Relation of an interleukin-23 receptor gene polymorphism to graft-versus-host disease after hematopoietic-cell transplantation

Current Advances in Graft-versus-host Disease After Intestinal Transplantation

Graft-versus-host disease (GvHD) remains a potentially fatal complication following intestinal transplant (ITx). Over the past decade, advances in the understanding of the pathophysiology of this complex immunological phenomenon have led to the reassessment of the host systemic immune response and have created a gateway for novel preventive and therapeutic strategies. Although sufficient evidence dictates the use of corticosteroids as a first-line option, the treatment for refractory disease remains contentious and lacks a standardized therapeutic approach. Timely diagnosis remains crucial, and the advent of chimerism detection and immunological biomarkers have transformed the identification, prognostication, and potential for survival after GvHD in ITx. The objectives of the following review aim to discuss the clinical and diagnostic features, pathophysiology, advances in immune biomarkers, as well as therapeutic opportunities in the prevention and treatment of GvHD in ITx.

Diyabetik Periferik Polinöropatili Hastalarda İnterlökin-23R Gen Polimofizmleri

Amaç: Diyabetik nöropatinin patogenezinde proinflamatuar ve nörovasküler değişiklikler suçlanmaktadır. Diyabetin vasküler inflamasyonu tetiklediği kabul edilse de inflamasyonun da diyabeti tetikleyebileceği öne sürülmüştür. İnterlökin-23 (IL-23) aktive makrofajlar ve dendritik hücreler tarafından salgılanan proinflamatuar bir sitokindir. Interleukin-23R'nin kronik inflamatuar hastalıklarda kritik bir rolü olduğu bilinmektedir. Bu çalışmanın amacı, IL-23R polimorfizmi ile diyabetik periferik nöropati arasındaki ilişkiyi incelemektir. Yöntem: Nöroloji polikliniğine başvuran 50 diyabetik periferik nöropati hastası ve hasta grubuna yaş ve cinsiyet açısından uyumlu 52 sağlıklı kontrol çalışmaya dahil edildi. Çalışmaya katılmayı kabul eden gönüllülerin tamamına elektromiyografi uygulandı ve EDTA'lı tüplere 2 ml kan örneği alındı. Pyrosequencing yöntemi ile IL-23R gen polimorfizmi analiz edildi. Bulgular: IL-23R gen varyantları rs2201841, rs199542433, rs201052419, rs11209026 diyabetik periferik nöropati (DPN) hastalarında ve kontrol grubunda analiz edildi. IL23R polimorfizmleri sıklıkları açısından hasta ve kontrol grupları arasında anlamlı bir fark saptanmadı. Ancak, odd’s oranlarına bakıldığında, rs2201841'in koruyucu rolü var gibi görünmekte, rs199542433 hem baskın hem de çekinik modellerde ve rs11209026 sadece çekinik modelde, DPN için 10 kata kadar daha yüksek risklerle ilişkili olabileceği görünmektedir. Sonuç: IL-23R gen polimorfizminin birçok otoimmün ve inflamatuar hastalık ile ilişkili olduğu gösterilmiştir. İnflamasyonun diyabet üzerinde önemli bir etkisi olduğu bilinmektedir. Diyabetik periferik nöropatide IL-23R gen polimorfizminin sıklığı anlamlı değildi. Çalışmamız diyabetik periferik nöropatide IL-23R gen polimorfizminin rolünü araştıran tek ve ilk çalışmadır. Etnik köken, genetik çalışmalarda çok önemlidir ve bu çalışmanın başka etnik kökene sahip hastalarda yapılması ve daha geniş çalışma gruplarının alınması, bize ilerisi için daha net bilgiler verecektir.

Anti-ICOS mAb Targets Pathogenic IL-17A-expressing Cells in Canine Model of Chronic GVHD

BACKGROUND

Chronic graft-versus-host disease (GVHD) is a significant cause of morbidity and mortality in transplant patients. We have previously shown that 3 doses of an anti-inducible costimulator (ICOS) mAb transiently ameliorated symptoms and extended survival of dogs affected by chronic GVHD over that of control dogs. The purpose of this study was to specifically correlate changes in T-cell populations in the peripheral blood with anti-ICOS treatment and chronic GVHD progression and regression to reach a better understanding of the mechanism of the disease and prioritize future studies.

METHODS

Peripheral blood cells from canines transplanted with DLA-mismatched bone marrow and peripheral blood mononuclear cells to generate chronic GVHD were analyzed by flow cytometry using a panel of antibodies specific to helper and cytolytic T cells.

RESULTS

Chronic GVHD was specifically associated with an increase in CD4+ICOS+ cells, ICOS+ cells expressing IL-17A, and CD8+ cells generating granzyme B. Treatment with anti-ICOS mAb at onset of chronic GVHD symptoms specifically targeted IL-17A+-expressing cells, transiently relieved symptoms, and lengthened survival but was unable to reduce the percentage of CD8+ T-cells expressing granzyme B.

CONCLUSIONS

These studies suggested a role for both CD4+ and CD8+ T cells in pathogenesis of chronic GVHD in the canine model. We propose that future studies should focus on further extending survival by developing a treatment that would control both CD4+ and CD8+ T cells.

Rejection of intestinal allotransplants is driven by memory T helper type 17 immunity and responds to infliximab

Intestinal transplantation (ITx) can be life-saving for patients with advanced intestinal failure experiencing complications of parenteral nutrition. New surgical techniques and conventional immunosuppression have enabled some success, but outcomes post-ITx remain disappointing. Refractory cellular immune responses, immunosuppression-linked infections, and posttransplant malignancies have precluded widespread ITx application. To shed light on the dynamics of ITx allograft rejection and treatment resistance, peripheral blood samples and intestinal allograft biopsies from 51 ITx patients with severe rejection, alongside 37 stable controls, were analyzed using immunohistochemistry, polychromatic flow cytometry, and reverse transcription-PCR. Our findings inform both immunomonitoring and treatment. In terms of immunomonitoring, we found that while ITx rejection is associated with proinflammatory and activated effector memory T cells in the blood, evidence of treatment efficacy can only be found in the allograft itself, meaning that blood-based monitoring may be insufficient. In terms of treatment, we found that the prominence of intra-graft memory TNF-α and IL-17 double-positive T helper type 17 (Th17) cells is a leading feature of refractory rejection. Anti-TNF-α therapies appear to provide novel and safer treatment strategies for refractory ITx rejection; with responses in 14 of 14 patients. Clinical protocols targeting TNF-α, IL-17, and Th17 warrant further testing.

Biomarkers for acute and chronic graft versus host disease: state of the art

INTRODUCTION

Despite significant advances in treatment and prevention, graft-versus-host disease (GVHD) still represents the main cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Thus, considerable research efforts have been made to find and validate reliable biomarkers for diagnosis, prognosis, and risk stratification of GVHD.

AREAS COVERED

In this review the most recent evidences on different types of biomarkers studied for GVHD, such as genetic, plasmatic, cellular markers, and those associated with microbiome, were summarized. A comprehensive search of peer-review literature was performed in PubMed including meta-analysis, preclinical and clinical trials, using the terms: cellular and plasma biomarkers, graft-versus-host disease, cytokines, and allogeneic hematopoietic stem cell transplantation.

EXPERT OPINION

In the near future, several validated biomarkers will be available to help clinicians in the diagnosis of GVHD, the identification of patients at high risk of GVHD development and in patients' stratification according to its severity. Then, immunosuppressive treatment could be tailored to each patient's real needs. However, more efforts are needed to achieve this goal. Although most of the proposed biomarkers currently lack validation with large-scale clinical data, their study led to improved knowledge of the biological basis of GVHD, and ultimately to implementation of GHVD treatment.

Seeking biomarkers for acute graft-versus-host disease: where we are and where we are heading?

Acute graft-versus-host disease (aGVHD) is one of the most important complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT), which would seriously affect the clinical outcomes of patients. Early diagnosis and early intervention are keys for improving its curative efficacy. Thus, seeking the biomarkers of aGVHD that can accurately identify and diagnose aGVHD is very important to guiding the intervention and treatment of aGVHD. For the past decades, many studies have focused on searching for aGVHD-related biological markers to assist in diagnosis, early warning, and risk stratification. Unfortunately, until now, no reliable aGVHD biomarker is available that is recognized and widely used in clinical practice. With the continuous development of biological technology, as well as our in-depth understanding of the pathophysiologic mechanism of aGVHD, the selection, examination and application of biological markers have changed much. In this review, we summarized the progress of aGVHD biological marker screening, identification, preliminary clinical application, and look forward to a promising development direction in the future.

The IL-12 Cytokine and Receptor Family in Graft-vs.-Host Disease

Allogeneic hematopoietic cell transplantation (allo-HCT) is performed with curative intent for high- risk blood cancers and bone marrow failure syndromes; yet the development of acute and chronic graft-vs.-host disease (GVHD) remain preeminent causes of death and morbidity. The IL-12 family of cytokines is comprised of IL-12, IL-23, IL-27, IL-35, and IL-39. This family of cytokines is biologically distinct in that they are composed of functional heterodimers, which bind to cognate heterodimeric receptor chains expressed on T cells. Of these, IL-12 and IL-23 share a common β cytokine subunit, p40, as well as a receptor chain: IL-12Rβ1. IL-12 and IL-23 have been documented as proinflammatory mediators of GVHD, responsible for T helper 1 (Th1) differentiation and T helper 17 (Th17) stabilization, respectively. The role of IL-27 is less defined, seemingly immune suppressive via IL-10 secretion by Type 1 regulatory (Tr1) cells yet promoting inflammation through impairing CD4⁺ T regulatory (Treg) development and/or enhancing Th1 differentiation. More recently, IL-35 was described as a potent anti-inflammatory agent produced by regulatory B and T cells. The role of the newest member, IL-39, has been implicated in proinflammatory B cell responses but has not been explored in the context of allo-HCT. This review is directed at discussing the current literature relevant to each IL-12-family cytokine and cognate receptor engagement, as well as the consequential downstream signaling implications, during GVHD pathogenesis. Additionally, we will provide an overview of translational strategies targeting the IL-12 family cytokines, their receptors, and subsequent signal transduction to control GVHD.

A novel predictive approach for GVHD after allogeneic SCT based on clinical variables and cytokine gene polymorphisms

Despite considerable advances in our understanding of the pathophysiology of graft-versus-host disease (GVHD), its prediction remains unresolved and depends mainly on clinical data. The aim of this study is to build a predictive model based on clinical variables and cytokine gene polymorphism for predicting acute GVHD (aGVHD) and chronic GVHD (cGVHD) from the analysis of a large cohort of HLA-identical sibling donor allogeneic stem cell transplant (allo-SCT) patients. A total of 25 SNPs in 12 cytokine genes were evaluated in 509 patients. Data were analyzed using a linear regression model and the least absolute shrinkage and selection operator (LASSO). The statistical model was constructed by randomly selecting 85% of cases (training set), and the predictive ability was confirmed based on the remaining 15% of cases (test set). Models including clinical and genetic variables (CG-M) predicted severe aGVHD significantly better than models including only clinical variables (C-M) or only genetic variables (G-M). For grades 3-4 aGVHD, the correct classification rates (CCR1) were: 100% for CG-M, 88% for G-M, and 50% for C-M. On the other hand, CG-M and G-M predicted extensive cGVHD better than C-M (CCR1: 80% vs. 66.7%, respectively). A risk score was calculated based on LASSO multivariate analyses. It was able to correctly stratify patients who developed grades 3-4 aGVHD (P < .001) and extensive cGVHD (P < .001). The novel predictive models proposed here improve the prediction of severe GVHD after allo-SCT. This approach could facilitate personalized risk-adapted clinical management of patients undergoing allo-SCT.

Genetic Polymorphism in Cytokines and Costimulatory Molecules in Stem Cell and Solid Organ Transplantation

There is growing evidence supporting the genetic variability outside of HLA system that is contributing to the variation in transplant outcomes. Determining novel predictors could help to identify patients at risk and tailor their immunosuppressive regimens. This article discusses the various single nucleotide polymorphisms in costimulatory molecules and cytokines that have been evaluated for their effect on transplantation. An overview of how gene polymorphism studies are conducted and factors to consider in the experimental design to ensure meaningful data can be concluded are discussed.

In Vitro Th17-Polarized Human CD4+ T Cells Exacerbate Xenogeneic Graft-versus-Host Disease

Acute graft-versus-host disease (aGVHD) is a severe complication of allogeneic hematopoietic stem cell transplantation. The role of Th17 cells in its pathophysiology remains a matter of debate. In this study, we assessed whether enrichment of human peripheral blood mononuclear cells (PBMCs) with in vitro Th17-polarized CD4⁺ T cells would exacerbate xenogeneic GVHD (xGVHD) into NOD-scid IL-2Rγ null (NSG) mice. Naive human CD4⁺ T cells were stimulated under Th17-skewing conditions for 8 to 10 days and then coinjected in NSG mice with fresh PBMCs from the same donor. We observed that Th17-polarized cells engrafted and migrated toward xGVHD target organs. They also acquired a double-expressing IL-17A⁺IFNγ⁺ profile in vivo. Importantly, cotransfer of Th17-polarized cells (1 × 10⁶) with PBMCs (1 × 10⁶) exacerbated xGVHD compared with transplantation of PBMCs alone (2 × 10⁶). Furthermore, PBMC cotransfer with Th17-polarized cells was more potent for xGVHD induction than cotransfer with naive CD4⁺ T cells stimulated in nonpolarizing conditions (Th0 cells, 1 × 10⁶ + 1 × 10⁶ PBMCs) or with Th1-polarized cells (1 × 10⁶ + 1 × 10⁶ PBMCs). In summary, our results suggest that human Th17-polarized cells can cooperate with PBMCs and be pathogenic in the NSG xGVHD model.

Replication and validation of genetic polymorphisms associated with survival after allogeneic blood or marrow transplant

Multiple candidate gene-association studies of non-HLA single-nucleotide polymorphisms (SNPs) and outcomes after blood or marrow transplant (BMT) have been conducted. We identified 70 publications reporting 45 SNPs in 36 genes significantly associated with disease-related mortality, progression-free survival, transplant-related mortality, and/or overall survival after BMT. Replication and validation of these SNP associations were performed using DISCOVeRY-BMT (Determining the Influence of Susceptibility COnveying Variants Related to one-Year mortality after BMT), a well-powered genome-wide association study consisting of 2 cohorts, totaling 2888 BMT recipients with acute myeloid leukemia, acute lymphoblastic leukemia, or myelodysplastic syndrome, and their HLA-matched unrelated donors, reported to the Center for International Blood and Marrow Transplant Research. Gene-based tests were used to assess the aggregate effect of SNPs on outcome. None of the previously reported significant SNPs replicated at P < .05 in DISCOVeRY-BMT. Validation analyses showed association with one previously reported donor SNP at P < .05 and survival; more associations would be anticipated by chance alone. No gene-based tests were significant at P < .05. Functional annotation with publicly available data shows these candidate SNPs most likely do not have biochemical function; only 13% of candidate SNPs correlate with gene expression or are predicted to impact transcription factor binding. Of these, half do not impact the candidate gene of interest; the other half correlate with expression of multiple genes. These findings emphasize the peril of pursing candidate approaches and the importance of adequately powered tests of unbiased genome-wide associations with BMT clinical outcomes given the ultimate goal of improving patient outcomes.

Protective role of R381Q (rs11209026) polymorphism in IL-23R gene in immune-mediated diseases: A comprehensive review

Interleukin-23 (IL-23) is a regulator of cellular immune responses involved in controlling infection and autoimmune diseases. Strong evidence has shown that IL-23 plays a role in the maintenance of immune responses by influencing the proliferation and survival of IL-17-producing T-helper (TH)-17 cells. The critical role of the IL-23/TH17 axis in immune-mediated diseases has emerged from different studies. It has also been seen that polymorphisms in the IL-23 receptor (IL-23R) gene might influence IL-23 responses. Interestingly, a functional single nucleotide polymorphism (SNP) in the IL-23 receptor gene (IL-23R; rs11209026, 1142 G wild-type A reduced function, Arg381Gln, R381Q) seems to confer a measure of protection against development of inflammatory bowel disease (IBD; Crohn's disease, ulcerative colitis), ankylosing spondylitis, rheumatoid arthritis, psoriasis, thyroiditis, recurrent spontaneous abortion and asthma, suggesting that a perturbation in the IL-23 signaling pathway is likely to be relevant to the pathophysiology of these diseases. The aim of this review was to provide an evaluation of what is currently known about the protective role of R381Q variant in IL-23R gene in immune-based diseases.

Translational opportunities for targeting the Th17 axis in acute graft-vs.-host disease

Allogeneic stem cell transplantation (allo-SCT) is a curative therapy for different life-threatening malignant and non-malignant hematologic disorders. Acute graft-vs.-host disease (aGVHD) and particularly gastrointestinal aGVHD remains a major source of morbidity and mortality following allo-SCT, which limits the use of this treatment in a broader spectrum of patients. Better understanding of aGVHD pathophysiology is indispensable to identify new therapeutic targets for aGVHD prevention and therapy. Growing amount of data suggest a role for T helper (Th)17 cells in aGVHD pathophysiology. In this review, we will discuss the current knowledge in this area in animal models and in humans. We will then describe new potential treatments for aGVHD along the Th17 axis.

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-12 and IL-23 cytokines: from discovery to targeted therapies for immune-mediated inflammatory diseases

The cytokine interleukin-12 (IL-12) was thought to have a central role in T cell-mediated responses in inflammation for more than a decade after it was first identified. Discovery of the cytokine IL-23, which shares a common p40 subunit with IL-12, prompted efforts to clarify the relative contribution of these two cytokines in immune regulation. Ustekinumab, a therapeutic agent targeting both cytokines, was recently approved to treat psoriasis and psoriatic arthritis, and related agents are in clinical testing for a variety of inflammatory disorders. Here we discuss the therapeutic rationale for targeting these cytokines, the unintended consequences for host defense and tumor surveillance and potential ways in which these therapies can be applied to treat additional immune disorders.

Non-HLA genomics: does it have a role in predicting haematopoietic stem cell transplantation outcome?

Haematopoietic stem cell transplantation (HSCT) remains the only cure for many haematological neoplasms; however, the mortality rate remains high, at around 30-80%. Complications after HSCT include relapse, graft-versus-host disease, graft rejection and infection. High-resolution HLA matching has improved survival in HSCT over recent years; however, GVHD still remains a serious complication. Single nucleotide polymorphisms (SNPS) within genes that are involved with an individual's capability to mount an immune response to infectious pathogens, residual leukaemia, alloantigens or genes involved in drug metabolism have been studied for their association with HSCT outcome. Indeed, over the last 15 years, several groups, including ourselves, have demonstrated that non-HLA gene polymorphisms can be predictive of HSCT outcome. Can genetic characteristics of the patient and donor be used in the future to tailor HSCT protocols and determine GVHD prophylaxis? This review summarizes some of the recent SNP association studies in HSCT and highlights some of the disparities therein, discussing the integral problems of performing genetic association studies on diseases with complex outcomes using heterogeneous cohorts. The review will comment on recent genomewide association studies (GWAS) and discuss their relevance in this field, and it will also comment on recent meta-analysis combining GWAS studies with other studies such as gene expression micro array data in the field of autoimmune disease and solid organ transplantation. It will mention possible novel candidate gene polymorphisms, for example SNPS in microRNAs. In addition, it will discuss some of the inherent problems associated with gene association studies including the GRIPs (genetic risk prediction studies) recommendations. In summary, this review will assess the usefulness of non-HLA genomic studies in HSCT with regard to predicting outcome and modifying therapy.

Selective targeting of the IL23 pathway: Generation and characterization of a novel high-affinity humanized anti-IL23A antibody

Herein, we describe the generation and characterization of BI 655066, a novel, highly potent neutralizing anti-interleukin-23 (IL23) monoclonal antibody in clinical development for autoimmune conditions, including psoriasis and Crohn's disease. IL23 is a key driver of the differentiation, maintenance, and activity of a number of immune cell subsets, including T helper 17 (Th17) cells, which are believed to mediate the pathogenesis of several immune-mediated disorders. Thus, IL23 neutralization is an attractive therapeutic approach. Designing an antibody for clinical activity and convenience for the patient requires certain properties, such as high affinity, specificity, and solubility. These properties were achieved by directed design of the immunization, lead identification, and humanization procedures. Favorable substance and pharmacokinetic properties were established by biophysical assessments and studies in cynomolgus monkeys.

Intestinal helminths regulate lethal acute graft-versus-host disease and preserve the graft-versus-tumor effect in mice

Donor T lymphocyte transfer with hematopoietic stem cells suppresses residual tumor growth (graft-versus-tumor [GVT]) in cancer patients undergoing bone marrow transplantation (BMT). However, donor T cell reactivity to host organs causes severe and potentially lethal inflammation called graft-versus-host disease (GVHD). High-dose steroids or other immunosuppressive drugs are used to treat GVHD that have limited ability to control the inflammation while incurring long-term toxicity. Novel strategies are needed to modulate GVHD, preserve GVT, and improve the outcome of BMT. Regulatory T cells (Tregs) control alloantigen-sensitized inflammation of GVHD, sustain GVT, and prevent mortality in BMT. Helminths colonizing the alimentary tract dramatically increase the Treg activity, thereby modulating intestinal or systemic inflammatory responses. These observations led us to hypothesize that helminths can regulate GVHD and maintain GVT in mice. Acute GVHD was induced in helminth (Heligmosomoides polygyrus)-infected or uninfected BALB/c recipients of C57BL/6 donor grafts. Helminth infection suppressed donor T cell inflammatory cytokine generation and reduced GVHD-related mortality, but maintained GVT. H. polygyrus colonization promoted the survival of TGF-β-generating recipient Tregs after a conditioning regimen with total body irradiation and led to a TGF-β-dependent in vivo expansion/maturation of donor Tregs after BMT. Helminths did not control GVHD when T cells unresponsive to TGF-β-mediated immune regulation were used as donor T lymphocytes. These results suggest that helminths suppress acute GVHD using Tregs and TGF-β-dependent pathways in mice. Helminthic regulation of GVHD and GVT through intestinal immune conditioning may improve the outcome of BMT.

Development and survival of Th17 cells within the intestines: the influence of microbiome- and diet-derived signals

Th17 cells have emerged as important mediators of host defense and homeostasis at barrier sites, particularly the intestines, where the greatest number and diversity of the microbiota reside. A critical balance exists between protection of the host from its own microbiota and pathogens and the development of immune-mediated disease. Breaches of local innate immune defenses provide critical stimuli for the induction of Th17 cell development, and additional cues within these tissues promote Th17 cell survival and/or plasticity. Normally, this results in eradication of the microbial threat and restitution of homeostasis. When dysregulated, however, Th17 cells can cause a range of immune-mediated diseases, whether directed against Ags derived from the microbiota, such as in inflammatory bowel disease, or against self-Ags in a range of autoimmune diseases. This review highlights recent discoveries that provide new insights into ways in which environmental signals impact Th17 cell development and function in the intestines.

Graft-versus-host disease biomarkers: omics and personalized medicine

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the most effective form of tumor immunotherapy available to date and the frequency of transplants continues to increase worldwide. However, while allo-HSCT usually induces a beneficial graft-versus leukemia effect, a major source of morbidity and mortality following allo-HSCT is graft-versus-host disease (GVHD). Currently available diagnostic and staging tools frequently fail to identify those at higher risk for GVHD morbidity, treatment unresponsiveness, and death. Furthermore, there are shortcomings in the risk stratification of patients before GVHD clinical signs develop. In parallel, recent years have been characterized by an explosive evolution of omics technologies, largely due to technological advancements in chemistry, engineering, and bioinformatics. Building on these opportunities, plasma biomarkers have been identified and validated as promising diagnostic and prognostic tools for acute GVHD. This review summarizes current information on the types of GVHD biomarkers, the omics tools used to identify them, the biomarkers currently validated as acute GVHD markers, and future recommendations for incorporating biomarkers into new grading algorithms for risk-stratifying patients and creating more personalized treatment courses. Future directions will include randomized evaluations of these biomarkers in multicenter prospective studies while extending on the need for biomarkers of chronic GVHD.

Role of non-HLA gene polymorphisms in graft-versus-host disease

A large number of reports have associated various non-HLA gene polymorphisms with the risk and severity of graft-versus-host disease (GVHD). To date, candidate gene studies and genome-wide association studies have been performed to investigate such non-HLA gene polymorphisms in relation to GVHD. Candidate gene studies are hypothesis-driven and cost-effective, whereas genome-wide association studies have the potential to discover new gene polymorphisms, including possible biomarkers and therapeutic targets. Some gene polymorphisms have the potential to affect protein function or gene expression, or to encode minor histocompatibility antigens. Non-HLA genotyping for genes influencing GVHD prior to transplantation should provide useful information that will facilitate choosing the donor, type of graft, conditioning treatment, and GVHD prophylaxis. However, attention should be paid to the need for validation studies and ethical issues.

Advances in predicting acute GVHD

Acute graft-versus-host disease (GVHD) is a leading cause of non-relapse mortality following allogeneic haematopoietic cell transplantation. Attempts to improve treatment response in clinically-established GVHD have not improved overall survival, often due to the increased risk of infectious complications. Alternative approaches to decrease GVHD-related morbidity and mortality have focused on the ability to predict GVHD prior to clinical manifestation in an effort to provide an opportunity to abort GVHD development, and to gain new insights into GVHD pathophysiology. This review outlines the research efforts to date that have identified clinical and laboratory-based factors that are predictive of acute GVHD and describes future directions in developing algorithms that will improve the ability to predict the development of clinically relevant GVHD.

New ways to separate graft-versus-host disease and graft-versus-tumour effects after allogeneic haematopoietic stem cell transplantation

A major challenge to transplant immunologists and physicians remains the separation of harmful graft-versus-host disease (GvHD) and beneficial graft-versus-tumour (GvT) effects after allogeneic haematopoietic stem cell transplantation. Recent advances in our understanding of the allogeneic immune response provide potential new opportunities to achieve this goal. Three potential new approaches that capitalize on this new knowledge are considered in depth; the manipulation of organ-specific cytokines and other pro-inflammatory signals, the selective manipulation of donor effector T cell migration, and the development of cell-mediated immunosuppressive strategies using donor-derived regulatory T cells. These new approaches could provide strategies for local control of allogeneic immune responses, a new paradigm to separate GvHD and GvT effects. Although these strategies are currently in their infancy and have challenges to successful translation to clinical practice, all have exciting potential for the future.

The IL-17 differentiation pathway and its role in transplant outcome

The limitations of allogeneic transplantation are graft-versus-host disease (both acute and chronic), infection, and relapse. Acute GVHD has traditionally been thought of as a Th1-mediated disease with inflammatory cytokines (eg, interferon [IFN]-γ and tumor necrosis factor [TNF]) and cellular cytolysis mediating apoptotic target tissue damage in skin, gut, and liver. Chronic GVHD has not fit neatly into either Th1 or Th2 (eg, IL-4, IL-13) paradigms. Increasingly, the Th17 pathway of differentiation has been shown to play important roles in acute and chronic GVHD (aGVHD, cGVHD), particularly in relation to skin and lung disease. Here we discuss the IL-17 pathway of T cell differentiation and the accumulating evidence suggesting it represents an important new target for the control of deleterious alloimmune responses.

Genomic studies of GVHD-lessons learned thus far

GVHD remains the most significant complication of hematopoietic SCT, despite advances in HLA matching and the identification of risk various factors. To account for the variation in the incidence and severity of this disease, many genetic association studies have been performed in order to explore the role of immunoregulatory gene polymorphisms. These genes include those that encode cytokines, chemokines, and costimulatory molecules. Polymorphisms in other classes of genes such as those involved in drug metabolism, protein folding, and DNA replication have also been studied. In this review, we address the current knowledge of the role of genetic polymorphisms in GVHD. We also discuss the potential pitfalls inherent in genetic association testing and alternative strategies to address these problems.

Evaluation of published single nucleotide polymorphisms associated with acute GVHD

Candidate genetic associations with acute GVHD (aGVHD) were evaluated with the use of genotyped and imputed single-nucleotide polymorphism data from genome-wide scans of 1298 allogeneic hematopoietic cell transplantation (HCT) donors and recipients. Of 40 previously reported candidate SNPs, 6 were successfully genotyped, and 10 were imputed and passed criteria for analysis. Patient and donor genotypes were assessed for association with grades IIb-IV and III-IV aGVHD, stratified by donor type, in univariate and multivariate allelic, recessive and dominant models. Use of imputed genotypes to replicate previous IL10 associations was validated. Similar to previous publications, the IL6 donor genotype for rs1800795 was associated with a 20%-50% increased risk for grade IIb-IV aGVHD after unrelated HCT in the allelic (adjusted P = .011) and recessive (adjusted P = .0013) models. The donor genotype was associated with a 60% increase in risk for grade III-IV aGVHD after related HCT (adjusted P = .028). Other associations were found for IL2, CTLA4, HPSE, and MTHFR but were inconsistent with original publications. These results illustrate the advantages of using imputed single-nucleotide polymorphism data in genetic analyses and demonstrate the importance of validation in genetic association studies.

Genetic variants and the risk for invasive mould disease in immunocompromised hematology patients

PURPOSE OF REVIEW

Single-nucleotide polymorphisms (SNPs) appear to influence the risk of invasive mould disease (IMD) in immunocompromised patients. This raises the question of whether genetic risk prediction can be used to alter clinical practice. This review focuses on the current status of genetic association studies regarding invasive fungal disease among hematology patients, with an emphasis on IMD.

RECENT FINDINGS

Many studies have shown that SNPs in genes encoding cytokines, chemokines, and their receptors can increase the risk for IMD. Greater emphasis has recently been placed on SNPs in pattern-recognition receptors, including Toll-like receptor 4 (TLR4) and dectin-1. An association has been found between SNPs in TLR4 and dectin-1 and invasive aspergillosis, which has been strengthened by biological evidence from in-vitro and in-vivo studies that showed a loss of function in the presence of the SNP. Nevertheless, despite improving our understanding of host antifungal defenses in immunocompromised hosts, clinical applicability is still a long way off. Current genetic associations need further validation, as virtually all studies suffer methodological limitations such as small sample size, heterogeneity of cohorts, selection bias, ill defined outcome measure, and statistical flaws, mainly the lack of adjustments for multiple comparisons.

SUMMARY

Genetic variations in immune genes are associated with the risk for IMD among hematology patients although inconsistencies are frequently reported. The next step will be to select consistent SNPs and test them for their value in assessing risk in larger, better designed multicenter studies that will necessitate collaboration of multiple institutions in national or international consortia.

Genetic variants of human granzyme B predict transplant outcomes after HLA matched unrelated bone marrow transplantation for myeloid malignancies

Serine protease granzyme B plays important roles in infections, autoimmunity, transplant rejection, and antitumor immunity. A triple-mutated granzyme B variant that encodes three amino substitutions (Q48R, P88A, and Y245H) has been reported to have altered biological functions. In the polymorphism rs8192917 (2364A>G), the A and G alleles represent wild type QPY and RAH mutant variants, respectively. In this study, we analyzed the impact of granzyme B polymorphisms on transplant outcomes in recipients undergoing unrelated HLA-fully matched T-cell-replete bone marrow transplantation (BMT) through the Japan Donor Marrow Program. The granzyme B genotypes were retrospectively analyzed in a cohort of 613 pairs of recipients with hematological malignancies and their unrelated donors. In patients with myeloid malignancies consisting of acute myeloid leukemia and myelodysplastic syndrome, the donor G/G or A/G genotype was associated with improved overall survival (OS; adjusted hazard ratio [HR], 0.60; 95% confidence interval [CI], 0.41–0.89; P = 0.01) as well as transplant related mortality (TRM; adjusted HR, 0.48; 95% CI, 0.27–0.86, P = 0.01). The recipient G/G or A/G genotype was associated with a better OS (adjusted HR, 0.68; 95% CI, 0.47–0.99; P = 0.05) and a trend toward a reduced TRM (adjusted HR, 0.61; 95% CI, 0.35–1.06; P = 0.08). Granzyme B polymorphism did not have any effect on the transplant outcomes in patients with lymphoid malignancies consisting of acute lymphoid leukemia and malignant lymphoma. These data suggest that there is an association between the granzyme B genotype and better clinical outcomes in patients with myeloid malignancies after unrelated BMT.

NKG2D gene polymorphism has a significant impact on transplant outcomes after HLA-fully-matched unrelated bone marrow transplantation for standard risk hematologic malignancies

BACKGROUND

NKG2D, an activating and co-stimulatory receptor expressed on natural killer cells and T cells, plays pivotal roles in immunity to microbial infections as well as in cancer immunosurveillance. This study examined the impact of donor and recipient polymorphisms in the NKG2D gene on the clinical outcomes of patients undergoing allogeneic T-cell-replete myeloablative bone marrow transplantation using an HLA-matched unrelated donor.

DESIGN AND METHODS

The NKG2D polymorphism was retrospectively analyzed in a total 145 recipients with hematologic malignancies and their unrelated donors. The patients underwent transplantation following myeloablative conditioning; the recipients and donors were matched through the Japan Marrow Donor Program.

RESULTS

In patients with standard-risk disease, the donor NKG2D-HNK1 haplotype, a haplotype expected to induce greater natural killer cell activity, was associated with significantly improved overall survival (adjusted hazard ratio, 0.44; 95% confidence interval, 0.23 to 0.85; p=0.01) as well as transplant related mortality (adjusted hazard ratio, 0.42; 95% confidence interval, 0.21 to 0.86; p=0.02), but had no impact on disease relapse or the development of grade II-IV acute graft-versus-host disease or chronic graft-versus-host disease. The NKG2D polymorphism did not significantly influence the transplant outcomes in patients with high-risk disease.

CONCLUSIONS

These data suggest an association between the donor HNK1 haplotype and better clinical outcome among recipients, with standard-risk disease, of bone marrow transplants from HLA-matched unrelated donors.

Polymorphisms in CCR6 are associated with chronic graft-versus-host disease and invasive fungal disease in matched-related hematopoietic stem cell transplantation

Graft-versus-host disease (GVHD) and fungal infections are frequent complications after allogeneic hematopoietic stem cell transplantation (HSCT). Single nucleotide polymorphisms (SNPs) in genes of the immune system can influence the inflammatory cascade and T cell-driven alloimmune reactions after HSCT, and thus increasing the incidence of GVHD and infectious complications. Here, we investigated the effect of SNPs in IL-23R and CCR6 on posttransplantation outcome in 161 recipients of partially T cell-depleted HSCT. Remarkably, IL-23R SNPs were not associated with clinical outcome, but we found that disparities in the CCR6 tagSNP rs2301436 and SNP rs3093023 are independently associated with the occurrence of chronic GVHD (cGVHD) and invasive fungal disease. In multivariate analysis, patients receiving a transplant from a homozygous rs2301436 G allele donor showed less cGVHD (odds ratio [OR]: 0.16; P = .002), as was the case for a homozygous donor rs3093023 G allele (OR: 0.24; P = .005). In parallel, the GG genotype at rs2301436 in donors was associated with a higher incidence of invasive fungal disease at day 100 after HSCT (OR: 3.59; P = .008). This study shows that CCR6 SNPs can be used to predict clinical outcome, and that polymorphisms in the CCR6 gene may influence T cell-mediated immune reactions after HSCT.

Immunity and tolerance to infections in experimental hematopoietic transplantation

Resistance and tolerance are two types of host defense mechanisms that increase fitness in response to fungi. Several genetic polymorphisms in pattern recognition receptors, most remarkably Toll-like receptors (TLRs), have been described to influence resistance and tolerance to aspergillosis in distinct clinical settings. TLRs on dendritic cells pivotally contribute in determining the balance between immunopathology and protective immunity to the fungus. Epithelial cells also contribute to this balance via selected TLRs converging on indoleamine-2,3-dioxygenase (IDO). Studies in experimental hematopoietic transplantation confirmed the dichotomy of pathways leading to resistance and tolerance to the fungus providing new insights on the relative contribution of the hematopoietic/nonhematopoietic compartments.

Association analysis of the NOD2 gene with susceptibility to graft-versus-host disease in a Japanese population

Members of the nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family participate in the innate immune system, exerting widespread effects on cytokine secretion, autophagy, and apoptosis. Recent studies in Caucasians revealed the association between mutants of NOD2, a member of the NLR family, and severity of acute graft-versus-host disease (GVHD). NOD2 polymorphism screening has been recommended for donor selection and risk assessment at bone marrow transplantation. To investigate whether NOD2 plays a role in the pathogenesis of GVHD in a Japanese population, we examined DNA from 142 bone marrow transplant patient/donor pairs to detect genetic variation in the NOD2 gene. No genetic variants of NOD2 were associated with the severity of acute GVHD in our patients. However, a weak association between a single nucleotide polymorphism in the NOD2 gene (R471C) and acute myeloid leukemia in the bone marrow patients (p = 0.029, odds ratio 4.08, 95% CI 1.22-13.67) was detected. This polymorphism was not prevalent in 479 Crohn's disease (CD) patients in Japan. These results suggest that, in the Japanese population, unlike the Caucasian, NOD2 is not a major contributor to susceptibility to severe acute GVHD.

Defining genetic risk for graft-versus-host disease and mortality following allogeneic hematopoietic stem cell transplantation

PURPOSE OF REVIEW

This review explores what is known about the genetics of hematopoietic stem cell transplantation (HCT) and how genetic polymorphism affects risk of graft-versus-host disease (GVHD) and mortality.

RECENT FINDINGS

Genetic variation found across the human genome can impact HCT outcome by causing genetic disparity between patient and donor and modifying gene function. Single nucleotide polymorphism (SNP) and structural variation can result in mismatching for cellular peptides known as histocompatibility antigens. At least 25-30 polymorphic genes are known to encode functional histocompatibility antigens in mismatched individuals, but their individual contribution to clinical GVHD is unclear. HCT outcome may also be affected by polymorphism in donor or recipient. Association studies have implicated several genes associated with GVHD and mortality, however results have been inconsistent most likely due to limited sample size, and differences in racial diversity and clinical covariates. New technologies using DNA arrays genotyping for a million or more SNPs promise genome-wide discovery of HCT-associated genes, however adequate statistical power requires study populations of several thousand patient-donor pairs.

SUMMARY

Available data offers strong preliminary support for the impact that genetic variation has on risk of GVHD and mortality following HCT. Definitive results however await future genome-wide studies of large multicenter HCT cohorts.

Genetic susceptibility to aspergillosis in allogeneic stem-cell transplantation

Invasive aspergillosis (IA) is a major threat to positive outcomes for allogeneic stem-cell transplantation (allo-SCT) patients. Despite presenting similar degrees of immunosuppression, not all individuals at-risk ultimately develop infection. Therefore, the traditional view of neutropenia as a key risk factor for aspergillosis needs to be accommodated within new conceptual advances on host immunity and its relationship to infection. Polymorphisms in innate immune genes, such as those encoding TLRs, cytokines and cytokine receptors, have recently been associated with susceptibility to IA in allo-SCT recipients. This suggests that understanding host-pathogen interactions at the level of host genetic susceptibility will allow the formulation of new targeted and patient-tailored antifungal therapeutics, including improved donor screening.

Dectin-1: a role in antifungal defense and consequences of genetic polymorphisms in humans

The clinical relevance of fungal infections has increased dramatically in recent decades as a consequence of the rise of immunocompromised populations, and efforts to understand the underlying mechanisms of protective immunity have attracted renewed interest. Here we review Dectin-1, a pattern recognition receptor involved in antifungal immunity, and discuss recent discoveries of polymorphisms in the gene encoding this receptor which result in human disease.

Immunoregulatory gene polymorphisms and graft-versus-host disease

Graft-versus-host disease (GVHD) remains a significant complication that greatly enhances morbidity and mortality associated with hematopoietic stem cell transplantation. Key immunoregulatory molecules have been implicated in the pathogenesis of GVHD, but the mechanisms by which these molecules affect the incidence and severity of GVHD have not been fully elucidated. The effects of genetic polymorphisms in immunoregulatory molecules, including cytokines, costimulatory and adhesion molecules, pharmacogenes and growth factors, have been shown to play a central role in GVHD. The results of these polymorphism studies contribute to the identification of predictive risk factors for GVHD based on individual polymorphism makeup. This review summarizes investigations of genetic polymorphisms in immunoregulatory molecules significantly associated with GVHD over the last 5 years.

Genetic variations of interleukin-23R (1143A>G) and BPI (A645G), but not of NOD2, are associated with acute graft-versus-host disease after allogeneic transplantation

Single nucleotide polymorphisms (SNPs) in genes of the immune system predict for aGVHD and mortality after allo-SCT. We investigated the effect of SNPs in the NOD2, BPI, and IL-23R genes on posttransplantation outcome in a cohort of 304 patients. NOD2 patient and donor genotype and BPI recipient genotype were not associated with the occurrence of aGVHD. However, IL-23R-SNP in the donor was correlated with less aGVHD. This association could be confirmed in multivariate analysis (odds ratio [OR], 0.39; P = .039), which identified in vivo T cell depletion (OR, 0.32; P < .001) and multiagent GVHD prophylaxis (OR, 0.51; P = .031) as other independent factors predicting for less-severe aGVHD. This multivariate model also revealed a trend toward less aGVHD in patients receiving a BPI G allele transplant (OR, 0.60; P = .067) and in those receiving a transplant from an HLA-matched donor (OR, 0.57; P = .058). In contrast, relapse was more frequent in patients with NOD2-SNPs (46.2% for SNP vs 33.2% for wild-type; P = .020). This association was found to be of borderline significance in multivariate analysis. Neither BPI nor IL-23R genotype predicted for relapse, and none of the investigated SNPs was correlated with 5-year overall survival. In our analysis, NOD2 SNPs did not predict aGVHD, but IL-23R(1142A>G) and BPI(A645G) SNPs appeared to be promising markers in this regard. The importance of these markers in prediction models for GVHD and relapse remain to be defined in large prospective clinical trials.

Prognostic significance of genetic variants in the IL-23/Th17 pathway for the outcome of T cell-depleted allogeneic stem cell transplantation

T helper (Th) 17 cells have emerged as important mediators in infectious and inflammatory diseases and, recently, in transplant rejection. We analyzed the associations between five common genetic variants in the IL-23/Th17 signaling pathway, namely in IL17A, IL17F and IL23R genes, and clinical outcome in T cell-depleted allogeneic SCT (allo-SCT). In the multivariate analysis, variants in IL23R and IL17A genes were the most important prognostic factors. Thus, patient GA genotype at rs11209026 in IL23R was associated with improved overall survival (hazard ratio (HR)=0.48; P=0.028) and, in donor, with decreased risk of fungal infections (P=0.05). In contrast, patient TC and CC genotypes at rs8193036 in IL17A gene were associated with increased risk of CMV infection (HR=3.68; P=0.011) and patient acute GVHD (HR=7.08; P=0.008), respectively. These results suggest that genetic variants in the IL-23/Th17 inflammatory pathway are important prognostic factors for the clinical outcome of allo-SCT. Although validation studies are ultimately required, our results would suggest the potential usefulness of IL-23/Th17 genotyping in donor selection and patient evaluation.

Insufficient evidence for association of NOD2/CARD15 or other inflammatory bowel disease-associated markers on GVHD incidence or other adverse outcomes in T-replete, unrelated donor transplantation

Previous European studies suggest NOD2/CARD15 and interleukin-23 receptor (IL-23R) donor or recipient variants are associated with adverse clinical outcomes in allogeneic hematopoietic stem cell transplantation. We reexamined these findings as well as the role of another inflammatory bowel disease (IBD) susceptibility gene (immunity-related GTPase family, M [IRGM]) on transplantation outcomes in 390 US patients and their matched unrelated donors, accrued between 1995 and 2004. Patients received T-replete grafts with mostly myeloablative conditioning regimens. Multivariate analyses were performed for overall survival, disease-free survival, transplantation-related mortality, relapse, and acute and chronic graft-versus-host disease. Of 390 pairs, NOD2/CARD15 variant single nucleotide polymorphisms (SNPs) were found in 14% of donors and 17% of recipients. In 3% both donor and recipient had a mutant SNP. Thirteen percent of donors and 16% of recipients had variant IL23R SNPs, with 3% having both donor and recipient variants. Twenty-three percent of both donors and recipients had variant IRGM SNPs. None of the 3 IBD-associated alleles showed a statistically significant association with any adverse clinical outcomes. Our results do not support an association between the 3 IBD-associated SNPs and adverse outcomes after matched unrelated donor hematopoietic cell transplantations in US patients.

Polymorphism of interleukin-23 receptor gene but not of NOD2/CARD15 is associated with graft-versus-host disease after hematopoietic stem cell transplantation in children

Graft-versus-host disease (GVHD) is a major cause of morbidity and mortality after hematopoietic stem cell transplantation (HSCT). The selection of a suitable donor is the most critical issue in preventing severe GVHD. Recent data suggest that the risk of GVHD does not only depend on human leukocyte antigens (HLA) but also on polymorphisms of genes that influence immune responses. We analyzed the 1142 G>A single-nucleotide polymorphism (SNP) in the interleukin-23 receptor gene (IL23R) and 3 SNPs in the NOD2/CARD15 gene in a cohort of 231 children who underwent allogeneic stem cell transplantation and/or their respective donors. No association was observed between any of the NOD2/CARD15 polymorphisms and GVHD in either donor or recipient. Likewise, the IL23R polymorphism in the recipient was not significantly associated with GVHD. We found a significantly reduced incidence of acute GVHD (aGVHD) grade II-IV in patients who were transplanted from a donor with the IL23R polymorphism (5.0% versus 33.3%; P=.009). There was no case of aGVHD grade III-IV if this polymorphism occurred in the donor. These findings could be particularly relevant for children with inborn metabolic or immunologic disorders who do not benefit from a graft-versus-tumor effect, and therefore, selection of a donor with the IL23R polymorphism might be beneficial.