Effect of Graft-versus-Host Disease Prophylaxis Regimens on T and B Cell Reconstitution after Allogeneic Hematopoietic Stem Cell Transplantation

Evaluation of Immunosuppression Levels and Risk of Graft-Versus-Host Disease in Allogeneic Blood or Marrow Transplantation With Post-Transplantation Cyclophosphamide

Post-transplantation cyclophosphamide (PTCy) is standard graft-versus-host disease (GVHD) prophylaxis for allogeneic blood or marrow transplantation (alloBMT), although optimal therapeutic levels of immunosuppression (IS) therapy combined with PTCy remain contested. Previously, with tacrolimus and methotrexate GVHD prophylaxis, week 1 tacrolimus levels >12 ng/mL were associated with a decreased incidence of grade 2 to 4 acute GVHD (aGVHD). We evaluated if associations between aGVHD and early IS levels were observed amongst patients receiving PTCy. This retrospective single-center study consisted of 349 patients who received PTCy and mycophenolate mofetil, with either tacrolimus (n = 185) or sirolimus (n = 164) from September 1, 2017, to September 30, 2019. The median age of patients receiving tacrolimus and sirolimus were 58 and 54 years, respectively. The primary diagnosed diseases for both cohorts were acute myeloid leukemia, acute lymphoblastic leukemia, myelodysplastic syndrome, and lymphoma. While most patients receiving tacrolimus were bone marrow graft sourced (78.4%), the majority of patients receiving sirolimus were peripheral blood sourced (80.5%). All patients were transplanted with FluCyTBI as the conditioning regimen. The primary outcome was grade 2 to 4 aGVHD incidence at 150 days post alloBMT between weekly IS levels <10 ng/mL versus ≥10 ng/mL throughout the 4 weeks post-alloBMT. Secondary endpoints included moderate to severe chronic GVHD (cGVHD) incidence, median overall survival (OS), relapse-free survival (RFS), and GVHD-free relapse-free survival (GRFS) at 2 years and the correlation between weekly IS levels <10 ng/mL versus ≥10 ng/mL throughout 4 weeks post-alloBMT. Patients receiving tacrolimus were compared to others in the tacrolimus cohort, and similarly for sirolimus. No correlation was found between IS levels at any individual week and cumulative aGVHD incidence for either tacrolimus or sirolimus. In the sirolimus cohort, no correlation for moderate to severe cGVHD was observed. However, at week 4, patients in the tacrolimus cohort with levels ≥10 ng/mL experienced significantly higher incidence of moderate to severe chronic GVHD than patients with weekly levels <10 ng/mL (20% versus 8%, P < .001). When evaluating survival outcomes, post-alloBMT week 1 tacrolimus levels ≥10 ng/mL were associated with decreased OS (HR 3.84, 95% CI [1.16 to 12.67]; P = .027), but no correlation was seen in RFS (HR 1.62, 95% CI [0.56 to 4.72]; P = .377), or GRFS (HR 1.56, 95% CI [0.89 to 2.74]; P = .124). Post-alloBMT week 1 sirolimus ≥10 ng/mL levels were associated with decreased OS (HR 2.74, 95% CI [1.37 to 5.48]; P = .004) and GRFS (HR 1.93, 95% CI [1.19 to 3.12]; P = .007), but not RFS (HR 1.60, 95% CI [0.78 to 3.30]; P = .202). Overall, early IS levels in patients receiving PTCy-based GVHD prophylaxis did not correlate with aGVHD incidence, although IS levels ≥10 ng/mL were associated with compromised outcomes. Targeting IS levels <10 ng/mL may be optimal when using PTCy-based GVHD prophylaxis.

Comparison of oral zinc supplement and placebo effect in improving the T-cells regeneration in patients undergoing autologous hematopoietic stem cell transplantation: Clinical trial study

BACKGROUND

Immune reconstitution is a significant factor in the success of "hematopoietic stem cell transplantation" (HSCT). Delaying the immune reconstitution increases the risk of infections and relapse after transplantation. T-cell recovery after HSCT is mainly thymus-dependent, and thymic atrophy is associated with various clinical conditions that correlate with HSCT outcomes. Thymus rejuvenation can improve immune reconstitution after transplantation.Zinc (Zn) plays a pivotal role in thymus rejuvenation. Zn deficiency can lead to thymic atrophy, which increases susceptibility to infections. Zn supplementation restores the immune system by increasing thymus output and T-cell repertoire production.We designed this protocol to investigate the effect of oral Zn supplementation on T-cell recovery in patients undergoing HSCT.

METHODS

Forty eligible candidates for autologous-HSCT will be selected. They will be randomly divided into Zn and placebo groups. Subsequently, they will receive 3 Zn or placebo tablets for the first 30 days post-HSCT (+1 to +30), followed by 1 pill or placebo for days (+31 to +90). The copy numbers of "recent thymic emigrants" T cells and "T cell Receptor Excision Circles" (TREC) will be assessed before and after the intervention in peripheral blood mononuclear cells (PBMCs). All patients will be followed up 365 days post-HSCT for relapse and infection.

CONCLUSION

This clinical trial is the first to determine the efficiency of "Zn gluconate" as daily Supplementation in T cell recovery post-HSCT.If successful, an available and inexpensive drug will improve immune system reconstruction after HSCT, reduce the risk of infection, particularly viral infections, and increase patient survival.

Impact of bone marrow fibrosis on outcomes of allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia

Bone marrow fibrosis (BMF) of unknown etiology was common in hematological malignancies, but its prognostic value for acute myeloid leukemia (AML) is unclear. We interrogated data from 532 newly diagnosed subjects with AML receiving allogeneic hematological stem cell transplantation to evaluate the prognostic impact of BMF on transplant outcomes. Using the European consensus on the grading of BMF at diagnosis, 255 (48%) subjects were BMF-0, 209 (39%), BMF-1 and 68 (13%), BMF-2-3. Subjects with BMF-2-3 had poor overall survival (P < 0.001), disease-free survival (P < 0.001) and a higher incidence of relapse (CIR, P < 0.001). Multi-variable analyses in subjects achieving pre-transplant complete remission showed BMF-2-3 was an independent risk factor for CIR (Hazard Ratio [HR] = 2.17, (95% CI, 1.11, 4,24); P = 0.02). Furthermore, BMF-2-3 group showed delayed neutrophil and platelet engraftment and delayed B cell recovery post-transplantation. These findings demonstrate the significance of BMF in transplant outcomes and attract more attention to AML with BMF.

A successfully cured case of cytomegalovirus multiple organ infection after hematopoietic stem cell transplantation: A case report

Cytomegalovirus (CMV) infection is one of the most common infectious complications following hematopoietic stem cell transplantation (HSCT); however, cases involving multiple organs at the same time are rare. The present study describes a case of CMV pneumonia combined with CMV DNAemia and CMV cystitis after HSCT. A 33-year-old male patient with acute myeloid leukemia was treated with HSCT. The first month after HSCT, the patient developed a cough and shortness of breath. At 2 months post-HSCT, the patient developed hematuria. The CMV DNA levels in the blood and urine were elevated; bronchoalveolar lavage fluid (BALF) was also positive for CMV DNA. Heterotypic cells exhibiting a large nuclear morphology were observed in the BALF and bronchial brushes. Recurrent and progressive ground-glass opacities were evident on chest computed tomography. The patient was diagnosed with CMV pneumonia complicated by CMV DNAemia and CMV cystitis, and was treated with a combination of ganciclovir and foscarnet, along with immunoglobulin therapy. The patient was cured and discharged. It was determined that the CMV DNA in the blood was inconsistent with that in the BALF, which delayed the early diagnosis of CMV pneumonia. The association between T-cell immune function and the therapeutic efficacy for CMV multi-organ infection following HSCT is known to be significant. Moreover, the timely administration of ganciclovir and foscarnet in combination with immunoglobulin therapy demonstrated favorable clinical outcomes.

T cell receptor excision circles are potential predictors of survival in adult allogeneic hematopoietic stem cell transplantation recipients with acute myeloid leukemia

Background

Lymphocyte neogenesis from primary lymphoid organs is essential for a successful reconstitution of immunity after allogeneic hematopoietic stem cell transplantation (HSCT). This single-center retrospective study aimed to evaluate T cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC) as surrogate markers for T and B cell recovery, as predictors for transplantation-related outcomes in adult acute myeloid leukemia (AML) patients.

Methods

Ninety adult patients diagnosed with AML and treated with HSCT between 2010 and 2015 were included in the study. TREC and KREC levels were measured by quantitative PCR at 1, 3, 6, and 12 months after transplantation.

Results

Overall, excision circle levels increased between 3 and 6 months post-HSCT for TREC (p = 0.005) and 1 and 3 months for KREC (p = 0.0007). In a landmark survival analysis at 12 months post-HSCT, TREC levels were associated with superior overall survival (HR: 0.52, 95% CI: 0.34 - 0.81, p = 0.004). The incidence of viral infections within the first 100 days after transplantation was associated with lower TREC levels at 6 months (p = 0.0002). CMV reactivation was likewise associated with lower TREC levels at 6 months (p = 0.02) post-HSCT. KREC levels were not associated with clinical outcomes in statistical analyzes.

Conclusions

Results from the present study indicate that TREC measurement could be considered as part of the post-HSCT monitoring to identify AML patients with inferior survival after transplantation. Further prospective studies are warranted to validate these findings.

Donor genetic determinant of thymopoiesis rs2204985 impacts clinical outcome after single HLA mismatched hematopoietic stem cell transplantation

A common genetic variant within the T cell receptor alpha (TCRA)-T cell receptor delta (TCRD) locus (rs2204985) has been recently found to associate with thymic function. Aim of this study was to investigate the potential impact of donor rs2204985 genotype on patient’s outcome after unrelated hematopoietic stem cell transplantation (uHSCT). 2016 adult patients were retrospectively analyzed. rs2204985 genotyping was performed by next generation sequencing, p < 0.05 was considered significant and donor rs2204985 GG/AG genotypes were set as reference vs. the AA genotype. Multivariate analysis of the combined cohort regarding the impact of donor’s rs2204985 genotype indicated different risk estimates in 10/10 and 9/10 HLA matched transplantations. A subanalysis on account of HLA incompatibility revealed that donor AA genotype in single HLA mismatched cases (n = 624) associated with significantly inferior overall- (HR: 1.48, p = 0.003) and disease-free survival (HR: 1.50, p = 0.001). This effect was driven by a combined higher risk of relapse incidence (HR: 1.40, p = 0.026) and non-relapse mortality (HR: 1.38, p = 0.042). This is the first study to explore the role of rs2204985 in a clinical uHSCT setting. Our data suggest that donor rs2204985 AA genotype in combination with single HLA mismatches may adversely impact post-HSCT outcome and should thus be avoided.

Naive T Cells in Graft Versus Host Disease and Graft Versus Leukemia: Innocent or Guilty?

The outcome of allogeneic hematopoietic cell transplantation (allo-HCT) largely depends on the development and management of graft-versus-host disease (GvHD), infections, and the occurrence of relapse of malignancies. Recent studies showed a lower incidence of chronic GvHD and severe acute GvHD in patients receiving naive T cell depleted grafts compared to patients receiving complete T cell depleted grafts. On the other hand, the incidence of acute GvHD in patients receiving cord blood grafts containing only naive T cells is rather low, while potent graft-versus-leukemia (GvL) responses have been observed. These data suggest the significance of naive T cells as both drivers and regulators of allogeneic reactions. The naive T cell pool was previously thought to be a quiescent, homogenous pool of antigen-inexperienced cells. However, recent studies showed important differences in phenotype, differentiation status, location, and function within the naive T cell population. Therefore, the adequate recovery of these seemingly innocent T cells might be relevant in the imminent allogeneic reactions after allo-HCT. Here, an extensive review on naive T cells and their contribution to the development of GvHD and GvL responses after allo-HCT is provided. In addition, strategies specifically directed to stimulate adequate reconstitution of naive T cells while reducing the risk of GvHD are discussed. A better understanding of the relation between naive T cells and alloreactivity after allo-HCT could provide opportunities to improve GvHD prevention, while maintaining GvL effects to lower relapse risk.

Practical guidance for the diagnosis and management of secondary hypogammaglobulinemia: A Work Group Report of the AAAAI Primary Immunodeficiency and Altered Immune Response Committees

Secondary hypogammaglobulinemia (SHG) is characterized by reduced immunoglobulin levels due to acquired causes of decreased antibody production or increased antibody loss. Clarification regarding whether the hypogammaglobulinemia is secondary or primary is important because this has implications for evaluation and management. Prior receipt of immunosuppressive medications and/or presence of conditions associated with SHG development, including protein loss syndromes, are histories that raise suspicion for SHG. In patients with these histories, a thorough investigation of potential etiologies of SHG reviewed in this report is needed to devise an effective treatment plan focused on removal of iatrogenic causes (eg, discontinuation of an offending drug) or treatment of the underlying condition (eg, management of nephrotic syndrome). When iatrogenic causes cannot be removed or underlying conditions cannot be reversed, therapeutic options are not clearly delineated but include heightened monitoring for clinical infections, supportive antimicrobials, and in some cases, immunoglobulin replacement therapy. This report serves to summarize the existing literature regarding immunosuppressive medications and populations (autoimmune, neurologic, hematologic/oncologic, pulmonary, posttransplant, protein-losing) associated with SHG and highlights key areas for future investigation.

An ISCT Stem Cell Engineering Committee Position Statement on Immune Reconstitution: the importance of predictable and modifiable milestones of immune reconstitution to transplant outcomes

Allogeneic stem cell transplantation is a potentially curative therapy for some malignant and non-malignant disease. There have been substantial advances since the approaches first introduced in the 1970s, and the development of approaches to transplant with HLA incompatible or alternative donors has improved access to transplant for those without a fully matched donor. However, success is still limited by morbidity and mortality from toxicity and imperfect disease control. Here we review our emerging understanding of how reconstitution of effective immunity after allogeneic transplant can protect from these events and improve outcomes. We provide perspective on milestones of immune reconstitution that are easily measured and modifiable.

Adoptive transfer of ex vivo expanded regulatory T-cells improves immune cell engraftment and therapy-refractory chronic GvHD

Graft-versus-Host-Disease (GvHD) is still the major non-relapse, life-limiting complication following hematopoietic stem cell transplantation. Modern pharmacologic immunosuppression is often insufficient and associated with significant side effects. Novel treatment strategies now include adoptive transfer of ex vivo expanded regulatory T-cells (Tregs), but their efficacy in chronic GvHD is unknown. We treated three children suffering from severe, therapy-refractory GvHD with polyclonally expanded Tregs generated from the original stem cell donor. Third-line maintenance immunosuppression was tapered to Cyclosporin A and low-dose steroids shortly before cell transfer. Regular follow-up included assessment of the subjective and objective clinical development, safety parameters and in-depth immune monitoring. All patients showed marked clinical improvement with substantially reduced GvHD activity. Laboratory follow-up showed a significant enhancement of the immunologic engraftment including lymphocytes and dendritic cells. Monitoring the fate of Tregs by next generation sequencing demonstrated clonal expansion. In summary, adoptive transfer of Tregs was well tolerated and able to modulate an established undesired T-cell mediated allo-response. Although no signs of overimmunosuppression were detectable, treatment of patients with invasive opportunistic infections should be undertaken with caution. Further controlled studies, are necessary to confirm these encouraging effects and eventually pave the way for adoptive Treg therapy in chronic GvHD.

Increased Infections and Delayed CD4+ T Cell but Faster B Cell Immune Reconstitution after Post-Transplantation Cyclophosphamide Compared to Conventional GVHD Prophylaxis in Allogeneic Transplantation

Post-transplantation cyclophosphamide (PTCy) is being increasingly used for graft-versus-host disease (GVHD) prophylaxis after allogeneic hematopoietic cell transplantation (allo-HCT) across various donor types. However, immune reconstitution and infection incidence after PTCy-based versus conventional GVHD prophylaxis has not been well studied. We evaluated the infection density and immune reconstitution (ie, absolute CD4⁺ T cell, CD8⁺ T cell, natural killer cell, and B cell counts) at 3 months, 6 months, and 1 year post-HCT in 583 consecutive adult patients undergoing allo-HCT with myeloablative (n = 223) or reduced-intensity (n = 360) conditioning between 2012 and 2018. Haploidentical (haplo; n = 75) and 8/8 HLA-matched unrelated (MUD; n = 08) donor types were included. GVHD prophylaxis was PTCy-based in all haplo (n = 75) and in 38 MUD allo-HCT recipients, whereas tacrolimus/methotrexate (Tac/MTX) was used in 89 and Tac/Sirolimus (Tac/Sir) was used in 381 MUD allo-HCT recipients. Clinical outcomes, including infections, nonrelapse mortality (NRM), relapse, and overall survival (OS), were compared across the 4 treatment groups. The recovery of absolute total CD4⁺ T-cell count was significantly lower in the haplo-PTCy and MUD-PTCy groups compared with the Tac/MTX and Tac/Sir groups throughout 1 year post-allo-HCT (P = .025). In contrast, CD19⁺ B-cell counts at 6 months and thereafter were higher in the haplo-PTCy and MUD-PTCy groups compared with the Tac/MTX and Tac/Sir groups (P < .001). Total CD8⁺ T cell and NK cell recovery was not significantly different among the groups. Infection density analysis showed a significantly higher frequency of total infections in the haplo-PTCy and MUD-PTCy groups compared with the Tac/MTX and Tac/Sir groups (5.0 and 5.0 vs 1.8 and 2.6 per 1000-person days; P < .01) within 1 year of allo-HCT. The cumulative incidence of cytomegalovirus reactivation/infection at 1 year post-allo-HCT was higher in the haplo-PTCy group (51%) compared with the MUD-PTCy (26%), Tac/MTX (26%), or Tac/Sir (13%) groups (P < .001). The incidence of BK, human herpesvirus 6, and other viruses were also higher in the PTCy-based groups. Overall, the treatment groups had similar 2 year NRM (P = .27) and OS (P = .78) outcomes. Our data show that PTCy-based GVHD prophylaxis is associated with delayed CD4⁺ T cell but faster B cell immune reconstitution and a higher frequency of infections compared with conventional GVHD prophylaxis but has no impact on nonrelapse mortality or overall survival.

Immune control of cytomegalovirus reactivation in stem cell transplantation

The reactivation of viruses from latency after allogeneic stem cell transplantation (SCT) continues to represent a major clinical challenge requiring sophisticated monitoring strategies in the context of prophylactic and/or pre-emptive antiviral drugs that are associated with significant expense, toxicity, and rates of failure. Accumulating evidence has demonstrated the association of polyfunctional virus-specific T-cells with protection from viral reactivation, affirmed by the ability of adoptively transferred virus-specific T-cells to prevent and treat reactivation and disease. The roles of innate cells (NK cells) in early viral surveillance, and dendritic cells in priming of T-cells have also been delineated. Most recently, a role for strain-specific humoral responses in preventing early cytomegalovirus (CMV) reactivation has been demonstrated in preclinical models. Despite these advances, many unknowns remain: what are the critical innate and adaptive responses over time, is the origin (e.g. recipient versus donor) and localization (e.g. in parenchymal tissue versus lymphoid organs) of these responses important, how does GVHD and the prevention/treatment thereof (e.g. high dose steroids) impact the functionality and relevance of a particular immune axis, do the immune parameters that control latency, reactivation and dissemination differ, and what is the impact of new antiviral drugs on the development of enduring antiviral immunity. Thus, whilst antiviral drugs have provided major improvements over the last two decades, understanding the immunological paradigms underpinning protective antiviral immunity after SCT offers the potential to generate non-toxic immune-based therapeutic approaches for lasting protection from viral reactivation.

The role of the thymus in allogeneic bone marrow transplantation and the recovery of the peripheral T-cell compartment

As the thymus represents the primary site of T-cell development, optimal thymic function is of paramount importance for the successful reconstitution of the adaptive immunity after allogeneic hematopoietic stem cell transplantation. Thymus involutes as part of the aging process and several factors, including previous chemotherapy treatments, conditioning regimen used in preparation to the allograft, occurrence of graft-versus-host disease, and steroid therapy that impair the integrity of the thymus, thus affecting its role in supporting T-cell neogenesis. Although the pathways governing its regeneration are still poorly understood, the thymus has a remarkable capacity to recover its function after damage. Measurement of both recent thymic emigrants and T-cell receptor excision circles is valuable tools to assess thymic output and gain insights on its function. In this review, we will extensively discuss available data on factors regulating thymic function after allogeneic hematopoietic stem cell transplantation, as well as the strategies and therapeutic approaches under investigation to promote thymic reconstitution and accelerate immune recovery in transplanted patients, including the use of cytokines, sex-steroid ablation, precursor T-cells, and thymus bioengineering. Although none of them is routinely used in the clinic, these approaches have the potential to enhance thymic function and immune recovery, not only in patients given an allograft but also in other conditions characterized by immune deficiencies related to a defective function of the thymus.

Evaluating Thymic Function After Human Hematopoietic Stem Cell Transplantation in the Personalized Medicine Era

Hematopoietic stem cell transplantation (HSCT) is an effective treatment option for several malignant and non-malignant hematological diseases. The clinical outcome of this procedure relies to a large extent on optimal recovery of adaptive immunity. In this regard, the thymus plays a central role as the primary site for de novo generation of functional, diverse, and immunocompetent T-lymphocytes. The thymus is exquisitely sensitive to several insults during HSCT, including conditioning drugs, corticosteroids, infections, and graft-vs.-host disease. Impaired thymic recovery has been clearly associated with increased risk of opportunistic infections and poor clinical outcomes in HSCT recipients. Therefore, better understanding of thymic function can provide valuable information for improving HSCT outcomes. Recent data have shown that, besides gender and age, a specific single-nucleotide polymorphism affects thymopoiesis and may also influence thymic output post-HSCT, suggesting that the time of precision medicine of thymic function has arrived. Here, we review the current knowledge about thymic role in HSCT and the recent work of genetic control of human thymopoiesis. We also discuss different transplant-related factors that have been associated with impaired thymic recovery and the use of T-cell receptor excision circles (TREC) to assess thymic output, including its clinical significance. Finally, we present therapeutic strategies that could boost thymic recovery post-HSCT.

A Multiplex, Droplet Digital PCR Assay for the Detection of T-Cell Receptor Excision Circles and Kappa-Deleting Recombination Excision Circles

BACKGROUND

T-cell receptor excision circles (TREC) and κ-deleting recombination receptor excision circles (KREC) concentrations can be used to assess and diagnose immune deficiencies, monitor thymic and bone marrow immune reconstitution, or follow responses to drug therapy. We developed an assay to quantify TREC, KREC, and a reference gene in a single reaction using droplet digital PCR (ddPCR).

METHODS

PCR was optimized for 3 targets: TREC, KREC, and ribonuclease P/MRP subunit p30 (RPP30) as the reference gene. Multiplexing was accomplished by varying the target's fluorophore and concentration. Correlation with clinical results was evaluated using 47 samples from healthy donors, 59 samples with T-cell and B-cell markers within the reference interval from the flow cytometry laboratory, 20 cord blood samples, and 34 samples submitted for exome sequencing for severe combined immunodeficiency disease (SCID).

RESULTS

The limit of the blank was 4 positive droplets, limit of detection 9 positive droplets, and limit of quantification 25 positive droplets, or 2.0 copies/μL. TREC and KREC copies/μL were as expected in the healthy donors and cord blood samples and concordant with the healthy flow cytometry results. Of the samples from the SCID Panel, 56.5% had a TREC count <20 copies/μL and 17.7% had a KREC count <20 copies/μL, suggestive of low T- and B-cell numbers, respectively.

CONCLUSIONS

Our multiplex ddPCR assay is an analytically sensitive and specific method for the absolute quantification of TREC and KREC. To the best of our knowledge, this paper is the first to describe the simultaneous quantification of TREC, KREC, and a reference gene by use of ddPCR.

Reconstitution of T Cell Subsets Following Allogeneic Hematopoietic Cell Transplantation

Allogeneic (allo) hematopoietic cell transplantation (HCT) is the only curative treatment option for patients suffering from chemotherapy-refractory or relapsed hematological malignancies. The occurrence of morbidity and mortality after allo-HCT is still high. This is partly correlated with the immunological recovery of the T cell subsets, of which the dynamics and relations to complications are still poorly understood. Detailed information on T cell subset recovery is crucial to provide tools for better prediction and modulation of adverse events. Here, we review the current knowledge regarding CD4+ and CD8+ T cells, γδ T cells, iNKT cells, Treg cells, MAIT cells and naive and memory T cell reconstitution, as well as their relations to outcome, considering different cell sources and immunosuppressive therapies. We conclude that the T cell subsets reconstitute in different ways and are associated with distinct adverse and beneficial events; however, adequate reconstitution of all the subsets is associated with better overall survival. Although the exact mechanisms involved in the reconstitution of each T cell subset and their associations with allo-HCT outcome need to be further elucidated, the data and suggestions presented here point towards the development of individualized approaches to improve their reconstitution. This includes the modulation of immunotherapeutic interventions based on more detailed immune monitoring, aiming to improve overall survival changes.

Meta-Analysis of Genome-Wide Association and Gene Expression Studies Implicates Donor T Cell Function and Cytokine Pathways in Acute GvHD

Graft-vs.-host disease (GvHD) is a major complication after allogeneic hematopoietic stem cell transplantation that causes mortality and severe morbidity. Genetic disparities in human leukocyte antigens between the recipient and donor are known contributors to the risk of the disease. However, the overall impact of genetic component is complex, and consistent findings across different populations and studies remain sparse. To gain a comprehensive understanding of the genes responsible for GvHD, we combined genome-wide association studies (GWAS) from two distinct populations with previously published gene expression studies on GvHD in a single gene-level meta-analysis. We hypothesized that genes driving GvHD should be associated in both data modalities and therefore could be detected more readily through their combined effects in the integrated analysis rather than in separate analyses. The meta-analysis yielded a total of 51 acute GvHD-associated genes (false detection rate [FDR] <0.1). In support of our hypothesis, this number was significantly higher than that in a permutation meta-analysis involving the whole data set, as well as in separate meta-analyses on the GWAS and gene expression data sets. The genes indicated by the meta-analysis were significantly enriched in 277 Gene Ontology terms (FDR < 0.05), such as T cell function and cytokine-mediated signaling pathways, and the results highlighted several established immune mediators, such as interleukins and JAK-STAT signaling, and presented TRAF6 and TERT as potential effector candidates. Altogether, the results support the chosen methodological approach, implicate a role of gene-level variation in donors' key immunological regulators predisposing patients to acute GVHD, and present potential targets for therapeutic intervention.

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.

Clinical significance of T cell receptor excision circle (TREC) quantitation after allogenic HSCT

Background

Hematopoietic stem cell transplantation (HSCT) is a well-established treatment modality for a variety of diseases. Immune reconstitution is an important event that determines outcomes. The immune recovery of T cells relies on peripheral expansion of mature graft cells, followed by differentiation of donor-derived hematopoietic stem cells. The formation of new T cells occurs in the thymus and as a byproduct, T cell receptor excision circles (TRECs) are released. Detection of TRECs by PCR is a reliable method for estimating the amount of newly formed T cells in the circulation and, indirectly, for estimating thymic function. The aim of this study was to determine the role of TREC quantitation in predicting outcomes of human leucocyte antigen (HLA) identical allogenic HSCT.

Methods

The study was conducted on 100 patients receiving allogenic HSCT from an HLA identical sibling. TREC quantification was done by real time PCR using a standard curve.

Results

TREC levels were inversely related to age (P=0.005) and were significantly lower in patients with malignant diseases than in those with benign diseases (P=0.038). TREC levels could predict relapse as an outcome but not graft versus host disease (GvHD) and infections.

Conclusion

Age and nature of disease determine the TREC levels, which are related to relapse.