Primary graft failure after myeloablative allogeneic hematopoietic cell transplantation for hematologic malignancies

Impact of total body irradiation- vs chemotherapy-based myeloablative conditioning on outcomes of haploidentical hematopoietic cell transplantation for acute myelogenous leukemia

The optimal myeloablative conditioning (MAC) for patients undergoing haploidentical hematopoietic cell transplantation (haplo-HCT) is unknown. We studied the outcomes of total body irradiation (TBI) vs chemotherapy (CT) based MAC regimens in acute myeloid leukemia (AML) patients. The study included 1008 patients who underwent first haplo-HCT with post-transplant cyclophosphamide, following TBI (N = 89, 9%) or CT (n = 919, 91%) based MAC. Patients in the TBI cohort were younger (median age, 38 vs 47 years, P < .01) and more likely to receive BM graft (57% vs 43%, P = .01). Two-year overall chronic GVHD (cGVHD) incidence was 42% vs 27% (P < .01) and extensive cGVHD incidence was 9% vs 12% (P = .33) in TBI and CT cohorts, respectively. Graft failure was reported in two (2%) TBI- and 65 (7%) CT-MAC recipients (P = .08). Death from veno-occlusive disease was reported in one (3%) TBI and 11 (3%) CT patients who died during the study period. In the multivariate analysis, TBI was associated with increased risk for overall cGVHD (hazard ratio = 1.95, 95% confidence interval:1.2-3.1, P < .01) compared to CT-based MAC. The choice of conditioning regimen did not impact relapse incidence, leukemia-free survival, non-relapse mortality, overall survival or GVHD-relapse-free survival in multivariate analysis. In conclusion, major transplant outcomes were not statistically different between TBI-based MAC and CT-based MAC in patients with AML after haplo-HCT/PTCy.

Haploidentical Hematopoietic Stem Cell Transplantation for XIAP Deficiency: a Single-Center Report

PURPOSE

X-linked inhibitor of apoptosis (XIAP) deficiency caused by mutations in the XIAP/BIRC4 gene is a rare inherited primary immunodeficiency also known as X-linked lymphoproliferative syndrome type 2 (XLP2). Hematopoietic stem cell transplantation (HSCT) is currently the only curative strategy available. However, few studies of haploidentical HSCT have been published regarding the outcomes in patients with this syndrome.

METHODS

We evaluated the XIAP gene analysis and clinical characteristics of four Chinese patients with XIAP who underwent haploidentical HSCT.

RESULTS

The mutations in the two of four patients had not yet been reported in the literature. All of the patients had recurrent hemophagocytic lymphohistiocytosis but did not have a good matched donor and underwent haploidentical HSCT at BCH in China between September 2016 and December 2018. All four patients received antithymocyte globulin with fludarabine-based regimens. Two patients underwent reduced intensity conditioning (RIC), and the other two received modified myeloablative conditioning (MAC) regimens. Three of the four patients survived. Three patients experienced complications with mixed chimerism. One of the four patients who underwent RIC had early graft loss and then developed grade IV acute graft-versus-host disease (GVHD) after donor lymphocyte infusion with bone marrow. The two patients who received MAC survived with no or mild GVHD, even though one of them developed hepatic veno-occlusive disease in the early stage of transplantation.

CONCLUSIONS

Haploidentical HSCT may be a treatment option for patients with XIAP deficiency who lack a good matched donor. More studies are needed to determine whether modified MAC with reduced toxicity is more suitable for haploidentical transplantation.

ASC Modulates CTL Cytotoxicity and Transplant Outcome Independent of the Inflammasome

The adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) is known to facilitate caspase-1 activation, which is essential for innate host immunity via the formation of the inflammasome complex, a multiprotein structure responsible for processing IL1β and IL18 into their active moieties. Here, we demonstrated that ASC-deficient CD8⁺ T cells failed to induce severe graft-versus-host disease (GVHD) and had impaired capacity for graft rejection and graft-versus-leukemia (GVL) activity. These effects were inflammasome independent because GVHD lethality was not altered in recipients of caspase-1/11-deficient T cells. We also demonstrated that ASC deficiency resulted in a decrease in cytolytic function, with a reduction in granzyme B secretion and CD107a expression by CD8⁺ T cells. Altogether, our findings highlight that ASC represents an attractive therapeutic target for improving outcomes of clinical transplantation.

Determinants of survival in myelofibrosis patients undergoing allogeneic hematopoietic cell transplantation

We aimed to evaluate the determinants of survival in myelofibrosis patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT) and to describe factors predicting the main post-HCT complications. This retrospective study by the European Society for Blood and Marrow Transplantation included 2916 myelofibrosis patients who underwent first allo-HCT from an HLA-identical sibling or unrelated donor between 2000 and 2016. After a median follow-up of 4.7 years from transplant, projected median survival of the series was 5.3 years. Factors independently associated with increased mortality were age ≥ 60 years and Karnofsky Performance Status <90% at transplant, and occurrence of graft failure, grades III-IV acute graft-vs.-host disease (aGVHD), and disease progression/relapse during follow-up. The opposing effects of chronic graft-vs.-host disease (GVHD) on non-relapse mortality and relapse incidence resulted in a neutral influence on survival. Graft failure increased in unrelated donor recipients and decreased with myeloablative conditioning (MAC) and negative donor/recipient cytomegalovirus serostatus. Risk of grades III-IV aGVHD was higher with unrelated donors and decreased with MAC. Relapse incidence tended to be higher in patients with intermediate-2/high-risk DIPSS categories and to decrease in CALR-mutated patients. Acute and chronic GVHD reduced the subsequent risk of relapse. This information has potential implications for patient counseling and clinical decision-making.

Comparison of the outcomes after haploidentical and cord blood salvage transplantations for graft failure following allogeneic hematopoietic stem cell transplantation

Graft failure (GF) is a life-threatening complication after allogeneic stem cell transplantation (SCT). Although salvage SCTs can be performed with haploidentical donor (HID) or cord blood (CB), no study has compared the performances of these two sources. Using nationwide registration data, we compared the transplant outcomes of patients who developed GF and underwent salvage transplantation from HID (n = 129) and CB (n = 570) from 2007 to 2016. The HID group demonstrated better neutrophil recovery (79.7 vs. 52.5% at 30 days, P < 0.001). With a median follow-up of 3 years, both groups demonstrated similar overall survival (OS) and nonrelapse mortality (NRM; 1-year OS, 33.1 vs. 34.6% and 1-year NRM, 45.1 vs. 49.8% for the HID and CB groups). After adjustments for other covariates, OS did not differ in both groups. However, HID was associated with a lower NRM (hazard ratio, 0.71; P = 0.038) than CB. The incidence of acute graft-versus-host disease (GVHD)-related deaths was significantly higher in the HID group, although infection-related deaths were observed more frequently in the CB group. HID may be a promising salvage SCT option after GF due to its faster engraftment and low NRM.

Prevalence and risk factors of having antibodies to class I and II human leukocyte antigens in older haploidentical allograft candidates

The effect of donor-specific anti-human leukocyte antigen (HLA) antibodies (DSAs) has been recognized as a factor in graft failure (GF) in patients who underwent umbilical cord blood transplantation (UBT), matched unrelated donor transplantation (MUDT), or haploidentical stem cell transplantation (haplo-SCT). Presently, we know little about the prevalence of and risk factors for having anti-HLA antibodies among older transplant candidates. Therefore, we analyzed 273 older patients with hematologic disease who were waiting for haplo-SCT. Among all patients, 73 (26.7%) patients had a positive panel-reactive antibody (PRA) result for class I, 38 (13.9%) for class II, and 32 (11.7%) for both. Multivariate analysis showed that females were at a higher risk for having a PRA result for class II (P = 0.001) and for having antibodies against HLA-C and HLA-DQ. Prior pregnancy was a risk factor for having a PRA result for class I (P < 0.001) and for having antibodies against HLA-A, HLA-B and HLA-DQ. Platelet transfusions were risk factors for the following: having a positive PRA result for class I (P = 0.014) and class II (P < 0.001); having antibodies against HLA-A, HLA-B, HLA-C, HLA-DP, HLA-DQ, and HLA-DR; and having higher mean fluorescence intensity (MFI) of PRA for class I (P = 0.042). In addition, previous total transfusions were at high risk for having higher numbers of antibodies to specific HLA loci (P = 0.005), and disease course (7.5 months or more) (P = 0.020) were related to higher MFI of PRAs for class I. Our findings indicated that female sex, prior pregnancy, platelet transfusions and disease courses are independent risk factors for older patients with hematologic disease for having anti-HLA antibodies, which could guide anti-HLA antibody monitoring and be helpful for donor selection.

Conditioned Medium from Human Tonsil-Derived Mesenchymal Stem Cells Enhances Bone Marrow Engraftment via Endothelial Cell Restoration by Pleiotrophin

Cotransplantation of mesenchymal stem cells (MSCs) with hematopoietic stem cells (HSCs) has been widely reported to promote HSC engraftment and enhance marrow stromal regeneration. The present study aimed to define whether MSC conditioned medium could recapitulate the effects of MSC cotransplantation. Mouse bone marrow (BM) was partially ablated by the administration of a busulfan and cyclophosphamide (Bu–Cy)-conditioning regimen in BALB/c recipient mice. BM cells (BMCs) isolated from C57BL/6 mice were transplanted via tail vein with or without tonsil-derived MSC conditioned medium (T-MSC CM). Histological analysis of femurs showed increased BM cellularity when T-MSC CM or recombinant human pleiotrophin (rhPTN), a cytokine readily secreted from T-MSCs with a function in hematopoiesis, was injected with BMCs. Microstructural impairment in mesenteric and BM arteriole endothelial cells (ECs) were observed after treatment with Bu–Cy-conditioning regimen; however, T-MSC CM or rhPTN treatment restored the defects. These effects by T-MSC CM were disrupted in the presence of an anti-PTN antibody, indicating that PTN is a key mediator of EC restoration and enhanced BM engraftment. In conclusion, T-MSC CM administration enhances BM engraftment, in part by restoring vasculature via PTN production. These findings highlight the potential therapeutic relevance of T-MSC CM for increasing HSC transplantation efficacy.

Role of interferon-γ in immune-mediated graft failure after allogeneic hematopoietic stem cell transplantation

Pathophysiology of graft failure (GF) occurring after allogeneic hematopoietic stem cell transplantation (HSCT) still remains elusive. We measured serum levels of several different cytokines/chemokines in 15 children experiencing GF, comparing their values with those of 15 controls who had sustained donor cell engraftment. Already at day +3 after transplantation, patients developing GF had serum levels of interferon (IFN)-γ and CXCL9 (a chemokine specifically induced by IFNγ) significantly higher than those of controls (8859±7502 vs. 0 pg/mL, P=0.03, and 1514.0±773 vs. 233.6±50.1 pg/mlL, P=0.0006, respectively). The role played by IFNγ in HSCT-related GF was further supported by the observation that a rat anti-mouse IFNγ-neutralizing monoclonal antibody promotes donor cell engraftment in Ifngr1-/-mice receiving an allograft. In comparison to controls, analysis of bone marrow-infiltrating T lymphocytes in patients experiencing GF documented a predominance of effector memory CD8+ cells, which showed markers of activation (overexpression of CD95 and downregulation of CD127) and exhaustion (CD57, CD279, CD223 and CD366). Finally, we obtained successful donor engraftment in 2 out of 3 children with primary hemophagocytic lymphohistiocytosis who, after experiencing GF, were re-transplanted from the same HLA-haploidentical donor under the compassionate use coverage of emapalumab, an anti-IFNγ monoclonal antibody recently approved by the US Food and Drug Administration for treatment of patients with primary hemophagocytic lymphohistiocytosis. Altogether, these results suggest that the IFNγ pathway plays a major role in GF occurring after HSCT. Increased serum levels of IFNγ and CXCL9 represent potential biomarkers useful for early diagnosis of GF and provide the rationale for exploring the therapeutic/preventive role of targeted neutralization of IFNγ.

[Graft failure after allogeneic hematopoietic stem cell transplantation: Definition and risk factors]

Allogeneic hematopoietic stem cell transplantation is the only curative therapy for numerous malignant and non-malignant haematological diseases. A sustained engraftment of the donor stem cells is essential for transplant success and overall outcome. Graft failure is a rare but severe event after allogeneic hematopoietic stem cell transplantation. While different risk factors such as underlying disease, graft source or HLA matching have been found to be consistently associated with graft failure, other factors such as ABO mismatch graft-versus-host disease prophylaxis or infections, particularly viral reactivations, are more controversial. In this article, we review the different factors associated with graft failure.

Prophylactic oral NAC reduced poor hematopoietic reconstitution by improving endothelial cells after haploidentical transplantation

Poor graft function (PGF) and prolonged isolated thrombocytopenia (PT) remain life-threatening complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Endothelial cells (ECs) play a crucial role in regulating hematopoiesis in the bone marrow (BM) microenvironment. However, whether the impaired BM ECs are responsible for defective hematopoiesis in PGF and PT patients requires clarification, and clinical management is challenging. Two prospective clinical trials were included in the current study. In the first trial (N = 68), PGF and PT patients demonstrated defective BM ECs pre-HSCT and impaired BM EC dynamic reconstitution at early time points post-HSCT, which was positively correlated with reactive oxygen species (ROS) levels. Receiver operating characteristic curves showed that BM EC < 0.1% pre-HSCT could identify high-risk patients with PGF and PT. The second trial enrolled patients (N = 35) with EC < 0.1% who accepted oral N-acetyl-l-cysteine (NAC; 400 mg 3 times per day) from -14 days pre-HSCT to +2 months post-HSCT continuously, whereas the remaining EC ≥ 0.1% patients (N = 39) received allo-HSCT only. Prophylactic NAC intervention was safe and effective in preventing the occurrence of PGF and PT in EC < 0.1% patients by promoting the dynamic reconstitution of BM ECs and CD34+ cells, along with reducing their ROS levels, which was further confirmed by in situ BM trephine biopsy analyses. These findings suggest that the impaired BM ECs pre-HSCT are responsible for the defective hematopoiesis in PGF and PT patients. Therefore, improvement of BM ECs through prophylactic NAC intervention may be a promising therapeutic approach to promote hematopoietic reconstitution post-HSCT. This trial was registered at www.clinicaltrials.gov as #NCT03236220 and #NCT02978274.

Clinical significance of low-dose total body irradiation in HLA-mismatched reduced-intensity stem cell transplantation

The significance of low-dose total body irradiation (TBI) in HLA-mismatched reduced-intensity conditioning stem cell transplantation (RICT) remains unknown. We, retrospectively, evaluated the impact of low-dose TBI in patients with hematological malignancies who received first RICT from ≥1 antigen-mismatched donors between 2004 and 2014. Of the 575 patients, 361 patients received low-dose TBI (2 or 4 Gy). There were no significant differences in neutrophil engraftment or platelet recovery between TBI and non-TBI groups. The benefit of low-dose TBI on neutrophil engraftment was not observed in any subgroups. Low-dose TBI was not associated with decreased secondary graft failure. Suppressed mixed chimerism and autologous hematopoiesis by low-dose TBI was observed. There were no significant differences in cumulative incidences of acute GVHD or nonrelapse mortality rates in either group; however, low-dose TBI improved overall survival (OS), especially in patients with high-risk disease, multi-HLA mismatch, and fludarabine/busulfan conditioning. Multivariate analysis demonstrated that low-dose TBI was an independent prognostic factor for OS. Compared with the non-TBI group, 4 Gy TBI, but not 2 Gy TBI, was associated with increased acute GVHD and reduced relapse. These findings suggest that low-dose TBI may be beneficial for patients at high risk for relapse in HLA-mismatched RICT.

Rescue haploidentical peripheral blood stem cell transplantation for engraftment failure: a single-centre case series

Graft failure affects approximately 5% of allogeneic stem cell transplants, with a poor prognosis. Salvage second allogeneic stem cell transplantation (alloSCT2) is limited by high rates of transplant-related mortality from infection and graft-versus-host disease. We report on five adult patients receiving rescue alloSCT2 using haploidentical peripheral blood stem cells. All patients achieved neutrophil engraftment, two subsequently died from sepsis and disease relapse, respectively. Three patients remain alive up to 2 years post-transplant. We suggest consideration of haploidentical alloSCT2 for patients with graft failure.

Menstrual Blood Stem Cell Transplantation in Mice Model of Acute Liver Failure: Does Gender of Recipient Affect the Outcome?

BACKGROUND

There exists a dramatic rise in liver failure and numerous patients undergo liver transplant for life-saving reasons annually. Introducing alternatives to allo-graft transplantation is necessary due to present limitations. Recently, a noninvasive stem cell population from Menstrual blood-derived Stem Cells (MenSCs) has been identified. There is an increasing interest in the application of MenSCs in tissue engineering; however, the fact that these gender-specific stem cells are safe for use in male sex is still not well defined.

METHODS

In this research, a model of acute liver failure was created in male and female immunocompetent Balb-C mice through intraperitoneal injection of Carbon tetrachlo-ride (CCl₄ ) and MenSCs were transplanted intravenously 48 hrs after induction of liver injury to evaluate their therapeutic potential. All mice were sacrificed on days 1, 7, and 30 post-transplantation to examine biochemical and molecular markers and pathological appearances.

RESULTS

Results showed the liver engraftment of MenSCs by immunofluorescence staining using anti-human mitochondrial antibody in both male and female treated groups. The restoration of serum markers of liver injury, aspartate aminotransferase and ala-nine aminotransferase, as well as expression levels of liver-specific genes, tyrosine aminotransferase and cholesterol 7 alpha-hydroxylase, were more significant in the female treated group compared with the male treated group on day 7 (p<0.05); however, after 30 days, there were no significant differences. Furthermore, hematoxylin and eosin and periodic acid-Schiff staining of liver sections demonstrated the considerable liver regeneration post cell therapy in both groups. Notably, data has shown that MenSCs could engraft into injured liver tissues and result in the same effect in the regeneration of liver function in both genders.

CONCLUSION

Results of this study introduce MenSCs therapy as an attractive alternative approach for liver repairing and regeneration which has no gender constraints.

Family Mismatched Allogeneic Stem Cell Transplantation for Myelofibrosis: Report from the Chronic Malignancies Working Party of European Society for Blood and Marrow Transplantation

This analysis included 56 myelofibrosis (MF) patients transplanted from family mismatched donor between 2009 and 2015 enrolled in the European Society for Blood and Marrow Transplantation database. The median age was 57years (range, 38 to 72); 75% had primary MF and 25% had secondary MF. JAK2 V617F was mutated in 61%. Donors were HLA mismatched at 2 or more loci. Stem cells were sourced from bone marrow in 66% and peripheral blood in 34%. The median CD34⁺ cell dose was 4.8 × 10⁶/kg (range, 1.7 to 22.9; n = 43). Conditioning was predominantly myeloablative in 70% and reduced intensity in the remainder. Regimens were heterogeneous with thiotepa, busulfan, fludarabine, and post-transplant cyclophosphamide used in 59%. The incidence of neutrophil engraftment by 28days was 82% (range, 70% to 93%), at a median of 21days (range, 19 to 23). At 2years the cumulative incidence of primary graft failure was 9% (95% CI 1% to 16%) and secondary graft failure was 13% (95% CI 4% to 22%). The cumulative incidence of acute graft-versus-host disease (GVHD) grades II to IV and III to IV was 28% (95% CI 16% to 40%) and 9% (95% CI 2% to 17%) at 100days. The cumulative incidence of chronic GVHD at 1 year was 45% (95% CI 32% to 58%), but the cumulative incidence of death without chronic GVHD by 1 year was 20% (95% CI 10% to 31%). With a median follow-up of 32 months, the 1- and 2-year overall survival was 61% (95% CI 48% to 74%) and 56% (95% CI 41% to 70%), respectively. The 1- and 2- year progression-free survival was 58% (95% CI 45% to 71%) and 43% (95% CI 28% to 58%), respectively, with a 2-year cumulative incidence of relapse of 19% (95% CI 7% to 31%). The 2-year nonrelapse mortality was 38% (95% CI 24% to 51%). This retrospective study of MF allo-SCT using family mismatched donors demonstrated feasibility of the approach, timely neutrophil engraftment in over 80% of cases, and acceptable overall and progression-free survival rates with relapse rates not dissimilar to the unrelated donor setting. However, strategies to minimize the risk of graft failure and the relatively high nonrelapse mortality need to be used, ideally in a multicenter prospective fashion.

Scoring System Based on Post-Transplant Complications in Patients after Allogeneic Hematopoietic Cell Transplantation for Myelodysplastic Syndrome: A Study from the SFGM-TC

PURPOSE

We developed a prognostic scoring system to evaluate the prognosis of myelodysplastic syndrome (MDS) patients surviving more than 100 days allogeneic hematopoietic cell transplantation after (allo-HCT).

PATIENTS AND METHODS

We performed a landmark analysis on a derivation cohort of 393 cases to identify prognostic factors for 3-year overall survival. Potential predictor variables included demographic and clinical data, transplantation modalities and early post-transplant complications. The scoring system was tested against a validation cohort which included 391 patients.

RESULTS

Complications occurring before day 100 such as relapse [HR = 6.7; 95%CI, 4.5-10.0] (4 points), lack of platelet recovery [HR, 3.6; 95%CI, 2.2-5.8] (2 points), grade-II acute GVHD [HR = 1.7; 95%CI, 1.2-2.5] (1 point) and grade-III/IV [HR = 2.6; 95%CI, 1.8 -3.8] (2 points) were the only independent predictors of 3-year OS. The 3-year OS associated with low (0), intermediate (1-3) and high (≥4) risk scores was respectively 70%, 46% and 6%. The model performed consistently in both cohorts, with good calibration.

CONCLUSION

This post-transplant scoring system is a powerful predictor of outcome after allo-HCT for MDS, and can provide useful guidance for clinicians. Additional studies are required to evaluate this scoring system for other hematologic malignancies.

Dysfunctional Bone Marrow Mesenchymal Stem Cells in Patients with Poor Graft Function after Allogeneic Hematopoietic Stem Cell Transplantation

Poor graft function (PGF) is a life-threatening complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and is characterized by defective hematopoiesis. Mesenchymal stem cells (MSCs) have been shown to support hematopoiesis, but little is known about the role of MSCs in the pathogenesis of PGF. In the current prospective case-control study, we evaluated whether the number and function of bone marrow (BM) MSCs in PGF patients differed from those in good graft function (GGF) patients. We found that BM MSCs from PGF patients expanded more slowly and appeared flattened and larger, exhibiting more apoptosis and senescence than MSCs from GGF patients. Furthermore, increased intracellular reactive oxygen species, p-p53, and p21 (but not p38) levels were detected in MSCs from PGF patients. Moreover, the ability of MSCs to sustain hematopoiesis was significantly reduced in PGF patients, as evaluated by cell number, apoptosis, and the colony-forming unit-plating efficiency of CD34⁺ cells. In summary, the biologic characteristics of PGF MSCs are different from those of GGF MSCs, and the in vitro hematopoiesis-supporting ability of PGF MSCs is significantly lower. Although requiring further validation, our study indicates that reduced and dysfunctional BM MSCs may contribute to deficient hematopoiesis in PGF patients. Therefore, improvement of BM MSCs may represent a promising therapeutic approach for PGF patients after allo-HSCT.

Graft-versus-host Disease-free, Relapse-free Survival After HLA-identical Sibling Peripheral Blood Stem Cell Transplantation With Tacrolimus-based Graft-versus-host Disease Prophylaxis in Japanese Patients

The ideal post-allogeneic hematopoietic cell transplantation recovery is not just the cure of hematologic malignancies but also freedom from ongoing morbidity. Recent studies have revealed that HLA-identical sibling peripheral blood stem cell transplantation (PBSCT) had been providing impaired graft-versus-host disease (GVHD)-free relapse-free survival (GRFS) due to a higher risk of GVHD. Study on GVHD prophylaxis bears clinical reliance when focused on Japanese population because risk of GVHD differs among races. We identified 15 consecutive Japanese patients who received tacrolimus-based GVHD prophylaxis after myeloablative HLA-identical sibling PBSCT. No episode of grade ≥ II acute GVHD and only one episode of grade III toxicity were documented, with the control of mean weekly blood tacrolimus concentrations during the first 4 weeks at 13 to 17 ng/mL. An estimated 46.7% (95% CI: 21.4% to 71.9%) of the patients enjoyed their GRFS at 3 years after transplantation, and failure in the treatment of chronic GVHD was not reported during the median follow-up period of 1059 days (range, 784 to 1778 days) after the development of chronic GVHD. The results suggest that the application of tacrolimus with the optimization of its blood concentrations may effectively prevent ongoing morbidities after HLA-identical sibling PBSCT.

Increased reactive oxygen species and exhaustion of quiescent CD34-positive bone marrow cells may contribute to poor graft function after allotransplants

Poor graft function (PGF) is a fatal complication following allogeneic haematopoietic stem cell transplantation. However, the underlying mechanism is unclear. Effective cross-talk between haematopoietic stem cells (HSCs) and bone marrow microenvironment is important for normal haematopoiesis. Normal HSCs reside in a hypoxic bone marrow microenvironment that protects them from oxidative stress that would otherwise inhibit their self-renewal and results in bone marrow failure. Whether an increased level of reactive oxygen species (ROS) causes PGF following allotransplant is unclear. Using a prospective case-pair study, we identified increased levels of ROS in CD34+ bone marrow cells in subjects with PGF. Elevated ROS levels was associated with an increased frequency of DNA strand breaks, apoptosis, exhaustion of quiescent CD34+ cells and defective colony-forming unit plating efficiency, particularly in the CD34+CD38- fraction. Up-regulated intracellular p53, p21, caspase-3 and caspase-9 levels (but not p38) were detected in CD34+ cells, particularly in the CD34+CD38- fraction. To further study the potential role of ROS levels in post-transplant haematopoiesis, CD34+ bone marrow cells from subjects with good graft function were treated with H2O2. This increased ROS levels resulting in defective CD34+ cells, an effect partially reversed by N-acetyl-L-cysteine. Moreover, CD34+ bone marrow cells from the donors to subjects with poor or good graft function exhibited comparable haematopoietic reconstitution capacities in the xeno-transplanted NOD-PrkdcscidIL2rgnull mice. Thus, even if the transplanted donors' bone marrow CD34+ cells are functionally normal pre-transplant, ROS-induced apoptosis may contribute to the exhaustion of CD34+ bone marrow cells in subjects with PGF following allotransplant.

Haploidentical hematopoietic stem cell transplantation in a myelofibrosis patient with primary graft failure

The prognosis of patients affected by myelofibrosis (MF) is usually dismal and allogeneic hematopoietic stem cell transplantation (HSCT) remains the only cure. The number of HSCTs in MF patients has recently increased. However, a major obstacle is still represented by primary graft failure (PGF). Currently there are no definitive guidelines for the treatment of PGF and a second HSCT can be performed only when an allogeneic donor is rapidly available. Herein we report on a MF patient with PGF after an unrelated HSCT, who was rescued by a non-myeloablative, unmanipulated, haploidentical HSCT that resulted in persistent engraftment and bone-marrow fibrosis regression, but not in a long-term disease control. Based on this experience we briefly review the role of different conditioning regimens and hematopoietic stem cell sources in the setting of HSCT for MF patients with PGF. The role of haploidentical donors in MF patients lacking HLAmatched relatives is also discussed.

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.

T Cell-Mediated Rejection of Human CD34+ Cells Is Prevented by Costimulatory Blockade in a Xenograft Model

A xenograft model of stem cell rejection was developed by co-transplantating human CD34⁺ and allogeneic CD3⁺ T cells into NOD-scid ɣ-chain^null mice. T cells caused graft failure when transplanted at any CD34/CD3 ratio between 1:50 and 1:.1. Kinetics experiments showed that 2 weeks after transplantation CD34⁺ cells engrafted the marrow and T cells expanded in the spleen. Then, at 4 weeks only memory T cells populated both sites and rejected CD34⁺ cells. Blockade of T cell costimulation was tested by injecting the mice with abatacept (CTLA4-IgG1) from day -1 to +27 (group A), from day -1 to +13 (group B), or from day +14 to +28 (group C). On day +56 groups B and C had rejected the graft, whereas in group A graft failure was completely prevented, although with lower stem cell engraftment than in controls (P = .03). Retransplantation of group A mice with same CD34⁺ cells obtained a complete reconstitution of human myeloid and B cell lineages and excluded latent alloreactivity. In this first xenograft model of stem cell rejection we showed that transplantation of HLA mismatched CD34⁺ cells may be facilitated by treatment with abatacept and late stem cell boost.

Aberrant T cell responses in the bone marrow microenvironment of patients with poor graft function after allogeneic hematopoietic stem cell transplantation

Background

Poor graft function (PGF) is a life-threatening complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Nevertheless, whether abnormalities of T cell subsets in the bone marrow (BM) immune microenvironment, including Th17, Tc17, Th1, Tc1, Th2, Tc2 cells and regulatory T cells (Tregs), are involved in the pathogenesis of PGF remains unclear.

Methods

This prospective nested case–control study enrolled 20 patients with PGF, 40 matched patients with good graft function (GGF) after allo-HSCT, and 20 healthy donors (HD). Th17, Tc17, Th1, Tc1, Th2, Tc2 cells, Tregs and their subsets were analyzed by flow cytometry.

Results

A significantly higher proportion of stimulated CD4⁺ and CD8⁺ T cells that produced IL-17 (Th17 and Tc17) was found in the BM of PGF patients than in the BM of GGF patients and HD, whereas the percentages of Tregs in PGF patients were comparable to those in GGF patients and HD, resulting in a dramatically elevated ratio of Th17 cells/Tregs in the BM of PGF patients relative to those in GGF patients. Moreover, both CD4⁺ and CD8⁺ T cells were polarized towards a type 1 immune response in the BM of PGF patients.

Conclusions

The present study revealed that aberrant T cell responses in the BM immune microenvironment may be involved in the pathogenesis of PGF after allo-HSCT. These findings will facilitate the optimization of immune regulation strategies and improve the outcome of PGF patients post-allotransplant.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1159-y) contains supplementary material, which is available to authorized users.

Non-myeloablative conditioning for second hematopoietic cell transplantation for graft failure in patients with non-malignant disorders: a prospective study and review of the literature

Allogeneic hematopoietic cell transplantation (HCT) effectively treats several non-malignant disorders such as selected lysosomal disorders, cerebral adrenoleukodystrophy and hemoglobinopathies. However, rates of graft failure (GF) in non-malignant populations exceed those of patients with malignant indications for HCT. Salvage conditioning regimens and outcomes for second HCT for GF vary immensely in the literature. We report 17 consecutive pediatric patients with non-malignant disorders who underwent a second allogenic HCT for GF using a non-myeloablative, low-dose busulfan-based regimen. Graft sources for the second transplant included umbilical cord blood, unrelated bone marrow and unrelated PBSCs. Median age at time of second HCT was 6.6 years (1.1-14.6 years). Fourteen of seventeen patients (82%) achieved engraftment, with a 3-year overall survival of 82% (95% CI, 54-94%). Day 100 transplant-related mortality was 12% (95% CI, 0-27%). CMV and adenovirus reactivation occurred in 30% and fungal infections in 18%. The incidence of grade II-IV acute GvHD disease was 35% (95% CI, 13-58%) with only 6% grade III-IV (95% CI, 0-17%). In summary, we illustrate excellent overall survival and acceptable toxicity using a non-myeloablative conditioning regimen for second HCT as salvage therapy for first GF in patients with non-malignant conditions.

The Impact of High-resolution HLA-A, HLA-B, HLA-C, and HLA-DRB1 on Transplant-related Outcomes in Single-unit Umbilical Cord Blood Transplantation in Pediatric Patients

Current practice for selecting donor units for umbilical cord blood transplant (UCBT) involves matching at HLA-A and HLA-B by low-resolution typing and the HLA-DRB1 allele by high-resolution (HR) typing. We retrospectively studied the impact of HR allele matching at HLA-A, HLA-B, HLA-C, and HLA-DRB1 on transplant-related outcomes in 60 single-unit UCBTs in pediatric patients with malignant and nonmalignant conditions. Five-year overall survival of our cohort was 71% (95% confidence interval, 58-81); 27% experienced primary graft failure. Applying HR typing, donor-recipient mismatch variability increased ranging from 1/8 to 8/8, however, no impact on primary graft failure, graft-versus-host disease or posttransplant infection was observed. UCBTs with ≥6/8 HR matches did have a better overall survival (P=0.04) and decreased transplant-related mortality (P=0.02) compared with <6/8 HR matches. Using standard HLA typing, we showed an increased incidence of acute graft-versus-host disease (grade II to IV) and decreased transplant-related mortality in comparing the matched (6/6) versus ≤5/6 group (P=0.05 and 0.05, respectively). These data support the use of current guidelines for umbilical cord blood selection and encourage utilization of HR typing to select umbilical cord blood units matched at ≥6/8 especially when appropriate ≥5/6 units are available.

Immunological Basis of Bone Marrow Failure after Allogeneic Hematopoietic Stem Cell Transplantation

Bone marrow failure (BMF) syndromes are severe complications of allogeneic hematopoietic stem cell transplantation (allo-HSCT). In this paper, we distinguish two different entities, the graft failure (GF) and the poor graft function (PGF), and we review the current understanding of the interactions between the immune and hematopoietic compartments in these conditions. We first discuss how GF occurs as the result of classical alloreactive immune responses mediated by residual host cellular and humoral immunity persisting after conditioning and prevented by host and donor regulatory T cells. We next summarize the current knowledge about the contribution of inflammatory mediators to the development of PGF. In situations of chronic inflammation complicating allo-HSCT, such as graft-versus-host disease or infections, PGF seems to be essentially the result of a sustained impairment of hematopoietic stem cells (HSC) self-renewal and proliferation caused by inflammatory mediators, such as interferon-γ (IFN-γ) and tumor necrosis factor-α, and of induction of apoptosis through the Fas/Fas ligand pathway. Interestingly, the production of inflammatory molecules leads to a non-MHC restricted, bystander inhibition of hematopoiesis, therefore, representing a promising target for immunological interventions. Finally, we discuss immune-mediated impairment of bone marrow microenvironment as a potential mechanism hampering hematopoietic recovery. Better understanding of immunological mechanisms responsible for BMF syndromes after allo-HSCT may lead to the development of more efficient immunotherapeutic interventions.

Donor and recipient sex in allogeneic stem cell transplantation: what really matters

We investigated whether and how recipient-donor sex affects transplantation outcomes of 11,797 patients transplanted between 2008 and 2010. Thirty-seven percent were male recipients with male donors, 21% male recipients with female donors, 25% female recipients with male donors, and 17% female recipients with female donors. In multivariable analyses, male recipients had inferior overall survival and progression-free survival compared to females regardless of donor sex, with an 11% relative increase in the hazard of death (P<0.0001) and a 10% relative increase in the hazard of death or relapse (P<0.0001). The detrimental effect of male recipients varied by donor sex. For male recipients with male donors, there was a 12% relative increase in the subdistribution hazard of relapse compared with female recipients with male donors (P=0.0036) and male recipients with female donors (P=0.0037). For male recipients with female donors, there was a 19% relative increase in the subdistribution hazard of non-relapse mortality compared with male recipients with male donors (P<0.0001) and a 22% relative increase compared with female recipients with male donors (P=0.0003). In addition, male recipients with female donors showed a 21% relative increase in the subdistribution hazard of chronic graft-versus-host disease (P<0.0001) compared with female recipients with male donors. Donor sex had no effect on outcomes for female recipients. Transplantation of grafts from male and female donors was associated with inferior overall survival and progression-free survival in male recipients with differing patterns of failure. Recipient sex is an important prognostic factor independent of donor sex.

Pure Red Cell Aplasia in Major ABO-Mismatched Allogeneic Hematopoietic Stem Cell Transplantation Is Associated with Severe Pancytopenia

In major ABO-mismatched allogeneic hematopoietic stem cell transplantation (HSCT) persistence of antidonor isohemagglutinins leads to pure red cell aplasia (PRCA). To investigate severe pancytopenia noted in a previous study of PRCA, we analyzed all major ABO-mismatched HSCT between January 2003 and December 2012. Of 83 PRCA patients, 13 (16%) had severe pancytopenia. Severe pancytopenia was defined as an absolute neutrophil count (ANC) < 1.5 K/μL or requiring granulocyte colony-stimulating factor, platelets < 50 K/μL or transfusion dependent, and PRCA with RBC transfusion dependence at post-transplant day 90. In 6 patients (46%) severe pancytopenia resolved after PRCA resolution. Two patients (15%) received a second transplant because of persistent pancytopenia/secondary graft failure, 1 (8%) died from secondary graft failure despite a stem cell boost, 1 (8%) did not recover his platelet counts despite RBC/ANC recovery, and 3 patients (23%) died from disease relapse. We found that severe pancytopenia is frequently associated with PRCA in 16% of major ABO-incompatible HSCT with a higher incidence in males and pancytopenia resolved with resolution of PRCA in 46% of patients.