Search

Graft versus host disease (GVHD) can occur at any period post allogeneic hematopoietic stem cell transplantation as a common clinical complication contributing to significant morbidity and mortality. Acute GVHD develops in approximately 30-50% of patients receiving transplants from matched related donors. High doses of steroids are used as first-line treatment, but are unsuccessful in around 40% of patients, resulting in the diagnosis of steroidrefractory acute GVHD. Consensus has yet to develop for the management of steroid-refractory acute GVHD, and prognosis at six months has been estimated at around 50%. Thus, it is critical to find effective treatments that increase survival of steroid-refractory acute GVHD. This article describes the currently known characteristics, pathophysiology, and treatments for GVHD, with a special focus on recent advances in cell therapies. In particular, a novel cell therapy using decidua stromal cells (DSCs) was recently shown to have promising results for acute GVHD, with improved effectiveness over previous treatments including mesenchymal stromal cells. At the Karolinska Institute, severe acute GVHD patients treated with placenta-derived DSCs supplemented with either 5% albumin or 10% AB plasma displayed a one-year survival rate of 76% and 47% respectively. Furthermore, patients with steroid-refractory acute GVHD, displayed survival rates of 73% with albumin and 31% with AB plasmasupplemented DSCs, compared to the 20% survival rate in the mesenchymal stromal cell control group. Adverse events and deaths were found to be attributed only to complications of hematopoietic stem cell transplant and GVHD, not to the study intervention. ASC Therapeutics, Inc, in collaboration with the Karolinska Institute, will soon initiate a phase 2 multicenter, open-label study to further assess the efficacy and safety of intravenous DSC treatment in sixty patients with Grade II-IV steroid-refractory acute GVHD. This novel cell therapy represents a promising treatment to combat the poor prognosis that steroid-refractory acute GVHD patients currently face. [ABSTRACT FROM AUTHOR]

Summary: Acute graft‐versus‐host disease (aGVHD) is a life‐threatening complication after allogeneic haematopoietic cell transplantation, with gastrointestinal (GI) tract involvement (GI aGVHD) being one of the leading causes of morbidity and mortality. Whilst systemic steroids are the standard first‐line treatment for aGVHD, approximately 50% of patients become steroid refractory (SR), which is associated with poor outcomes. Existing options for SR‐GVHD are limited, and there is a significant unmet need for new non‐immunosuppressive treatment approaches in patients with GI aGVHD. Here, we review newer concepts in the pathogenesis of GI aGVHD and present the evidence for the role of glucagon‐like peptide 2 (GLP‐2) in maintaining and protecting GI epithelial cells, including the enterocytes, intestinal stem cells and Paneth cells, which are direct targets of aGVHD. Finally, we discuss the therapeutic rationale for GLP‐2 treatment as a tissue regeneration approach and the potential use of the novel GLP‐2 analogue apraglutide as an adjunctive treatment for GI aGVHD. [ABSTRACT FROM AUTHOR]

To determine factors influencing the vaccination response against SARS-CoV-2 is of importance in recipients of allogeneic hematopoietic cell transplantation (allo-HCT) as they display an increased mortality after SARS-CoV-2 infection, an increased risk of extended viral persistence and reduced vaccination response. Real-life data on anti-SARS-CoV-2-S1-IgG titers (n = 192) and IFN-γ release (n = 110) of allo-HCT recipients were obtained using commercially available, validated assays after vaccination with either mRNA (Comirnaty™, Pfizer-BioNTech™, NY, US and Mainz, Germany or Spikevax™, Moderna™, Cambridge, Massachusetts, US) or vector-based vaccines (Vaxzevria™,AstraZeneca™, Cambridge, UK or Janssen COVID-19 vaccine™Johnson/Johnson, New Brunswick, New Jersey, US), or after a heterologous protocol (vector/mRNA). Humoral response (78% response rate) was influenced by age, time after transplantation, the usage of antithymocyte globulin (ATG) and ongoing immunosuppression, specifically corticosteroids. High counts of B cells during the vaccination period correlated with a humoral response. Only half (55%) of participants showed a cellular vaccination response. It depended on age, time after transplantation, ongoing immunosuppression with ciclosporin A, chronic graft-versus-host disease (cGvHD) and vaccination type, with vector-based protocols favoring a response. Cellular response failure correlated with a higher CD8+ count and activated/HLA-DR+ T cells one year after transplantation. Our data provide the basis to assess both humoral and cellular responses after SARS-CoV2 vaccination in daily practice, thereby opening up the possibility to identify patients at risk. [ABSTRACT FROM AUTHOR]

The intestinal tract is the largest immunological organ in the body and has a central function of regulating local immune responses, as the intestinal epithelial barrier is a location where the immune system interacts with the gut microbiome including bacteria, fungi, and viruses. Impaired immunity in the intestinal tract can lead to immunopathology, which manifests in different diseases such as inflammatory bowel disease or intestinal graft‐versus‐host disease. A disturbed communication between epithelial cells, immune cells, and microbiome will shape pathogenic immune responses to antigens, which need to be counterbalanced by tolerogenic mechanisms and repair mechanisms. Here, we review how impaired intestinal immune function leads to immunopathology with a specific focus on innate immune cells, the role of the microbiome, and the resulting clinical manifestations including intestinal graft‐versus‐host disease, inflammatory bowel disease, and enteropathy in primary immunodeficiency. [ABSTRACT FROM AUTHOR]

Acute Graft versus Host Disease (aGvHD) is a common immunological complication occurring in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). Moreover, aGvHD is associated with a higher risk of infections and metabolic complications, affecting non-relapse mortality. Progress in transplantation has changed the prophylactic and therapeutic strategies of aGvHD and improved patient outcomes. The standard first-line therapy remains steroids, with a response rate of about 50%. The Janus Kinase 2 (JAK2) inhibitor, ruxolitinib, is an effective second-line therapy. The management of patients who developed a disease that is refractory to steroids and ruxolitinib, especially in the severe gastrointestinal forms of aGvHD, is not validated and remains an unmet medical need. In the article, we present the current clinical practice, as well as the latest advances targeting pathophysiological pathways of GvHD and gut microbiota, which may be a potential future of aGvHD therapy. [ABSTRACT FROM AUTHOR]

Allogeneic hematopoietic cell transplantation (allo-HCT) is a curative therapy for patients with hematological malignancies. Acute Graft versus host diseases (GVHD) is a major immune mediated side effect of allo-HCT that can affect the central nervous system (CNS) in addition to post-allo-HCT vascular events, drug toxicity or infections. Here we summarize and discuss recent preclinical data on the CNS as a target of acute GVHD and the known mechanisms contributing to neurotoxicity with a focus on microglia and T cells. We also discuss open questions in the field and place the findings made in mouse models in a clinical context. While in mice the neurological deficits can be assessed in a controlled fashion, in patients the etiology of the CNS damage is difficult to attribute to acute GVHD versus infections, vascular events, and drug-induced toxicity. Ultimately, we discuss novel therapies for GVHD of the CNS. Our understanding of the biological mechanisms that lead to neurotoxicity after allo-HCT increased over the last decade. This review provides insights into CNS manifestations of GVHD versus other etiologies of CNS damage in mice and patients. [ABSTRACT FROM AUTHOR]

We report a single-center phase I/II trial exploring the combination of everolimus (EVE) and mycophenolate mofetil (MMF) as calcineurin inhibitor (CNI)-free GVHD prophylaxis for 24 patients with hematologic malignancies and indication for allogeneic HCT after a high dose or reduced-intensity ablative conditioning. The study was registered as EudraCT-2007-001892-12 and Clinicaltrials.gov as NCT00856505. All patients received PBSC grafts and no graft failure occurred. 7/24 patients (29%) developed acute grades III and IV GVHD (aGVHD), 16/19 evaluable patients (84%) developed chronic GVHD (cGVHD) of all grades, and 6/19 (31.6%) of higher grades. No severe toxicities related to study medication were observed. The median follow-up of all surviving patients is 2177 days. The 3-year OS was 45.2% (95% CI: 27.4–61.4%), and the 3-year PFS was 38.7% (95% CI: 22.0–55.1%). The cumulative incidence of relapse at 1 year and 3 year was 25% (95% CI: 12.5–50.0%), and 33.3% (95% CI: 18.9–58.7%), the cumulative incidence of NRM at 1 year and 3 years was 20.8% (95%CI: 9.6–45.5%), and 29.2% (95%CI: 15.6–54.4%), respectively. The utilization of CNI-free GVHD prophylaxis with EVE+MMF resulted in high rates of acute and chronic GVHD. Therefore, we do not recommend a CNI-free combination of mTOR inhibitor EVE with MMF as the sole GVHD prophylaxis. In subsequent studies, this combination should be modified, e.g., with further components like post-transplant cyclophosphamide (PTCy) or anti-thymocyte globulin (ATG). [ABSTRACT FROM AUTHOR]

Background: Chronic graft-versus-host disease (GVHD), a major complication of allogeneic stem-cell transplantation, becomes glucocorticoid-refractory or glucocorticoid-dependent in approximately 50% of patients. Robust data from phase 3 randomized studies evaluating second-line therapy for chronic GVHD are lacking. In retrospective surveys, ruxolitinib, a Janus kinase (JAK1-JAK2) inhibitor, showed potential efficacy in patients with glucocorticoid-refractory or -dependent chronic GVHD.Methods: This phase 3 open-label, randomized trial evaluated the efficacy and safety of ruxolitinib at a dose of 10 mg twice daily, as compared with the investigator's choice of therapy from a list of 10 commonly used options considered best available care (control), in patients 12 years of age or older with moderate or severe glucocorticoid-refractory or -dependent chronic GVHD. The primary end point was overall response (complete or partial response) at week 24; key secondary end points were failure-free survival and improved score on the modified Lee Symptom Scale at week 24.Results: A total of 329 patients underwent randomization; 165 patients were assigned to receive ruxolitinib and 164 patients to receive control therapy. Overall response at week 24 was greater in the ruxolitinib group than in the control group (49.7% vs. 25.6%; odds ratio, 2.99; P<0.001). Ruxolitinib led to longer median failure-free survival than control (>18.6 months vs. 5.7 months; hazard ratio, 0.37; P<0.001) and higher symptom response (24.2% vs. 11.0%; odds ratio, 2.62; P = 0.001). The most common (occurring in ≥10% patients) adverse events of grade 3 or higher up to week 24 were thrombocytopenia (15.2% in the ruxolitinib group and 10.1% in the control group) and anemia (12.7% and 7.6%, respectively). The incidence of cytomegalovirus infections and reactivations was similar in the two groups.Conclusions: Among patients with glucocorticoid-refractory or -dependent chronic GVHD, ruxolitinib led to significantly greater overall response, failure-free survival, and symptom response. The incidence of thrombocytopenia and anemia was greater with ruxolitinib. (Funded by Novartis and Incyte; REACH3 ClinicalTrials.gov number, NCT03112603.). [ABSTRACT FROM AUTHOR]

Chronic graft-versus-host disease (cGvHD) is a severe complication of allogeneic hematopoietic stem cell transplantation that affects various organs leading to a reduced quality of life. The condition often requires enduring immunosuppressive therapy, which can also lead to the development of severe side effects. Several approaches including small molecule inhibitors, antibodies, cytokines, and cellular therapies are now being developed for the treatment of cGvHD, and some of these therapies have been or are currently tested in clinical trials. In this review, we discuss these emerging therapies with particular emphasis on tyrosine kinase inhibitors (TKIs). TKIs are a class of compounds that inhibits tyrosine kinases, thereby preventing the dissemination of growth signals and activation of key cellular proteins that are involved in cell growth and division. Because they have been shown to inhibit key kinases in both B cells and T cells that are involved in the pathophysiology of cGvHD, TKIs present new promising therapeutic approaches. Ibrutinib, a Bruton tyrosine kinase (Btk) inhibitor, has recently been approved by the Food and Drug Administration (FDA) in the United States for the treatment of adult patients with cGvHD after failure of first-line of systemic therapy. Also, Janus Associated Kinases (JAK1 and JAK2) inhibitors, such as itacitinib (JAK1) and ruxolitinib (JAK1 and 2), are promising in the treatment of cGvHD. Herein, we present the current status and future directions of the use of these new drugs with particular spotlight on their targeting of specific intracellular signal transduction cascades important for cGvHD, in order to shed some light on their possible mode of actions. [ABSTRACT FROM AUTHOR]

Background: Acute graft-versus-host disease (GVHD) remains a major limitation of allogeneic stem-cell transplantation; not all patients have a response to standard glucocorticoid treatment. In a phase 2 trial, ruxolitinib, a selective Janus kinase (JAK1 and JAK2) inhibitor, showed potential efficacy in patients with glucocorticoid-refractory acute GVHD.Methods: We conducted a multicenter, randomized, open-label, phase 3 trial comparing the efficacy and safety of oral ruxolitinib (10 mg twice daily) with the investigator's choice of therapy from a list of nine commonly used options (control) in patients 12 years of age or older who had glucocorticoid-refractory acute GVHD after allogeneic stem-cell transplantation. The primary end point was overall response (complete response or partial response) at day 28. The key secondary end point was durable overall response at day 56.Results: A total of 309 patients underwent randomization; 154 patients were assigned to the ruxolitinib group and 155 to the control group. Overall response at day 28 was higher in the ruxolitinib group than in the control group (62% [96 patients] vs. 39% [61]; odds ratio, 2.64; 95% confidence interval [CI], 1.65 to 4.22; P<0.001). Durable overall response at day 56 was higher in the ruxolitinib group than in the control group (40% [61 patients] vs. 22% [34]; odds ratio, 2.38; 95% CI, 1.43 to 3.94; P<0.001). The estimated cumulative incidence of loss of response at 6 months was 10% in the ruxolitinib group and 39% in the control group. The median failure-free survival was considerably longer with ruxolitinib than with control (5.0 months vs. 1.0 month; hazard ratio for relapse or progression of hematologic disease, non-relapse-related death, or addition of new systemic therapy for acute GVHD, 0.46; 95% CI, 0.35 to 0.60). The median overall survival was 11.1 months in the ruxolitinib group and 6.5 months in the control group (hazard ratio for death, 0.83; 95% CI, 0.60 to 1.15). The most common adverse events up to day 28 were thrombocytopenia (in 50 of 152 patients [33%] in the ruxolitinib group and 27 of 150 [18%] in the control group), anemia (in 46 [30%] and 42 [28%], respectively), and cytomegalovirus infection (in 39 [26%] and 31 [21%]).Conclusions: Ruxolitinib therapy led to significant improvements in efficacy outcomes, with a higher incidence of thrombocytopenia, the most frequent toxic effect, than that observed with control therapy. (Funded by Novartis; REACH2 ClinicalTrials.gov number, NCT02913261.). [ABSTRACT FROM AUTHOR]

Summary: Acute graft‐versus‐host disease (GVHD) remains a major complication after allogeneic haematopoietic stem cell transplantation (allo‐HSCT). The emergence of different immuno‐prophylaxis strategies, such as post‐transplant cyclophosphamide or anti‐thymocyteglobulin has reduced the incidence of acute GVHD in recent years. The biology of the acute GVHD we observe in the clinic may change due to the use of novel immuno‐stimulatory agents, including immune checkpoint inhibitors or anti‐neoplastic immune‐modifiers, like lenalidomide, given before or after allo‐HSCT. Here we discuss the recent advances in our understanding of acute GVHD with a focus on early events of the disease, including tissue damaging factors, innate immune cells, costimulatory pathways, immune cell signalling, immuno‐regulatory cell types, biomarkers of GVHD and regenerative approaches. New insight in the pathogenesis of acute GVHD has revealed the role of pro‐inflammatory intracellular signalling, defects in intestinal tissue regeneration and anti‐bacterial defence, as well as a reduced diversity of the microbiome, which will be the basis for the development of novel therapies. [ABSTRACT FROM AUTHOR]

Background: Graft-versus-Host Disease (GvHD) causes significant morbidity and mortality in patients after allogeneic stem cell transplantation. Donor T-cells cause inflammation and tissue damage in GvHD target organs such as liver, gut and skin. Cytokine receptor associated kinases JAK1 and JAK2 are critical for inflammatory cytokine response in GvHD. Ruxolitinib is a small molecule inhibitor of JAK1 and JAK2. Preliminary data indicated substantial clinical activity in patients with steroid-refractory (SR) acute and chronic GvHD.Methods: The RIG-study is an investigator-initiated open-label, multicenter, prospective randomized controlled two-arm phase 2 study, comparing the efficacy of ruxolitinib and best available treatment (BAT) versus BAT in steroid-refractory acute GvHD (SR-aGvHD). Patients with acute skin, intestinal or liver GvHD > grade 1 and failure of previous treatment are eligible. The trial aims to include 160 patients who will be randomized in a 1:1 ratio and stratified by GvHD grade (≤ grade 3 versus grade 4) and number of previous immunosuppressive treatments (≤ 3 versus ≥4). The primary endpoint is the overall response rate at day 28, defined as: Improvement of at least one stage in the severity of acute GvHD in one organ without deterioration in any other organ, or disappearance of any GvHD signs from all organs without requirement for new systemic immunosuppressive treatment. Secondary objectives include time to response, overall survival, event-free survival, non-relapse mortality (NRM), failure-free survival, graft failure rates, quality of life and changes in serum levels of pro-inflammatory cytokines and GvHD-related biomarkers.Discussion: This randomized prospective trial will provide further evidence if the retrospectively collected data demonstrating activity of ruxolitinib for SR-aGvHD can be reproduced. A major advantage of ruxolitinib might be the limited and predictable toxicity profile compared to other immunosuppressive therapies that mainly includes viral reactivation and cytopenias. This trial will establish candidate biomarkers to predict and monitor responses to ruxolitinib. As a next step ruxolitinib might be tested upfront against steroids or in a preemptive manner to prevent GvHD to occur.Trial Registration: NCT02396628 (registration date 17.07.2015); DRKS00007939 (registration date 26.03.2015). [ABSTRACT FROM AUTHOR]

Over the last decade, our understanding of the pathophysiology of chronic graft-versus-host disease (cGVHD) has improved considerably. In this spotlight, we discuss emerging insights into the pathophysiology of cGVHD with a focus on B cells. First, we summarize supporting evidence derived from mouse and human studies. Next, novel cGVHD therapy approaches that target B cells will be covered to provide treating physicians with an overview of the rationale behind the emerging armamentarium against cGVHD. [ABSTRACT FROM AUTHOR]

The article focuses on acute graft-versus-host disease (GVHD). Topics discussed include maculopapular rash, hyperbilirubinemia with jaundice and anorexia as signs of typical acute GVHD; neoangiogenesis and infiltration of the intestinal tract by innate myeloid cells; and use of biomarkers tumor necrosis factor (TNF)-α receptor type 1, interleukin-2Rα chain, and islet-derived protein-3α; and combination of cyclosporine and methotrexate for treatment.

Graft-versus-host response after allogeneic hematopoietic stem cell transplantation (allo-HCT) represents one of the most intense inflammatory responses observed in humans. Host conditioning facilitates engraftment of donor cells, but the tissue injury caused from it primes the critical first steps in the development of acute graft-versus-host disease (GVHD). Tissue injuries release pro-inflammatory cytokines (such as TNF-α, IL-1β, and IL-6) through widespread stimulation of pattern recognition receptors (PRRs) by the release of danger stimuli, such as damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs). DAMPs and PAMPs function as potent stimulators for host and donor-derived antigen presenting cells (APCs) that in turn activate and amplify the responses of alloreactive donor T cells. Emerging data also point towards a role for suppression of DAMP induced inflammation by the APCs and donor T cells in mitigating GVHD severity. In this review, we summarize the current understanding on the role of danger stimuli, such as the DAMPs and PAMPs, in GVHD. [ABSTRACT FROM AUTHOR]

Allogeneic hematopoietic cell transplantation (allo-HCT) represents the only curative treatment approach for many patients with benign or malignant diseases of the hematopoietic system. However, post-transplant morbidity and mortality are significantly increased by the development of acute graft-versus-host disease (GvHD). While alloreactive T cells act as the main cellular mediator of the GvH reaction, recent evidence suggests a critical role of the innate immune system in the early stages of GvHD initiation. Danger-associated molecular patterns released from the intracellular space as well as from the extracellular matrix activate antigen-presenting cells and set pro-inflammatory pathways in motion. This review gives an overview about danger signals representing therapeutic targets with a clinical perspective with a particular focus on extracellular nucleotides and ectonucleotidases. [ABSTRACT FROM AUTHOR]

Acute graft-versus-host disease (GvHD) causes high mortality in patients undergoing allogeneic hematopoietic cell transplantation. An early event in the classical pathogenesis of acute GvHD is tissue damage caused by the conditioning treatment or infection that consecutively leads to translocation of bacterial products [pathogen-associated molecular patterns (PAMPs)] into blood or lymphoid tissue, as well as danger-associated molecular patterns (DAMPs), mostly intracellular components that act as pro-inflammatory agents, once they are released into the extracellular space. A subtype of DAMPs is nucleotides, such as adenosine triphosphate released from dying cells that can activate the innate and adaptive immune system by binding to purinergic receptors. Binding to certain purinergic receptors leads to a pro-inflammatory microenvironment and promotes allogeneic T cell priming. After priming, T cells migrate to the acute GvHD target organs, mainly skin, liver, and the gastrointestinal tract and induce cell damage that further amplifies the release of intracellular components. This review summarizes the role of different purinergic receptors in particular P2X7 and P2Y2 as well as nucleotides in the pathogenesis of GvHD. [ABSTRACT FROM AUTHOR]

Acute graft-versus-host disease ( aGVHD) is a major life-threatening complication of allogeneic haematopoietic cell transplantation (allo- HCT). Here we discuss the aGVHD pathophysiology initiated by multiple signals that cause alloreactive T-cell activation. The outcome of such donor T-cell activation is influenced by T-cell receptor-signal strength, anatomical location, co-stimulatory/co-inhibitory signals and differentiation stage (naive, effector/memory) of T-cells. Additionally, cross-priming of T cells to antigens expressed by pathogens can contribute to aGVHD-mediated tissue injury. In addition to the properties of donor T-cell activation, highly specialized tissue resident cell types, such as innate lymphoid cells, antigen-presenting cells, immune regulatory cells and various intestinal cell populations are critically involved in aGVHD pathogenesis. The role of the thymus and secondary lymphoid tissue injury, non-haematopoietic cells, intestinal microflora, cytokines, chemokines, micro RNAs, metabolites and kinases in aGVHD pathophysiology will be highlighted. Acute GVHD pathogenic mechanisms will be connected to novel therapeutic approaches under development for, and tested in, the clinic. [ABSTRACT FROM AUTHOR]

Allogeneic hematopoietic cell transplantation (allo-HCT) remains the only curative treatment option for myelofibrosis (MF) despite the emergence of novel targeted therapies. To reduce graft rejection and graft-versus-host disease (GvHD), current allo-HCT protocols often include in vivo T lymphocyte depletion using polyclonal anti-thymocyte globulin (ATG). Shortly after ATG administration, an immediate inflammatory response with fever, chills, and laboratory alterations such as cytopenias, elevation of serum C-reactive protein, bilirubin, and transaminases can develop. Here, we explore whether MF patients, who commonly exhibit extramedullary hematopoiesis in the liver, might be particularly susceptible to ATG-induced liver toxicity. To test this hypothesis, we analyzed 130 control and 94 MF patients from three transplant centers treated with or without ATG during the allo-HCT conditioning regimen. Indeed, hyperbilirubinemia was found in nearly every MF patient treated with ATG (MF-ATG 54/60 = 90 %) as compared to non-ATG treated MF (MF-noATG 15/34 = 44.1 %, p < 0.001) and respectively ATG-treated non-MF patients of the control group (control-ATG, 43/77 = 56 %, p < 0.001). In contrast, transaminases were only inconsistently elevated. Hyperbilirubinemia was in most cases self-limiting and not predictive of increased incidence of non-relapse mortality, hepatic sinusoidal obstruction syndrome (SOS) or liver GvHD. In sum, awareness of this stereotypic bilirubin elevation in MF patients treated with ATG provides a relatively benign explanation for hyperbilirubinemia occurring in these patients during the early transplant. However, attention to drug levels of biliary excreted drugs is warranted, since altered bile flow may influence their clearance and enhance toxicity (e.g., busulfan, antifungal agents). [ABSTRACT FROM AUTHOR]

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 their radiation 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. [ABSTRACT FROM AUTHOR]

The successful treatment of various hematologic diseases with allogeneic hematopoietic cell transplantation is often limited by the occurrence of graft-versus-host disease (GvHD). Several microRNAs (miRs) have recently been shown to impact the biology of GvHD by regulating pro- as well as anti-inflammatory target genes. There is increasing evidence that a single miR can have different effects by preferentially targeting certain genes depending on the cell type that the miR is analyzed in. This review will focus on the role of miRs in myeloid cells during the development of acute and chronic GvHD and autoimmune diseases. Because miRs act on the expression of multiple target genes and may thereby influence the immune system at different functional levels, they are potentially attractive targets for the modification of allogeneic immune responses using miR mimics and inhibitors. [ABSTRACT FROM AUTHOR]

Background: Acute graft-versus-host disease (aGVHD) poses a major limitation for broader therapeutic application of allogeneic hematopoietic cell transplantation (allo-HCT). Early diagnosis of aGVHD remains difficult and is based on clinical symptoms and histopathological evaluation of tissue biopsies. Thus, current aGVHD diagnosis is limited to patients with established disease manifestation. Therefore, for improved disease prevention it is important to develop predictive assays to identify patients at risk of developing aGVHD. Here we address whether insights into the timing of the aGVHD initiation and effector phases could allow for the detection of migrating alloreactive T cells before clinical aGVHD onset to permit for efficient therapeutic intervention. Methods: Murine major histocompatibility complex (MHC) mismatched and minor histocompatibility antigen (miHAg) mismatched allo-HCT models were employed to assess the spatiotemporal distribution of donor T cells with flow cytometry and in vivo bioluminescence imaging (BLI). Daily flow cytometry analysis of peripheral blood mononuclear cells allowed us to identify migrating alloreactive T cells based on homing receptor expression profiles. Results: We identified a time period of 2 weeks of massive alloreactive donor T cell migration in the blood after miHAg mismatch allo-HCT before clinical aGVHD symptoms appeared. Alloreactive T cells upregulated α4β7 integrin and P-selectin ligand during this migration phase. Consequently, targeted preemptive treatment with rapamycin, starting at the earliest detection time of alloreactive donor T cells in the peripheral blood, prevented lethal aGVHD. Conclusions: Based on this data we propose a critical time frame prior to the onset of aGVHD symptoms to identify alloreactive T cells in the peripheral blood for timely and effective therapeutic intervention. [ABSTRACT FROM AUTHOR]

The therapeutic principle of allogeneic haematopoietic cell transplantation (allo- HCT) is based on an active donor immune system that eliminates host-derived tumour cells. We hypothesized that in addition to the alloantigen-driven anti-tumour response, disruption of the immunological microenvironment within the tumour is responsible for its elimination after allo- HCT. We observed that induction of graft-versus-host disease ( GvHD) significantly reduced the abundance of luc+ Fox P3+ regulatory T ( Treg) cells in the tumour tissue, which is indicative of impaired or over-ridden tumour recruitment signals towards Treg cells. Analysis of the intestines and liver revealed chemokines and purine nucleotides as candidates for attracting Treg to these sites of inflammation. Despite its expression on tissue-residing Treg cells, the chemokine receptor CCR3 was not critical for Treg-cell function following allo- HCT. Extracellular ATP can attract immune cells via P2 Y2. P2 Y2 was found to be expressed on Treg cells, and we found a partial reduction of GvHD prevention when P2 Y2−/− rather than P2 Y2+/+ Treg cells were given. Exogenous local inflammation reduced Treg-cell accumulation in the tumour, suggesting a potential clinical approach to prevent Treg-cell-mediated tumour escape. In conclusion, we demonstrate that GvHD-related inflammation reduced Treg-cell numbers at the tumour sites, which may in turn help to explain the observation that patients with GvHD have a lower risk of tumour relapse. [ABSTRACT FROM AUTHOR]

Extensive cell death with consecutive release of danger signals can cause immune-mediated tissue destruction. The abundance of cell death is likely to determine the relevance of the danger signals as physiological mechanisms that counteract immune activation may be overruled. Such constellation is conceivable in chemo-/radiotherapy-induced tissue damage, reperfusion injury, trauma, and severe infection. Studies on graft-versus-host disease (GvHD) development have to consider the effects of chemo-/radiotherapy-related tissue damage leading to the release of exogenous and endogenous danger signals. Our previous work has demonstrated a role for adenosine-5′-triphosphate (ATP) as an endogenous danger signal in GvHD. Besides ATP, uric acid or soluble extracellular matrix components are functional danger signals that activate the NLRP3 inflammasome when released from dying cells or from extracellular matrix. In contrast to sterile inflammation, GvHD is more complex since bacterial components that leak through damaged intestinal barriers and the skin can activate pattern recognition receptors and directly contribute to GvHD pathogenesis. These exogenous danger signals transmit immune activation via toll-like receptors and NOD-like receptors of the innate immune system. This review covers both the impact of endogenous and exogenous danger signals activating innate immunity in GvHD. [ABSTRACT FROM AUTHOR]

Danger signals released upon cell damage can cause excessive immune-mediated tissue destruction such as that found in acute graft-versus-host disease (GVHD), allograft rejection and systemic inflammatory response syndrome. Given that ATP is found in small concentrations in the extracellular space under physiological conditions, and its receptor P2X7R is expressed on several immune cell types, ATP could function as a danger signal when released from dying cells. We observed increased ATP concentrations in the peritoneal fluid after total body irradiation, and during the development of GVHD in mice and in humans. Stimulation of antigen-presenting cells (APCs) with ATP led to increased expression of CD80 and CD86 in vitro and in vivo and actuated a cascade of proinflammatory events, including signal transducer and activator of transcription-1 (STAT1) phosphorylation, interferon-γ (IFN-γ) production and donor T cell expansion, whereas regulatory T cell numbers were reduced. P2X7R expression increased when GVHD evolved, rendering APCs more responsive to the detrimental effects of ATP, thereby providing positive feedback signals. ATP neutralization, early P2X7R blockade or genetic deficiency of P2X7R during GVHD development improved survival without immune paralysis. These data have major implications for transplantation medicine, as pharmacological interference with danger signals that act via P2X7R could lead to the development of tolerance without the need for intensive immunosuppression. [ABSTRACT FROM AUTHOR]

Acute graft-versus-host disease (GVHD) is a primary T-cell-mediated complication of allogeneic hematopoietic stem cell transplantation (HSCT), occurring when donor-derived T cells are stimulated by host antigen-presenting cells (APCs), enhanced by proinflammatory cytokines such as interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha. Recent data indicate that besides differences in major histocompatibility and minor histocompatibility antigens, cytokine gene polymorphisms have a predictive value for the complication of GVHD. Patients with a high anti-inflammatory IL-10 production have been demonstrated to be protected from GVHD while patients with high TNF-alpha serum levels were more at risk for GVHD. Pharmacological immunosuppression for GVHD prophylaxis and therapy, including unspecific approaches with corticosteroids or methotrexate (MTX), as well as more specific therapy with cyclosporin A (CsA), tacrolimus (FK506), sirolimus, mycophenolate mofetil (MMF), antithymocyte globulin (ATG), and monoclonal antibodies (MAbs) directed against CD3, CD25, CD52, cytotoxic T-lymphocyte antigen (CTLA)-4, CD40 ligand, or TNF-alpha, have been proven to be effective. Recent data on novel techniques to selectively deplete alloreactive T cells by removal, destruction, or anergy induction while preserving leukemia-specific T-cell clones suggest a clinical benefit from these approaches. Gene-modified T cells that can selectively be depleted and CD4+CD25+ regulatory T cells are under investigation for their ability to modulate alloreactivity after HSCT. With a better understanding of the immunopathogenesis of acute GVHD and the technical improvement of recently described therapeutic approaches, such as removal of naive T cells, selection of Th2 cells, suicide gene transduced T cells, and adoptive transfer of regulatory T cells, the use of alloreactivity as a treatment modality may be expanded to nonhematological disease entities such as solid tumors or autoimmune disorders. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including clinical studies on chronic graft-versus host disease (GVHD), pathogenic B-cell receptor signaling, and production of antibodies.

As a result of impressive increases in our knowledge of rodent and human immunology, the understanding of the pathophysiologic mechanisms underlying graft-versus-host disease (GVHD) has dramatically improved in the past 15 years. Despite improved knowledge, translation to clinical care has not proceeded rapidly, and results from experimental models have been inconsistent in their ability to predict the clinical utility of new therapeutic agents. In parallel, new tools in immunology have allowed in-depth analyses of the human system and have recently been applied in the field of clinical GVHD. Notwithstanding these advances, there is a relative paucity of mechanistic insights into human translational research, and this remains an area of high unmet need. Here we review selected recent advances in both preclinical experimental transplantation and translational human studies, including new insights into human immunology, the microbiome, and regenerative medicine. We focus on the fact that both approaches can interactively improve our understanding of both acute and chronic GVHD biology and open the door to improved therapeutics and successes. [ABSTRACT FROM AUTHOR]

An editorial is presented which discusses graft-versus-leukemia (GVL) effects is relied upon heavily by a large group of hematological malignancies while using allogeneic hematopoietic cell transplantation (allo-HCT) as a curative approach.

The author comments on a study by T. Toubai et al on sialic acid-binding immunoglobulin-like lectins (Siglecs) which are immune receptors whose main function is to mediate inhibitory signaling in immune cells which, in turn functions as a natural antagonist of damage-associated molecular patterns (DAMPs). Topics include the unique ability of Siglecs to recognize sialylated carbohydrates, and a simplified sketch of Siglec-G-CD24 axis in graft-versus-host-disease (GVHD).

Clinical studies investigating the impact of natural killer (NK) cells in allogeneic hematopoietic stem cell transplantation settings have yielded promising results. However, NK cells are a functionally and phenotypically heterogeneous population. Therefore, we addressed the functional relevance of specific NK cell subsets distinguished by expression of CD117, CD27 and CD11b surface markers in graft-versus-leukemia (GVL)-reaction and graft-versus-host-disease (GVHD). Our results clearly demonstrate that the subset of c-Kit−CD27−CD11b+NK cells expressed multiple cytotoxic pathway genes and provided optimal graft-versus-leukemia-effects, while significantly reducing T cell proliferation induced by allogeneic dendritic cells. Furthermore, these NK cells migrated to inflamed intestinal tissues where graft-versus-host-colitis was efficiently mitigated. For the first time, we identified the c-Kit−CD27−CD11b+NK cell population as the specific effector NK cell subset capable of significantly diminishing GVHD in fully mismatched bone marrow transplantation settings. In conclusion, the subset of c-Kit−CD27−CD11b+NK cells not only supports GVL, but also plays a unique role in the protection against GVHD by migrating to the peripheral GVHD target organs where they exert efficient immunoregulatory activities. These new insights demonstrate the importance of selecting the optimal NK cell subset for cellular immunotherapy following allogeneic hematopoietic stem cell transplantation. [ABSTRACT FROM PUBLISHER]

Graft-versus-host disease (GVHD) continues to be a leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Recent insights into intestinal homeostasis and uncovering of new pathways and targets have greatly reconciled our understanding of GVHD pathophysiology and will reshape contemporary GVHD prophylaxis and treatment. Gastrointestinal (GI) GVHD is the major cause of mortality. Emerging data indicate that intestinal stem cells (ISCs) and their niche Paneth cells are targeted, resulting in dysregulation of the intestinal homeostasis and microbial ecology. The microbiota and their metabolites shape the immune system and intestinal homeostasis, and they may alter host susceptibility to GVHD. Protection of the ISC niche system and modification of the intestinal microbiota and metabolome to restore intestinal homeostasis may, thus, represent a novel approach to modulate GVHD and infection. Damage to the intestine plays a central role in amplifying systemic GVHD by propagating a proinflammatory cytokine milieu. Molecular targeting to inhibit kinase signaling may be a promising approach to treat GVHD, ideally via targeting the redundant effect of multiple cytokines on immune cells and enterocytes. In this review, we discuss insights on the biology of GI GVHD, interaction of microflora and metabolome with the hosts, identification of potential new target organs, and identification and targeting of novel T cell–signaling pathways. Better understanding of GVHD biology will, thus, pave a way to develop novel treatment strategies with great clinical benefits. [ABSTRACT FROM AUTHOR]

• First-line treatment is applied relatively homogeniously among German, Austrian, and Swiss transplant centers except initial treatment of progressive onset. • Second-line treatment varies considerably with new agents entering clinic through the last 10 years. • Even in the presence of evidence clinical practice in treatment of lung manifestations varies considerably. Chronic graft-versus-host disease (cGVHD) remains the leading cause of late morbidity and mortality. Despite the growing number of treatment options in cGVHD, evidence remains sparse. The German-Austrian-Swiss GVHD Consortium performed a survey on clinical practice in treatment of cGVHD among transplant centers in Germany, Austria, and Switzerland in 2009 and 2018 and compared the results. The survey performed in 2009 contained 20 questions on first-line treatment and related issues and 4 questions on second-line scenarios followed by a survey on all systemic and topic treatment options known and applied, with 31 of 36 transplant centers (86%) responding. The survey in 2018 repeated 7 questions on first-line treatment and 3 questions on second-line scenarios followed by an updated survey on all current systemic treatment options known and applied, with 29 of 66 centers (43%) responding. In summary, the results show a large overlap of first-line treatment practice between centers and the 2 surveys because of a lack of new data that changes practice, except significant heterogeneity of treatment of cGVHD progressive onset type, which can be explained by the lack of trials focusing on this high-risk entity. In contrast, treatment options applied to second-line therapy vary considerably, with new agents like ibrutinib and ruxolitinib entering clinical practice. Moreover, treatment of bronchiolitis obliterans syndrome demonstrates heterogeneity in applied therapeutic options and sequence because of a lack of controlled data and different conclusions from already existing evidence. In summary, the survey results demonstrate an increasing number of treatment options applied to cGVHD accompanied by a significant heterogeneity in second-line treatment and underline the urgent need for clinical trials and registry analyses on rare entities with high mortality like progressive onset type and lung involvement of cGVHD. [ABSTRACT FROM AUTHOR]

Recent studies have underscored the critical role of retinoic acid (RA) in the development of lineage-committed CD4 and CD8 T cells in vivo. We have shown that under acute graft-versus-host disease (GVHD) inflammatory conditions, RA is upregulated in the intestine and is proinflammatory, as GVHD lethality was attenuated when donor allogeneic T cells selectively expressed a dominant negative RA receptor α that blunted RA signaling. RA can function in an autocrine and paracrine fashion, and as such, the host cell lineage responsible for the production of RA metabolism and the specific RA-metabolizing enzymes that potentiate GVHD severity are unknown. In this study, we demonstrate that enhancing RA degradation in the host and to a lesser extent donor hematopoietic cells by overexpressing the RA-catabolizing enzyme CYP26A1 reduced GVHD. RA production is facilitated by retinaldehyde isoform-2 (RALDH2) preferentially expressed in dendritic cells (DCs). Conditionally deleted RA-synthesizing enzyme RALDH2 in host or to a lesser extent donor DCs reduced GVHD lethality. Improved survival in recipients with RALDH2-deleted DCs was associated with increased T cell death, impaired T effector function, increased regulatory T cell frequency, and augmented coinhibitory molecule expression on donor CD4+ T cells. In contrast, retinaldehydrogenase isoform-1 (RALDH1) is dominantly expressed in intestinal epithelial cells. Unexpectedly, conditional host intestinal epithelial cells RALDH1 deletion failed to reduce GVHD. These data demonstrate the critical role of both donor and especially host RALDH2+ DCs in driving murine GVHD and suggest RALDH2 inhibition or CYP26A1 induction as novel therapeutic strategies to prevent GVHD. [ABSTRACT FROM AUTHOR]

Highlights • Incidence of BOS after reduced-intensity conditioning. • Mild small airway disease before transplantation predicts bronchiolitis obliterans. • Pulmonary cause of death is linked to pretransplantation severe small airway disease. • Mixed lung disease after transplantation is associated with non-relapse mortality Abstract Lung function deterioration contributes to treatment-related morbidity and mortality in patients after allogeneic hematopoietic cell transplantation (allo-HCT). Better understanding of impaired lung function including bronchiolitis obliterans syndrome (BOS) as chronic manifestation of graft-versus-host disease (GVHD) might improve outcomes of patients after allo-HCT. To detect early pulmonary function test abnormalities associated with BOS incidence and outcome after allo-HCT, we performed a retrospective analysis of homogenous-treated 445 patients (median age, 61.9 years; range, 19 to 76 years) with a reduced intensity/toxicity conditioning protocol. The cumulative incidence of BOS was 4.1% (95% confidence interval [CI], 2.6 to 6.4) at 1 year and 8.6% (95% CI, 6.3 to 11.6) at 5 years after allo-HCT with a median follow-up of 43.2 months (range, 3.3 to 209 months). In multivariate analysis, pre-existence of moderate small airway disease reflected by decreased midexpiratory flows before allo-HCT was associated with increased risk for BOS development. In addition, severe small airway disease before allo-HCT and combined restrictive/obstructive lung disease at day +100 after allo-HCT were associated with higher risk for nonrelapse mortality (NRM) due mainly to pulmonary cause of death. In summary, we identified novel pulmonary function test abnormalities prior and after allo-HCT associated with BOS development and NRM. These findings might help to identify a risk population and result in personalized GVHD prophylaxis and preventive or early therapeutic interventions. [ABSTRACT FROM AUTHOR]

Conditioning-induced damage of the intestinal tract plays a critical role during the onset of acute graft-versus-host disease (GVHD). Therapeutic interference with these early events of GVHD is difficult, and currently used immunosuppressive drugs mainly target donor T cells. However, not donor T cells but neutrophils reach the sites of tissue injury first, and therefore could be a potential target for GVHD prevention. A detailed analysis of neutrophil fate during acute GVHD and the effect on T cells is difficult because of the short lifespan of this cell type. By using a novel photoconverter reporter system, we show that neutrophils that had been photoconverted in the ileum postconditioning later migrated to mesenteric lymph nodes (mLN). This neutrophil migration was dependent on the intestinal microflora. In the mLN, neutrophils colocalized with T cells and presented antigen on major histocompatibility complex (MHC)-II, thereby affecting T cell expansion. Pharmacological JAK1/JAK2 inhibition reduced neutrophil influx into the mLN and MHC-II expression, thereby interfering with an early event in acute GVHD pathogenesis. In agreement with this finding, neutrophil depletion reduced acute GVHD. We conclude that neutrophils are attracted to the ileum, where the intestinal barrier is disrupted, and then migrate to the mLN, where they participate in alloantigen presentation. JAK1/JAK2-inhibition can interfere with this process, which provides a potential therapeutic strategy to prevent early events of tissue damage-related innate immune cell activation and, ultimately, GVHD. [ABSTRACT FROM AUTHOR]

Graft-versus-host disease (GVHD) continues to be a leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Recent insights into intestinal homeostasis and uncovering of new pathways and targets have greatly reconciled our understanding of GVHD pathophysiology and will reshape contemporary GVHD prophylaxis and treatment. Gastrointestinal (GI) GVHD is the major cause of mortality. Emerging data indicate that intestinal stem cells (ISCs) and their niche Paneth cells are targeted, resulting in dysregulation of the intestinal homeostasis and microbial ecology. The microbiota and their metabolites shape the immune system and intestinal homeostasis, and they may alter host susceptibility to GVHD. Protection of the ISC niche system and modification of the intestinal microbiota and metabolome to restore intestinal homeostasis may, thus, represent a novel approach to modulate GVHD and infection. Damage to the intestine plays a central role in amplifying systemic GVHD by propagating a proinflammatory cytokine milieu. Molecular targeting to inhibit kinase signaling may be a promising approach to treat GVHD, ideally via targeting the redundant effect of multiple cytokines on immune cells and enterocytes. In this review, we discuss insights on the biology of GI GVHD, interaction of microflora and metabolome with the hosts, identification of potential new target organs, and identification and targeting of novel T cell–signaling pathways. Better understanding of GVHD biology will, thus, pave a way to develop novel treatment strategies with great clinical benefits. [ABSTRACT FROM AUTHOR]

During allogeneic hematopoietic cell transplantation (alloHCT), nonhematopoietic cell interleukin-33 (IL-33) is augmented and released by recipient conditioning to promote type 1 alloimmunity and lethal acute graft-versus-host disease (GVHD). Yet, IL-33 is highly pleiotropic and exhibits potent immunoregulatory properties in the absence of coincident proinflammatory stimuli. We tested whether peri-alloHCT IL-33 delivery can protect against development of GVHD by augmenting IL-33-associated regulatory mechanisms. IL-33 administration augmented the frequency of regulatory T cells (Tregs) expressing the IL-33 receptor, suppression of tumorigenicity-2 (ST2), which persist following total body irradiation. ST2 expression is not exclusive to Tregs and IL-33 expands innate immune cells with regulatory or reparative properties. However, selective depletion of recipient Foxp3+ cells concurrent with peri-alloHCT IL-33 administration accelerated acute GVHD lethality. IL-33-expanded Tregs protected recipients from GVHD by controlling macrophage activation and preventing accumulation of effector T cells in GVHD-target tissue. IL-33 stimulation of ST2onTregs activates p38MAPK, which drives expansion of theST2+ Treg subset. Associated mechanistic studies revealed that proliferating Tregs exhibit IL-33-independent upregulation of ST2 and the adoptive transfer of st2+ but not st2- Tregs mediated GVHD protection. In total, these data demonstrate the protective capacity of peri-alloHCT administration of IL-33 and IL-33-responsive Tregs in mouse models of acute GVHD. These findings provide strong support that the immunoregulatory relationship between IL-33 and Tregs can be harnessed therapeutically to prevent GVHD after alloHCT for treatment of malignancy or as a means for tolerance induction in solid organ transplantation. [ABSTRACT FROM AUTHOR]

Acute graft-versus-host disease (GvHD) is a life-threatening complication of allogeneic hematopoietic cell transplantation. During the initiation phase of acute GvHD, endogenous danger signals such as ATP are released and inform the innate immune system via activation of the purinergic receptor P2X7 that a noninfectious damage has occurred. A second ATP-activated purinergic receptor involved in inflammatory diseases is P2Y2. In this study, we used P2y2-/- mice to test the role of this receptor in GvHD. P2y2-/- recipients experienced reduced GvHD-related mortality, IL-6 levels, enterocyte apoptosis, and histopathology scores. Chimeric mice with P2y2 deficiency restricted to hematopoietic tissues survived longer after GvHD induction than did wild-type mice. P2y2 deficiency of the recipient was connected to lower levels of myeloperoxidase in the intestinal tract of mice developing GvHD and a reduced myeloid cell signature. Selective deficiency of P2Y2 in inflammatory monocytes decreased GvHD severity. Mechanistically, P2y2-/- inflammatory monocytes displayed defective ERK activation and reactive oxygen species production. Compatible with a role of P2Y2 in human GvHD, the frequency of P2Y2+ cells in inflamed GvHD lesions correlated with histopathological GvHD severity. Our findings indicate a novel function for P2Y2 in ATP-activated recipient myeloid cells during GvHD, which could be exploited when targeting danger signals to prevent GvHD. [ABSTRACT FROM AUTHOR]

Myeloid-derived suppressor cells (MDSCs) are a naturally occurring immune regulatory population associated with inhibition of ongoing inflammatory responses. In vitro generation of MDSCs from bone marrow has been shown to enhance survival in an acute model of lethal graft-versus-host disease (GVHD). However, donor MDSC infusion only partially ameliorates GVHD lethality. In order to improve the potential therapeutic benefit and ultimately survival outcomes, we set out to investigate the fate of MDSCs after transfer in the setting of acute GVHD (aGVHD). MDSCs transferred to lethally irradiated recipients of allogeneic donor hematopoietic grafts are exposed to an intense inflammatory environment associated with aGVHD, which we now show directly undermines their suppressive capacity. Under a conditioning regimen and GVHD inflammatory settings, MDSCs rapidly lose suppressor function and their potential to inhibit GVHD lethality, which is associated with their induced conversion toward a mature inflammasome-activated state. We find even brief in vitro exposure to inflammasome-activating mediators negates the suppressive potential of cultured murine and human-derived MDSCs. Consistent with a role for the inflammasome, donor MDSCs deficient in the adaptor ASC (apoptosis-associated speck-like protein containing a CARD), which assembles inflammasome complexes, conferred improved survival of mice developing GVHD compared with wild-type donor MDSCs. These data suggest the use of MDSCs as a therapeutic approach for preventing GVHD and other systemic inflammatory conditions will be more effective when combined with approaches limiting in vivo MDSC inflammasome activation, empowering MDSCs to maintain their suppressive potential. [ABSTRACT FROM AUTHOR]

Members of the B7 family have been shown to be important for regulating immune responses by providing either positive or negative costimulatory signals. The function of B7-H3 has been controversial. We show that B7-H3 is upregulated in graft-versus-host disease (GVHD) target organs, including the colon, liver, and lung. Infusion of allogeneic donor T cells into B7-H3-/- vs wild-type (WT) recipients resulted in increased GVHD lethality associated with increased T-cell proliferation, colonic inflammatory cytokines, and destruction of epithelial barriers. Allogeneic B7-H3-/- vs WT donor T cells also had increased T-cell proliferation and GVHD lethality associated with increased proliferation and cytokine secretion in the spleen, intraepithelial lymphocyte inflammatory cytokines, and intestinal permeability. Both resting and activated regulatory T cells (Tregs) lack B7-H3 messenger RNA. Consistent with these data, GVHD was augmented in recipients of B7-H3-/- Treg-depleted grafts. In two delayed lymphocyte infusion (DLI) models, T cells lacking B7-H3 are capable of providing graft-versus-leukemia (GVL) effects. We conclude that B7-H3 is responsible for providing a negative costimulatory signal. Our studies provide support for developing and testing new therapies directed toward the B7-H3 pathway, including approaches to augment host B7-H3 early after bone marrow transplantation to prevent GVHD and to develop potent antagonistic antibodies later after transplant to facilitate DLl-mediated GVL without GVHD complications. [ABSTRACT FROM AUTHOR]

The common γ chain (CD132) is a subunit of the interleukin (IL) receptors for IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21. Because levels of several of these cytokines were shown to be increased in the serum of patients developing acute and chronic graft-versus-host disease (GVHD), we reasoned that inhibition of CD132 could have a profound effect on GVHD. We observed that anti-CD132 monoclonal antibody (mAb) reduced acute GVHD potently with respect to survival, production of TNF, IFN-γ and IL-6, and GVHD histopathology. Anti-CD132 mAb afforded protection from GVHD partly via inhibition of granzyme B production in CD8 T cells, while exposure of CD8 T cells to IL-2, IL-7, IL-15, and IL-21 increased granzyme B production. Also, T cells exposed to anti-CD132 mAb displayed a more naive phenotype in microarray based analyses and showed reduced JAK3 phosphorylation upon activation. Consistent with a role of JAK3 in GVHD, Jak3-/- T cells caused less severe GVHD. Additionally, anti-CD132 mAb treatment of established chronic GVHD reversed liver and lung fibrosis, and pulmonary dysfunction characteristic of bronchiolitis obliterans. We conclude that acute GVHD and chronic GVHD, caused by T cells activated by common γ-chain cytokines, each represent therapeutic targets for anti-CD132 mAb immunomodulation. [ABSTRACT FROM AUTHOR]

Acute graft-versus-host disease (GVHD) limits the success of allogeneic hematopoietic cell transplantation (allo-HCT); therefore, a better understanding of its biology may improve therapeutic options. We observed miR-146a up-regulation in T cells of mice developing acute GVHD compared with untreated mice. Transplanting miR-146a-/- T cells caused increased GVHD severity, elevated tumor necrosis factor (TNF) serum levels, and reduced survival. TNF receptor-associated factor 6 (TRAF6), a verified target of miR-146a, was up-regulated in miR-146a-/- T cells following alloantigen stimulation. Higher TRAF6 levels translated into increased nuclear factor-κB activity and TNF production in miR-146a-/- T cells. Conversely, the detrimental effect of miR-146a deficiency in T cells was antagonized by TNF blockade, whereas phytochemical induction of miR-146a or its overexpression using a miR-146a mimic reduced GVHD severity. In humans, the minor genotype of the single nucleotide polymorphism rs2910164 in HCT donors, which reduces expression of miR-146a, was associated with severe acute GVHD (grade III/IV). We show that miR-146a functions as a negative regulator of donor T cells in GVHD by targeting TRAF6, leading to reduced TNF transcription. Because miR-146a expression can be exogenously enhanced, our results provide a novel targeted molecular approach to mitigate GVHD. [ABSTRACT FROM AUTHOR]

Acute graft-versus-host disease (GvHD) is a complex process involving endothelial damage and neovascularization. Better understanding of the pathophysiology of neovascularization during GvHD could help to target this process while leaving T-cell function intact. Under ischemic conditions, neovascularization is regulated by different micro RNAs (miRs), which potentially play a role in inflamed hypoxic GvHD target organs. We observed strong neovascularization in the murine inflamed intestinal tract (IT) during GvHD. Positron emission tomography imaging demonstrated abundant αvβ3 integrin expression within intestinal neovascularization areas. To interfere with neovascularization, we targeted αv integrin-expressing endothelial cells, which blocked their accumulation in the IT and reduced GvHD severity independent of immune re-constitution and graft-versus-tumor effects. Additionally, enhanced neovascularization and αv integrin expression correlated with GvHD severity in humans. Expression analysis of miRs in the inflamed IT of mice developing GvHD identified miR-100 as significantly downregulated. Inactivation of miR-100 enhanced GvHD indicating a protective role for miR-100 via blocking inflammatory neovascularization. Our data from the mouse model and patients indicate that inflammatory neovascularization is a central event during intestinal GvHD that can be inhibited by targeting αv integrin. We identify negative regulation of GvHD-related neovascularization by miR-1 00, which indicates common pathomechanistic features of GvHD and ischemia. [ABSTRACT FROM AUTHOR]

Extracellular ATP and adenosine have immunoregulatory roles during inflammation. Elevated extracellular ATP is known to exacerbate GVHD, and the pharmacologic activation of the adenosine A2A receptor is protective. However, the role of endogenous adenosine is unknown. We used gene-targeted mice and a pharmacologic inhibitor to test the role of adenosine generated by CD73/ecto-5'-nucleotidase in GVHD. In allogeneic transplants, both donor and recipient CD73 were protective, with recipient CD73 playing the dominant role. CD73 deficiency led to enhanced T-cell expansion and IFN-&ggr; and IL-6 production, and the migratory capacity of Cd73-&sol;_h T cells in vitro was increased. However, the number of regulatory T cells and expression of costimulatory molecules on antigen-presenting cells were unchanged. A2A receptor deficiency led to increased numbers of allogeneic T cells, suggesting that signaling through the A2A receptor via CD73-generated adenosine is a significant part of the mechanism by which CD73 limits the severity of GVHD. Pharmacologic blockade of CD73 also enhanced graft-versus-tumor activity. These data have clinical implications, as both the severity of GVHD and the strength of an alloimmune antitumor response could be manipulated by enhancing or blocking CD73 activity or adenosine receptor signaling depending on the clinical indication. [ABSTRACT FROM AUTHOR]

Graft-versus-host disease (GVHD) in the gastrointestinal (GI) tract is the principal determinant of lethality following allogeneic bone marrow transplantation (BMT). Here, we examined the mechanisms that initiate GVHD, including the relevant antigen-presenting cells. MHC class II was expressed on intestinal epithelial cells (IECs) within the ileum at steady state but was absent from the IECs of germ-free mice. IEC-specific deletion of MHC class II prevented the initiation of lethal GVHD in the GI tract. MHC class II expression on IECs was absent from mice deficient in the TLR adaptors MyD88 and TRIF and required IFNγ secretion by lamina propria lymphocytes. IFNγ responses are characteristically driven by IL-12 secretion from myeloid cells. Antibiotic-mediated depletion of the microbiota inhibited IL-12/23p40 production by ileal macrophages. IL-12/23p40 neutralization prevented MHC class II upregulation on IECs and initiation of lethal GVHD in the GI tract. Thus, MHC class II expression by IECs in the ileum initiates lethal GVHD, and blockade of IL-12/23p40 may represent a readily translatable therapeutic strategy. • The microbiota influences MHC class II expression on IECs in the ileum • MHC class II expression on IECs requires an IL-12-IFNγ cytokine axis • MHC class II+ IECs present antigen, activate CD4+ T cells, and initiate lethal gut GVHD • IL-12/23p40 neutralization pretransplant prevents the initiation of lethal GVHD Graft-versus-host disease in the gastrointestinal tract is the principal determinant of lethality following allogeneic bone marrow transplantation. Koyama et al. find that MHC class II-dependent antigen presentation by ileal intestinal epithelial cells (IECs) is critical for the initiation of lethal GVHD in the gut, define the requirements for IEC MHC class II expression, and propose IL-12 neutralization as a therapeutic strategy for GVHD. [ABSTRACT FROM AUTHOR]