Acute graft-versus-host disease: from the bench to the bedside

Mesenchymal Stromal Cells Stimulate the Proliferation and IL-22 Production of Group 3 Innate Lymphoid Cells

Infusion of mesenchymal stromal cells (MSCs) is a promising and increasingly applied therapy for patients who suffer from a variety of inflammatory diseases, including graft-versus-host disease (GvHD), a common and life-threatening complication after allogeneic hematopoietic stem cell transplantation. The therapeutic effect of MSCs is mainly ascribed to their ability to suppress T cells and to support tissue repair. However, clinical response rates in patients with GvHD are limited to 50%, and the determinants for MSC responsiveness are unknown. We recently reported that high frequencies of activated group 3 innate lymphoid cells (ILC3s) before and after allogeneic hematopoietic stem cell transplantation were associated with a lower risk of GvHD. This may be related to IL-22 production by ILC3s, a cytokine important for intestinal epithelial cell homeostasis. In this study, we investigated whether ILC3s may contribute to the therapeutic effect of MSCs by studying the interaction between MSCs and ILC3s in vitro. ILC3s isolated from human tonsils were cocultured with human bone marrow-derived MSCs for 5 d in the presence of IL-2. Coculture with MSCs enhanced the proliferation and IL-22 production of ILC3s. Reciprocally, ILC3s promoted ICAM-1 and VCAM-1 expression on MSCs. For both directions, the activation was mainly mediated by cell-cell contact and by MSC-derived IL-7 and likely by aryl hydrocarbon receptor ligands. Thus, in addition to inhibiting the proliferation of alloreactive T cells, MSCs also promote the expansion and IL-22 production of ILC3s, which may contribute to healthy homeostasis and wound repair in the treatment of various inflammatory conditions in the intestine, including GvHD.

Culture-Expanded Human Invariant Natural Killer T Cells Suppress T-Cell Alloreactivity and Eradicate Leukemia

Graft-versus-host disease (GVHD) is a major cause of significant morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). Invariant natural killer T (iNKT) cells are potent regulators of immune responses, protect from lethal GVHD, and promote graft-versus-leukemia effects in murine studies. Since iNKT cells constitute less than 0.5% of human peripheral blood mononuclear cells (PBMCs), in vitro expansion with their glycolipid ligands is required before they can be used for cytotherapy and experimental purposes. Three weeks of cell culture and autologous restimulation with either KRN7000, PBS44, or PBS57 resulted in a robust proliferation of iNKT cells from human PBMCs. Next, iNKT cells were sorted to a purity higher than 90% being crucial for further experimental and clinical applications. These iNKT cells significantly decreased activation and proliferation of allogeneic CD3+ T lymphocytes. In addition, leukemia cell lines and primary leukemia cells were efficiently lysed by culture-expanded iNKT cells. Importantly, culture-expanded donor iNKT cells promoted robust antileukemia activity against HLA-matched allogeneic patient leukemia cells. Our data indicate that the adoptive transfer of culture-expanded iNKT cells could be a powerful cytotherapeutic approach to induce immune tolerance and prevent leukemia relapse after allogeneic HCT in humans.

Bat-mouse bone marrow chimera: a novel animal model for dissecting the uniqueness of the bat immune system

Bats are an important animal model with long lifespans, low incidences of tumorigenesis and an ability to asymptomatically harbour pathogens. Currently, in vivo studies of bats are hampered due to their low reproduction rates. To overcome this, we transplanted bat cells from bone marrow (BM) and spleen into an immunodeficient mouse strain NOD-scid IL-2R^−/− (NSG), and have successfully established stable, long-term reconstitution of bat immune cells in mice (bat-mice). Immune functionality of our bat-mouse model was demonstrated through generation of antigen-specific antibody response by bat cells following immunization. Post-engraftment of total bat BM cells and splenocytes, bat immune cells survived, expanded and repopulated the mouse without any observable clinical abnormalities. Utilizing bat’s remarkable immunological functions, this novel model has a potential to be transformed into a powerful platform for basic and translational research.

Simple, Reproducible, and Efficient Clinical Grading System for Murine Models of Acute Graft-versus-Host Disease

Acute graft-versus-host disease (aGVHD) represents a challenging complication after allogeneic hematopoietic stem cell transplantation. Despite the intensive preclinical research in the field of prevention and treatment of aGVHD, and the presence of a well-established clinical grading system to evaluate human aGVHD, such a valid tool is still lacking for the evaluation of murine aGVHD. Indeed, several scoring systems have been reported, but none of them has been properly evaluated and they all share some limitations: they incompletely reflect the disease, rely on severity stages that are distinguished by subjective assessment of clinical criteria and are not easy to discriminate, which could render evaluation more time consuming, and their reproducibility among different experimenters is uncertain. Consequently, clinical murine aGVHD description is often based merely on animal weight loss and mortality. Here, we propose a simple scoring system of aGVHD relying on the binary (yes or no) evaluation of five important visual parameters that reflect the complexity of the disease without the need to sacrifice the mice. We show that this scoring system is consistent with the gold standard histological staging of aGVHD across several donor/recipient mice combinations. This system is also a strong predictor of survival of recipient mice when used early after transplant and is highly reproducible between experimenters.

Therapeutic effects of STAT3 inhibition by nifuroxazide on murine acute graft graft-vs.-host disease: Old drug, new use

Graft-vs.-host disease (GvHD) is a major and lethal complication of allogeneic bone marrow transplantation (allo-BMT). Although great development has been made, the treatment progress of this disorder is slow. Research has illustrated that STAT3 was critical for T cell alloactivation in GvHD. In the present study, the authors hypothesized that nifuroxazide, as the STAT3 inhibitor, treatment may attenuate the development of acute GvHD (aGvHD). The results demonstrated that nifuroxazide suppressed the development of aGvHD and significantly delayed aGvHD-induced lethality. Mice receiving nifuroxazide had mostly normal-appearing skin with minimal focal ulceration, mild edema and congestion in the liver, and a less-pronounced villus injury and less inflammatory infiltrate in the small intestine. Treatment with nifuroxazide inhibited the activation of STAT3, resulting in the regulation of the CD4⁺ T cells and CD4⁺CD25⁺ T cells and reduction of interferon-γ and tumor necrosis factor-α levels. In conclusion, nifuroxazide may be efficacious for post-transplant of GvHD, providing a potent drug for use as a prophylactic or as a second-line therapy for aGvHD in clinical trials.

In-vitro characterization of canine multipotent stromal cells isolated from synovium, bone marrow, and adipose tissue: a donor-matched comparative study

Background

The dog represents an excellent large animal model for translational cell-based studies. Importantly, the properties of canine multipotent stromal cells (cMSCs) and the ideal tissue source for specific translational studies have yet to be established. The aim of this study was to characterize cMSCs derived from synovium, bone marrow, and adipose tissue using a donor-matched study design and a comprehensive series of in-vitro characterization, differentiation, and immunomodulation assays.

Methods

Canine MSCs were isolated from five dogs with cranial cruciate ligament rupture. All 15 cMSC preparations were evaluated using colony forming unit (CFU) assays, flow cytometry analysis, RT-PCR for pluripotency-associated genes, proliferation assays, trilineage differentiation assays, and immunomodulation assays. Data were reported as mean ± standard deviation and compared using repeated-measures analysis of variance and Tukey post-hoc test. Significance was established at p < 0.05.

Results

All tissue samples produced plastic adherent, spindle-shaped preparations of cMSCs. Cells were negative for CD34, CD45, and STRO-1 and positive for CD9, CD44, and CD90, whereas the degree to which cells were positive for CD105 was variable depending on tissue of origin. Cells were positive for the pluripotency-associated genes NANOG, OCT4, and SOX2. Accounting for donor and tissue sources, there were significant differences in CFU potential, rate of proliferation, trilineage differentiation, and immunomodulatory response. Synovium and marrow cMSCs exhibited superior early osteogenic activity, but when assessing late-stage osteogenesis no significant differences were detected. Interestingly, bone morphogenic protein-2 (BMP-2) supplementation was necessary for early-stage and late-stage osteogenic differentiation, a finding consistent with other canine studies. Additionally, synovium and adipose cMSCs proliferated more rapidly, displayed higher CFU potential, and formed larger aggregates in chondrogenic assays, although proteoglycan and collagen type II staining were subjectively decreased in adipose pellets as compared to synovial and marrow pellets. Lastly, cMSCs derived from all three tissue sources modulated murine macrophage TNF-α and IL-6 levels in a lipopolysaccharide-stimulated coculture assay.

Conclusions

While cMSCs from synovium, marrow, and adipose tissue share a number of similarities, important differences in proliferation and trilineage differentiation exist and should be considered when selecting cMSCs for translational studies. These results and associated methods will prove useful for future translational studies involving the canine model.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0639-6) contains supplementary material, which is available to authorized users.

Sphingosine 1-Phosphate Signaling and Its Pharmacological Modulation in Allogeneic Hematopoietic Stem Cell Transplantation

Allogeneic haemopoietic stem cell transplantation (HSCT) is increasingly used to treat haematological malignant diseases via the graft-versus-leukaemia (GvL) or graft-versus-tumour effects. Although improvements in infectious disease prophylaxis, immunosuppressive treatments, supportive care, and molecular based tissue typing have contributed to enhanced outcomes, acute graft-versus-host disease and other transplant related complications still contribute to high mortality and significantly limit the more widespread use of HSCT. Sphingosine 1-phosphate (S1P) is a zwitterionic lysophospholipid that has been implicated as a crucial signaling regulator in many physiological and pathophysiological processes including multiple cell types such as macrophages, dendritic cells, T cells, T regulatory cells and endothelial cells. Recent data suggested important roles for S1P signaling in engraftment, graft-versus-host disease (GvHD), GvL and other processes that occur during and after HSCT. Based on such data, pharmacological intervention via S1P modulation may have the potential to improve patient outcome by regulating GvHD and enhancing engraftment while permitting effective GvL.

Harnessing the CD1 restricted T cell response for leukemia adoptive immunotherapy

Disease recurrence following chemotherapy and allogeneic hematopoietic cell transplantation is the major unmet clinical need of acute leukemia. Adoptive cell therapy (ACT) with allogeneic T lymphocytes can control recurrences at the cost of inducing detrimental GVHD. Targeting T cell recognition on leukemia cells is therefore needed to overcome the problem and ensure safe and durable disease remission. In this review, we discuss adoptive cells therapy based on CD1-restricted T cells specific for tumor associated self-lipid antigens. CD1 molecules are identical in every individual and expressed essentially on mature hematopoietic cells and leukemia blasts, but not by parenchymatous cells, while lipid antigens are enriched in malignant cells and unlike to mutate upon immune-mediated selective pressure. Redirecting T cells against self-lipids presented by CD1 molecules can thus provide an appealing cell therapy strategy for acute leukemia that is patient-unrestricted and can minimize risks for GVHD, implying potential prognostic improvement for this cancer.

Preclinical Testing of Antihuman CD28 Fab' Antibody in a Novel Nonhuman Primate Small Animal Rodent Model of Xenogenic Graft-Versus-Host Disease

BACKGROUND

Graft-versus-host disease (GVHD) is a severe complication of hematopoietic stem cell transplantation. Current therapies to prevent alloreactive T cell activation largely cause generalized immunosuppression and may result in adverse drug, antileukemia and antipathogen responses. Recently, several immunomodulatory therapeutics have been developed that show efficacy in maintaining antileukemia responses while inhibiting GVHD in murine models. To analyze efficacy and better understand immunological tolerance, escape mechanisms, and side effects of clinical reagents, testing of species cross-reactive human agents in large animal GVHD models is critical.

METHODS

We have previously developed and refined a nonhuman primate (NHP) large animal GVHD model. However, this model is not readily amenable to semi-high throughput screening of candidate clinical reagents.

RESULTS

Here, we report a novel, optimized NHP xenogeneic GVHD (xeno-GVHD) small animal model that recapitulates many aspects of NHP and human GVHD. This model was validated using a clinically available blocking, monovalent anti-CD28 antibody (FR104) whose effects in a human xeno-GVHD rodent model are known.

CONCLUSIONS

Because human-reactive reagents may not be fully cross-reactive or effective in vivo on NHP immune cells, this NHP xeno-GVHD model provides immunological insights and direct testing on NHP-induced GVHD before committing to the intensive NHP studies that are being increasingly used for detailed evaluation of new immune therapeutic strategies before human trials.

Ceramide synthesis regulates T cell activity and GVHD development

Allogeneic hematopoietic cell transplantation (allo-HCT) is an effective immunotherapy for a variety of hematologic malignances, yet its efficacy is impeded by the development of graft-versus-host disease (GVHD). GVHD is characterized by activation, expansion, cytokine production, and migration of alloreactive donor T cells. Hence, strategies to limit GVHD are highly desirable. Ceramides are known to contribute to inflammation and autoimmunity. However, their involvement in T-cell responses to alloantigens is undefined. In the current study, we specifically characterized the role of ceramide synthase 6 (CerS6) after allo-HCT using genetic and pharmacologic approaches. We found that CerS6 was required for optimal T cell activation, proliferation, and cytokine production in response to alloantigen and for subsequent induction of GVHD. However, CerS6 was partially dispensable for the T cell-mediated antileukemia effect. At the molecular level, CerS6 was required for efficient TCR signal transduction, including tyrosine phosphorylation, ZAP-70 activation, and PKCθ/TCR colocalization. Impaired generation of C16-ceramide was responsible for diminished allogeneic T cell responses. Furthermore, targeting CerS6 using a specific inhibitor significantly reduced T cell activation in mouse and human T cells in vitro. Our study provides a rationale for targeting CerS6 to control GVHD, which would enhance the efficacy of allo-HCT as an immunotherapy for hematologic malignancies in the clinic.

PD-1 blockade for relapsed lymphoma post-allogeneic hematopoietic cell transplant: high response rate but frequent GVHD

Given the limited treatment options for relapsed lymphoma post-allogeneic hematopoietic cell transplantation (post-allo-HCT) and the success of programmed death 1 (PD-1) blockade in classical Hodgkin lymphoma (cHL) patients, anti-PD-1 monoclonal antibodies (mAbs) are increasingly being used off-label after allo-HCT. To characterize the safety and efficacy of PD-1 blockade in this setting, we conducted a multicenter retrospective analysis of 31 lymphoma patients receiving anti-PD-1 mAbs for relapse post-allo-HCT. Twenty-nine (94%) patients had cHL and 27 had ≥1 salvage therapy post-allo-HCT and prior to anti-PD-1 treatment. Median follow-up was 428 days (range, 133-833) after the first dose of anti-PD-1. Overall response rate was 77% (15 complete responses and 8 partial responses) in 30 evaluable patients. At last follow-up, 11 of 31 patients progressed and 21 of 31 (68%) remain alive, with 8 (26%) deaths related to new-onset graft-versus-host disease (GVHD) after anti-PD-1. Seventeen (55%) patients developed treatment-emergent GVHD after initiation of anti-PD-1 (6 acute, 4 overlap, and 7 chronic), with onset after a median of 1, 2, and 2 doses, respectively. GVHD severity was grade III-IV acute or severe chronic in 9 patients. Only 2 of these 17 patients achieved complete response to GVHD treatment, and 14 of 17 required ≥2 systemic therapies. In conclusion, PD-1 blockade in relapsed cHL allo-HCT patients appears to be highly efficacious but frequently complicated by rapid onset of severe and treatment-refractory GVHD. PD-1 blockade post-allo-HCT should be studied further but cannot be recommended for routine use outside of a clinical trial.

Imaging of Abdominal and Pelvic Manifestations of Graft-Versus-Host Disease After Hematopoietic Stem Cell Transplant

OBJECTIVE

Graft-versus-host disease (GVHD) is a common complication of hematopoietic stem cell transplant (HSCT). GVHD predominantly affects the skin, gastrointestinal system and hepatobiliary systems. Imaging findings in the gastrointestinal tract include bowel wall thickening with mucosal enhancement, mesenteric edema, and vascular engorgement. In the hepatobiliary system, hepatosplenomegaly, periportal edema, bile duct dilatation, and gallbladder and biliary wall thickening are seen. Although the imaging findings of GVHD are nonspecific, with a known history of HSCT, GVHD should be considered.

CONCLUSION

GVHD is a serious complication of HSCT, which involves multiple organ systems, with imaging manifestations most commonly seen in the gastrointestinal tract and hepatobiliary system. Knowledge of the imaging manifestations of GVHD, which alone may be relatively nonspecific, taken in conjunction with clinical history including the timing and type of HSCT, laboratory values, stool studies, and dermatologic findings can increase radiologist confidence in suggesting this diagnosis.

Recipient Immune Modulation with Atorvastatin for Acute Graft-versus-Host Disease Prophylaxis after Allogeneic Transplantation

Atorvastatin administration to both the donors and recipients of matched related donor (MRD) allogeneic hematopoietic cell transplantation (allo-HCT) as acute graft-versus-host disease (GVHD) prophylaxis has been shown to be safe and effective. However, its efficacy as acute GVHD prophylaxis when given only to allo-HCT recipients is unknown. We conducted a phase II study to evaluate the safety and efficacy of atorvastatin-based acute GVHD prophylaxis given only to the recipients of MRD (n = 30) or matched unrelated donor (MUD) (n = 39) allo-HCT, enrolled in 2 separate cohorts. Atorvastatin (40 mg/day) was administered along with standard GVHD prophylaxis consisting of tacrolimus and methotrexate. All patients were evaluable for acute GVHD. The cumulative incidences of grade II to IV acute GVHD at day +100 in the MRD and MUD cohorts were 9.9% (95% confidence interval [CI], 0 to 20%) and 29.6% (95% CI,15.6% to 43.6%), respectively. The cumulative incidences of grade III and IV acute GVHD at day +100 in the MRD and MUD cohorts were 3.4% (95% CI, 0 to 9.7%) and 18.3% (95% CI, 6.3% to 30.4%), respectively. The corresponding rates of moderate/severe chronic GVHD at 1 year were 28.1% (95% CI, 11% to 45.2%) and 38.9% (95% CI, 20.9% to 57%), respectively. In the MRD cohort, the 1-year nonrelapse mortality, relapse rate, progression-free survival, and overall survival were 6.7% (95% CI, 0 to 15.4%), 43.3% (95% CI, 24.9% to 61.7%), 50% (95% CI, 32.1% to 67.9%), and 66.7% (95% CI, 49.8% to 83.6%), respectively. The respective figures for the MUD cohort were 10.3% (95% CI, 8% to 19.7%), 20.5% (95% CI, 7.9% to 33.1%), 69.2% (95% CI, 54.7% to 83.7%), and 79.5% (95% CI, 66.8% to 92.2%), respectively. No grade 4 toxicities attributable to atorvastatin were seen. In conclusion, the addition of atorvastatin to standard GVHD prophylaxis in only the recipients of MRD and MUD allo-HCT appears to be feasible and safe. The preliminary efficacy seen here warrants confirmation in randomized trials.

Rat acute GvHD is Th1 driven and characterized by predominant donor CD4+ T-cell infiltration of skin and gut

Acute graft-versus-host disease (aGvHD) remains a significant hurdle to successful treatment of many hematological disorders. The disease is caused by infiltration of alloactivated donor T cells primarily into the gastrointestinal tract and skin. Although cytotoxic T cells mediate direct cellular damage, T helper (Th) cells differentially secrete immunoregulatory cytokines. aGvHD is thought to be initiated primarily by Th1 cells but a consensus is still lacking regarding the role of Th2 and Th17 cells. The aim of this study was to determine the contribution of distinct T-cell subsets to aGvHD in the rat. aGvHD was induced by transplanting irradiated rats with T-cell-depleted major histocompatibility complex-mismatched bone marrow, followed 2 weeks later by donor lymphocyte infusion. Near complete donor T-cell chimerism was achieved in the blood and lymphatic tissues, in contrast to mixed chimerism in the skin and gut. Skin and gut donor T cells were predominantly CD4⁺, in contrast to T cells in the blood and lymphatic tissues. Genes associated with Th1 cells were upregulated in gut, liver, lung, and skin tissues affected by aGvHD. Increased serum levels of CXCL10 and IL-18 preceded symptoms of aGvHD, accompanied by increased responsiveness to CXCL10 by blood CD4⁺ T cells. No changes in the expression of Th2- or Th17-associated genes were observed, indicating that aGvHD in this rat model is mainly Th1 driven. The rat model of aGvHD could be instrumental for further investigations of donor T-cell subsets in the skin and gut and for exploring therapeutic options to ameliorate symptoms of aGvHD.

A phase 3 randomized trial comparing inolimomab vs usual care in steroid-resistant acute GVHD

Treatment of steroid-resistant acute graft-versus-host disease (GVHD) remains an unmet clinical need. Inolimomab, a monoclonal antibody to CD25, has shown encouraging results in phase 2 trials. This phase 3 randomized, open-label, multicenter trial compared inolimomab vs usual care in adult patients with steroid-refractory acute GVHD. Patients were randomly selected to receive treatment with inolimomab or usual care (the control group was treated with antithymocyte globulin [ATG]). The primary objective was to evaluate overall survival at 1 year without changing baseline allocated therapy. A total of 100 patients were randomly placed: 49 patients in the inolimomab arm and 51 patients in the ATG arm. The primary criteria were reached by 14 patients (28.5%) in the inolimomab and 11 patients (21.5%) in the ATG arms, with a hazard ratio of 0.874 (P = .28). With a minimum follow-up of 1 year, 26 (53%) and 31 (60%) patients died in the inolimomab and ATG arms, respectively. Adverse events were similar in the 2 arms, with fewer viral infections in the inolimomab arm compared with the ATG arm. The primary end point of this randomized phase 3 trial was not achieved. The lack of a statistically significant effect confirms the need for development of more effective treatments for acute GVHD. This trial is registered to https://www.clinicaltrialsregister.eu/ctr-search/search as EUDRACT 2007-005009-24.

Notch pathway plays a novel and critical role in regulating responses of T and antigen-presenting cells in aGVHD

Graft-versus-host disease (GVHD) induced by host antigen-presenting cells (APCs) and donor-derived T cells remains the major limitation of allogeneic bone marrow transplantation (allo-BMT). Notch signaling pathway is a highly conserved cell-cell communication that is important in T cell development. Recently, Notch signaling pathway is reported to be involved in regulating GVHD. To investigate the role of Notch inhibition in modulating GVHD, we established MHC-mismatched murine allo-BMT model. We found that inhibition of Notch signaling pathway by γ-secretase inhibitor in vivo could reduce aGVHD, which was shown by the onset time of aGVHD, body weight, clinical aGVHD scores, pathology aGVHD scores, and survival. Inhibition of Notch signaling pathway by DAPT ex vivo only reduced pathology aGVHD scores in the liver and intestine and had no impact on the onset time and clinical aGVHD scores. We investigated the possible mechanism by analyzing the phenotype of host APCs and donor-derived T cells. Notch signaling pathway had a broad effect on both host APCs and donor-derived T cells. The expressions of CD11c, CD40, and CD86 as the markers of activated dendritic cells (DCs) were decreased. The proliferative response of CD8+ T cell decreased, while CD4⁺ Notch-deprived T cells had preserved expansion with increased expressions of CD25 and Foxp3 as markers of regulatory T cells (Tregs). In conclusion, Notch inhibition may minimize aGVHD by decreasing proliferation and activation of DCs and CD8⁺ T cells while preserving Tregs expansion.

IL-22 promoted CD3+ T cell infiltration by IL-22R induced STAT3 phosphorylation in murine acute graft versus host disease target organs after allogeneic bone marrow transplantation

Graft versus host disease (GVHD) is a life threatening complication of bone marrow stem cell transplantation, in which considerable numbers of proinflammatory cytokines secreted by allo-reactive donor T cells are involved. We and other previous studies have found that interleukin-22 (IL-22) was able to aggravate the target organs damage of GVHD. However, the mechanism and the signal pathway of IL-22 in murine acute GVHD was not clear. Here, we observed that compared with GVHD group, more serious pathological damage and more CD3(+) T cells infiltrated in GVHD target organs were detected in the mice injected with IL-22. Meanwhile, transcription factor T-bet, RORγt and AhR respectively associated with Th1, Th17 and Th22 cells changed in varying degrees in different GVHD target organs. Furthermore, the increased expression of IL-22R and its downstream protein P-STAT3 were detected in GVHD mice with IL-22 treated. These results suggested that the pathological role of IL-22 in GVHD target organs contribute to exogenous injected IL-22 as well as secreted IL-22 from the infiltrated allo-reactive effector T cells. In addition, the IL-22R-STAT3 pathway may play important role in GVHD tissue injury and target this way may yield new approaches for reduction of GVHD.

The Role of Animal Models in the Study of Hematopoietic Stem Cell Transplantation and GvHD: A Historical Overview

Bone marrow transplantation (BMT) is the only therapeutic option for many hematological malignancies, but its applicability is limited by life-threatening complications, such as graft-versus-host disease (GvHD). The last decades have seen great advances in the understanding of BMT and its related complications; in particular GvHD. Animal models are beneficial to study complex diseases, as they allow dissecting the contribution of single components in the development of the disease. Most of the current knowledge on the therapeutic mechanisms of BMT derives from studies in animal models. Parallel to BMT, the understanding of the pathophysiology of GvHD, as well as the development of new treatment regimens, has also been supported by studies in animal models. Pre-clinical experimentation is the basis for deep understanding and successful improvements of clinical applications. In this review, we retrace the history of BMT and GvHD by describing how the studies in animal models have paved the way to the many advances in the field. We also describe how animal models contributed to the understanding of GvHD pathophysiology and how they are fundamental for the discovery of new treatments.

Matched unrelated donor transplants-State of the art in the 21st century

Hematopoietic stem cell transplantation (HSCT) is the therapy of choice in many hematological malignant and non-malignant diseases by using human leukocyte antigen (HLA)-matched siblings as stem cell source but only one third of the patients will have HLA-matched siblings. Hence, physicians rely on the availability of matched unrelated donors (URD). The possibility of finding a matched URD is now more than 70% due to continuous expansion of URD registries around the world. The use of URD in adult patients is steadily increasing and in the last 8 years has superseded the numbers of matched sibling donor transplants and has become the most commonly used stem cell source. There is also an increasing trend to use peripheral blood (PB) stem cells rather than bone marrow (BM) stem cells. Outcomes following URD transplants depend mainly upon the indication and urgency of transplant, age and comorbidities of recipients, cytomegalovirus (CMV) matching/mismatching between donor and the recipient, and degree of HLA matching. In some studies outcome of unrelated stem cell transplants in terms of treatment-related mortality (TRM), disease-free survival (DFS), and overall survival (OS) is comparable to sibling donors.

GRIM19 ameliorates acute graft-versus-host disease (GVHD) by modulating Th17 and Treg cell balance through down-regulation of STAT3 and NF-AT activation

BACKGROUND

T helper (Th) 17 cells are a subset of T helper cells that express interleukin (IL)-17 and initiate the inflammatory response in autoimmune diseases. Regulatory T cells (Tregs) are a subpopulation of T cells that produce forkhead box P3 (FOXP3) and inhibit the immune response. Graft versus host disease (GVHD) is a complication of allogeneic tissue transplantation, and Th17 cells and their proinflammatory activity play a central role in the pathogenesis of GVHD. Gene associated with retinoid-interferon-induced mortality (GRIM) 19, originally identified as a nuclear protein, is expressed ubiquitously in various human tissues and regulate signal transducer and activator of transcription (STAT)3 activity.

METHODS

Splenoytes and bone marrow cells were transplanted into mice with GVHD. The alloresponse of T cells and GVHD clinical score was measured. Realtime-polymerase chain reaction (realtime-PCR) was used to examine mRNA level. Flow cytometry and enzyme linked immunosorbent assay (ELISA) was used to evaluate protein expression.

RESULTS

A GRIM19 transgenic cell transplant inhibited Th17 cell differentiation, alloreactive T cell responses, and STAT3 expression in mice with GVHD. On the other hand, the differentiation of Tregs and STAT5 production were enhanced by GRIM19. Overall, the severity of GVHD was decreased in mice that had received GRIM19 transgenic bone marrow and spleen transplants. Transplantation from GRIM19-overexpressing cells downregulated the expression of nuclear factor of activated T cells (NFATc1) but promoted the expression of regulator of calcineurin (RCAN)3 while downregulating NFAT-dependent cytokine gene expression. This complex mechanism underlies the therapeutic effect of GRIM19.

CONCLUSIONS

We observed that GRIM19 can reduce Th17 cell differentiation and alloreactive T cell responses in vitro and in vivo. Additionally, GRIM19 suppressed the severity of GVHD by modulating STAT3 activity and controlling Th17 and Treg cell differentiation. These results suggest that GRIM19 attenuates acute GVHD through the inhibition of the excessive inflammatory response mediated by T cell activation.

Programmed death ligand-1 expression on donor T cells drives graft-versus-host disease lethality

Programmed death ligand-1 (PD-L1) interaction with PD-1 induces T cell exhaustion and is a therapeutic target to enhance immune responses against cancer and chronic infections. In murine bone marrow transplant models, PD-L1 expression on host target tissues reduces the incidence of graft-versus-host disease (GVHD). PD-L1 is also expressed on T cells; however, it is unclear whether PD-L1 on this population influences immune function. Here, we examined the effects of PD-L1 modulation of T cell function in GVHD. In patients with severe GVHD, PD-L1 expression was increased on donor T cells. Compared with mice that received WT T cells, GVHD was reduced in animals that received T cells from Pdl1-/- donors. PD-L1-deficient T cells had reduced expression of gut homing receptors, diminished production of inflammatory cytokines, and enhanced rates of apoptosis. Moreover, multiple bioenergetic pathways, including aerobic glycolysis, oxidative phosphorylation, and fatty acid metabolism, were also reduced in T cells lacking PD-L1. Finally, the reduction of acute GVHD lethality in mice that received Pdl1-/- donor cells did not affect graft-versus-leukemia responses. These data demonstrate that PD-L1 selectively enhances T cell-mediated immune responses, suggesting a context-dependent function of the PD-1/PD-L1 axis, and suggest selective inhibition of PD-L1 on donor T cells as a potential strategy to prevent or ameliorate GVHD.

Clinicopathologic Threshold of Acute Colorectal Graft-versus-Host Disease

Colon biopsies are often used to determine the presence and severity of acute gastrointestinal graft-versus-host disease following bone marrow transplant.Context.—

To establish a threshold consensus within our institution on the number of crypt apoptotic bodies (CAB) indicative of grade 1 acute colorectal graft-versus-host disease, we retrospectively reviewed colon biopsies from posttransplant patients and incorporated clinical and endoscopic findings to validate recently proposed minimum criteria for grade 1 graft-versus-host disease as 7 or more CAB per 10 contiguous crypts.Objective.—

Eighty-one biopsies performed for suspected graft-versus-host disease from 74 individual patients were initially stratified based on their prior (prestudy) diagnoses: no significant abnormality, grade 1 graft-versus-host disease, and descriptive diagnoses mentioning increased apoptosis. A chart review was performed to assess the clinical and endoscopic impression at the time of biopsy and to determine the subsequent management and outcome.Design.—

Twenty-six biopsies with an average of 3 CAB were considered true-negative cases, and 32 biopsies with an average of 9.75 CAB were considered true-positive cases (t = 3.95999, P &lt; .001). True-negative cases had an average density of 1.36 CAB per crypt, and true-positive cases had an average density of 2.97 CAB per crypt (t = 3.950178, P &lt; .001).Results.—

A threshold of 7 or more CAB per 10 contiguous crypts promotes appropriate treatment of grade 1 acute graft-versus-host disease after other diagnostic entities are excluded. Although this threshold is 100% specific to grade 1 acute colorectal graft-versus-host disease after other histologic mimics are excluded, this threshold has a low sensitivity (59.4%) as patients with less than 7 CAB per 10 contiguous crypts constitute a heterogeneous group.Conclusions.—

Novel approaches for preventing acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Allogeneic hematopoietic stem cell transplantation (alloHSCT) offers potential curative treatment for a wide range of malignant and nonmalignant hematological disorders. However, its success may be limited by post-transplant acute graft-versus-host disease (aGVHD), a systemic syndrome in which donor's immune cells attack healthy tissues in the immunocompromised host. aGVHD is one of the main causes of morbidity and mortality after alloHSCT. Despite standard GVHD prophylaxis regimens, aGVHD still develops in approximately 40-60% of alloHSCT recipients.

AREAS COVERED

In this review, after a brief summary of current knowledge on the pathogenesis of aGVHD, the authors review the current combination of a calcineurin inhibitor with an antimetabolite with or without added anti-thymocyte globulin (ATG) and emerging strategies for GVHD prevention.

EXPERT OPINION

A new understanding of the involvement of cytokines, intracellular signaling pathways, epigenetics and immunoregulatory cells in GVHD pathogenesis will lead to new standards for aGVHD prophylaxis allowing better prevention of severe aGVHD without affecting graft-versus-tumor effects.

The Gut Microbiota and Immune System Relationship in Human Graft-versus-Host Disease

Gut microbiota has gained increasing interest in the pathogenesis of immune-related diseases. In this context, graft-versus-host disease is a condition characterized by an immune response which frequently complicates and limits the outcomes of hematopoietic stem cell transplantations. Past studies, carried mostly in animals, already supported a relationship between gut microbiota and graft-versus-host disease. However, the possible mechanisms underlying this connection remain elusory. Moreover, strategies to prevent graft-versus-host disease are of great interest as well as the potential role of gut microbiota modulation. We reviewed the role of gut microbiota in the development of immune system and its involvement in the graft-versus-host disease, focusing on data available on humans.

Therapeutics for Graft-versus-Host Disease: From Conventional Therapies to Novel Virotherapeutic Strategies

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has a curative potential for many hematologic malignancies and blood diseases. However, the success of allo-HSCT is limited by graft-versus-host disease (GVHD), an immunological syndrome that involves inflammation and tissue damage mediated by donor lymphocytes. Despite immune suppression, GVHD is highly incident even after allo-HSCT using human leukocyte antigen (HLA)-matched donors. Therefore, alternative and more effective therapies are needed to prevent or control GVHD while preserving the beneficial graft-versus-cancer (GVC) effects against residual disease. Among novel therapeutics for GVHD, oncolytic viruses such as myxoma virus (MYXV) are receiving increased attention due to their dual role in controlling GVHD while preserving or augmenting GVC. This review focuses on the molecular basis of GVHD, as well as state-of-the-art advances in developing novel therapies to prevent or control GVHD while minimizing impact on GVC. Recent literature regarding conventional and the emerging therapies are summarized, with special emphasis on virotherapy to prevent GVHD. Recent advances using preclinical models with oncolytic viruses such as MYXV to ameliorate the deleterious consequences of GVHD, while maintaining or improving the anti-cancer benefits of GVC will be reviewed.

Preclinical models of acute and chronic graft-versus-host disease: how predictive are they for a successful clinical translation?

Despite major advances in recent years, graft-versus-host disease (GVHD) remains a major life-threatening complication of allogeneic hematopoietic cell transplantation (allo-HCT). To improve our therapeutic armory against GVHD, preclinical evidence is most frequently generated in mouse and large animal models of GVHD. However, because every model has shortcomings, it is important to understand how predictive the different models are and why certain findings in these models could not be translated into the clinic. Weaknesses of the animal GVHD models include the irradiation only-based conditioning regimen, the homogenous donor/recipient genetics in mice, canine or non-human primates (NHP), anatomic site of T cells used for transfer in mice, the homogenous microbial environment in mice housed under specific pathogen-free conditions, and the lack of pharmacologic GVHD prevention in control groups. Despite these major differences toward clinical allo-HCT, findings generated in animal models of GVHD have led to the current gold standards for GVHD prophylaxis and therapy. The homogenous nature of the preclinical models allows for reproducibility, which is key for the characterization of the role of a new cytokine, chemokine, transcription factor, microRNA, kinase, or immune cell population in the context of GVHD. Therefore, when carefully balancing reasons to apply small and large animal models, it becomes evident that they are valuable tools to generate preclinical hypotheses, which then have to be rigorously evaluated in the clinical setting. In this study, we discuss several clinical approaches that were motivated by preclinical evidence, novel NHP models and their advantages, and highlight the recent advances in understanding the pathophysiology of GVHD.

Coenzyme Q10 Exerts Anti-Inflammatory Activity and Induces Treg in Graft Versus Host Disease

The objective of this study was to determine whether coenzyme Q10 (CoQ10) can reduce the severity of graft versus host disease (GVHD) by inducing regulatory T cells (Tregs). CoQ10 or vehicle was orally administrated once a day for 22 days to mice with GVHD. We measured the alloresponse of the T cells and the GVHD clinical scores. Real-time polymerase chain reaction was used to examine messenger RNA (mRNA) level. Flow cytometry and enzyme-linked immunosorbent assay were used to evaluate protein expression. CoQ10 reduced the T-cell alloresponse and the expression of interferon (IFN)-γ and interleukin (IL)-17. The severity of GVHD and gene expressions of IL-6 and tumor necrosis factor (TNF)-α decreased with CoQ10 treatment. Furthermore, CoQ10 promoted weight gain and survival in GVHD mice. Flow cytometry revealed that CoQ10 dose dependently induced Treg differentiation, but FK506, an immunosuppressive drug, decreased Treg differentiation dose dependently. In conclusion, CoQ10 downregulates the alloreactivity of T cells and reduces GVHD severity, enhancing the differentiation of Tregs.

Understanding Luminal Microorganisms and Their Potential Effectiveness in Treating Intestinal Inflammation

The human intestine contains 10¹⁴ bacteria, which outnumber the mammalian cells 10-fold. Certain other commensal or infectious agents, like helminthic parasites, become members of this microbial ecosystem, especially in populations living under less hygienic conditions. Intestinal microbes, also called the microbiome or microbiota, shape the host immune reactivity to self and nonself throughout life. Changes in microbiome composition may impair the maturation of immune regulatory pathways and predispose the host to develop various forms of inflammatory disorders, like Crohn's disease or ulcerative colitis. The microbiome is also critical to successful transplantation of organs or grafts. After allogeneic hematopoietic stem cell transplantation, when the new donor cells, such as T lymphocytes learn to discriminate "the new self from nonself" in the transplant recipient, they need healthy microbiota-derived signals to preserve the immune homeostasis. Restoring microbiota through intestinal delivery of bacterial strains, helminths, fecal microbiota transplantation, or stool substitutes have the potential to improve and correct aberrant immune reactivity in various disorders.

IL-1 Receptor Blockade Alleviates Graft-versus-Host Disease through Downregulation of an Interleukin-1β-Dependent Glycolytic Pathway in Th17 Cells

T helper (Th) 17 cells are a subset of Th cells expressing interleukin- (IL-) 17 and initiating an inflammatory response in autoimmune diseases. Graft-versus-host disease (GVHD) is an immune inflammatory disease caused by interactions between the adaptive immunity of donor and recipient. The Th17 lineage exhibits proinflammatory activity and is believed to be a central player in GVHD. IL-1 performs a key function in immune responses and induces development of Th17 cells. Here, we show that blockade of IL-1 signaling suppresses Th17 cell differentiation and alleviates GVHD severity. We hypothesized that the IL-1 receptor antagonist (IL-1Ra) would suppress Th17 cell differentiation in vitro via inhibition of glycolysis-related genes. Blockade of IL-1 using IL-1Ra downregulated Th17 cell differentiation, an alloreactive T cell response, and expression of genes of the glycolysis pathway. Severity of GVHD was reduced in mice with a transplant of IL-Ra-treated cells, in comparison with control mice. To clarify the mechanisms via which IL-1Ra exerts the therapeutic effect, we demonstrated in vivo that IL-1Ra decreased the proportion of Th17 cells, increased the proportion of FoxP3-expressing T regulatory (T_reg) cells, and inhibited expression of glycolysis-related genes and suppressed Th17 cell development and B-cell activation. These results suggest that blockade of IL-1 signaling ameliorates GVHD via suppression of excessive T cell-related inflammation.

Dynamic regulation of effector IFN-γ-producing and IL-17-producing T cell subsets in the development of acute graft-versus-host disease

Graft-versus-host disease (GVHD) as the predominant complication of allogeneic hematopoietic stem cell transplantation remains to be fully understood. It is known that the cytokines produced by allogeneic reactive effector CD4+ and CD8+ T cells are involved in GVHD. However, the regulation and coordination of IFN-γ-producing and IL-17-producing effector T cells remain unclear. The present study aimed to investigate the dynamic changes of alloantigen-specific effector CD4+ T and CD8+ T cell subsets by flow cytometry, which produce inflammatory cytokines involved in the multistep GVHD pathogenesis progress. The results demonstrated that IL-17-producing CD8+ T (Tc17) cells and IFN-γ+CD8+ T (Tc1) cells were detected in the early stage of GVHD. The differentiation of CD4+ T cells into Th1 cell (IFN-γ+CD4+ T) and Th17 (IL-17+CD4+ T) cells was later than that of the Tc1 and Tc17 cells. The effector CD4+ T and CD8+ T cell subsets either became exhausted or became memory cells, exhibiting a CD62L-CD44+ phenotype following marked expansion during GVHD. Furthermore, T cell-associated type I (IL-2 and IFN-γ) and type II (IL-4 and IL-10) classical cytokines exhibited coordinated dynamic regulation. It was concluded that the differentiation of cytokine-producing Tc1 and Tc17 cells may be the key step in the initiation of GVHD, whereas CD4+ effector Th1 and Th17 cells are considered to be pathophysiological factors leading to the continuous aggravation of GVHD.

A preclinical acute GVHD mouse model based on chemotherapy conditioning and MHC-matched transplantation

Animal disease models have been criticized for lack of resemblance to human illnesses, hampering transfer of knowledge from preclinical research to clinical medicine. In the field of allogeneic hematopoietic stem cell transplantation (allo-HSCT), it is standard practice to study GVHD in lethal TBI-based murine models. Frequently, MHC-mismatched donors are used in GVHD models. In contrast, in clinical allo-HSCT conditioning with chemotherapy (+/-TBI) is common and donors are often MHC-matched. Aiming at a more clinically oriented situation, we established and characterized a murine MHC-matched, minor histocompatibility antigen mismatched GVHD model (LP/J [H2k(b)]-->C57BL/6 [H2k(b)]) using busulfan and cyclophosphamide conditioning. We found typical clinical and histological features of acute GVHD. T-cell infiltration, GVHD-specific damage and systemic inflammation were similar to observations made in patients after allo-HSCT. In survivors of acute GVHD, we found expansion of CD4+ T cells and the development of scleroderma-like chronic GVHD. The use of chemotherapy-based, minor histocompatibility antigen (miHA)-mismatched GVHD animal models may be a good option when studying clinically relevant questions in the field of allo-HSCT.

MicroRNA-181a, a potential diagnosis marker, alleviates acute graft versus host disease by regulating IFN-γ production

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a valuable therapeutic strategy for a wide variety of diseases. Acute graft-versus-host disease (aGVHD) is a major complication in up to 75% of allo-HSCT. The absence of a reliable predicative marker for aGVHD onset prevents preemptive treatment and impedes widespread and successful application of this therapy. In this study we found that after allo-HSCT, the levels of miR-181a were reduced significantly prior to the onset of aGVHD. More importantly, the degree of its reduction correlated with the severity of aGVHD. Mechanistically, miR-181a affects the function of T lymphocytes by down-regulating IFN-γ in a dose-dependent manner. Meanwhile, we confirmed that miR-181a can effectively preserve the anti-leukemic effect in vitro. Using a murine allo-HSCT model, we demonstrated that murine miR-181b, the human miR-181a homolog, served as an effective predictor of aGVHD. Moreover, expression of this microRNA ameliorated the severity of aGVHD. Collectively, these results show that the level of miR-181a may serve as a reliable marker for the diagnosis and prognosis the onset of aGVHD. Am. J. Hematol. 90:998-1007, 2015. © 2015 Wiley Periodicals, Inc.

Housing Temperature-Induced Stress Is Suppressing Murine Graft-versus-Host Disease through β2-Adrenergic Receptor Signaling

Graft-versus-host disease (GVHD) is the major complication of allogeneic hematopoietic cell transplantation, a potentially curative therapy for hematologic diseases. It has long been thought that murine bone marrow-derived T cells do not mediate severe GVHD because of their quantity and/or phenotype. During the course of experiments testing the impact of housing temperatures on GVHD, we discovered that this apparent resistance is a function of the relatively cool ambient housing temperature. Murine bone marrow-derived T cells have the ability to mediate severe GVHD in mice housed at a thermoneutral temperature. Specifically, mice housed at Institutional Animal Care and Use Committee-mandated, cool standard temperatures (∼ 22°C) are more resistant to developing GVHD than are mice housed at thermoneutral temperatures (∼ 30°C). We learned that the mechanism underlying this housing-dependent immunosuppression is associated with increased norepinephrine production and excessive signaling through β-adrenergic receptor signaling, which is increased when mice are cold stressed. Treatment of mice housed at 22°C with a β2-adrenergic antagonist reverses the norepinephrine-driven suppression of GVHD and yields similar disease to mice housed at 30°C. Conversely, administering a β2-adrenergic agonist decreases GVHD in mice housed at 30°C. In further mechanistic studies using β2-adrenergic receptor-deficient (β2-AR(-/-)) mice, we found that it is host cell β2-AR signaling that is essential for decreasing GVHD. These data reveal how baseline levels of β-adrenergic receptor signaling can influence murine GVHD and point to the feasibility of manipulation of β2-AR signaling to ameliorate GVHD in the clinical setting.

Importance of early absolute lymphocyte count after allogeneic stem cell transplantation: a retrospective study

INTRODUCTION

Early lymphocyte recovery after allogeneic hematopoietic stem cell transplantation (HSCT) is related to the prevention of serious infections and the clearing of residual tumor cells.

METHODS

We analyzed the absolute lymphocyte count at 20 (D+20) and 30 (D+30) days after HSCT in 100 patients with malignant hematologic diseases and correlated with the risk of transplant-related mortality, overall survival (OS), disease-free survival (DFS), nonrelapsed mortality (NRM), and risk of infection.

RESULTS

Patients presenting with lymphocyte counts of <300 × 103/μL on D+30 have a 3.76 times greater risk of death in <100 days. Over a medium follow-up of 20 months OS, DFS, and NRM were similar between the groups.

CONCLUSION

In our group of patients delayed lymphocyte recovery after HSCT was a predictor of early death post-HSCT.

The imbalance between Tregs, Th17 cells and inflammatory cytokines among renal transplant recipients

Background

A significant barrier to organ transplantation is the cellular rejection that occurs and mediated by antibodies, T cells, and innate immune cells. This study was aimed to determine the number of CD4⁺CD25⁺Foxp3⁺ Treg, CD4⁺IFN-γ⁻IL-17⁺ Th17, CD4⁺IFN-γ⁺IL-17⁻ Th1 and CD4⁺IFN-γ⁺IL-17⁺ Th1/17 cells in renal transplant recipients (RTR).

Methods

Renal transplantation was performed for a total of 35 patients with end-stage renal failure. The number of CD4⁺CD25⁺Foxp3⁺ Treg, CD4⁺IFN-γ⁻IL-17⁺ Th17, CD4⁺IFN-γ⁺IL-17⁻ Th1 and CD4⁺IFN-γ⁺IL-17⁺ Th1/17 cells, and the serum level of IFN-γ, TNF-α, IL-2, IL-4, IL-6, IL-10, and IL-17 were measured in pre- and post-transplant patients and 10 healthy controls (HC) using flow cytometry and Cytometric Bead Array (CBA). The association between the number of different subsets of CD4⁺ T-cells and clinical parameters were analyzed among the pre- and post-transplant patients, and the healthy controls.

Results

The number of CD4⁺IFN-γ⁻IL-17⁺ Th17, CD4⁺IFN-γ⁺IL-17⁻ Th1 and CD4⁺IFN-γ⁺IL-17⁺ Th1/17 cells were significantly increased in patients with End-Stage Renal Failure (ESRF) compared to the HC. Stratification analysis indicated that AMR (Acute antibody mediated acute rejection), AR (acute rejection) and CR (chronic rejection) groups displayed greater number of CD4⁺IFN-γ⁻IL-17⁺ Th17, CD4⁺IFN-γ⁺IL-17⁻ Th1 and CD4⁺IFN-γ⁺IL-17⁺ Th1/17 cells as well as high level of serum IL-2, IFN-γ, TNF-α and IL-17. But, the AMR, AR and CR groups have shown lower level of CD4⁺CD25⁺Foxp3⁺ T cells and serum IL-10 compared to transplant stable (TS) patients. Moreover, the number of Tregs were negatively correlated with the number of Th17 cells in RTR patients. The number of Tregs and Th17 cells were positively correlated with the eGFR and serum creatinine values, respectively.

Conclusion

The imbalance between different types of CD4⁺ T cells and dysregulated inflammatory cytokines may contribute towards renal transplantation rejection.

Adoptive Transfer of Treg Cells Combined with Mesenchymal Stem Cells Facilitates Repopulation of Endogenous Treg Cells in a Murine Acute GVHD Model

Therapeutic effects of combined cell therapy with mesenchymal stem cells (MSCs) and regulatory T cells (Treg cells) have recently been studied in acute graft-versus-host-disease (aGVHD) models. However, the underlying, seemingly synergistic mechanism behind combined cell therapy has not been determined. We investigated the origin of Foxp3+ Treg cells and interleukin 17 (IL-17+) cells in recipients following allogeneic bone marrow transplantation (allo-BMT) to identify the immunological effects of combined cell therapy. Treg cells were generated from eGFP-expressing C57BL/6 mice (Tregegfp cells) to distinguish the transferred Treg cells; recipients were then examined at different time points after BMT. Systemic infusion of MSCs and Treg cells improved survival and GVHD scores, effectively downregulating pro-inflammatory Th×and Th17 cells. These therapeutic effects of combined cell therapy resulted in an increased Foxp3+ Treg cell population. Compared to single cell therapy, adoptively transferred Tregegfp cells only showed prolonged survival in the combined cell therapy group on day 21 after allogeneic BMT. In addition, Foxp3+ Treg cells, generated endogenously from recipients, significantly increased. Significantly higher levels of Tregegfp cells were also detected in aGVHD target organs in the combined cell therapy group compared to the Treg cells group. Thus, our data indicate that MSCs may induce the long-term survival of transferred Treg cells, particularly in aGVHD target organs, and may increase the repopulation of endogenous Treg cells in recipients after BMT. Together, these results support the potential of combined cell therapy using MSCs and Treg cells for preventing aGVHD.

Numerical impairment of nestin(+) bone marrow niches in acute GvHD after allogeneic hematopoietic stem cell transplantation for AML

The nestin(+) perivascular bone marrow (BM) stem cell niche (N(+)SCN) may be involved in GvHD. To investigate whether acute GvHD (aGvHD) reduces the number of N(+)SCN, we examined patients with AML who had undergone allogeneic hematopoietic stem cell transplantation. In the test cohort (n=8), the number of N(+)SCN per mm(2) in BM biopsies was significantly reduced in aGvHD patients at the time of aGvHD compared with patients who did not have aGvHD (1.2±0.78 versus 2.6±0.93, P=0.04). In the validation cohort (n=40), the number of N(+)SCN was reduced (1.9±0.99 versus 2.6±0.90 N(+)SCN/mm(2), P=0.05) in aGvHD patients. Receiver operating curves suggested that the cutoff score that best discriminated between patients with and without aGvHD was 2.29 N(+)SCN/mm(2). Applying this cutoff score, 9/11 patients with clinically relevant aGvHD (⩾grade 2) and 13/20 with any type of GvHD had decreased N(+)SCN numbers compared with only 10/29 patients without clinically relevant aGvHD (P=0.007) and 6/20 patients without any type of GvHD (P=0.028). In patients tracked over time, N(+)SCN density returned to normal after aGvHD resolved or remained stable in patients who did not have aGvHD. Our results show a decrease in the number of N(+)SCN in aGvHD.

Atorvastatin for the Prophylaxis of Acute Graft-versus-Host Disease in Patients Undergoing HLA-Matched Related Donor Allogeneic Hematopoietic Stem Cell Transplantation (allo-HCT)

Statins possess potent immunomodulatory effects that may play a role in preventing acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic cell transplantation (allo-HCT). We performed a phase II study of atorvastatin for aGVHD prophylaxis when given to allo-HCT recipients and their HLA-matched sibling donors. Atorvastatin (40 mg/day) was administered to sibling donors, beginning 14 days before the anticipated start of stem cell collection. Allo-HCT recipients (n = 40) received atorvastatin (40 mg/day) in addition to standard aGVHD prophylaxis. The primary endpoint was cumulative incidence of grades II to IV aGVHD at day 100. Atorvastatin was well tolerated, with no attributable grades III to IV toxicities in donors or their recipients. Day 100 and 180 cumulative incidences of grades II to IV aGVHD were 30% (95% confidence interval [CI], 17% to 45%) and 40% (95% CI, 25% to 55%), respectively. One-year cumulative incidence of chronic GVHD was 43% (95% CI, 32% to 69%). One-year nonrelapse mortality and relapse incidences were 5.5% (95% CI, .9% to 16.5%) and 38% (95% CI, 18% to 47%), respectively. One-year progression-free and overall survival rates were 54% (95% CI, 38% to 71%) and 82% (95% CI, 69% to 94%). One-year GVHD-free, relapse-free survival was 27% (95% CI, 16% to 47%). These results did not differ from our historical control subjects (n = 96). Although safe and tolerable, the addition of atorvastatin did not appear to provide any benefit to standard GVHD prophylaxis alone.

Tocilizumab for steroid refractory acute graft-versus-host disease

Acute graft-versus-host-disease (aGVHD) is a frequent and often lethal complication of allogeneic hematopoietic stem cell transplant despite prophylaxis. Tocilizumab is a humanized anti-IL-6 receptor monoclonal antibody that has evidence of activity in patients with steroid refractory (SR) GVHD. We retrospectively report on nine patients with grade 3 or 4 SR aGVHD who received tocilizumab. Eight mg/kg of tocilizumab was administered intravenously every 3-4 weeks. aGVHD grading and responses were based on consensus criteria. Median age at transplant was 48 years. Five patients had alternate donor sources. Median time from aGVHD onset to tocilizumab administration was 44 days. Two patients had complete responses and two had partial responses. Median survival from start of tocilizumab was 26 days (range 13-1054). Our limited experience demonstrated an overall response rate of 44% (CR + PR); however, this response was not durable. Further studies are needed to determine the optimal time for tocilizumab initiation.

MicroRNA-17-92 controls T-cell responses in graft-versus-host disease and leukemia relapse in mice

MicroRNAs (miRs) play important roles in orchestrating many aspects of the immune response. The miR-17-92 cluster, which encodes 6 miRs including 17, 18a, 19a, 20a, 19b-1, and 92-1, is among the best characterized of these miRs. The miR-17-92 cluster has been shown to regulate a variety of immune responses including infection, tumor, and autoimmunity, but the role of this cluster in T-cell response to alloantigens has not been previously explored. By using major histocompatibility complex (MHC)-matched, -mismatched, and haploidentical murine models of allogeneic bone marrow transplantation (allo-BMT), we demonstrate that the expression of miR-17-92 on donor T cells is essential for the induction of graft-versus-host disease (GVHD), but dispensable for the graft-versus-leukemia (GVL) effect. The miR-17-92 plays a major role in promoting CD4 T-cell activation, proliferation, survival, and Th1 differentiation, while inhibiting Th2 and iTreg differentiation. Alternatively, miR-17-92 may promote migration of CD8 T cells to GVHD target organs, but has minimal impact on CD8 T-cell proliferation, survival, or cytolytic function, which could contribute to the preserved GVL effect mediated by T cells deficient for miR-17-92. Furthermore, we evaluated a translational approach and found that systemic administration of antagomir to block miR-17 or miR-19b in this cluster significantly inhibited alloreactive T-cell expansion and interferon-γ (IFNγ) production, and prolonged the survival in recipients afflicted with GVHD while preserving the GVL effect. Taken together, the current work provides a strong rationale and demonstrates the feasibility to target miR-17-92 for the control of GVHD while preserving GVL activity after allo-BMT.

Mechanistic Assessment of PD-1H Coinhibitory Receptor-Induced T Cell Tolerance to Allogeneic Antigens

PD-1H is a recently identified cell surface coinhibitory molecule of the B7/CD28 immune modulatory gene family. We showed previously that single injection of a PD-1H agonistic mAb protected mice from graft-versus-host disease (GVHD). In this study, we report two distinct mechanisms operate in PD-1H-induced T cell tolerance. First, signaling via PD-1H coinhibitory receptor potently arrests alloreactive donor T cells from activation and expansion in the initiation phase. Second, donor regulatory T cells are subsequently expanded to maintain long-term tolerance and GVHD suppression. Our study reveals the crucial function of PD-1H as a coinhibitory receptor on alloreactive T cells and its function in the regulation of T cell tolerance. Therefore, PD-1H may be a target for the modulation of alloreactive T cells in GVHD and transplantation.

GLCCI1 and Glucocorticoid Receptor Genetic Diversity and Response to Glucocorticoid-Based Treatment of Graft-versus-Host Disease

The genetic diversity of loci implicated in glucocorticoid (GC) response has been associated with interindividual variations in responsiveness to GC in various diseases, such as asthma and inflammatory bowel disorders. In acute graft-versus-host disease (aGVHD), similar differences of first-line therapy responsiveness are also observed, with approximately 40% of patients failing to respond to GC. Here, the distribution of functionally relevant single nucleotide polymorphisms (SNP) belonging to the GC-induced transcript 1 GLCCI1 (rs37972) and the glucocorticoid receptor (rs41423247, rs6195 and rs6198) gene loci were analyzed alongside clinical factors for their association with the response to corticosteroids in aGVHD. The frequencies of variant alleles did not differ significantly between corticoresistant patients, their donors, and their corticosensitive peers (P = .10 to 1.00). Severe and early onset of aGVHD, bone marrow as the stem cell source, and an HLA mismatch were associated with the failure to respond to GC in logistic regression. After including the single SNPs to the model, carriers of the rs41423247 polymorphism had a higher probability of responding to GC, whereas all other polymorphisms did not affect the likelihood of response.