Polymorphisms in TNFA and TNFR2 affect outcome of unrelated bone marrow transplantation

The Role of TNFR2 and DR3 in the In Vivo Expansion of Tregs in T Cell Depleting Transplantation Regimens

Regulatory T cells (Tregs) are essential for the maintenance of tolerance to self and non-self through cell-intrinsic and cell-extrinsic mechanisms. Peripheral Tregs survival and clonal expansion largely depend on IL-2 and access to co-stimulatory signals such as CD28. Engagement of tumor necrosis factor receptor (TNFR) superfamily members, in particular TNFR2 and DR3, contribute to promote peripheral Tregs expansion and sustain their survival. This property can be leveraged to enhance tolerance to allogeneic transplants by tipping the balance of Tregs over conventional T cells during the course of immune reconstitution. This is of particular interest in peri-transplant tolerance induction protocols in which T cell depletion is applied to reduce the frequency of alloreactive T cells or in conditioning regimens that allow allogeneic bone marrow transplantation. These conditioning regimens are being implemented to limit long-term side effects of continuous immunosuppression and facilitate the establishment of a state of donor-specific tolerance. Lymphopenia-induced homeostatic proliferation in response to cytoreductive conditioning is a window of opportunity to enhance preferential expansion of Tregs during homeostatic proliferation that can be potentiated by agonist stimulation of TNFR.

High-resolution HLA phased haplotype frequencies to predict the success of unrelated donor searches and clinical outcome following hematopoietic stem cell transplantation

HLA matching is a critical factor for successful allogeneic hematopoietic stem cell transplantation. For unrelated donor searches, matching is usually based on high-resolution typing at five HLA loci, looking for a 10/10 match. Some studies have proposed that further matching at the haplotype level could be beneficial for clinical outcome. In this study, we determined the phased haplotypes of 291 patients using family members and segregation analysis. The sum of ranks of the haplotypes carried by patients was used as a surrogate predictor of a successful unrelated donor search. The putative impact of haplotypes was then analyzed in a cohort of 211 recipients transplanted with 10/10 matched unrelated donors. A logistic regression analysis showed a highly significant effect of the haplotypes in the outcome of a search, but we did not find any significant effect on overall survival, graft versus host disease or relapse/progression following HSCT. This study provides useful data for the optimization of unrelated bone marrow donor searches, but does not confirm previous reports that matching at the haplotype level has a clinical impact following HSCT. Due to the extreme polymorphism of HLA genes, further studies are warranted to better understand the many factors at play.

Role of TNF-TNF Receptor 2 Signal in Regulatory T Cells and Its Therapeutic Implications

Tumor necrosis factor α (TNFα) is a pleiotropic cytokine which signals through TNF receptor 1 (TNFR1) and TNF receptor 2 (TNFR2). Emerging evidence has demonstrated that TNFR1 is ubiquitously expressed on almost all cells, while TNFR2 exhibits a limited expression, predominantly on regulatory T cells (Tregs). In addition, the signaling pathway by sTNF via TNFR1 mainly triggers pro-inflammatory pathways, and mTNF binding to TNFR2 usually initiates immune modulation and tissue regeneration. TNFα plays a critical role in upregulation or downregulation of Treg activity. Deficiency in TNFR2 signaling is significant in various autoimmune diseases. An ideal therapeutic strategy for autoimmune diseases would be to selectively block the sTNF/TNFR1 signal through the administration of sTNF inhibitors, or using TNFR1 antagonists while keeping the TNFR2 signaling pathway intact. Another promising strategy would be to rely on TNFR2 agonists which could drive the expansion of Tregs and promote tissue regeneration. Design of these therapeutic strategies targeting the TNFR1 or TNFR2 signaling pathways holds promise for the treatment of diverse inflammatory and degenerative diseases.

TNFR2: The new Treg switch?

Three recent publications identified the TNF/TNR2 pathway as a new target to reduce graft-versus-host-disease through regulatory T cells activation or to potentially switch on a strong anti-leukemic effect through regulatory T cells blockade in allogeneic hematopoietic stem cell transplantation. This identified the TNF/TNR2 pathway as a swith and as a new target for immune checkpoint therapy to modulate the immune regulation in this clinical setting.

Impact of CTLA4 genotype and other immune response gene polymorphisms on outcomes after single umbilical cord blood transplantation

We evaluated the impact of recipient and cord blood unit (CBU) genetic polymorphisms related to immune response on outcomes after unrelated cord blood transplantations (CBTs). Pretransplant DNA samples from 696 CBUs with malignant diseases were genotyped for NLRP1, NLRP2, NLRP3, TIRAP/Mal, IL10, REL, TNFRSF1B, and CTLA4. HLA compatibility was 6 of 6 in 10%, 5 of 6 in 39%, and ≥4 of 6 in 51% of transplants. Myeloablative conditioning was used in 80%, and in vivo T-cell depletion in 81%, of cases. The median number of total nucleated cells infused was 3.4 × 10⁷/kg. In multivariable analysis, patients receiving CBUs with GG-CTLA4 genotype had poorer neutrophil recovery (hazard ratio [HR], 1.33; P = .02), increased nonrelapse mortality (NRM) (HR, 1.50; P < .01), and inferior disease-free survival (HR, 1.41; P = .02). We performed the same analysis in a more homogeneous subset of cohort 1 (cohort 2, n = 305) of patients who received transplants for acute leukemia, all given a myeloablative conditioning regimen, and with available allele HLA typing (HLA-A, -B, -C, and -DRB1). In this more homogeneous but smaller cohort, we were able to demonstrate that GG-CTLA4-CBU was associated with increased NRM (HR, 1.85; P = .01). Use of GG-CTLA4-CBU was associated with higher mortality after CBT, which may be a useful criterion for CBU selection, when multiple CBUs are available.

TNF Receptor 2 and Disease: Autoimmunity and Regenerative Medicine

The regulatory cytokine tumor necrosis factor (TNF) exerts its effects through two receptors: TNFR1 and TNFR2. Defects in TNFR2 signaling are evident in a variety of autoimmune diseases. One new treatment strategy for autoimmune disease is selective destruction of autoreactive T cells by administration of TNF, TNF inducers, or TNFR2 agonism. A related strategy is to rely on TNFR2 agonism to induce T-regulatory cells (T_regs) that suppress cytotoxic T cells. Targeting TNFR2 as a treatment strategy is likely superior to TNFR1 because of its more limited cellular distribution on T cells, subsets of neurons, and a few other cell types, whereas TNFR1 is expressed throughout the body. This review focuses on TNFR2 expression, structure, and signaling; TNFR2 signaling in autoimmune disease; treatment strategies targeting TNFR2 in autoimmunity; and the potential for TNFR2 to facilitate end organ regeneration.

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.

The major histocompatibility complex: a model for understanding graft-versus-host disease

Acute graft-versus-host disease (GVHD) afflicts as much as 80% of all patients who receive an unrelated donor hematopoietic cell transplant (HCT) for the treatment of blood disorders, even with optimal donor HLA matching and use of prophylactic immunosuppressive agents. Of patients who develop acute GVHD, many are at risk for chronic GVHD and bear the burden of considerable morbidity and lowered quality of life years after transplantation. The immunogenetic basis of GVHD has been the subject of intensive investigation, with the classic HLA genetic loci being the best-characterized determinants. Recent information on the major histocompatibility complex (MHC) region of chromosome 6 as an important source of untyped genetic variation has shed light on novel GVHD determinants. These data open new paradigms for understanding the genetic basis of GVHD.

The impact of frequent HLA haplotypes in high linkage disequilibrium on donor search and clinical outcome after unrelated haematopoietic SCT

The MHC region on chromosome 6 contains a large number of non-HLA genes next to the HLA genes. Matching for HLA in unrelated hematopoietic SCT (HSCT) does not necessarily mean that these non-HLA genes are also matched. We selected 348 Northwest European patients transplanted with an HLA-A-, -B-, -C-, -DRB1-, -DQB1-matched unrelated donor (MUD) between 1987 and 2008. Patients' haplotypes were identified via descend. We were unable to determine the haplotypes of the donor; therefore we used frequent haplotypes (FH) in high linkage disequilibrium (LD) as a proxy for haplotype matching. Presence of a FH in a patient positively affected the probability and speed of identifying a matched unrelated donor. Competing risk survival analysis showed that patients with one or two FH have a statistically significantly decreased probability of developing ≥ grade II acute GVDH (aGVHD) without increased risk of relapse compared to patients without FH (HR (95% CI): 0.53 (0.31-0.91)). This association was strongest for those FH with the highest LD between both HLA-A and -C or -B, and HLA-C or -B and -DRB1 (HR (95% CI): 0.49 (0.26-0.92)). These results extend evidence that non-HLA allele coding regions have a significant impact on development of ≥ grade II aGVHD. We conclude that there is more to successful HSCT than matching for HLA genes.

Single nucleotide polymorphisms and outcome risk in unrelated mismatched hematopoietic stem cell transplantation: an exploration study

Genetic risk factors contribute to adverse outcome of hematopoietic stem cell transplantation (HSCT). Mismatching of the HLA complex most strongly determines outcomes, whereas non-HLA genetic polymorphisms are also having an impact. Although the majority of HSCTs are mismatched, only few studies have investigated the effects of non-HLA polymorphisms in the unrelated HSCT and HLA-mismatched setting. To understand these effects, we genotyped 41 previously studied single nucleotide polymorphisms (SNPs) in 2 independent, large cohorts of HSCT donor-recipient pairs (n = 460 and 462 pairs) from a homogeneous genetic background. The study population was chosen to pragmatically represent a large clinically homogeneous group (acute leukemia), allowing all degrees of HLA matching. The TNF-1031 donor-recipient genotype mismatch association with acute GVHD grade 4 was the only consistent association identified. Analysis of a subgroup of higher HLA matching showed consistent associations of the recipient IL2-330 GT genotype with risk of chronic GVHD, and the donor CTLA4-CT60 GG genotype with protection from acute GVHD. These associations are strong candidates for prediction of risk in a clinical setting. This study shows that non-HLA gene polymorphisms are of relevance for predicting HSCT outcome, even for HLA mismatched transplants.

Signal transduction by tumor necrosis factor receptors

Tumor necrosis factor (TNF) is a key mediator in the inflammatory response which is implicated in the onset of a number of diseases. Research on TNF led to the characterization of the largest family of cytokines known until now, the TNF superfamily, which exert their biological effects through the interaction with transmembrane receptors of the TNFR superfamily. TNF itself exerts its biological effects interacting with two different receptors: TNFR1 and TNFR2. TNFR1 presents a death domain on its intracellular region. In contrast to TNFR1, TNFR2 does not have a death domain. Activation of TNFR1 implies the consecutive formation of two different TNF receptor signalling complexes. Complex I controls the expression of antiapoptotic proteins that prevent the triggering of cell death processes, whereas Complex II triggers cell death processes. TNFR2 only signals for antiapoptotic reactions. However, recent evidence indicates that TNFR2 also signals to induce TRAF2 degradation. TRAF2 is a key mediator in signal transduction of both TNFR1 and TNFR2. Thus, this novel signalling pathway has two important implications: on one hand, it represents an auto regulatory loop for TNFR2; on the other hand, when this signal is triggered TNFR1 activity is modified so that antiapoptotic pathways are inhibited and apoptotic reactions are enhanced.

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.

TNF receptor 2 pathway: drug target for autoimmune diseases

Although drug development has advanced for autoimmune diseases, many current therapies are hampered by adverse effects and the frequent destruction or inactivation of healthy cells in addition to pathological cells. Targeted autoimmune therapies capable of eradicating the rare autoreactive immune cells that are responsible for the attack on the body's own cells are yet to be identified. This Review presents a new emerging approach aimed at selectively destroying autoreactive immune cells by specific activation of tumour necrosis factor receptor 2 (TNFR2), which is found on autoreactive and normal T lymphocytes, with the potential of avoiding or reducing the toxicity observed with existing therapies.

Impact of highly conserved HLA haplotype on acute graft-versus-host disease

Although the effects of human leukocyte antigen (HLA) locus matching on clinical outcome in unrelated hematopoietic stem cell transplantations have been characterized, the biologic implications of HLA haplotypes have not been defined. We demonstrated the genetic fixity of Japanese conserved extended haplotypes by multi-single nucleotide polymorphism analysis in 1810 Japanese donor-recipient pairs matching with HLA-A, -B, -C, -DRB1, and -DQB1 alleles. Three major Japanese conserved extended haplotypes (named HP-P1, HP-P2, and HP-P3) were essentially completely conserved at least in the 3.3-Mb HLA region from HLA-A to -DPB1, and extended far beyond HLA-A. The risk of acute graft-versus-host disease (GVHD) of these HLA haplotypes was assessed with multivariate Cox regression in 712 patients transplanted from HLA fully (HLA-A, B, C, DRB1, DQB1, and DPB1) matched unrelated donors. HP-P2 itself reduced the risk of grade 2 to 4 acute GVHD (hazard ratio [HR] = 0.63; P = .032 compared with HP-P2-negative), whereas HP-P3 tended to increase the risk (HR = 1.38; P = .07). Among 381 patients with HP-P1, HP-P1/P3 (HR = 3.35; P = .024) significantly increased the risk of acute GVHD compared with homozygous HP-P1. This study is the first to demonstrate that a genetic difference derived from HLA haplotype itself is associated with acute GVHD in allogeneic hematopoietic stem cell transplantation.

Tumor necrosis factor-alpha gene polymorphisms are associated with severity of acute graft-versus-host disease following matched unrelated donor bone marrow transplantation in children: a Pediatric Blood and Marrow Transplant Consortium study

Tumor necrosis factor (TNF)-alpha plays a significant role in conditioning related toxicities and the development of acute graft-versus-host disease (aGVHD). TNF-alpha gene polymorphisms are associated with rejection after organ transplantation and aGVHD in matched related donor blood and marrow transplantation (BMT) recipients. Few studies have been published on unrelated donor BMT in the pediatric age group. In this study, we examined the relationship between specific polymorphisms in TNF pathway genes and the occurrence and severity of aGVHD. Recipient single-nucleotide polymorphisms (SNPs) in TNF-alpha and TNF receptor superfamily members 1A (TNFRSF1A) and 1B (TNFRSF1B) were investigated. In a multi-institutional Pediatric Blood and Marrow Transplant Consortium trial, a total of 180 pediatric patients (mean age, 11.0 years) were prospectively evaluated for clinical outcomes after matched unrelated donor BMT. All patients received myeloablative conditioning and two-drug GVHD prophylaxis with cyclosporine or tacrolimus, with methotrexate in the majority of patients. TNF-alpha genotypes were not correlated with the overall incidence of aGVHD. Significant associations were seen between TNF-alpha variant alleles and the severity of aGVHD (grade II-IV and grade III-IV), especially when analyzed in whites only (n = 165). Grade II-IV aGVHD was correlated with recipient -857T allele (hazard ratio [HR], 0.47; P = .04), -238A allele (HR, 1.76; P = .002), and d3/d3 genotype (HR, 0.64; P = .03). Severe (grade III-IV) aGVHD was associated with TNF-alpha -1031C allele (HR, 2.38; P = .03), -863A allele (HR, 3.18; P = .003), and d4/d4 genotype (HR, 2.82; P = .01). After adjusting for clinical factors, the association of -1031C, -863A, -238A, and d4/d4 genotypes with severity of aGVHD remained statistically significant. No correlation between selected SNPs in TNFRSF1A or TNFRSF1B and the incidence or severity of aGVHD was found. Our findings indicate clinically important relationships between genetic polymorphisms in TNF-alpha and the severity of aGVHD in this cohort. Improved understanding of this relationship may allow for a risk-adjusted approach to GVHD prevention in pediatric BMT.

TNF, LTA and TGFB1 genotype distributions among acute graft-vs-host disease subsets after HLA-matched unrelated hematopoietic stem cell transplantation: a pilot study

Cytokine single nucleotide polymorphisms and consequent production levels have been associated with acute graft-vs-host disease (aGVHD) development. The aim of this pilot study was to determine whether polymorphisms in tumor necrosis factor (TNF), lymphotoxin alpha (LTA) and transforming growth factor beta 1 (TGFB1) showed any association with aGVHD severity. Novel alleles and polymorphisms were identified for each cytokine locus. Genotype distributions were examined in 38 recipient-donor pairs (all chronic myelogenous leukemia in the first chronic phase) with either low-grade (grades 0-I) or high-grade (grades III-IV) aGVHD. Although no significant differences were found, some trends were noted in genotype distributions among aGVHD-grade groups. Power calculations determined that substantially more pairs would be required to show significant associations in distributions among aGVHD-grade groups.

Nutrition, anthropometry, gastrointestinal dysfunction, and circulating levels of tumour necrosis factor alpha receptor I and interleukin-1 receptor antagonist in children during stem cell transplantation

To evaluate anthropometry, nutrition and gastrointestinal dysfunction, and to characterize the relation between these parameters and the inflammatory activity evaluated by plasma levels of soluble tumour necrosis factor alpha receptor I (sTNFRI) and interleukin-1 receptor antagonist (IL-1Ra) levels during stem cell transplantation (SCT) in children. Clinical assessments and blood sampling were performed on days -3, 0, +7, +15 and +31 in eight children undergoing SCT. Energy intake, anthropometry, gastrointestinal dysfunction (WHO toxicity score) and sTNFRI and IL-1Ra were evaluated. The energy intake was below recommended levels. There was a loss of lean body mass (arm muscle area)(median, 2031 mm(2) (day -3) vs 1477 mm(2) (day 31); p = 0.04), and of fat mass (arm fat area) (791 mm(2) (day -3) vs 648 mm(2) (day +31); p = 0.04). sTNFRI was elevated throughout the course of transplantation, and peaked after the day of graft infusion (day 0). sTNFRI levels at day 0 predicted changes in weight SDS (r = 0.65; p = 0.05), triceps skinfold SDS (r = 0.85; p = 0.007) and gastrointestinal dysfunction (r = 0.88; p = 0.004). Likewise, IL-1Ra levels at day 0 correlated with the gastrointestinal dysfunction (r = 0.83; p = 0.01) and with the change in weight SDS (r = 0.77; p = 0.03). This study suggests that pretransplant levels of inflammatory markers are associated with posttransplant symptoms of gastrointestinal dysfunction and loss of both fat and lean body mass. Future studies should address if the use of conditioning regimens with limited proinflammatory cytokine inducing activity, anti-inflammatory agents, or more optimised nutritional support can reduce the burden of such posttransplant complications.

Polymorphisms of cytokine and innate immunity genes and GVHD

In the last 10 years, non-HLA genotypes have been investigated for their potential roles in the occurrence and severity of graft-versus-host disease (GVHD) as well as for their contribution to overall transplant-related mortality, infectious episodes, and overall survival. This chapter will review the latest results of cytokine gene polymorphisms between patient and donor which may cause the production of high or low levels of cytokines during the three-stage process of the GVHD 'cytokine storm'. More recent investigations into innate immunity and the interaction with subsequent downstream cytokine production and ultimate tissue damage are discussed. The potential of these non-HLA genetics to aid in predicting GVHD and post-transplant survival and the relevance of this information to the clinic are reviewed.

IL2 and TNFA gene polymorphisms and the risk of graft-versus-host disease after allogeneic haematopoietic stem cell transplantation

This study aimed to analyse the association of gene polymorphisms with the outcome of allogeneic haematopoietic stem cell transplantation. We studied 122 donor/recipient pairs who received HLA-identical transplants from siblings at the Universidade Estadual de Campinas, Brazil, between June 1996 and June 2006. Donor/recipient alleles for TNFA-238 and IL2-330/+166 single-nucleotide polymorphisms (SNP) were analysed by PCR-SSP. No association was observed between the risk of acute graft-versus-host disease (GVHD) and these SNP. However, our findings suggest that the polymorphism of promoter gene TNFA-238GA is associated with the occurrence and severity of chronic GVHD. The probability of chronic GVHD in patients with GA genotype at position -238 of TNFA gene is 91.7% in contrast to 59.4% in patients with GG genotype (P = 0.038). In patients with donor GA genotype the probability of chronic GVHD is 90.8%, and 57.9% in patients with donor GG genotype (P = 0.038). The probability of extensive chronic GVHD in patients with TNFA-238GA is 91.7% compared with 46.3% in patients with TNFA-238GG (P = 0.0046). In patients with donor GA genotype at position -238 of the TNFA gene, it is 81.7%, compared with 44.5% in patients with donor GG genotype (P = 0.016). However, further studies with more patients are required to identify cytokine gene polymorphisms and their association with transplant-related complication in Brazil, particularly due to ethnic background, the relatively low power of detection of genetic markers of this study, and the complexity of the MHC region.

Haematopoietic stem cell transplantation: can our genes predict clinical outcome?

Haematopoietic stem cell transplantation (HSCT) is currently the only curative treatment for many patients with malignant and non-malignant haematological diseases. The success of HSCT is greatly reduced by the development of complications, which include graft-versus-host disease (GVHD), relapse and infection. Human leukocyte antigen (HLA) matching of patients and donors is essential, but does not completely prevent these complications; non-HLA genes may also have an impact upon transplant outcome. Polymorphisms within genes that are associated with an individual's capability to mount an immune response to alloantigen and infectious pathogens and/or response to drugs (pharmacogenomics) are all currently being studied for their association with HSCT outcome. This review summarises the potential role of non-HLA polymorphisms in predicting HSCT outcome, from studies on retrospective transplant cohorts of HLA-identical siblings and matched unrelated donors. The clinical relevance and interpretation of non-HLA genetics, and how these could be used alongside clinical risk factors in HSCT, are also discussed.

Mapping MHC-resident transplantation determinants

Graft-versus-host disease (GVHD) accounts for increased morbidity and mortality after HLA-identical unrelated hematopoietic cell transplantation (HCT). To test the hypothesis that the major histocompatibility complex (MHC) encodes functional variation other than the classical HLA genes, we measured risks associated with donor-recipient MHC microsatellite (Msat) marker mismatching in 819 HCT recipients and their HLA-A, -B, -C, -DRB1, and -DQB1 allele-matched unrelated donors. Suggestive trends of association with transplant outcome were observed for 5 Msats. Donor-recipient mismatching for the extended class I D6S105, class III D6S2787, and class II D6S2749 markers was each associated with an increased risk of death (hazard ratio, 1.32; 95% confidence interval, 1.02-1.71; P=.03; hazard ratio, 1.26; 95% confidence interval, 1.03-1.53; P=.02; hazard ratio, 1.37; 95% confidence interval, 1.08-1.72; P=.007, respectively) whereas mismatching for the class I D6S2811 marker was associated with a decreased risk of death (hazard ratio, 0.80; 95% confidence interval, 0.66-0.98; P=.03). Mismatching for the class I D6S265 marker was associated with a decreased risk of grades III-IV acute GVHD (odds ratio, 0.67; 95% confidence interval, 0.45-0.98; P=.04). These results suggest that Msats may be informative for mapping MHC-resident genetic variation of clinical importance in HCT.

Non-HLA gene polymorphisms in stem cell transplantation

An increasing number of gene polymorphisms of immune regulatory molecules are being associated with clinical performance following stem cell transplantation (SCT). These polymorphisms affect structural or regulatory changes on immune regulatory molecules including cytokines . In contrast to polymorphisms of the major histocompatibility complex, the genome variations found in these non-human leukocyte antigen genes are simple to detect, allowing studies to be done in many laboratories and transplant centres. Many forms of DNA polymorphism detection are now available, allowing even modest laboratories to mount studies of their own. Despite these advances, studies in SCT have a number of problems relating to the complex clinical situation that they study; issues of study design and data interpretation in transplant studies are complex and challenging and are the main limiting factors, which inhibit progress in confirming genetic features which influence the success of SCT.

Risk assessment in haematopoietic stem cell transplantation: Pre–transplant patient and donor factors: non-HLA genetics

Non-HLA genetics involving the study of single-nucleotide polymorphisms (SNPs) and microsatellites of cytokine and cytokine receptor genes, and as well as genes associated with response to infection and therapeutic drugs, are currently being studied for associations with diseases, including autoimmune disease, cancer and solid-organ transplant rejection. This chapter will summarize the potential role of non-HLA genetics in predicting outcome of haematopoietic stem-cell transplantation (HSCT) and how genotyping for non-HLA genes may give insight into the immunobiology of HSCT complications, including GvHD and infectious episodes. Future directions - including the role of pharmacogenomics, use of the research results for individualized medicine, and interpretation of data - will also be discussed.

New directions in the genomics of allogeneic hematopoietic stem cell transplantation

Despite optimal supportive care and high-resolution HLA matching, complications such as GVHD and infection remain major barriers to the success of allogeneic HCT (allo-HCT). This has led to growing interest in the non-HLA genetic determinants of complications after allo-HCT. Most studies have examined genetic predictors of GVHD, relapse, and mortality and have focused on 3 main areas: minor histocompatibility antigen (miHAs), inflammatory mediators of GVHD, and more recently NK cell-mediated allorecognition. The genetic basis of other outcomes such as infection and drug toxicity are less well studied but are being actively investigated. High-throughput methodologies such as single nucleotide polymorphism arrays are enabling the study of hundreds of thousands of genetic markers throughout the genome and the interrogation of novel genetic variants such as copy number variations. These data offer the opportunity to better predict those at risk of complications and to identify novel targets for therapeutic intervention. This review examines the current data regarding the non-HLA genomics of allo-HCT and appraises the promises and pitfalls for integration of this new genetic information into clinical transplantation practice.

Genetics of Risk Factors for Graft-Versus-Host Disease

Modern understanding of the genetic basis of graft-versus-host disease (GVHD) in allogeneic hematopoietic stem cell transplantation (HSCT) involves knowledge of human leukocyte antigen (HLA), killer immunoglobulin-like receptors (KIR), cytokine genes, and their interactions. Insights into the immunogenetic basis of GVHD come from long-standing clinical experience in the use of myeloablative conditioning regimens and donor bone marrow as the grafting source. Under these circumstances, donor T-cell recognition of host HLA can cause GVHD. The recent elucidation of HLA class I as ligands for natural killer (NK) cell inhibitory KIR demonstrates that GVHD is the result of a complex interplay between the innate and adaptive immune responses. The extent to which T cells and NK cells contribute to clinical GVHD is a function of the host post-conditioning environment, immunosuppressive treatments, and the content of the graft source. The contribution of donor and host genetic differences in cytokine genes in modulating risks of GVHD has recently been recognized.

Non-HLA immunogenetics in hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) provides a unique environment in which to evaluate the role of immunogenetics of both the donor and the recipient to success of the procedure. The central role of HLA matching in HSCT has been established; however, recipients of allogeneic HSCT incur the risk of graft versus host disease (GVHD) even when the donor is a sibling who shares the major histocompatibility genes. Therefore, the perfect HLA match does not represent the optimal genetic make up. Other genetic systems operate and affect the various outcomes of HSCT, including GVHD, infections, transplant-related mortality, and overall survival. Minor histocompatibility antigens contribute to the control of GVHD as well as graft versus leukaemia reactions. In addition, genes controlling inflammatory processes, including cytokines, chemokines and their receptors, can modulate GVHD, and genes from both arms of the immune response (innate and adaptive) are strong candidates for susceptibility factors to infections in allogenic transplantation.

Comparative modeling of TNFRSF25 (DR3) predicts receptor destabilization by a mutation linked to rheumatoid arthritis

We constructed a three-dimensional model of TNFRSF25 (death receptor-3; DR3), a tumor necrosis-receptor family member that is expressed on immune cells and on osteoblasts, to determine whether mutations that are linked to rheumatoid arthritis are likely to have effects on receptor function. Since the crystal structure of DR3 is not known, comparative modeling was used, aligning structural elements of the primary sequences of DR3 with TNFs which have been determined by crystallography, substituting the amino acids of the target protein for those in the known structure, introducing necessary deletions or insertions, followed by energy minimization to yield a putative structure. This approach has been validated by studies of other TNF-family receptors. The results show that the DR3 extracellular domain is comprised of four homologous cysteine-rich domains (CRDs), and that a mutation linked to rheumatoid arthritis is in a region critical for structural integrity of ligand-receptor complexes at the end of CRD3. Specifically, the D158G mutation eliminates two hydrogen bonds normally present in a N/D-T-V/D-C consensus motif typically found flanking the last cysteine of each CRD. This may cause aberrations in either T cell function or in response of bone cells to DR3 ligands, which may contribute to pathology in rheumatoid arthritis. Comparison of RA mutants to mutants in other TNFRSF receptors shows that these occur in homologous positions in CRDs, so that this site is proposed to be a 'hot spot' for mutations in TNFRSF family proteins.

Genetic polymorphisms predicting the outcome of bone marrow transplants

Analysis of non-histocompatibility leucocyte antigen (HLA) functional genomics, together with conventional risk factors in haematopoietic stem cell transplantation (HSCT) can lead to predicting outcome in HLA-matched sibling transplant recipients. Polymorphisms of cytokine genes including tumour necrosis factor alpha, interleukin-10, interferon gamma and interleukin (IL)-6, associate with more severe acute graft-versus-host disease (aGvHD). Donor genotype for IL-1 receptor antagonist (IL-1Ra) has been associated with reduced aGvHD severity. Other genotypes (patient IL-1Ra, IL-6 and donor IL-1 alpha) have been associated with chronic GvHD, or overall survival (Vitamin D receptor and oestrogen receptor). Polymorphisms within genes associated with host defence/inflammatory responses (mannose binding lectin genes, myeloperoxidase genes and the FC gamma receptors) have been associated with infections. Polymorphisms of pharmacogenes, such as methylenetetrahydrofolate-reductase, have been associated with aGvHD and other post-transplant complications. The NOD2 gene polymorphism, associated with Crohn's disease, has been shown to be associated with risk of gut GvHD. The majority of the studies have been carried out in single centre HLA-matched sibling cohorts and in relatively few matched unrelated donor transplants. This review gives an overall perspective of the current field of non-HLA genetics with regard to HSCT outcome, clinical relevance and potential application of the results to clinical management of HSCT.

Target Antigens Determine Graft-versus-Host Disease Phenotype

Chronic graft-vs-host disease (cGVHD) is an increasingly frequent complication of allogeneic stem cell transplantation. Phenotypically, cGVHD differs from patient to patient; in particular, a subset of patients develops extensive cutaneous fibrosis. Similarly, graft-vs-host disease (GVHD) is distinct in inbred murine donor:recipient pairings, indicating a genetic component to disease phenotype. The B10.D2 -->BALB/c (H-2d) strain pairing uniquely recapitulates key pathologic features of fibrotic human cutaneous cGVHD. To distinguish whether this genetic component is due to differences in genes that modulate immune responses or to the specific Ags targeted, we asked whether skin-dominant cGVHD also develops in the B10 -->BALB.B (H-2b) and B10.BR -->BALB.K (H-2k) MHC-congenic pairings. Because each MHC haplotype presents different peptides and selects different T cell repertoires, GVHD in each donor:recipient pair undoubtedly targets different Ags. We found that, in contrast to BALB/c recipients, BALB.B mice never manifested skin disease while BALB.K mice developed a modified form of skin disease. Instead, BALB.B and BALB.K recipients developed systemic GVHD which was absent in BALB/c mice. Moreover, in (B10 x B10.D2)F1 -->(BALB.B x BALB/c)F1 H-2b/d transplants, recipients developed both cutaneous and systemic disease. Thus, the selection of immunodominant Ags determines the target and character of GVHD, providing insight into the genetic basis for different forms of GVHD.

Association of tumor necrosis factor receptor type 2 +587 gene polymorphism with severe chronic periodontitis

BACKGROUND

Genetic polymorphisms for cytokines and their receptors have been proposed as potential markers for periodontal disease. Tumor necrosis factor receptor 2 (TNFR2) is one of the cell surface receptors for TNF-alpha. Recent studies have suggested that TNFR2 gene polymorphism is involved in autoimmune and other diseases.

OBJECTIVES

The aim of the present study is to evaluate whether TNFR2(+587T/G) gene polymorphism is associated with chronic periodontitis (CP).

METHODS

One hundred and ninety-six unrelated subjects (age 40-65 years) with different levels of CP were identified according to established criteria, including measurements of probing pocket depth (PPD), clinical attachment level (CAL), and alveolar bone loss (BL). All subjects were of Japanese descent and non-smokers. Single nucleotide polymorphism at position +587(T/G) in the TNFR2 gene was detected by a polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) method.

RESULTS

The frequency and the positivity of the +587G allele were significantly higher in severe CP patients than in controls (p=0.0097; odds ratio=2.61, p=0.0075; odds ratio=3.06). In addition, mean values of PPD, CAL, and BL were significantly higher in the +587G allele positive than in the negative subjects (p=0.035, 0.022, and 0.018, respectively).

CONCLUSIONS

These findings suggest that the TNFR2(+587G) polymorphic allele could be associated with severe CP in Japanese.

The biology of TNF blockade

Rheumatoid arthritis and Crohn's disease are costly diseases that result in significant long-term patient disability. They are chronic inflammatory diseases that are associated with increased production of Tumor Necrosis Factor (TNF). Blockage of this cytokine with bio-engineered compounds has significantly changed therapy of these diseases and has ushered in the era of biological therapy. The pro-inflammatory role of TNF is mediated by its essential respiratory burst function that is effectively inhibited by anti-TNF therapy. Anti-TNF therapy is effective in approximately two-thirds of patients to whom it is administered, but the effect is temporary. Lack of response to anti-TNF therapy stems from interplay of host-factors including: host cytokine response, disease phenotype, and antibody response to the anti-TNF agents. NOD 2, a defect present in approximately 50% of Crohn's disease patients, bears no relationship to non-response. Additionally, TNF promoter gene polymorphisms and TNF receptor gene heterogeneity play a significant role in non-response and disease course/severity. Adverse effects of anti-TNF therapy include early and delayed hypersensitivity reactions, cell-mediated infections, lupus-like syndrome, demyelinating diseases, and exacerbation of CHF.

Interleukin-10 and tumor necrosis factor alpha region haplotypes predict transplant-related mortality after unrelated donor stem cell transplantation

Certain cytokine gene polymorphisms have been shown to correlate with outcome of human leukocyte antigen (HLA) identical sibling donor stem cell transplantation (SCT), but in unrelated donor SCT such information is scarce. We have studied the association between cytokine gene polymorphism and transplant-related mortality (TRM) in 182 unrelated SCTs performed at a single center. We found association of polymorphism in the tumor necrosis factor alpha (TNF alpha) and interleukin-10 (IL-10) gene and TRM. Both the TNFd4 allele and the TNF alpha -1031C alleles are associated with high risk for TRM. Statistical analysis showed that both polymorphisms were present on a single haplotype. This haplotype was associated with high risk of TRM when present in recipient or donor, 55% (43%-67%) compared with 21% (12%-30%) when absent from both (P <.01). A further allele associated with this haplotype, TNFa5, is also associated with increased risk of TRM. For IL-10, presence of the donor R2-G-C-C haplotype was associated with decreased risk of TRM, 61% (43%-79%) versus 34% (25%-43%), P =.01. In contrast, possession of the R3-G-C-C haplotype by the donor predicted reduced risk of TRM, 30% (19%-41%, 95% CI) versus 53% (40%-66%, 95% CI), P =.01. No independent associations of cytokine polymorphisms with acute graft-versus-host disease were shown.

Tumour necrosis factor receptor type II 196M/R genotype correlates with circulating soluble receptor levels in normal subjects and with graft-versus-host disease after sibling allogeneic bone marrow transplantation1

BACKGROUND

A single nucleotide polymorphism in the tumor necrosis factor type II receptor (TNFRII) gene, codon 196, results in the substitution of arginine (R allele) for methionine (M allele). The 196R allele is reportedly associated with an increased susceptibility to autoimmune disease, and donor 196R allele carriage correlates with increased severity of acute graft-versus-host disease (GVHD) after matched unrelated bone marrow transplantation (BMT).

METHODS

We investigated the impact of donor and recipient TNFRII genotype on GVHD incidence and severity among 104 adult recipients of myeloablative sibling BMTs.

RESULTS

196R allele frequency was 0.28 among recipients, donors, and controls. There was an increased incidence of acute GVHD among 196R-positive recipients (odds ratio [OR] 3.6, P=0.05). This association was confirmed in multivariate analysis (relative risk 4, P=0.04), correcting for previously established clinical and genetic risk factors. Donor 196R homozygosity was associated with an increased incidence of extensive chronic GVHD (OR 18.5, P=0.02). This association was also confirmed in multivariate analysis (OR 11, P=0.02). To investigate the functional impact of the TNFRII 196 M/R polymorphism, 79 volunteer blood donors were genotyped at this locus, by polymerase chain reaction and single-strand conformational polymorphism analysis, and plasma soluble TNFRII (sTNFRII) levels were measured by ELISA. Mean plasma sTNFRII levels (pg/mL: +/-SEM) were 1224 (+/-26) and 1063 (+/-65) for 196M-postive (196 M homozygous or heterozygous) individuals and 196R homozygotes, respectively (P=0.02).

CONCLUSIONS

Because sTNFRIIs can act as TNF antagonists, the association between recipient and donor TNFRII 196R allele status and acute or extensive chronic GVHD incidence, respectively, may reflect reduced circulating sTNFRII.

Polymorphisms of interleukin-1alpha constitute independent risk factors for chronic graft-versus-host disease after allogeneic bone marrow transplantation

The interleukin-1 (IL-1) family of cytokines is widely involved in inflammatory processes and diseases with an inflammatory component. Polymorphisms of the IL-1alpha, IL-1beta and IL-1Ra genes have been implicated in a number of autoimmune or inflammatory conditions, with polymorphism of the IL-1Ra gene showing association with severity of graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation (BMT). We compared the clinical outcomes (GVHD and survival) of 115 patients after human leucocyte antigen (HLA)-identical sibling allogeneic BMT with their genotype for two polymorphisms present in the IL-1alpha gene, which have been implicated in immune-related pathology. Possession of allele 2 of the IL-1alpha-889 polymorphism and allele 2 of the IL-1alpha variable number tandem repeat (VNTR) polymorphism in the donor genotype was associated with the occurrence of chronic, but not acute GVHD. A local normal population was also genotyped for these polymorphisms, and subsequent analysis identified conserved haplotypes in this gene region. Haplotypes containing allele 2 at both IL-1alpha-889 and IL-1alpha VNTR loci were extremely uncommon, suggesting that both risk alleles would be inherited independently. Both loci could therefore function as independent disease association markers. The polymorphisms of the IL-1alpha gene could be used to predict chronic GVHD in HLA-matched sibling transplants alongside clinical risk factors.

New Developments in Allotransplant Immunology

After allogeneic stem cell transplantation, the establishment of the donor’s immune system in an antigenically distinct recipient confers a therapeutic graft-versus-malignancy effect, but also causes graft-versus-host disease (GVHD) and protracted immune dysfunction. In the last decade, a molecular-level description of alloimmune interactions and the process of immune recovery leading to tolerance has emerged. Here, new developments in understanding alloresponses, genetic factors that modify them, and strategies to control immune reconstitution are described.

In Section I, Dr. John Barrett and colleagues describe the cellular and molecular basis of the alloresponse and the mechanisms underlying the three major outcomes of engraftment, GVHD and the graft-versus-leukemia (GVL) effect. Increasing knowledge of leukemia-restricted antigens suggests ways to separate GVHD and GVL. Recent findings highlight a central role of hematopoietic-derived antigen-presenting cells in the initiation of GVHD and distinct properties of natural killer (NK) cell alloreactivity in engraftment and GVL that are of therapeutic importance. Finally, a detailed map of cellular immune recovery post-transplant is emerging which highlights the importance of post-thymic lymphocytes in determining outcome in the critical first few months following stem cell transplantation. Factors that modify immune reconstitution include immunosuppression, GVHD, the cytokine milieu and poorly-defined homeostatic mechanisms which encourage irregular T cell expansions driven by immunodominant T cell–antigen interactions.

In Section II, Prof. Anne Dickinson and colleagues describe genetic polymorphisms outside the human leukocyte antigen (HLA) system that determine the nature of immune reconstitution after allogeneic stem cell transplantation (SCT) and thereby affect transplant outcomethrough GVHD, GVL, and transplant-related mortality. Polymorphisms in cytokine gene promotors and other less characterized genes affect the cytokine milieu of the recipient and the immune reactivity of the donor. Some cytokine gene polymorphisms are significantly associated with transplant outcome. Other non-HLA genes strongly affecting alloresponses code for minor histocompatibility antigens (mHA). Differences between donor and recipient mHA cause GVHD or GVL reactions or graft rejection. Both cytokine gene polymorphisms (CGP) and mHA differences resulting on donor-recipient incompatibilities can be jointly assessed in the skin explant assay as a functional way to select the most suitable donor or the best transplant approach for the recipient.

In Section III, Dr. Nelson Chao describes non-pharmaceutical techniques to control immune reconstitution post-transplant. T cells stimulated by host alloantigens can be distinguished from resting T cells by the expression of a variety of activation markers (IL-2 receptor, FAS, CD69, CD71) and by an increased photosensitivity to rhodamine dyes. These differences form the basis for eliminating GVHD-reactive T cells in vitro while conserving GVL and anti-viral immunity. Other attempts to control immune reactions post-transplant include the insertion of suicide genes into the transplanted T cells for effective termination of GVHD reactions, the removal of CD62 ligand expressing cells, and the modulation of T cell reactivity by favoring Th2, Tc2 lymphocyte subset expansion. These technologies could eliminate GVHD while preserving T cell responses to leukemia and reactivating viruses.

Cytokines, viruses, and graft-versus-host disease

Proinflammatory cytokines released by host tissues during conditioning treatment and interferon gamma released from donor T cells play a major role in acute graft-versus-host disease (GVHD). In the past year the interaction of cytokines has been elucidated further. Host antigen-presenting cells play a key role in the induction of allogeneic recognition. Their activity is modulated by cytokines such as flt3-ligand, viruses, and donor T cells. Expansion of donor T cells is crucial for the pathogenesis of acute GVHD. Cytokines of the T helper 1 response-IFN-gamma, IL-12, and IL-18-regulate the expansion of donor and host cells via the induction of Fas and FasL and subsequent apoptosis. However TNF-alpha, FasL, and IL-1 also cause damage to target cells. Cytokine and receptor gene polymorphism has an impact on the activity of both host and donor cell activation. Genetic factors, conditioning treatment, lipopolysaccharides (LPS) from gram-negative microorganisms, viral infections, and donor T cells determine the activity level of host antigen-presenting cells and macrophages, which have an impact on acute GVHD and other complications of allogeneic stem cell transplantation.