A Day 14 Endpoint for Acute GVHD Clinical Trials

The overall response rate (ORR) 28 days after treatment has been adopted as the primary endpoint for clinical trials of acute graft versus host disease (GVHD). However, physicians often need to modify immunosuppression earlier than day (D) 28, and non-relapse mortality (NRM) does not always correlate with ORR at D28. We studied 1144 patients that received systemic treatment for GVHD in the Mount Sinai Acute GVHD International Consortium (MAGIC) and divided them into a training set (n=764) and a validation set (n=380). We used a recursive partitioning algorithm to create a Mount Sinai model that classifies patients into favorable or unfavorable groups that predicted 12 month NRM according to overall GVHD grade at both onset and D14. In the Mount Sinai model grade II GVHD at D14 was unfavorable for grade III/IV GVHD at onset and predicted NRM as well as the D28 standard response model. The MAGIC algorithm probability (MAP) is a validated score that combines the serum concentrations of suppression of tumorigenicity 2 (ST2) and regenerating islet-derived 3-alpha (REG3α) to predict NRM. Inclusion of the D14 MAP biomarker score with the D14 Mount Sinai model created three distinct groups (good, intermediate, poor) with strikingly different NRM (8%, 35%, 76% respectively). This D14 MAGIC model displayed better AUC, sensitivity, positive and negative predictive value, and net benefit in decision curve analysis compared to the D28 standard response model. We conclude that this D14 MAGIC model could be useful in therapeutic decisions and may offer an improved endpoint for clinical trials of acute GVHD treatment.

A Validated Risk Stratification That Incorporates MAGIC Biomarkers Predicts Long-Term Outcomes in Pediatric Patients with Acute GVHD

Acute graft versus host disease (GVHD) is a common and serious complication of allogeneic hematopoietic cell transplantation (HCT) in children but overall clinical grade at onset only modestly predicts response to treatment and survival outcomes. Two tools to assess risk at initiation of treatment were recently developed. The Minnesota risk system stratifies children for risk of nonrelapse mortality (NRM) according to the pattern of GVHD target organ severity. The Mount Sinai Acute GVHD International Consortium (MAGIC) algorithm of 2 serum biomarkers (ST2 and REG3α) predicts NRM in adult patients but has not been validated in a pediatric population. We aimed to develop and validate a system that stratifies children at the onset of GVHD for risk of 6-month NRM. We determined the MAGIC algorithm probabilities (MAPs) and Minnesota risk for a multicenter cohort of 315 pediatric patients who developed GVHD requiring treatment with systemic corticosteroids. MAPs created 3 risk groups with distinct outcomes at the start of treatment and were more accurate than Minnesota risk stratification for prediction of NRM (area under the receiver operating curve (AUC), .79 versus .62, P = .001). A novel model that combined Minnesota risk and biomarker scores created from a training cohort was more accurate than either biomarkers or clinical systems in a validation cohort (AUC .87) and stratified patients into 2 groups with highly different 6-month NRM (5% versus 38%, P < .001). In summary, we validated the MAP as a prognostic biomarker in pediatric patients with GVHD, and a novel risk stratification that combines Minnesota risk and biomarker risk performed best. Biomarker-based risk stratification can be used in clinical trials to develop more tailored approaches for children who require treatment for GVHD.

Easix Score Correlates With Endothelial Dysfunction Biomarkers and Predicts Risk of Acute Graft-Versus-Host Disease After Allogeneic Transplantation

Plasma biomarkers of endothelial dysfunction have been postulated for the diagnosis and prognosis of acute graft-versus-host disease (aGVHD). However, their use is not validated in clinical practice yet. The endothelial activation and stress index (EASIX), a simple score based on routine laboratory parameters, is considered to be an indirect marker of endothelial damage. High value of EASIX was correlated with worse non-relapse mortality (NRM) and overall survival (OS) and a high risk of sinusoidal obstructive syndrome and transplant-associated thrombotic microangiopathy (TA-TMA). This study investigates the predictive value of plasma biomarkers and the EASIX score for the prediction of aGVHD. We assessed vascular cell adhesion molecule-1 (VCAM-1), tumor necrosis factor receptor 1 (TNFR1), and VWF:Ag plasma levels and the EASIX score before allogeneic hematopoietic stem cell transplantation (allo-HSCT) and on days 0, 3, 7, 14, and 21 in an experimental cohort (n = 33). EASIX was transformed to a base-2 logarithm to perform the analysis. For the most relevant biomarkers, we estimate the optimal cutoff values and the discriminatory ability to differentiate patients with high-risk of aGVHD. The conclusions obtained in the experimental cohort were validated in a large cohort of 321 patients at the same institution. Plasma biomarkers and EASIX showed similar post-transplantation dynamics consisting of a progressive increase. Multivariate analysis showed an association between high TNFR1 levels and Log-2 EASIX score on day 7 after transplantation with an increased likelihood of developing aGVHD (hazard ratio [HR] = 1, P = .002; HR = 2.31, P = .013, respectively). Patients with TNFR1 ≥1300 ng/mL (HR = 7.19, P = .006) and Log2-EASIX ≥3 (HR = 14.7, P <.001) at day 7 after transplantation were more likely to develop aGVHD with high predictive accuracy (C-index of 74% and 81%, respectively). In the validation cohort, patients with Log2-EASIX ≥3 on day 7 after transplantation presented a significantly higher incidence of grade II-IV aGVHD (HR = 1.94, P = .004) independent of GVHD prophylaxis (HR = 0.38, P = .004), conditioning regimen (HR = 0.59, P =.02) and type of donor (HR = 2.38, P = .014). Differential degree of endothelial damage can be measured using both EASIX score and plasma biomarkers in the early post-transplantation period. Patients at risk of developing aGVHD could be easily identified by a high EASIX score. Both indicators of endothelial activation represent a promising approach to predict aGVHD.

Interferon regulatory factor 4 plays a pivotal role in the development of aGVHD-associated colitis

Interferon regulatory factor 4 (IRF4) is a master transcription factor that regulates T helper cell (Th) differentiation. It interacts with the Basic leucine zipper transcription factor, ATF-like (BATF), depletion of which in CD4+ T cells abrogates acute graft-versus-host disease (aGVHD)-induced colitis. Here, we investigated the immune-regulatory role of Irf4 in a mouse model of MHC-mismatched bone marrow transplantation. We found that recipients of allogenic Irf4-/- CD4+ T cells developed less GVHD-related symptoms. Transcriptome analysis of re-isolated donor Irf4-/- CD4+ T helper (Th) cells, revealed gene expression profiles consistent with loss of effector T helper cell signatures and enrichment of a regulatory T cell (Treg) gene expression signature. In line with these findings, we observed a high expression of the transcription factor BTB and CNC homolog 2; (BACH2) in Irf4-/- T cells, which is associated with the formation of Treg cells and suppression of Th subset differentiation. We also found an association between BACH2 expression and Treg differentiation in patients with intestinal GVHD. Finally, our results indicate that IRF4 and BACH2 act as counterparts in Th cell polarization and immune homeostasis during GVHD. In conclusion, targeting the BACH2/IRF4-axis could help to develop novel therapeutic approaches against GVHD.

Nutritional intervention with TGF-beta enriched food for special medical purposes (TGF-FSMP) is associated with a reduction of malnutrition, acute GVHD, pneumonia and may improve overall survival in patients undergoing allogeneic hematopoietic stem transplantation

Malnutrition in allogeneic stem cell transplant (allo-SCT) is associated with poor outcomes. Supplementation with Foods for Special Medical Purposes may be a valid alternative to enteral nutrition or total parental nutrition to reduce malnutrition in allo-SCT. In this study, 133 patients consecutively allo-transplanted were assessed for nutritional status by Patient- Generated Subjective Global Assessment (PG-SGA) and supplemented with TGF-beta enriched Food for Special Medical Purposes (TGF-FSMP). PG-SGA, gold standard for nutritional assessment in oncologic patients, was assessed at admission and on day 0, +7, +14, +21, and + 28 from transplant and categorized as follows: A = good nutritional status; B = moderate malnutrition; C = severe malnutrition. TGF-FSMP (Modulen-IBD) is currently used in Inflammatory Bowel Diseases (IBD) as primary nutritional support and in this study the dose was calculated according to BMI and total daily energy expenditure (TDEE). The patients assuming ≥50% of the prescribed TGF-FSMP dose were classified in Group A; the patients who received < 50% were included in Group B per protocol. The primary endpoint of the study was the assessment of the malnourished patients in Group A and B at day+28 after transplantation, according to the criteria of PG-SGA C categorization. At day +28 after transplant: i) patients in Group A were significantly less severely malnourished than patients in the Group B (21/76,28% vs 42/53, 79% respectively, OR 2.86 - CI 1.94-4.23 -, p = 0.000); ii) the incidence of severe (MAGIC II-IV) aGVHD and of any grade gastrointestinal (GI) aGVHD was higher in Group B than in Group A, (43% vs 21% p = 0.003) and (34.5% vs 9.2% p = 0.001); iii) Pneumonia was more frequent in the malnourished patients of Group B than in well/moderate nourished patients of Group A (52.7% vs 27.6% p = 0.002). In group A parenteral nutrition was avoided more frequently than in group B (67.5% vs 33.3% p = 0.000) and a median hospital stay of 27 days in comparison to 32 was reported (p = 0.006). The estimated median overall survival (OS) of the population was 33 months in Group A and 25.1 months in group B (p = 0.03). By multivariate and ANN analysis, TGF-FSMP TR < 50% assumption was significantly correlated with malnutrition, severe and GI aGVHD, pneumonia and reduced OS.

Phase I-II Trial of Early Azacitidine after Matched Unrelated Donor Hematopoietic Cell Transplantation

Graft-versus-host disease (GVHD) is a major complication after allogeneic hematopoietic cell transplantation (allo-HCT). The hypomethylating agent azacitidine (AZA) has been shown to be effective in preclinical and clinical studies for the prevention of acute GVHD (aGVHD). We sought to determine the maximum tolerated dose (MTD) of AZA when given on days 1 to 5 of a 28-day cycle for 4 cycles, starting on day +7 after allo-HCT, as well as its impact on aGVHD and chronic GVHD (cGVHD), relapse, and overall survival (OS) in patients undergoing matched unrelated donor allo-HCT. This study was a single-arm, single-center, open-label phase I-II study with a total of 15 and 38 patients enrolled in the phase I and II portions of the trial, respectively. A standard 3+3 study design was used in phase I, and all patients in phase II received AZA at the MTD determined in phase I. The MTD of AZA starting at day +7 post-transplantation was 45 mg/m2. Phase II of the study was halted after enrolling 38 of the planned 46 patients following an interim analysis that suggested futility. Overall, AZA at 45 mg/m2 exhibited a side effect profile consistent with prior reports and had a minimal impact on engraftment. The cumulative incidence of clinically significant aGVHD by day +180 was 39.9% (95% confidence interval [CI], 22% to 53.7%). The incidence of all-grade cGVHD was 61.4% (95% CI, 40.3% to 75%). At 1 year, OS was 73.7% (95% CI, 60.9% to 89.1%), and the disease relapse rate was 11.4% (95% CI, .2% to 21.3%). Our results suggest that early post-allo-HCT AZA has limited efficacy in preventing aGVHD and cGVHD but could have a beneficial effect in preventing disease relapse.

Vedolizumab for children with intestinal graft-versus-host disease: a case report and literature review

Acute graft-versus-host disease (aGVHD) is a challenging complication of allogeneic hematopoietic stem cell transplantation, and alternative therapies for patients showing inadequate response to steroids are limited. Vedolizumab, an anti-α4β7 integrin antibody widely used for treating inflammatory bowel diseases, has recently been studied in adult patients with steroid-refractory intestinal aGVHD. However, few studies have examined its safety and effectiveness in pediatric patients with intestinal aGVHD. We report the case of a male patient with intestinal late-onset aGVHD treated with vedolizumab. He underwent allogeneic cord blood transplantation for warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome and developed intestinal late-onset aGVHD 31 months after transplantation. The patient was refractory to steroids; however, vedolizumab was initiated 43 months after transplantation (at the age of 7 years) and the symptoms of intestinal aGVHD were alleviated. Additionally, favorable endoscopic findings were observed, such as reduction of erosion and regenerative epithelial growth. We also evaluated the efficacy of vedolizumab in 10 patients with intestinal aGVHD (9 from the literature review and the present case). Six patients (60%) showed an objective response to vedolizumab. No serious adverse events were observed in any patients. Vedolizumab is a potential treatment option for steroid-refractory intestinal aGVHD in pediatric patients.

[Diagnosis, prophylaxis and therapeutic management of acute GVH: Guidelines from the SFGM-TC]

Acute GVHD is a potentially severe complication of hematopoietic stem cell transplantation, responsible for morbidity and mortality that can affect the prognosis after transplantation. Within the framework of the 12th workshop of practice harmonization of the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC), diagnostic modalities of acute GVHD are updated. The conventional prevention (depending on donor, conditioning, and stem cell source) and treatment schemes (depending on affected organ and intensity) of aGVHD are clarified, and new therapeutic options are discussed.

Immunological influence of serum-free manufactured umbilical cord-derived mesenchymal stromal cells for steroid-resistant acute graft-versus-host disease

This study investigated the safety, efficacy, and immunological influence of allogeneic umbilical cord-derived mesenchymal stromal cells (IMSUT-CORD) processed in serum-free medium and cryoprotectant, for treating steroid-resistant acute graft-versus-host disease (aGVHD). In a phase I dose-escalation trial, IMSUT-CORD were infused intravenously twice weekly over two cycles with up to two additional cycles. Four patients received a dose of 1 × 10⁶ cells/kg, while three received 2 × 10⁶/kg. Of 76 total adverse events, fourteen associated or possibly associated adverse events included 2 cases of a hot flash, headache, and peripheral neuropathy, 1 each of upper abdominal pain, hypoxia, increased γ-GTP, somnolence, peripheral vascular pain at the injection site, thrombocytopenia, hypertension, and decreased fibrinogen. At 16 weeks after the initial IMSUT-CORD infusion, three patients showed complete response (CR), two partial response (PR), one mixed response, and one no response. The overall response rate was 71.4%, and the continuous CR/PR rate was 100% for over 28 days after CR/PR. NK cell count significantly increased and correlated with treatment response, whereas IL-12, IL-17, and IL-33 levels decreased, but did not correlate with treatment response. CCL2 and CCL11 levels increased during IMSUT-CORD therapy. IMSUT-CORD are usable in patients with steroid-resistant aGVHD (UMIN000032819: https://www.umin.ac.jp/ctr ).

Optimal Active Anti-Thymocyte Globulin Exposure Associated with Minimum Risk of Virus Reactivation and Comparable Acute Graft-Versus-Host Disease Under Adult Myeloablative Haploidentical Peripheral Blood Stem Cell Transplantation

Anti-thymocyte globulin (ATG) is often included in the conditioning regimen to prevent graft-versus-host disease (GVHD) in allogeneic hematopoietic cell transplantation (allo-HCT). However, the risk of virus reactivation increases significantly. We conducted a single-center prospective study to identify the optimal ATG exposure that ensures engraftment, effectively prevents acute GVHD, and reduces the risk of virus reactivation without increasing relapse of malignant diseases in haploidentical peripheral blood stem cell transplantation (haplo-PBSCT). From September 2018 to June 2020, 106 patients (median age, 32 years) with malignant hematological diseases who received haplo-PBSCT for the first time were enrolled. All patients received 10 mg/kg rabbit ATG (thymoglobulin) divided for 4 days (days -5 to -2). Pre-transplant, post-transplant, and total areas under the concentration-time curve (AUCs) of active ATG were calculated. Total AUC of active ATG was shown to be the best predictor for virus reactivation and acute GVHD of grades II to IV or grades III and IV. The optimal total AUC range of active ATG was 100 to 148.5 UE/mL/day. The median time was 14 versus 13 days (P = .184) for myeloid engraftment and 13 versus 13 days (P = .263) for platelet engraftment in the optimal and non-optimal AUC groups, respectively. The optimal AUC group showed a lower cumulative incidence of cytomegalovirus (CMV) reactivation and persistent CMV viremia than the non-optimal AUC group: 60.6% (95% confidence interval [CI], 48.3%-73.1%) versus 77.1% (95% CI, 64.5%-87.7%; P = .016) and 31.5% (95% CI, 21.2%-45.3%) versus 56.3% (95% CI, 42.9%-70.4%; P = .007), respectively. The cumulative incidence of persistent Epstein-Barr virus (EBV) viremia in the optimal AUC group was significantly lower than the non-optimal total AUC group: 33.1% (95% CI, 22.5%-46.8%) versus 52.6% (95% CI, 39.3%-67.2%; P = .048). However, there was no difference in EBV reactivation (P = .752). Similar outcomes were observed for grade II to IV and grade III and IV acute GVHD between the two groups: 48.6% (95% CI, 36.8%-62.0%) versus 37.0% (95% CI, 24.8%-52.5%; P = .113) and 10.4% (95% CI, 4.8%-21.7%) versus 4.2% (95% CI, 1.0%-15.6%; P = .234, respectively. Relapse, non-relapse mortality, and disease-free survival demonstrated no significant differences between the two groups. But, overall survival at 2 years tended to increase in the optimal AUC group: 75.7% (95% CI, 62.4%-84.8%) versus 57.8% (95% CI, 42.4%-70.4%; P = .061). These data support an optimal active ATG exposure of 110 to 148.5 UE/mL/day in haplo-PBSCT. Individualized dosing of ATG in allo-HCT might reduce the risk of virus reactivation and effectively prevent acute GVHD simultaneously.

Roles of the intestinal microbiota and microbial metabolites in acute GVHD

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is one of the most curative strategies for the treatment of many hematologic malignancies and diseases. However, acute graft-versus-host disease (GVHD) limits the success of allo-HSCT. The prevention and treatment of acute GVHD is the key issue for improving the efficacy of allo-HSCT and has become a research hotspot. The intestine is the primary organ targeted by acute GVHD, and the intestinal microbiota is critical for maintaining the homeostasis of the intestinal microenvironment and the immune response. Many studies have demonstrated the close association between the intestinal microbiota and the pathogenesis of acute GVHD. Furthermore, dysbiosis of the microbiota, which manifests as alterations in the diversity and composition of the intestinal microbiota, and alterations of microbial metabolites are pronounced in acute GVHD and associated with poor patient prognosis. The microbiota interacts with the host directly via microbial surface antigens or microbiota-derived metabolites to regulate intestinal homeostasis and the immune response. Therefore, intervention strategies targeting the intestinal microbiota, including antibiotics, prebiotics, probiotics, postbiotics and fecal microbiota transplantation (FMT), are potential new treatment options for acute GVHD. In this review, we discuss the alterations and roles of the intestinal microbiota and its metabolites in acute GVHD, as well as interventions targeting microbiota for the prevention and treatment of acute GVHD.

Improved outcome in children compared to adolescents and young adults after allogeneic hematopoietic stem cell transplant for acute myeloid leukemia: a retrospective study from the Francophone Society of Bone Marrow Transplantation and Cell Therapy (SFGM-TC)

Background

There are currently few data on the outcome of acute myeloid leukemia (AML) in adolescents after allogeneic HSCT. The aim of this study is to describe the outcome and its specific risk factors for children, adolescents and young adults after a first allogeneic HSCT for AML.

Methods

In this retrospective study, we compared the outcome of AML patients receiving a first allogeneic HSCT between 2005 and 2017 according to their age at transplantation’s time: children (< 15 years, n = 564), adolescent and post-adolescent (APA) patients (15–25 years, n = 647) and young adults (26–40 years; n = 1434).

Results

With a median follow-up of 4.37 years (min–max 0.18–14.73 years), the probability of 2-year overall survival (OS) was 71.4% in children, 61.1% in APA patients and 62.9% in young adults (p = 0.0009 for intergroup difference). Both relapse and non-relapse mortality (NRM) Cumulative Incidence (CI) estimated at 2 years were different between the age groups (30.8% for children, 35.2% for APA patients and 29.4% for young adults—p = 0.0254, and 7.0% for children, 10.6% for APA patients and 14.2% for young adults, p < 0.0001; respectively). Whilst there was no difference between the three groups for grade I to IV acute GVHD CI at 3 months, the chronic GVHD CI at 2 years was higher in APA patients and young adults (31.4% and 36.4%, respectively) in comparison to the children (17.5%) (p < 0.0001). In multivariable analysis, factors associated with death were AML cytogenetics (HR1.73 [1.29–2.32] for intermediate risk 1, HR 1.50 [1.13–2.01] for intermediate risk 2, HR 2.22 [1.70–2.89] for high cytogenetics risk compared to low risk), use of TBI ≥ 8 Grays (HR 1.33 [1.09–1.61]), disease status at transplant (HR 1.40 [1.10–1.78] for second Complete Remission (CR), HR 2.26 [1.02–4.98] for third CR and HR 3.07 [2.44–3.85] for active disease, compared to first CR), graft source (HR 1.26 [1.05–1.50] for Peripheral Blood Stem Cells compared to Bone Marrow) and donor age (HR 1.01 (1–1.02] by increase of 1 year).

Conclusion

Age is an independent risk factor for NRM and extensive chronic GVHD. This study suggests that APA patients with AML could be beneficially treated with a chemotherapy-based MAC regimen and bone marrow as a stem cells source.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00432-021-03761-w.

IFNG-AS1 and MAF4 long non-coding RNAs are upregulated in acute leukemia patients who underwent bone marrow transplantation

PURPOSE OF THE STUDY

Acute graft versus host disease (aGVHD) is an immune-mediated reaction that results in impaired immune and body function after allogeneic hematopoietic stem cell transplantation (allo-HSCT). lncRNAs have been discovered as particular T cell regulators, and alloreactive T cells have been known as a critical factor in aGVHD. As a result, we investigated the importance of lnc-MAF4 and IFNG-AS1 expression levels in aGVHD patients versus non-aGVHD patients.

MATERIAL AND METHODS

This research included 38 patients with hematological disorders who were undergoing primary allo-HSCT. Human identical siblings or unrelated donors were used to collect stem cell. Samples were taken within days 0, 7, 14, 28, and 52±8 after transplantation. The expression of lncRNA levels was measured using the QRT-PCR technique. And the data were analyzed using GraphPad Prism 6 RESULTS: Our data revealed that LncRNA MAF4 and INFG-AS1 expression levels in aGVHD were not significantly different compared to the non-GVHD group immediately after transplantation, nor at day 7 or 14. However, the aGVHD group showed an overt up-regulation of the two lncRNAs on samples taken at day 28 and 52±8 compared to non-GVHD patients.

DISCUSSION

Since the intracellular pathway of these lncRNAs shows a direct relationship with the IFNγ cytokine production resulting in differentiation to TH1 cells and inhibition of differentiation to TH2 cells, they can be, therefore, considered as suitable molecular candidates for the prediction of aGVHD in patients receiving HSCT.

CD52/GPI- T-Cells Are Enriched for Alloreactive Specificity and Predict Acute Graft-Versus-Host-Disease After Stem Cell Transplantation

Alemtuzumab is a CD52-specific lympho-depleting antibody. CD52- T cells emerge under alemtuzumab selection pressure. We sought to investigate the phenotype and function of the CD52- T cell fraction and related their presence to clinical outcome. We obtained longitudinal peripheral blood samples from 67 consecutive patients undergoing allo-HSCT between 2013-2016. Forty-seven patients (70%) had a myeloid disease (acute myelogenous leukemia or myelodysplastic syndrome) whereas 20 patients had lymphoid disease. All patients received in vivo alemtuzumab (10 mg/d from day -5 for 5 days) as part of their conditioning protocol. Sixty-three (94%) received reduced-intensity conditioning chemotherapy, whereas 4 (6%) received a myeloablative regimen. All patients received post-transplantation cyclosporine A for graft-versus-host disease (GVHD) prophylaxis. Six (9%) also received methotrexate, whereas 2 (3%) patients also received mycophenolate mofetil. Overall survival at 2 years was 68%, and relapse-free survival was 48%. Twenty-none percent of patients experienced acute GVHD (grade 2 or above), and 15% developed chronic GVHD. CD52- T cells were detectable in 66 of 67 consecutive patients. CD52- T cells demonstrated low binding of fluorescent aerolysin, indicating downregulation of the glycophosphatidylinositol anchor, although we did not detect any mutations in the PIG-A gene as is typically seen in patients with paroxysmal nocturnal hemoglobinuria. CD52- T cells were almost exclusively CD4+ and exhibited a dominant memory phenotype with only small numbers of CD25+ CD127low Foxp3+ regulatory T cells. CD52- T cells exhibited alloreactive specificity in vitro and have a distinct TCR repertoire to CD52+ T cells. Early after allo-hematopoietic stem cell transplantation, the presence of a significant population of CD52- T cells (comprising >51% of the T cell fraction) was found to be an independent risk factor for acute GvHD. This was confirmed in a validation cohort of 28 patients obtained between 2017-2018. These data suggest that the CD52- T cell fraction may represent a residual "footprint" of an early CD4+ T cell alloreactive response and may have been rescued from alemtuzumab-mediated lysis by antigen engagement in vivo. These data help to delineate the nature of T cell escape from alemtuzumab surveillance and contribute to increasing interest in the importance of CD4+ T cells in alloreactive immune responses, which could help inform immunotherapy protocols.

Local immune cell infiltration in cutaneous acute graft versus host disease

Background

Hematopoietic stem cell transplant is a crucial intervention to definitively treat many hematopoietic malignancies, but it carries great risks of morbidity and mortality often associated with graft-versus-host disease (GVHD). Acute and chronic GVHD are distinct entities, defined by a combination of historical, clinical, and pathologic data, but both are generally thought to stem from self-propagating aberrantly activated immune cells inflicting end organ damage, with the potential to cause significant illness or even death. Event-free survival rates after hematopoietic stem cell transplant continue to improve each year, but GVHD remains a major hurdle in improving the efficacy and safety of transplant.

Objective

Recent studies demonstrating tissue-specific immune effector phenotypes underscore the need for a deeper understanding of the cellular and molecular pathways driving the destruction of target tissues in patients with acute GVHD.

Methods

Samples were collected from lesional and unaffected skin in five patients with acute cutaneous GHVD. Fresh tissue was processed for fluorescence-activated cell sorting and analysis of macrophages and lymphocytes.

Results

The percentage of lymphocytes and macrophages as a representation of total cells varied among patients and was not always consistent between lesional and unaffected sites. The heterogeneity in immune cell profiling observed in patients in this study could reflect the diverse demographics, conditioning, and transplant conditions of each individual.

Conclusion

This study provides initial insight into the underlying molecular mechanisms of cutaneous GVHD progression and paves the way for additional studies to examine the cellular and molecular landscape in greater detail.

Extracorporeal photopheresis as first-line strategy in the treatment of acute graft-versus-host disease after hematopoietic stem cell transplantation: A single-center experience

BACKGROUND AIMS

Corticosteroids are the standard first-line treatment for acute graft-versus-host disease (aGVHD), but they are associated with many complications, and less than half of patients have a sustained response.

METHODS

To improve outcomes, we performed a retrospective study to analyze the efficacy of the addition of extracorporeal photopheresis (ECP) to low-dose corticosteroids in 37 adult patients (median age, 57 years) with skin-predominant aGVHD (grade I, n = 17; grade II, n = 18; and grade III, n = 2). All patients received ECP in combination with 1 mg/kg prednisone (n = 26) or topical steroids (n = 11).

RESULTS

Overall response rate was 81% after a median of three ECP procedures (range, 2-8), including 22 complete responses (CR, 59%) and eight very good partial responses (VGPR, 22%). The 11 patients treated with topical corticosteroids achieved CR. Furthermore, 16 (62%) patients reached prednisone withdrawal at a median of 100 days (range, 42-174 days) after its initiation. Eighteen patients developed chronic GVHD (cGVHD); 11 of them (who were in CR of aGVHD) had a new-onset cGVHD, and seven experienced progressive cGVHD (five non-responding and two VGPR patients). A second-line immunosuppressive treatment was initiated in only five (14%) non-responding patients. With a median follow-up of 31 months (range, 6-57 months) 2-year overall survival and non-relapse mortality were 74% and 11%, respectively.

CONCLUSIONS

Overall, the combination of low-dose corticosteroids and ECP appear to be safe and effective for first-line treatment of skin predominant aGVHD.

Biosimilar infliximab administration for the management of acute graft-versus-host disease

INTRODUCTION

Acute graft-versus-host disease (aGVHD) is a significant immune-mediated complication of allogeneic hematopoietic stem cell transplant (HSCT). Despite prophylactic immunosuppression, the incidence of grades II-IV aGVHD post-HSCT varies from 20 to 80%. Tumor necrosis factor (TNF) is an important cytokine involved in the pathogenesis of GVHD, and medications such as infliximab (Remicade®) have been utilized as second-line treatment options in patients with steroid-refractory GHVD. Infliximab-dyyb (Inflectra®) and infliximab-qbtx (Ixifi®) are biosimilars approved by the FDA for a variety of autoimmune disorders. This is the first case report documenting the utility of infliximab-dyyb and -qbtx for the management of steroid-refractory aGVHD.

CASE REPORT

We report the post-transplant course of three patients treated with infliximab biosimilars as a part of therapy for management of steroid-refractory aGVHD.

MANAGEMENT AND OUTCOME

Steroid-refractory aGVHD is associated with poor prognosis and its management, as highlighted in our three patient cases, and can be very diverse often requiring different therapeutic modalities which overlap in administration.

DISCUSSION

In these patients with steroid-refractory aGVHD, we were able to show that infliximab biosimilars could be used in lieu of the reference infliximab product. Although we had important limitations, this case report supports the use of anti-TNF agents in highly mortal steroid-refractory acute GI GVHD and that replacement of infliximab with its biosimilars is feasible.

Prevention and Treatment of Acute Graft-versus-Host Disease in Children, Adolescents, and Young Adults

Acute graft-versus-host disease (GVHD) continues to be a major cause of morbidity and mortality after allogeneic hematopoietic cell transplant (HCT) in pediatric patients (ie, children and adolescent and young adults) and limits broader application of the therapy. Pediatric HCT patients have faced major obstacles to access clinical trials that test new agents for GVHD prevention and treatment. According to a recent search, only 6 clinical trials of interventions for prevention or treatment of acute GVHD were conducted specifically in pediatric patients in the United States over the past decade, with 8 internationally. In this review, we summarize the studies that were performed and specifically enrolled and reported on pediatric patients after allogeneic HCT and provide a listing of studies currently under way.

Ruxolitinib treatment for SR-aGVHD in patients with EBV-HLH undergoing allo-HSCT

Ruxolitinib is a promising option for treating steroid-refractory acute graft-versus-host disease (SR-aGVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). In this study, we describe ruxolitinib treatment for SR-aGVHD in HSCT patients with Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH) to evaluate its effectiveness. We evaluated the outcomes of 12 patients who received ruxolitinib for SR-aGVHD between January 2017 and March 2019. Of the 12 patients who received ruxolitinib, 7 patients achieved a complete response (CR), 3 had a partial response (PR), and 2 experienced treatment failure (TF). OS and CR rates were 83.3% and 58.3%, respectively. Moreover, CR was achieved by the six patients who had aGVHD with skin involvement. The mean time of steroid application in the patients who received ruxolitinib was 28.1 days. Median survival after HSCT was 64.6 weeks. The adverse effects of ruxolitinib included grades 3 to 4 neutropenia (n = 7) and grades 3 to 4 thrombocytopenia (n = 6). Cytomegalovirus reactivation was observed in three patients. A high rate of CR and short steroid application time of ruxolitinib as a salvage treatment were observed in HSCT patients with EBV-HLH. Consequently, from this study, it was determined that ruxolitinib is an optimal choice to treat SR-aGVHD in patients with EBV-HLH.

MAGIC biomarkers of acute graft-versus-host disease: Biology and clinical application

Acute graft-versus-host disease (GVHD) is the major complication of allogeneic hematopoietic cell transplantation and is the primary cause of early non-relapse mortality (NRM) after transplant. GVHD of the gastrointestinal (GI) tract fuels the systemic inflammatory reaction and consequently is the principal driver of mortality. Recently, the MAGIC algorithm probability (MAP) that is computed from two biomarkers of GI GVHD has been validated to accurately predict risk of NRM throughout the course of early acute GVHD. This review focuses on the biology, clinical evidence, and practical application of the biomarkers in the measurement of acute GVHD.

Co-activation of macrophages and T cells contribute to chronic GVHD in human IL-6 transgenic humanised mouse model. EBioMedicine. 2019;41:584-596. [PMID: 30772305 PMCID: PMC6441951 DOI: 10.1016/j.ebiom.2019.02.001]

Background

Graft-versus host disease (GVHD) is a complication of stem cell transplantation associated with significant morbidity and mortality. Non-specific immune-suppression, the mainstay of treatment, may result in immune-surveillance dysfunction and disease recurrence.

Methods

We created humanised mice model for chronic GVHD (cGVHD) by injecting cord blood (CB)-derived human CD34⁺CD38⁻CD45RA⁻ haematopoietic stem/progenitor cells (HSPCs) into hIL-6 transgenic NOD/SCID/Il2rgKO (NSG) newborns, and compared GVHD progression with NSG newborns receiving CB CD34⁻ cells mimicking acute GVHD. We characterised human immune cell subsets, target organ infiltration, T-cell repertoire (TCR) and transcriptome in the humanised mice.

Findings

In cGVHD humanised mice, we found activation of T cells in the spleen, lung, liver, and skin, activation of macrophages in lung and liver, and loss of appendages in skin, obstruction of bronchioles in lung and portal fibrosis in liver recapitulating cGVHD. Acute GVHD humanised mice showed activation of T cells with skewed TCR repertoire without significant macrophage activation.

Interpretation

Using humanised mouse models, we demonstrated distinct immune mechanisms contributing acute and chronic GVHD. In cGVHD model, co-activation of human HSPC-derived macrophages and T cells educated in the recipient thymus contributed to delayed onset, multi-organ disease. In acute GVHD model, mature human T cells contained in the graft resulted in rapid disease progression. These humanised mouse models may facilitate future development of new molecular medicine targeting GVHD.

T Regulatory Cells in Donor Grafts May Predict the Severity of Acute Graft Versus Host Disease After Matched Sibling Donor Allogenic Peripheral Blood Stem Cell Transplantation

Acute graft-versus-host disease (aGVHD) and relapse are major issues for patients undergoing allogenic hematopoietic stem cell transplant (allo-HSCT). T-regulatory (Treg) cells in the donor graft are negatively correlated with the incidence of aGVHD without any impact on relapse. In this study to determine the association of Treg cells with aGVHD in allo-HSCT patients. Thirty-two patients with hematological disorders, who underwent allo-HSCT. Twenty-nine patients who achieved engraftment were enrolled in the study. Treg cells were quantified in donor graft by flowcytometry and were assessed for their association with aGVHD and other clinical outcomes. Fifteen of 29 patients developed aGVHD. According to the occurrence and severity of aGVHD, patients were divided into two groups: 20 (68.9%) patients with grade 0-I aGVHD and 9 (31.1%) patients with grade II-IV aGVHD. Treg cells/CD4 ratio was significantly higher in the grade 0-I aGVHD group than in grade II-IV aGVHD group, (p = 0.0002). We could not find the association of CD34 dose (p = 0.55) or CD3 dose (p = 0.57) with the severity of aGVHD. Higher Treg cells/CD4 ratio in donor graft was associated with less severe aGVHD. Though more studies are needed, Treg cells/CD4 ratio may be used as a predictive marker for severity of aGVHD in post allo-HSCT.

Effects of Prophylactic Foscarnet on Human Herpesvirus-6 Reactivation and Encephalitis in Cord Blood Transplant Recipients: A Prospective Multicenter Trial with an Historical Control Group

Cord blood transplantation (CBT) is a distinct risk factor for human herpesvirus-6 (HHV-6) reactivation and HHV-6 encephalitis. In a prospective multicenter trial we investigated the effects of prophylactic foscarnet (90 mg/kg i.v. infusion from days 7 to 27 after CBT) on the occurrence of HHV-6 reactivation, HHV-6 encephalitis, and acute graft-versus-host disease (aGVHD) in CBT recipients. Between 2014 and 2016, 57 patients were included in a foscarnet-prophylaxis group. Outcomes were compared with an historical control group who received CBT between 2010 and 2014 (standard-treatment group, n = 63). The cumulative incidence of high-level HHV-6 reactivation, defined as plasma HHV-6 DNA ≥ 10⁴ copies/mL, at 60 days after CBT was significantly lower in the foscarnet-prophylaxis group than in the standard-treatment group (18.3% versus 57.3%, P < .001). Multivariate analysis revealed that myeloablative preconditioning and standard treatment were significant risk factors for high-level HHV-6 reactivation. The cumulative incidence of HHV-6 encephalitis at 60 days after CBT was not different between the groups (foscarnet-prophylaxis group, 12.4%; standard-treatment group, 4.9%; P = .14). The cumulative incidences of grades II to IV and grades III to IV aGVHD at 60 days after CBT were not different between the groups (grades II to IV aGVHD: foscarnet-prophylaxis group, 42.0%; standard-treatment group, 40.5%; P = .96; grades III to IV aGVHD: foscarnet-prophylaxis group, 14.5%; standard-treatment group, 14.5%; P = 1.00). In the setting of this study foscarnet significantly suppressed systemic HHV-6 reactivation in CBT recipients but failed to prevent the development of HHV-6 encephalitis. Suppression of HHV-6 reactivation by foscarnet did not show any effects against the incidence of aGVHD.

Post-Transplantation Natural Killer Cell Count: A Predictor of Acute Graft-Versus-Host Disease and Survival Outcomes After Allogeneic Hematopoietic Stem Cell Transplantation

BACKGROUND

Reconstitution of the immune system after allogeneic hematopoietic stem cell transplantation (allo-HSCT) plays an important role in post-transplant outcomes. However, the clinical relevance of the lymphocyte subset (LST) counts to transplant-related complications and survival outcomes after allo-HSCT has not been fully elucidated.

PATIENTS AND METHODS

A total of 70 patients who had undergone allo-HSCT from 2007 to 2013, with LST results both 7 days before conditioning and 30 or 90 days after allo-HSCT were included. The LST counts in the peripheral blood were determined using 6-color flow cytometry. Clinical information, including transplant-related events during the first 100 days after allo-HSCT, was reviewed, and any association between these events and LST was analyzed.

RESULTS

At 30 days after allo-HSCT, the CD4⁺ T-cell (P = .009) and B-cell (P = .035) counts were lower and the natural killer (NK) cell count was greater (P < .001) than before conditioning. The CD8⁺ T-cell (P = .001) and NK cell (P < .001) counts were high 90 days after transplantation. The hazard ratios for a low NK cell count on days 30 and 90 for acute graft-versus-host disease were 6.22 and 14.67, respectively. Patients with low NK cell counts at 30 and 90 days after allo-HSCT had poorer overall survival (P = .043 and P = .028, respectively) and greater nonrelapse mortality (P = .036 and P = .033, respectively). A low NK cell count on day 30 was still prognostic for overall survival (P = .039) on multivariable analysis.

CONCLUSION

NK cell counts after allo-HSCT, especially on day 30, were predictive of acute graft-versus-host disease, nonrelapse mortality, and survival. Serial lymphocyte subset analysis can be used to identify and treat patients at risk during the early period after allo-HSCT.

Does defibrotide prophylaxis decrease the risk of acute graft versus host disease following allogeneic hematopoietic cell transplantation?

There is some preliminary evidence, that veno-occlusive disease prophylaxis with defibrotide (DF) may also have a role in decreasing risk of acute graft-versus-host disease (aGvHD) by preventing tissue damage. In this study, we aimed to investigate the role of DF prophylaxis on the development of aGvHD at D+180. One hundred ninety-five consecutive adult patients receiving allogeneic HCT were retrospectively evaluated in 3 groups: no DF, DF/post-HCT (DF D+1 to D+14) and DF/pre-HCT (DF for 14 days concurrently with conditioning). The total (p: 0.057) and grades III/IV (p: 0.051) aGvHD rates at D+180 were 46.5%, 40%, 25.5% and 15.5%, 11.2%, 0% in patients on no DF, DF/post-HCT and DF/pre-HCT. DF may have a role in decreasing incidence and severity of aGvHD, especially if used concurrently with conditioning regimen.

Cytokine Profile of Engraftment Syndrome in Pediatric Hematopoietic Stem Cell Transplant Recipients

The biology of engraftment syndrome is poorly understood, and the degree of overlap with acute graft-versus-host disease (GVHD) is unclear. To understand engraftment syndrome better, plasma cytokine profiles were evaluated in 56 pediatric allogeneic bone marrow transplant recipients before transplant, on the day of stem cell infusion, and weekly until day +100. Patients were divided into 4 groups: those with isolated engraftment syndrome (n = 8), acute GVHD (n = 12), both engraftment syndrome and acute GVHD (n = 4), and neither engraftment syndrome nor acute GVHD (n = 32). Engraftment syndrome was observed a median of 13.5 days (range, 10 to 28) after transplant, whereas acute GVHD was diagnosed a median of 55 days (range, 19 to 95) after transplant. Four patients developed both engraftment syndrome at a median of 10.5 days (range, 10 to 11) and acute GVHD at a median of 35 days (range, 23 to 56) after stem cell infusion. Median plasma levels of IL-1β, IL-6, IL-12, IL-4, and IL-13 were significantly elevated in patients with isolated engraftment syndrome when compared with isolated acute GVHD. A rise of proinflammatory cytokines (IL-1β, IL-6, and IL-12) was followed by surge in anti-inflammatory cytokines (IL-4 and IL-13) in patients with isolated engraftment syndrome. The observation of elevated IL-1β suggests that engraftment syndrome could be an inflammasome mediated phenomenon.

Granulocyte Colony-Stimulating Factor-Mobilized Allografts Contain Activated Immune Cell Subsets Associated with Risk of Acute and Chronic Graft-versus-Host Disease

We defined associations among immune cell subsets in granulocyte colony-stimulating factor (G-CSF)-mobilized allografts and clinical outcomes after allogeneic hematopoietic cell transplantation (alloHCT). Fresh peripheral blood stem cell (PBSC) aliquots from 238 G-CSF-mobilized allografts were extensively characterized by immunophenotype. Subset-specific transplanted cells were correlated with acute graft-versus-host disease (aGVHD), chronic GVHD (cGVHD), malignant disease relapse, nonrelapse mortality, and overall survival. Of 238 assessable alloHCT recipients, 185 patients (78%) received reduced-intensity conditioning and 152 (64%) antithymocyte globulin-based serotherapy. Incidences of aGVHD and cGVHD were 58% and 48%, respectively. Median follow-up was 21 months (range, 1.4 to 41.1). In multivariable analyses adjusted for relevant clinical factors, allograft activated natural killer (NK) cells (CD56(+)CD16(+)CD69(+)CD158b(+)) were associated with a significantly lower risk of aGVHD (P = .0016; HR, .51; 95% confidence interval, .33 to .78), whereas late-activated HLA-DR(+) CD3(+) cells were associated with significantly higher aGVHD (P < .0005; HR, 2.31; 95% confidence interval, 1.55 to 3.43). In a subgroup of patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), receipt of an allograft from an older donor (≥40 years) was associated with a higher incidence of relapse (P = .0042; HR, 2.99); allograft content of early activated CD3(+) cells (CD3(+)CD69(+); P = .0024; HR, .4) and NKT cells (CD3(+)CD56(+); P = .0006; HR, .54) were associated with a lower incidence of relapse. Presence of HLA-Bw4-80Ile(+) genotype was associated with lower relapse incidence. In conclusion, activated NK cells within PBSC allografts associate with lower aGVHD risk, whereas HLA-DR(+) T cells associate with higher aGVHD and cGVHD risk. NKT cells and early activated T cells are associated with lower relapse risk in AML and MDS patients. These findings may have implications in therapeutic targeting of select populations in the allograft to minimize incidence of GVHD.

Combination Therapy with Inolimomab and Etanercept for Severe Steroid-Refractory Acute Graft-versus-Host Disease

Steroid-refractory acute graft-versus-host disease (aGVHD) remains an important cause of morbidity and mortality after allogeneic stem cell transplantation (SCT). A protocol on the management of aGVHD was introduced in our center that incorporated a prospective study on combination therapy with inolimomab (anti-IL-2Rα) and etanercept (anti-tumor necrosis factor-α) for steroid-refractory aGVHD. We evaluated the efficacy and safety in 21 consecutively treated patients. The patients had developed refractory aGVHD after SCT (n = 16) or donor lymphocyte infusion (n = 5), and aGVHD was classified as severe in all patients, mostly due to gastrointestinal involvement stages 2 to 4. No drug-related side effects were observed apart from the infections expected to occur in these severely immunocompromised patients. Overall response at day 28 of second-line therapy was 48% (10/21), with 6 and 4 patients achieving a complete and partial response, respectively. Eventually, 19 patients died (90%), with early mortality (<6 months) predominantly resulting from refractory aGVHD and secondary infections and late mortality resulting from relapse of the underlying disease. With a median follow-up of 55 days, the estimated rates of 6-month and 2-year overall survival were dismal, 29% and 10%, respectively. In conclusion, the combination of inolimomab and etanercept for steroid-refractory aGVHD failed to improve the dismal prognosis of severe steroid-refractory aGVHD.

Sca1(+) mesenchymal stromal cells inhibit graft-versus-host disease in mice after bone marrow transplantation

Mesenchymal stromal cells (MSCs) have therapeutic potential for the prevention and treatment of graft-versus-host disease (GVHD). However, MSCs comprise several subpopulations, which have not been individually assessed for their role in GVHD suppression. In this study, we assessed the immunosuppressive effect of bone-related Sca1(+) MSCs on acute GVHD in a MHC-mismatched mouse model of allogeneic hematopoietic stem cell transplantation (HCT). Our results showed that Sca1(+) MSCs decreased the severity of acute GVHD (aGVHD) and prolonged the survival period of allogeneic HCT recipients. This effect was exerted through lowered T lymphocyte infiltration in target organs and by inhibition of CD80/86 expression on host dendritic cells. Furthermore, the expression of cytotoxic T-lymphocyte antigen-4 (CTLA-4), a negative regulator of T cells, was elevated in the recipient splenocytes. In conclusion, bone-related Sca1(+) MSCs subpopulation suppressed GVHD and could be a novel treatment for acute GVHD.

Administration of anti-CD20 mAb is highly effective in preventing but ineffective in treating chronic graft-versus-host disease while preserving strong graft-versus-leukemia effects

Chronic graft-versus-host disease (cGVHD) is an autoimmune-like syndrome, and donor B cells play important roles in augmenting its pathogenesis. B cell-depleting anti-CD20 mAb has been administered before or after cGVHD onset for preventing or treating cGVHD in the clinic. Although administration before onset appeared to be more effective, the effect is variable and sometimes minimal. Here, we used 2 mouse cGVHD models to evaluate the preventive and therapeutic effect of anti-CD20 mAb. With the model of DBA/2 donor to MHC-matched BALB/c recipient, 1 intravenous injection of anti-CD20 mAb (40 mg/kg) the following day or on day 7 after hematopoietic cell transplantation when serum autoantibodies were undetectable effectively prevented induction of cGVHD and preserved a strong graft-versus-leukemia (GVL) effect. The separation of GVL effect from GVHD was associated with a significant reduction of donor CD4(+) T cell proliferation and expansion and protection of host thymic medullary epithelial cells. Anti-CD20 mAb administration also prevented expansion of donor T cells and induction of cGVHD in another mouse model of C57BL/6 donor to MHC-mismatched BALB/c recipients. In contrast, administration of anti-CD20 mAb after GVHD onset was not able to effectively deplete donor B cells or ameliorate cGVHD in either model. These results indicate that administration of anti-CD20 mAb before signs of cGVHD can prevent induction of autoimmune-like cGVHD while preserving a GVL effect; there is little effect if administered after cGVHD onset. This provides new insights into clinical prevention and therapy of cGVHD with B cell-depleting reagents.

Translating in vitro prediction of cytotoxic T cell alloreactivity to hematopoietic stem cell transplantation outcome

INTRODUCTION

Previously we developed a weighted amino acid (AA) mismatch score predictive for cytotoxic T cell (CTL) alloreactivity (in vitro CTLp assay) based on the structure of the HLA class I molecule. The aim of this study is to confirm the clinical relevance of the CTLp assay and to validate the AA mismatch score as an alternative and easy to use tool to predict permissible mismatches in hematopoietic stem cell transplantation (HSCT).

METHODS

We selected patients transplanted with a 9/10 single HLA class I mismatched graft (n=171) at three Dutch HSCT centers. A CTLp assay was performed in 73 donor-recipient pairs. As a control we selected 168 10/10 HLA matched pairs that were matched to the 9/10 single HLA class I mismatched pairs for HSCT year, donor type, patient age and diagnosis.

RESULTS

We observed that pairs with negative a CTLp assay had statistically significant decreased incidence of mortality after HSCT comparable to that of 10/10 HLA matched pairs. However, the weighted AA mismatch score did not significantly predict any HSCT end point of interest.

CONCLUSION

Further investigation is needed to unravel the mechanisms involved in causing the beneficial effect of a negative CTLp assay, before other alternative tools to predict HSCT outcome may be developed.