietic cell transplantation (alloHCT), the role of postgraft immunosuppression in alloHCT, and the pharmacokinetics, pharmacodynamics, and pharmacogenomics of the calcineurin inhibitors and methotrexate. In this article (Part II), we review the pharmacokinetics, pharmacodynamics, and pharmacogenomics of mycophenolic acid (MPA), sirolimus, and the antithymocyte globulins (ATG). We then discuss target concentration intervention (TCI) of these postgraft immunosuppressants in alloHCT patients, with a focus on current evidence for TCI and on how TCI may improve clinical management in these patients. Currently, TCI using trough concentrations is conducted for sirolimus in alloHCT patients. Several studies demonstrate that MPA plasma exposure is associated with clinical outcomes, with an increasing number of alloHCT patients needing TCI of MPA. Compared with MPA, there are fewer pharmacokinetic/dynamic studies of rabbit ATG and horse ATG in alloHCT patients. Future pharmacokinetic/dynamic research of postgraft immunosuppressants should include '-omics'-based tools: pharmacogenomics may be used to gain an improved understanding of the covariates influencing pharmacokinetics as well as proteomics and metabolomics as novel methods to elucidate pharmacodynamic responses.

Exploratory research for optimal GvHD prophylaxis after single unit CBT in adults: short-term methotrexate reduced the incidence of severe GvHD more than mycophenolate mofetil

In order to examine GvHD prophylaxis in umbilical cord blood transplantation (UCBT) in more detail, we compared transplant outcomes after UCBT for acute leukemia among GvHD prophylaxes using registry data. We selected patients transplanted with a calcineurin inhibitor and methotrexate (MTX)/mycophenolate mofetil (MMF) combination. A total of 1516 first myeloablative UCBT between 2000 and 2012 (Cyclosporine A (CyA) plus MTX, 824, Tacrolimus (Tac) plus MTX, 554, Tac plus MMF, 138) were included. With adjusted analyses, Tac plus MMF showed a significantly higher risk for grade II-IV and III-IV acute GvHD than CyA or Tac plus MTX. Although NRM was similar, Tac plus MMF showed a significantly lower risk of relapse than CyA or Tac plus MTX. A significant difference was observed in the risk of overall mortality (OM) between the MTX-containing group and MMF-containing group. In patients with standard-risk disease, there was no significant difference in the risk of OM in any GvHD prophylaxis. However, in patients with advanced-risk disease, Tac plus MMF showed a significantly lower risk of OM. Therefore, MTX-containing prophylaxis is preferred in UCBT for standard-risk disease, whereas MMF-containing prophylaxis is preferred for advanced-risk disease. A prospective study to identify optimal GvHD prophylaxis for UCBT is warranted.

Early and Long-Term Impaired T Lymphocyte Immune Reconstitution after Cord Blood Transplantation with Antithymocyte Globulin

Immune reconstitution is crucial to the success of allogeneic hematopoietic stem cell transplantation. Umbilical cord blood transplantation (UCBT) has been associated with delayed immune reconstitution. We characterized the kinetics and investigated the risk variables affecting recovery of the main lymphocyte subsets in 225 consecutive pediatric and adult patients (males, n = 126; median age, 15; range, .3 to 60; interquartile range, 4 to 35) who underwent myeloablative single UCBT between 2005 and 2015 for malignant and nonmalignant disorders. Low CD4⁺ and CD8⁺ T cell counts were observed up to 12 months after UCBT. In contrast, B and natural killer cells recovered rapidly early after transplantation. In a multivariate regression model, factors favoring CD4⁺ T cell recovery ≥ 200 cells/µL were lower dose antithymocyte globulin (ATG) (hazard ratio [HR], 3.93; 95% confidence interval [CI], 2.3 to 5.83; P = .001), negative recipient cytomegalovirus (CMV) serostatus (HR, 3.76; 95% CI, 1.9 to 5.74; P = .001), and younger age (HR, 2.61; 95% CI, 1.01 to 3.47; P = .03). Factors favoring CD8⁺ T cell recovery ≥ 200 cells/µL were lower dose ATG (HR, 3.03; 95% CI, 1.4 to 5.1; P = .03) and negative recipient CMV serostatus (HR, 1.9; 95% CI, 1.63 to 2.15; P = .01). Our results demonstrate the significant negative impact of ATG on lymphocyte recovery. A reduction of the dose or omission of ATG could improve immune reconstitution and perhaps reduce opportunistic infections after UCBT.

Impact of Graft-Recipient ABO Compatibility on Outcomes after Umbilical Cord Blood Transplant for Nonmalignant Disease

Existing literature shows mixed conclusions regarding the impact of ABO incompatibility on outcomes after hematopoietic stem cell transplantation. Because the future for umbilical cord blood (UCB) expansion technologies is bright, we assessed whether this typically overlooked graft characteristic impacted various outcomes after UCB transplantation (UCBT) for nonmalignant disorders (NMDs). A prospectively maintained institutional blood and marrow transplant program database was queried for all patients undergoing first UCBT for NMDs. UCB and recipient ABO compatibility was considered as matched, major mismatched, minor mismatched, or bidirectional mismatched. The impact of ABO incompatibility was assessed on overall survival, graft failure, acute and chronic graft-versus-host disease (GVHD), time to neutrophil and platelet recovery, day 0 to day 100 RBC transfusion burden, and donor hematopoietic chimerism. Through December 2014, 270 patients have undergone first UCBT for various NMDs. In both univariable and multivariable analyses, ABO compatibility status did not appear to impact any outcomes assessed, although a trend toward increased grades III to IV acute GVHD was seen in recipients of major mismatched units. When considering UCBT for treatment of NMDs, ABO compatibility between the donor unit and intended recipient does not appear to be an important consideration in the UCB unit choice.

Excellent T-cell reconstitution and survival depend on low ATG exposure after pediatric cord blood transplantation

Successful immune reconstitution (IR) is associated with improved outcomes following pediatric cord blood transplantation (CBT). Usage and timing of anti-thymocyte globulin (ATG), introduced to the conditioning to prevent graft-versus-host disease and graft failure, negatively influences T-cell IR. We studied the relationships among ATG exposure, IR, and clinical outcomes. All pediatric patients receiving a first CBT between 2004 and 2015 at the University Medical Center Utrecht were included. ATG-exposure measures were determined with a validated pharmacokinetics model. Main outcome of interest was early CD4⁺ IR, defined as CD4⁺ T-cell counts >50 × 10⁶/L twice within 100 days after CBT. Other outcomes of interest included event-free survival (EFS). Cox proportional-hazard and Fine-Gray competing-risk models were used. A total of 137 patients, with a median age of 7.4 years (range, 0.2-22.7), were included, of whom 82% received ATG. Area under the curve (AUC) of ATG after infusion of the cord blood transplant predicted successful CD4⁺ IR. Adjusted probability on CD4⁺ IR was reduced by 26% for every 10-point increase in AUC after CBT (hazard ratio [HR], 0.974; P < .0001). The chance of EFS was higher in patients with successful CD4⁺ IR (HR, 0.26; P < .0001) and lower ATG exposure after CBT (HR, 1.005; P = .0071). This study stresses the importance of early CD4⁺ IR after CBT, which can be achieved by reducing the exposure to ATG after CBT. Individualized dosing of ATG to reach optimal exposure or, in selected patients, omission of ATG may contribute to improved outcomes in pediatric CBT.

Strategies before, during, and after hematopoietic cell transplantation to improve T-cell immune reconstitution

T-cell immune reconstitution (IR) after allogeneic hematopoietic cell transplantation (allo-HCT) is highly variable between patients and may take several months to even years. Patients with delayed or unbalanced T-cell IR have a higher probability of developing transplantation-related morbidity, mortality, and relapse of disease. Hence, there is a need for strategies to better predict and improve IR to reduce these limitations of allo-HCT. In this review, we provide an update of current and in-near-future clinically relevant strategies before, during, and after transplantation to achieve successful T-cell IR. Potent strategies are choosing the right HCT source (eg, donor-recipient matching, cell dose, graft manipulation), individualized conditioning and serotherapy (eg, antithymocyte globulin), nutritional status, exercise, home care, modulation of microbiota, enhancing homeostatic peripheral expansion, promoting thymopoiesis, and the use of adjuvant-targeted cellular immunotherapies. Strategies to prevent graft-versus-host disease are important as well because this complication and the subsequent need for immunosuppression affects T-cell IR and function. These options aim for personalized precision transplantation, where allo-HCT therapy is designed to boost a well-balanced T-cell IR and limit complications in individual patients, resulting in overall lower morbidity and higher survival chances.

A trial of unrelated donor marrow transplantation for children with severe sickle cell disease

Children with sickle cell disease experience organ damage, impaired quality of life, and premature mortality. Allogeneic bone marrow transplant from an HLA-matched sibling can halt disease progression but is limited by donor availability. A Blood and Marrow Transplant Clinical Trials Network (BMT CTN) phase 2 trial conducted from 2008 to 2014 enrolled 30 children aged 4 to 19 years; 29 were eligible for evaluation. The primary objective was 1-year event-free survival (EFS) after HLA allele-matched (at HLA-A, -B, -C, and -DRB1 loci) unrelated donor transplant. The conditioning regimen included alemtuzumab, fludarabine, and melphalan. Graft-versus-host disease (GVHD) prophylaxis included calcineurin inhibitor, short-course methotrexate, and methylprednisolone. Transplant indications included stroke (n = 12), transcranial Doppler velocity >200 cm/s (n = 2), ≥3 vaso-occlusive pain crises per year (n = 12), or ≥2 acute chest syndrome episodes (n = 4) in the 2 years preceding enrollment. Median follow-up was 26 months (range, 12-62 months); graft rejection was 10%. The 1- and 2-year EFS rates were 76% and 69%, respectively. The corresponding rates for overall survival were 86% and 79%. The day 100 incidence rate of grade II-IV acute GVHD was 28%, and the 1-year incidence rate of chronic GVHD was 62%; 38% classified as extensive. There were 7 GVHD-related deaths. A 34% incidence of posterior reversible encephalopathy syndrome was noted in the first 6 months. Although the 1-year EFS met the prespecified target of ≥75%, this regimen cannot be considered sufficiently safe for widespread adoption without modifications to achieve more effective GVHD prophylaxis. The BMT CTN #0601 trial was registered at www.clinicaltrials.gov as #NCT00745420.

Haploidentical cord transplantation-The best of both worlds

Haploidentical (haplo)-cord transplantation combines infusion of an umbilical cord blood (UCB) unit with CD34-selected cells usually from human leukocyte antigen (HLA) mismatched donors. Initial rapid count recovery from the haplo-hematopoietic progenitors, is gradually replaced by durable engraftment from UCB progenitors. UCB grafts used for haplo-cord are smaller, but better matched than those required for single or double UCB stem cell transplant (SCT). More than 200 patients with hematological malignancies have been transplanted. Median age was 54 years (range 17-74) and 77 were over age 60. One-year survival was 64% for patients with intermediate- and low-risk disease, with no deaths beyond 2 years. In high-risk disease, 1-year survival was 44%. In a comparison with patients undergoing double UCB SCT, haplo-cord transplant resulted in faster hematopoietic recovery, lower rates of acute and chronic graft-versus-host disease (GVHD), lower rates of disease recurrence, and improved GVHD- and relapse-free survival (GRFS). Excellent results were also reported for patients with aplastic anemia where 18 of 21 patients had sustained cord blood engraftment. Rates of GVHD and of disease recurrence after haplo-cord are encouraging. However, in the approximately 10% of patients with failure of the UCB graft disease recurrence is high, supporting the important role of UCB-mediated graft-versus-leukemia (GVL). Ongoing efforts are aimed at identifying determinants of UCB engraftment, at reducing rates of disease recurrence in high risk patients and at optimizing dose and schedule of ATG -necessary to avoid early haplo-graft rejection, but also contributing to early post-transplant immunocompromise. For those lacking haploidentical donors, unrelated donors have been successfully utilized.

Cord blood chimerism and relapse after haplo-cord transplantation

Haplo-cord stem cell transplantation combines the infusion of CD34 selected hematopoietic progenitors from a haplo-identical donor with an umbilical cord blood (UCB) graft from an unrelated donor and allows faster count recovery, with low rates of disease recurrence and chronic graft-versus-host disease (GVHD). But the contribution of the umbilical cord blood graft to long-term transplant outcome remains unclear. We analyzed 39 recipients of haplo-cord transplants with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), engrafted and in remission at 2 months. Median age was 66 (18-72) and all had intermediate, high, or very-high risk disease. Less than 20% UCB chimerism in the CD33 lineage was associated with an increased rate of disease recurrence (54% versus 11% p < 0.0001) and decrease in one year progression-free (20% versus 55%, p = 0.004) and overall survival (30% versus 62%, p = 0.02). Less than 100% UCB chimerism in the CD3 lineage was associated with increase rate of disease recurrence (46% versus 12%, p = 0.007). Persistent haplo-chimerism in the CD3 lineage was associated with an increased rate of disease recurrence (40% versus 15%, p = 0.009) Chimerism did not predict for treatment related mortality. The cumulative incidence of acute GVHD by day 100 was 43%. The cumulative incidence of moderate/severe chronic GVHD was only 5%. Engraftment of the umbilical cord blood grafts provides powerful graft-versus-leukemia (GVL) effects which protect against disease recurrence and is associated with low risk of chronic GVHD. Engraftment of CD34 selected haplo-identical cells can lead to rapid development of circulating T-cells, but when these cells dominate, GVL-effects are limited and rates of disease recurrence are high.

Cord Blood Units with High CD3(+) Cell Counts Predict Early Lymphocyte Recovery After In Vivo T Cell-Depleted Single Cord Blood Transplantation

Although high absolute lymphocyte count (ALC) early after transplantation is a simple surrogate for immune reconstitution, few studies to date have established the predictive factors for ALC after umbilical cord blood transplantation (UCBT). We retrospectively studied the factors associated with early lymphocyte recovery and the impact of the ALC on day +42 (ALC42) of ≥300 × 10(6)/L on outcomes in 210 consecutive pediatric and adult patients (112 males; median age, 15 years; range, 0.3 to 60 years; interquartile range, 4 to 36 years) who underwent myeloablative in vivo T cell-depleted single UCBT between 2005 and 2014 for malignant and nonmalignant disorders. In a logistic multivariate regression model, factors favoring a higher ALC42 were higher infused CD3(+) cell dose (odds ratio [OR], 2.7; 95% CI, 1.4 to 5.2; P = .004), lower antithymocyte globulin dose (OR, 2.3; 95% CI, 1.2 to 4.5; P = .01), and better HLA match (OR, 2.1; 95% CI, 1.1 to 4.1; P = .03). In multivariate analysis, lower ALC42 was associated with higher nonrelapse mortality (hazard ratio [HR], 1.76; 95% CI, 1.34 to 2.32; P = .001), whereas a higher ALC42 was associated with better disease-free survival (HR, 2.03; 95% CI, 1.15 to 3.6; P < .001) and overall survival (HR, 2.03; 95% CI, 1.17 to 3.6; P < .001). Our study suggests that the selection of better HLA-matched cord blood units containing higher CD3(+) cell counts and the use of conditioning regimens with lower ATG doses could improve immune reconstitution after UCBT.