IL2RA/CD25 polymorphisms contribute to multiple sclerosis susceptibility

Regulatory T cells in rheumatoid arthritis: functions, development, regulation, and therapeutic potential

Rheumatoid arthritis (RA) is an autoimmune disease that mainly affects the joints but also leads to systemic inflammation. Auto-reactivity and dysregulation of self-tolerance are thought to play a vital role in disease onset. In the pathogenesis of autoimmune diseases, disturbed immunosuppressive properties of regulatory T cells contribute to the dysregulation of immune homeostasis. In RA patients, the functions of Treg cells and their frequency are reduced. Therefore, focusing on the re-establishment of self-tolerance by increasing Treg cell frequencies and preventing a loss of function is a promising strategy for the treatment of RA. This approach could be especially beneficial for those patients who do not respond well to current therapies. In this review, we summarize and discuss the current knowledge about the function, differentiation and regulation of Treg cells in RA patients and in animal models of autoimmune arthritis. In addition, we highlight the therapeutic potential as well as the challenges of Treg cell targeting treatment strategies.

The IL-2 - IL-2 receptor pathway: Key to understanding multiple sclerosis

The development, progression, diagnosis and treatment of autoimmune diseases, such as multiple sclerosis (MS), are convoluted processes which remain incompletely understood. Multiple studies demonstrated that the interleukin (IL)-2 – IL-2 receptor (IL-2R) pathway plays a pivotal role within these processes. The most striking functions of the IL-2 – IL-2R pathway are the differential induction of autoimmune responses and tolerance. This paradoxical function of the IL-2 – IL-2R pathway may be an attractive therapeutic target for autoimmune diseases such as MS. However, the exact mechanisms that lead to autoimmunity or tolerance remain to be elucidated. Furthermore, another factor of this pathway, the soluble form of the IL-2R (sIL-2R), further complicates understanding the role of the IL-2 – IL-2R pathway in MS. The challenge is to unravel these mechanisms to prevent, diagnose and recover MS. In this review, first, the current knowledge of MS and the IL-2 – IL-2R pathway are summarized. Second, the key findings of the relation between the IL-2 – IL-2R pathway and MS have been highlighted. Eventually, this review may launch broad interest in the IL-2 – IL-2R pathway propelling further research in autoimmune diseases, including MS.

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The IL-2 – IL-2R pathway determines the balance between immunity and tolerance.

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The IL-2 – IL-2R pathway is involved in the pathogenesis of multiple sclerosis.

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The role of soluble IL-2R is controversial and requires further investigation.

Association of HLA-DRA and IL2RA Polymorphisms with the Severity and Relapses Rate of Multiple Sclerosis in an Iranian Population

Background

Multiple sclerosis (MS) is a multifactorial condition in which many genetic and environmental factors interfere. The association between genes involved in the immune system and MS was previously reported. The aims of this study were to evaluate 14 SNPs of HLA-DRA, 14 SNPs of IL2RA with severity of MS through Expanded Disability Status Scale (EDSS) and Annualized Relapse Rate (ARR).

Methods

102 patients with MS referred to Sina hospital in Tehran, Iran, were diagnosed and studied based on McDonald's guideline, clinical signs, and brain imaging procedures. All patients were included in the study following informed consent. Genotyping study of 14 variants in the HLA-DRA, and 14 variants in IL2RA was conducted by Sanger sequencing. Disease outcomes including EDSS and ARR were registered. Outcome measures between different genotypes of each SNPs were compared separately.

Results

Among 14 SNPs in IL 2RA the genotypes of rs12722489 showed a significant association with ARR in two consecutive years. Mean ARR1 was 1.06±1.12, 0.20±0.34 and 0.31±.50 for AA, GA, and GG genotypes, respectively (p value= 0.008). Mean ARR2 was 1.5±1.08, 0.28±0.40, and 0.42±0.55 for AA, GA, and GG, respectively (p value= 0.001). Regression analysis showed a significant association between rs12722489 with ARR1 and ARR2, removing the potential confounding mediators. No significant association was found between SNPs in HLA-DRA with the attack rate and severity of MS.

Conclusion

The rs12722489 of IL-2RA has an association with ARR, but not with EDSS.

Regulatory T Cell Development

Foxp3-expressing CD4⁺ regulatory T (Treg) cells play key roles in the prevention of autoimmunity and the maintenance of immune homeostasis and represent a major barrier to the induction of robust antitumor immune responses. Thus, a clear understanding of the mechanisms coordinating Treg cell differentiation is crucial for understanding numerous facets of health and disease and for developing approaches to modulate Treg cells for clinical benefit. Here, we discuss current knowledge of the signals that coordinate Treg cell development, the antigen-presenting cell types that direct Treg cell selection, and the nature of endogenous Treg cell ligands, focusing on evidence from studies in mice. We also highlight recent advances in this area and identify key unanswered questions.

A genetic link between CXCR5 and IL2RA gene polymorphisms and susceptibility to multiple sclerosis

OBJECTIVES

Multiple sclerosis (MS) is a T-cell-mediated disease of the central nervous system that develops in individuals possessing a complex susceptibility trait. We explored relationship between gene polymorphisms in MS.

METHODS

To identify the associations of CXCR5 and IL2RA gene polymorphisms with susceptibility to MS, we recruited 263 MS patients from the Han nationality and 138 from the Hui nationality as MS group and 284 healthy volunteers from the Han nationality and 156 from the Hui nationality as controls. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was employed to test gene polymorphisms of IL2RA (rs2104286 and rs12722489). Sequenom MassARRAY system was applied to analyze genotyping of CXCR5 (rs3922).

RESULTS

The genotypes and allele frequency distributions at the loci of IL2RA rs2104286 and rs12722489 showed significant differences between the MS and control groups. The gene polymorphisms at the loci of IL2RA rs2104286 and rs12722489 may increase the onset risk of MS. IL2RA-rs2104286 showed a positive relationship with CXCR5-rs3922. The same relationship was also observed between IL2RA-rs12722489 and CXCR5-rs3922. The genotypes and allele frequencies of loci of rs2104286 and rs12722489 were significantly different in MS clinical subtypes and severity (EDSS score). Additionally, CAC and TGC haplotype at rs3922-rs12722489-rs2104286 may reduce the risk of MS, while CGT and TGT haplotypes increase the risk.

CONCLUSION

The gene polymorphisms at the loci of IL2RA rs2104286 and rs12722489 are closely associated with susceptibility to MS in the Han and Hui nationalities.

[Clinical and molecular genetic analysis of a case of familial multiple sclerosis in the Republic of Bashkortostan]

AIM

To investigate clinical manifestations of multiple sclerosis (MS) and the genetic makeup of six affected members of one family.

MATERIAL AND METHODS

Six members of the family of Russian ethnic origin were examined. Pedigree analysis and genotyping of polymorphic markers of candidate genes for multiple sclerosis were performed.

RESULTS AND CONCLUSION

The accumulation of alleles that were associated with autoimmune diseases according to the results of genome-wide association studies (rs1109670*C, rs3129934*T, rs9523762*G, rs1570538*T) was found in the family. The results confirm the contribution of several genetic variants to familial forms of MS.

CD6 gene polymorphism rs17824933 is associated with multiple sclerosis in Indian population

Background:

Multiple sclerosis (MS) prevalence has increased worldwide. The known genetic association for MS in the west has not been studied in detail in nonwhite populations and particularly Indians.

Objective:

The objective of this study was to evaluate some known genetic variations outside the major histocompatibility complex (MHC) region associated with MS in patients of Indian origin.

Materials and Methods:

We investigated 10 gene-associated single nucleotide polymorphisms (SNP's) outside the MHC region in 300 patients and 720 unrelated controls. Genotyping was performed on an ABI7500 real-time polymerase chain reaction genotyping platform using predesigned TaqMan SNP genotyping assays.

Results:

CD6 gene associated SNP (rs17824933) showed significant association with MS (P = 4.2 × 10⁻⁵, odds ratio [OR] = 2.24, confidence interval (CI) = 1.51–3.33). A modest association was also noted for TMEM39A rs1132200 (P = 0.023, OR = 1.41, CI = 1.05–1.91) and IL2RA rs2104286 (P = 0.04, OR = 1.3, CI = 1.006–1.67). In the remaining SNPs, the allele frequencies were overexpressed in patients when compared to healthy controls.

Conclusion:

Our data illustrate the similarity in risk association between Indian and European populations for MS.

Signals and pathways controlling regulatory T cells

Induction of specific immune tolerance to grafts remains the sought-after standard following transplantation. Defined by expression of the Foxp3 (forkhead box protein 3) transcription factor, the regulatory T-cell (Treg) lineage has been noted to exert potent immunoregulatory functions that contribute to specific graft tolerance. In this review, we discuss the known signals and pathways which govern Treg development, both in the thymus and in peripheral sites, as well as lineage maintenance and homeostasis. In particular, we highlight the roles of T-cell receptor signaling, CD28 costimulation, and signals through phosphatidyl inositol 3-kinase (PI3K) and related metabolic pathways in multiple aspects of Treg biology.

Where is the causal variant? On the advantage of the family design over the case-control design in genetic association studies

Many associated single-nucleotide polymorphisms (SNPs) have been identified by association studies for numerous diseases. However, the association between a SNP and a disease can result from a causal variant in linkage disequilibrium (LD) with the considered SNP. Assuming that the true causal variant is among the genotyped SNPs, other authors demonstrated that the power to discriminate between it and other SNPs in LD is low. Here, we propose to take advantage of the information provided by family data to improve the inference on the causal variant: we exploit the linkage information provided by affected sib pairs to discriminate the causal variant from the associated SNPs. The family-based approach improves discrimination power requiring up to five times less individuals than its case-control equivalent. However, the main advantage of family design is the possibility to carry out the procedure one step further: the linkage information allows inference on causal variants, which are not genotyped but in LD with tag-SNPs displaying association, which is impossible with case-control design. By means of Bayesian methods, we estimate the LD between the observed SNPs and an unobserved causal variant, as well as the allelic odds ratio at the unobserved causal variant. The proposed procedure is illustrated on a multiple sclerosis (MS) family data set including genotypes of SNPs in IL2RA, confirming the advantage of using a family design to identify causal variants. The results of our method on this data suggest the existence of two distinct causal variants in this gene for the MS.

Plasma concentrations of soluble IL-2 receptor α (CD25) are increased in type 1 diabetes and associated with reduced C-peptide levels in young patients

AIMS/HYPOTHESIS

Type 1 diabetes is a common autoimmune disease that has genetic and environmental determinants. Variations within the IL2 and IL2RA (also known as CD25) gene regions are associated with disease risk, and variation in expression or function of these proteins is likely to be causal. We aimed to investigate if circulating concentrations of the soluble form of CD25, sCD25, an established marker of immune activation and inflammation, were increased in individuals with type 1 diabetes and if this was associated with the concentration of C-peptide, a measure of insulin production that reflects the degree of autoimmune destruction of the insulin-producing beta cells.

METHODS

We used immunoassays to measure sCD25 and C-peptide in peripheral blood plasma from patient and control samples.

RESULTS

We identified that sCD25 was increased in patients with type 1 diabetes compared with controls and replicated this result in an independent set of 86 adult patient and 80 age-matched control samples (p = 1.17 × 10(-3)). In 230 patients under 20 years of age, with median duration-of-disease of 6.1 years, concentrations of sCD25 were negatively associated with C-peptide concentrations (p = 4.8 × 10(-3)).

CONCLUSIONS/INTERPRETATION

The 25% increase in sCD25 in patients, alongside the inverse association between sCD25 and C-peptide, probably reflect the adverse effects of an on-going, actively autoimmune and inflammatory immune system on beta cell function in patients.

Multiple autoimmune-associated variants confer decreased IL-2R signaling in CD4+ CD25(hi) T cells of type 1 diabetic and multiple sclerosis patients

IL-2 receptor (IL-2R) signaling is essential for optimal stability and function of CD4⁺CD25^hiFOXP3⁺ regulatory T cells (Treg); a cell type that plays an integral role in maintaining tolerance. Thus, we hypothesized that decreased response to IL-2 may be a common phenotype of subjects who have autoimmune diseases associated with variants in the IL2RA locus, including T1D and MS, particularly in cells expressing the high affinity IL-2R alpha chain (IL-2RA or CD25). To examine this question we used phosphorylation of STAT5 (pSTAT5) as a downstream measure of IL-2R signaling, and found a decreased response to IL-2 in CD4⁺CD25^hi T cells of T1D and MS, but not SLE patients. Since the IL2RArs2104286 haplotype is associated with T1D and MS, we measured pSTAT5 in controls carrying the rs2104286 risk haplotype to test whether this variant contributed to reduced IL-2 responsiveness. Consistent with this, we found decreased pSTAT5 in subjects carrying the rs2104286 risk haplotype. Reduced IL-2R signaling did not result from lower CD25 expression on CD25^hi cells; instead we detected increased CD25 expression on naive Treg from controls carrying the rs2104286 risk haplotype, and subjects with T1D and MS. However the rs2104286 risk haplotype correlated with increased soluble IL-2RA levels, suggesting that shedding of the IL-2R may account in part for the reduced IL-2R signaling associated with the rs2104286 risk haplotype. In addition to risk variants in IL2RA, we found that the T1D-associated risk variant of PTPN2rs1893217 independently contributed to diminished IL-2R signaling. However, even when holding genotype constant at IL2RA and PTPN2, we still observed a significant signaling defect in T1D and MS patients. Together, these data suggest that multiple mechanisms converge in disease leading to decreased response to IL-2, a phenotype that may eventually lead to loss of tolerance and autoimmunity.

Association of variants in IL2RA with progression of joint destruction in rheumatoid arthritis

OBJECTIVE

Heritability studies have suggested an important role of genetic predisposition in the progression of joint destruction in rheumatoid arthritis (RA); the heritability is estimated at 45-58%. Several single-nucleotide polymorphisms (SNPs) have been identified as being associated with RA susceptibility. Our objective was to study the association of several of these loci with progression of joint destruction.

METHODS

We studied 1,750 RA patients in 4 independent data sets with 4,732 radiographs scored using the modified Sharp/van der Heijde method. Thirteen susceptibility SNPs that were not previously associated with joint destruction were tested in 596 Dutch RA patients. Subsequently, significant SNPs were studied in data sets of RA patients from North America and Iceland. Data were summarized in inverse-weighted variance meta-analyses. Further, the association with circulating protein levels was studied and the associated region was fine-mapped.

RESULTS

In stage 1, 3 loci (AFF3, IL2RA, and BLK) were significantly associated with the rate of joint destruction and were further analyzed in the additional data sets. In the combined meta-analyses, the minor (C) allele of IL2RA (rs2104286) was associated with less progression of joint destruction (P = 7.2 × 10(-4) ). Furthermore, the IL2RA (rs2104286) protective genotype was associated with lower (0.85-fold [95% confidence interval 0.77-0.93], P = 1.4 × 10(-3) ) circulating levels of soluble interleukin-2 receptor α (sIL-2Rα). Additionally, lower sIL-2Rα levels were associated with a lower rate of joint destruction (P = 3.4 × 10(-3) ). The association of IL2RA with the rate of joint destruction was further localized to a 40-kb region encompassing the IL2RA intron 1 and the 5' region of IL2RA and RBM17.

CONCLUSION

The present genetic and serologic data suggest that inherited altered genetic constitution at the IL2RA locus may predispose to a less destructive course of RA.

Intersection between genetic polymorphisms and immune deviation in type 1 diabetes

PURPOSE OF REVIEW

Above 60 non-HLA genes have been associated with T1D, many of which are immune-related genes. One challenge following identification of these genes is finding causative connections between risk alleles and disease. Phenotypes linked to T1D-associated genetic variants are beginning to help us better understand the cellular and molecular mechanisms underlying T1D.

RECENT FINDINGS

The list of immune-related genes with T1D-associated polymorphisms will be reviewed and cellular phenotypes correlating with these variants will be described highlighting recent finding from variants in the PTPN22 gene and genes encoding proteins in theIL-2/IL2R signaling pathway.

SUMMARY

Building from extensive genome-wide association studies, we are discovering cellular and molecular phenotypes that may help unravel the underlying causes of T1D.

High dose antigen treatment with a peptide epitope of myelin basic protein modulates T cells in multiple sclerosis patients

One of the auto-antigens aberrantly targeted in Multiple sclerosis is myelin basic protein (MBP). In this study, chronic progressive multiple sclerosis (CPMS) patients receiving the experimental drug MBP8298, on a compassionate care trial, were examined before and after high dose peptide treatment for their circulating regulatory T-cell numbers and their responses to the common mitogens, phytohemagglutinin and poke-weed mitogen. Peripheral blood mononuclear cells (PBMCs) isolated from these patients before treatment displayed anergy upon stimulation with phytohemagglutinin; measured through reduced proliferation, IFN-γ and IL-17A secretion in an in vitro cell culture system. 6 Weeks and 6months after treatment their PBMCs displayed a reversal of anergy with phytohemagglutinin stimulation. There was also a marked increase in their CD4(+)CD25(+hi)FoxP3(+) T-cells regulatory T-cells. These results suggest that high dose MBP8298 treatment has a profound effect on the circulating T-cells of CPMS patients, capable of reversing peripheral anergy and establishing T regulation.

Immunogenetic mechanisms leading to thyroid autoimmunity: recent advances in identifying susceptibility genes and regions

The autoimmune thyroid diseases (AITD) include Graves’ disease (GD) and Hashimoto’s thyroiditis (HT), which are characterised by a breakdown in immune tolerance to thyroid antigens. Unravelling the genetic architecture of AITD is vital to better understanding of AITD pathogenesis, required to advance therapeutic options in both disease management and prevention. The early whole-genome linkage and candidate gene association studies provided the first evidence that the HLA region and CTLA-4 represented AITD risk loci. Recent improvements in; high throughput genotyping technologies, collection of larger disease cohorts and cataloguing of genome-scale variation have facilitated genome-wide association studies and more thorough screening of candidate gene regions. This has allowed identification of many novel AITD risk genes and more detailed association mapping. The growing number of confirmed AITD susceptibility loci, implicates a number of putative disease mechanisms most of which are tightly linked with aspects of immune system function. The unprecedented advances in genetic study will allow future studies to identify further novel disease risk genes and to identify aetiological variants within specific gene regions, which will undoubtedly lead to a better understanding of AITD patho-physiology.

Sample reproducibility of genetic association using different multimarker TDTs in genome-wide association studies: characterization and a new approach

Multimarker Transmission/Disequilibrium Tests (TDTs) are very robust association tests to population admixture and structure which may be used to identify susceptibility loci in genome-wide association studies. Multimarker TDTs using several markers may increase power by capturing high-degree associations. However, there is also a risk of spurious associations and power reduction due to the increase in degrees of freedom. In this study we show that associations found by tests built on simple null hypotheses are highly reproducible in a second independent data set regardless the number of markers. As a test exhibiting this feature to its maximum, we introduce the multimarker-Groups TDT (), a test which under the hypothesis of no linkage, asymptotically follows a distribution with degree of freedom regardless the number of markers. The statistic requires the division of parental haplotypes into two groups: disease susceptibility and disease protective haplotype groups. We assessed the test behavior by performing an extensive simulation study as well as a real-data study using several data sets of two complex diseases. We show that test is highly efficient and it achieves the highest power among all the tests used, even when the null hypothesis is tested in a second independent data set. Therefore, turns out to be a very promising multimarker TDT to perform genome-wide searches for disease susceptibility loci that may be used as a preprocessing step in the construction of more accurate genetic models to predict individual susceptibility to complex diseases.

Genetics of experimental allergic encephalomyelitis supports the role of T helper cells in multiple sclerosis pathogenesis

OBJECTIVE

The major histocompatibility complex (MHC) is the primary genetic contributor to multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE), but multiple additional interacting loci are required for genetic susceptibility. The identity of most of these non-MHC genes is unknown. In this report, we identify genes within evolutionarily conserved genetic pathways leading to MS and EAE.

METHODS

To identify non-MHC binary and quantitative trait loci (BTL/QTL) important in the pathogenesis of EAE, we generated phenotype-selected congenic mice using EAE-resistant B10.S and EAE-susceptible SJL mice. We hypothesized that genes linked to EAE BTL/QTL and MS-GWAS can be identified if they belong to common evolutionarily conserved pathways, which can be identified with a bioinformatic approach using Ingenuity software.

RESULTS

Many known BTL/QTL were retained and linked to susceptibility during phenotype selection, the most significant being a region on chromosome 17 distal to H2 (Eae5). We show in pathway analysis that T helper (T(H))-cell differentiation genes are critical for both diseases. Bioinformatic analyses predicted that Eae5 is important in CD4 T-effector and/or Foxp3(+) T-regulatory cells (Tregs), and we found that B10.S-Eae5(SJL) congenic mice have significantly greater numbers of lymph node CD4 and Tregs than B10.S mice.

INTERPRETATION

These results support the polygenic model of MS/EAE, whereby MHC and multiple minor loci are required for full susceptibility, and confirm a critical genetic dependence on CD4 T(H)-cell differentiation and function in the pathogenesis of both diseases.

A variant of the Il2ra / Cd25 gene predisposing to graves' disease is associated with increased levels of soluble interleukin-2 receptor

Alpha-subunit of the IL-2 receptor (IL-2Rα) encoded by the IL2RA/CD25 gene binds IL-2 that plays a pivotal role in the regulation of T cell function. Levels of a soluble form of IL-2Rα (sIL-2Rα) lacking the transmembrane and cytoplasmic domains were shown to be increased in several autoimmune diseases including Graves' disease (GD). Recent studies showed association between the IL2RA/CD25 gene variants and several autoimmune diseases including GD. In this study, we analyzed whether polymorphic markers rs2104286, rs41295061, and rs11594656 located at the IL2RA/CD25 locus confer susceptibility to GD and are related to increased concentrations of sIL-2Rα. A total of 1474 Russian GD patients and 1609 control subjects were genotyped for rs2104286, rs41295061, and rs11594656 using a Taqman assay. Concentrations of sIL-2Rα in sera of affected and non-affected individuals were measured using an ELISA test. A minor allele A of rs41295061 showed significant association with increased risk of GD [odds ratio (OR) = 1.43, P(c)  = 0.00102]. The allele A of rs41295061 and allele A of rs11594656 constitute a higher risk haplotype AA (OR = 1.47, P(c)  = 0.0477). Compared to carriers of the protective haplogenotype GT/GT, the carriage of two copies of the haplogenotype AA/AA was associated with elevated levels of sIL-2Rα in both GD patients (AA/AA versus GT/GT: 1.35 ± 0.47 ng/ml versus 1.12 ± 0.45 ng/ml, P = 0.0065) and healthy controls (AA/AA versus GT/GT: 0.67 ± 0.28 ng/ml versus 0.51 ± 0.33 ng/ml, P = 0.0098). This is the first report presenting correlation between the carriage of disease-associated variants of IL2RA/CD25 with increased levels of sIL-2Rα in GD.

Determination of the real effect of genes identified in GWAS: the example of IL2RA in multiple sclerosis

Genome-wide association studies (GWAS), although efficient to detect genes involved in complex diseases, are not designed to measure the real effect of the genes. This is illustrated here by the example of IL2RA in multiple sclerosis (MS). Association between IL2RA and MS is clearly established, although the functional variation is still unknown: the effect of IL2RA might be better described by several SNPs than by a single one. This study investigates whether a pair of SNPs better explains the observed linkage and association data than a single SNP. In total, 522 trio families and 244 affected sib-pairs were typed for 26 IL2RA SNPs. For each SNP and pairs of SNPs, the phased genotypes of patients and controls were compared to determine the SNP set offering the best risk discrimination. Consistency between the genotype risks provided by the retained set and the identical by descent allele sharing in affected sib-pairs was assessed. After controlling for multiple testing, the set of SNPs rs2256774 and rs3118470, provides the best discrimination between the case and control genotype distributions (P-corrected=0.009). The relative risk between the least and most at-risk genotypes is 3.54 with a 95% confidence interval of [2.14-5.94]. Furthermore, the linkage information provided by the allele sharing between affected sibs is consistent with the retained set (P=0.80) but rejects the SNP reported in the literature (P=0.006). Establishing a valid modeling of a disease gene is essential to test its potential interaction with other genes and to reconstruct the pathophysiological pathways.

Interleukin 2 Receptor α Gene Polymorphism and Risk of Multiple Sclerosis: A Meta-Analysis

This meta-analysis studied the association between interleukin 2 receptor a (IL2RA) gene polymorphisms rs2104286 and rs12722489 and susceptibility to multiple sclerosis (MS). Case-control genetic association studies published before January 2011 were retrieved from the PubMed and EMBASE databases and the Cochrane Library. Eight studies comprising 13 569 patients and 23 435 controls met the selection criteria for meta-analysis of the IL2RA rs2104286 polymorphism. Using a fixed-effects model, the T allele and the TT and TT + TC genotypes of the IL2RA rs2104286 polymorphism were found to be associated with MS. Five studies comprising 5643 patients and 6415 controls met the selection criteria for meta-analysis of the IL2RA rs12722489 polymorphism. Using a fixed-effects model, the C allele and the CC genotype of the IL2RA rs12722489 polymorphism were found to be associated with MS but the CC + CT genotype was not. It was concluded that both of the IL2RA gene polymorphisms, rs2104286 and rs12722489, were associated with increased susceptibility to MS.

An autoimmune-associated variant in PTPN2 reveals an impairment of IL-2R signaling in CD4(+) T cells

The IL-2/IL-2R signaling pathway has an important role in autoimmunity. Several genes identified in genome-wide association (GWA) studies encode proteins in the IL-2/IL-2R signaling cascade that are associated with autoimmune diseases. One of these, PTPN2, encodes a protein tyrosine phosphatase that is highly expressed in T cells and regulates cytokine signaling. An intronic risk allele in PTPN2, rs1893217(C), correlated with decreased IL-2R signaling in CD4(+) T cells as measured by phosphorylation of STAT5 (phosphorylated STAT5 (pSTAT5)). We modeled an additive single nucleotide polymorphism (SNP) genotype, in which each copy of the risk allele conferred a decrease in IL-2R signaling (P=4.4 × 10(-8)). Decreased pSTAT5 impacted IL-2Rβ chain signaling resulting in reduced FOXP3 expression in activated cells. This phenotype was not due to overt differences in expression of the IL-2R, molecules in the IL-2R signaling cascade or defects in STAT5. However, the rs1893217(C) risk variant did correlate with decreased PTPN2 expression in CD4(+)CD45RO T cells (P=0.0002). Thus, the PTPN2rs1893217(C) risk allele associated with reduced pSTAT5 in response to IL-2 and reduced PTPN2 expression. Together, these data suggest that decreased expression of PTPN2 may indirectly modulate IL-2 responsiveness. These findings, identified through genotype/phenotype relationships, may lead to identification of novel mechanisms underlying dysregulation of cytokine signaling in autoimmunity.

Transcriptional characteristics of CD4+ T cells in multiple sclerosis: relative lack of suppressive populations in blood

BACKGROUND

Multiple sclerosis (MS) is hypothetically caused by autoreactive Th1 and Th17 cells, whereas Th2 and regulatory T cells may confer protection. The development of Th subpopulations is dependant on the expression of lineage-specific transcription factors.

OBJECTIVE

The aim of this study was to assess the balance of CD4(+)T cell populations in relapsing-remitting MS.

METHODS

Blood mRNA expression of TBX21, GATA3, RORC, FOXP3 and EBI3 was assessed in 33 patients with relapsing-remitting MS and 20 healthy controls. In addition, flow cytometry was performed to assess T lymphocyte numbers.

RESULTS

In relapsing-remitting MS, diminished expression of FOXP3 (Treg) was found (p < 0.05), despite normal numbers of CD4(+)CD25(hi)Treg. Immunoregulatory EBI3 and Th2-associated GATA3 ([a-z]+) was also decreased in MS (p < 0.005 and p < 0.05, respectively). Expression of TBX21 (Th1) and RORC (Th17) did not differ between patients and controls. Similar changes were observed when analysing beta-interferon treated (n = 12) or untreated (n = 21) patients. Analysis of transcription factor ratios, comparing TBX21/GATA3 and RORC/FOXP3, revealed an increase in the RORC/FOXP3 ratio in patients with relapsing-remitting MS (p < 0.005).

CONCLUSION

Our findings indicate systemic defects at the mRNA level, involving downregulation of beneficial CD4(+)phenotypes. This might play a role in disease development by permitting activation of harmful T cell populations.

Validation of the CD6 and TNFRSF1A loci as risk factors for multiple sclerosis in Spain

A recent meta-analysis of genome-wide association screens coupled to a replication exercise in a combined US/UK collection led to the identification of 4 single nucleotide polymorphisms (SNPs) in three gene loci, i.e. TNFRSF1A, CD6 and IRF8, as novel risk factors for multiple sclerosis with genome-wide level of significance. In the present study, using a combined all-Spain collection of 2515 MS patients and 2942 healthy controls, we demonstrate significant association of rs17824933 in CD6 (P(CMH)=0.004; OR=1.14; 95% CI 1.04-1.24) and of rs1860545 in TNFRSF1A (P(CMH)=0.001; OR=1.15; 95% CI 1.06-1.25) with MS, while the low-frequency coding non-synonymous SNP rs4149584 in TNFRSF1A displayed a trend for association (P(CMH)=0.062; OR=1.27; 95% CI 0.99-1.63). This data reinforce a generic role for CD6 and TNFRSF1A in susceptibility to MS, extending to populations of southern European ancestry.

Polymorphisms in the IL2, IL2RA and IL2RB genes in multiple sclerosis risk

Interleukin (IL)-2/IL-2R signalling promotes proliferation and survival of activated T cells and has an essential non-redundant role in the production of regulatory T cells. Associations with different autoimmune diseases of polymorphisms in a linkage disequilibrium block in which the IL2/IL21 genes map (4q27), and also in genes encoding the IL2RA and IL2RB subunits (located in 10p15 and 22q13, respectively), were identified through genome-wide studies. Polymorphisms in these three genes were studied in 430 multiple sclerosis (MS) patients and in 550 ethnically matched controls from Madrid (Spain). Replication and meta-analysis with results from an independent cohort of 771 MS patients and 759 controls from Andalucía (Spain) confirmed the association of polymorphisms in the IL2RA gene (P(Mantel-Haenszel,) odds ratio (OR)(M-H) (95% confidence interval, CI) for rs2104286: 0.0001, 0.75 (0.65-0.87); for rs11594656/rs35285258: 0.004, 1.19 (1.06-1.34); for rs41295061: 0.03, 0.77 (0.60-0.98)); showed a trend for association of the IL2/IL21 rs6822844 (P(M-H)=0.07, OR(M-H) (95% CI)=0.86 (0.73-1.01)), but did not corroborate the association for IL2RB. Regression analyses of the combined Spanish cohort revealed the independence of two IL2RA association signals: rs2104286 and rs11594656/rs35285258. The relevant role of the IL2RA gene on MS susceptibility adds support to its common effect on autoimmune risk and the suggestive association of IL2/IL21 warrants further investigation.

MGAT5 alters the severity of multiple sclerosis

Multiple Sclerosis (MS) is a genetically complex immune mediated, demyelinating disease of the central nervous system. To date no genetic variants have been unambiguously linked to disease severity. We have conducted a genome wide screen, using Affymetrix Genechip 500K technology, for severity in 1040 MS patients. Two markers within MGAT5, a gene coding for a glycosylation enzyme, were found to be significantly associated with outcome in the screening as well as in an independent population (combined p-values: 2.8 x 10(-6) and 1.5 x 10(-7)).

Tag-SNP analysis of the GFI1-EVI5-RPL5-FAM69 risk locus for multiple sclerosis

A recent genome-wide association study conducted by the International Multiple Sclerosis Genetic Consortium (IMSGC) identified, among others, a number of putative multiple sclerosis (MS) susceptibility variants at position 1p22. Twenty-one SNPs positively associated with MS were located at the GFI-EVI5-RPL5-FAM69A locus. In this study, we performed an analysis and fine mapping of this locus, genotyping eight Tag-SNPs in 732 MS patients and 974 controls from Spain. We observed an association with MS in three of eight Tag-SNPs: rs11804321 (P=0.008, OR=1.29; 95% CI=1.08-1.54), rs11808092 (P=0.048, OR=1.19; 95% CI=1.03-1.39) and rs6680578 (P=0.0082, OR=1.23; 95% CI=1.07-1.41). After correcting for multiple comparisons and using logistic regression analysis to test the addition of each SNP to the most associated SNPs, we observed that rs11804321 alone was sufficient to model the association. This Tag-SNP captures two SNPs in complete linkage disequilibrium (r(2)=1), both located within the 17th intron of the EVI5 gene. Our findings agree with the corresponding data of the recent IMSGC study and present new genetic evidence that points to EVI5 as a factor of susceptibility to MS.

TNF-alpha promoter polymorphisms in multiple sclerosis: no association with -308 and -238 alleles, but the -857 alleles in associated with the disease in Turkish patients

Dysregulation in the expression of pro- and anti-inflammatory cytokines is one of the milestones in multiple sclerosis (MS) development and progression. Tumour necrosis factor (TNF-alpha), a proinflammatory cytokine is believed to play an important role in MS pathogenesis. The objective of this study is to investigate the association between TNF-alpha promoter region (TNF-alpha-238, -308 and -857) and susceptibility to MS and clinical course of the disease. Eighty-six relapsing remitting MS patients and 150 sex-, age- and ethnic-matched controls were enrolled in the study. Genotyping was performed by PCR-RFLP method. We observed a statistically significant increase in TNF-alpha 857 CC genotype in MS patients than controls (P < 0.001) while TNF-alpha 857 CT genotype showed a significant negative correlation with MS patients (P = 0.033). No differences in the distribution of the TNF-alpha-238 and -308 alleles were observed. None of the three polymorphisms (-238, -308 and -857) did not show relation with disease duration, Expanded Disability Status Scale or age of onset. On the other hand, significant difference of TNF -857 CC genotype was identified with the low disease index (P = 0.025). Although the study group is small, the results indicate that TNF-alpha 857 CC genotype may cause susceptibility to MS in the Turkish population.

Hexose-6-phosphate dehydrogenase: a new risk gene for multiple sclerosis

A recent genome-wide association study (GWAS) performed by the The Wellcome Trust Case-Control Consortium based on 12 374 nonsynonymous single-nucleotide polymorphisms (SNPs) provided evidence for several genes involved in multiple sclerosis (MS) susceptibility. In this study, we aimed at verifying the association of 19 SNPs with MS, with P-values < or =0.005, in an independent cohort of 732 patients and 974 controls, all Caucasian from the South of Spain. We observed an association of the rs17368528 polymorphism with MS (P=0.04, odds ratio (OR)=0.801, 95% confidence interval (CI)=0.648-0.990). The association of this polymorphism with MS was further validated in an independent set of 1318 patients from the Canadian Collaborative Project (P=0.04, OR=0.838, 95% CI=0.716-0.964). This marker is located on chromosome 1p36.22, which is 1 Mb away from the MS-associated kinesin motor protein KIF1B, although linkage disequilibrium was not observed between these two markers. The rs17368528 SNP results in an amino-acid substitution (proline to leucine) in the fifth exon of the hexose-6-phosphate dehydrogenase (H6PD) gene, in which some variants have been reported to attenuate or abolish H6PD activity, in individuals with cortisone reductase deficiency. This study corroborates the association of one locus determined by GWAS and points to H6PD as a new candidate gene for MS.

Low frequency of CD4+CD25+ Treg in SLE patients: a heritable trait associated with CTLA4 and TGFbeta gene variants

Background

CD4⁺CD25⁺ regulatory T cells play an essential role in maintaining immune homeostasis and preventing autoimmunity. Therefore, defects in Treg development, maintenance or function have been associated with several human autoimmune diseases including Systemic Lupus Erythematosus (SLE), a systemic autoimmune disease characterized by loss of tolerance to nuclear components and significantly more frequent in females.

Results

To investigate the involvement of Treg in SLE pathogenesis, we determined the frequency of CD4⁺CD25⁺CD45RO⁺ T cells, which encompass the majority of Treg activity, in the PBMC of 148 SLE patients (76 patients were part of 54 families), 166 relatives and 117 controls. SLE patients and their relatives were recruited in several Portuguese hospitals and through the Portuguese Lupus Association. Control individuals were blood donors recruited from several regional blood donor centers. Treg frequency was significantly lower in SLE patients than healthy controls (z = -6.161, P < 0.00001) and intermediate in the relatives' group. Remarkably, this T cell subset was also lower in females, most strikingly in the control population (z = 4.121, P < 0.001). We further ascertained that the decreased frequency of Treg in SLE patients resulted from the specific reduction of bona fide FOXP3⁺CD4⁺CD25⁺ Treg. Treg frequency was negatively correlated with SLE activity index (SLEDAI) and titers of serum anti-dsDNA antibodies. Both Treg frequency and disease activity were modulated by IVIg treatment in a documented SLE case. The segregation of Treg frequency within the SLE families was indicative of a genetic trait. Candidate gene analysis revealed that specific variants of CTLA4 and TGFβ were associated with the decreased frequency of Treg in PBMC, while FOXP3 gene variants were associated with affection status, but not with Treg frequency.

Conclusion

SLE patients have impaired Treg production or maintenance, a trait strongly associated with SLE disease activity and autoantibody titers, and possibly resulting from the inability to convert FOXP3⁺CD25^- into FOXP3⁺CD25⁺ T cells. Treg frequency is highly heritable within SLE families, with specific variants of the CTLA4 and TGFβ genes contributing to this trait, while FOXP3 contributes to SLE through mechanisms not involving a modulation of Treg frequency. These findings establish that the genetic components in SLE pathogenesis include genes related to Treg generation or maintenance.

IL2RA/CD25 gene polymorphisms: uneven association with multiple sclerosis (MS) and type 1 diabetes (T1D)

BACKGROUND

IL-2 receptor (IL2R) alpha is the specific component of the high affinity IL2R system involved in the immune response and in the control of autoimmunity.

METHODS AND RESULTS

Here we perform a replication and fine mapping of the IL2RA gene region analyzing 3 SNPs previously associated with multiple sclerosis (MS) and 5 SNPs associated with type 1 diabetes (T1D) in a collection of 798 MS patients and 927 matched Caucasian controls from the south of Spain. We observed association with MS in 6 of 8 SNPs. The rs1570538, at the 3'- UTR extreme of the gene, previously reported to have a weak association with MS, is replicated here (P = 0.032). The most associated T1D SNP (rs41295061) was not associated with MS in the present study. However, the rs35285258, belonging to another independent group of SNPs associated with T1D, showed the maximal association in this study but different risk allele. We replicated the association of only one (rs2104286) of the two IL2RA SNPs identified in the recently performed genome-wide association study of MS.

CONCLUSIONS

These findings confirm and extend the association of this gene with MS and reveal a genetic heterogeneity of the associated polymorphisms and risk alleles between MS and T1D suggesting different immunopathological roles of IL2RA in these two diseases.

IL2RA genetic heterogeneity in multiple sclerosis and type 1 diabetes susceptibility and soluble interleukin-2 receptor production

Multiple sclerosis (MS) and type 1 diabetes (T1D) are organ-specific autoimmune disorders with significant heritability, part of which is conferred by shared alleles. For decades, the Human Leukocyte Antigen (HLA) complex was the only known susceptibility locus for both T1D and MS, but loci outside the HLA complex harboring risk alleles have been discovered and fully replicated. A genome-wide association scan for MS risk genes and candidate gene association studies have previously described the IL2RA gene region as a shared autoimmune locus. In order to investigate whether autoimmunity risk at IL2RA was due to distinct or shared alleles, we performed a genetic association study of three IL2RA variants in a DNA collection of up to 9,407 healthy controls, 2,420 MS, and 6,425 T1D subjects as well as 1,303 MS parent/child trios. Here, we report “allelic heterogeneity” at the IL2RA region between MS and T1D. We observe an allele associated with susceptibility to one disease and risk to the other, an allele that confers susceptibility to both diseases, and an allele that may only confer susceptibility to T1D. In addition, we tested the levels of soluble interleukin-2 receptor (sIL-2RA) in the serum from up to 69 healthy control subjects, 285 MS, and 1,317 T1D subjects. We demonstrate that multiple variants independently correlate with sIL-2RA levels.

Multiple sclerosis (MS) and type 1 diabetes (T1D) are common, organ-specific inflammatory disorders that continue to increase in global prevalence. The processes leading to both T1D and MS are genetically determined and are thought to involve an autoimmune mechanism. After decades of research into the genetic basis of both MS and T1D, the Human Leukocyte Antigen Complex was the only known susceptibility locus for both T1D and MS. The sequencing of the human genome followed by the generation of the haplotype map, a catalogue of common genetic variation, has allowed the elucidation of allelic variants that define disease risk. Our groups have performed genome-wide association scans and candidate gene studies in both T1D and MS; the final results have identified loci outside the HLA harboring fully replicated risk alleles. Here, we show that the IL-2RA gene encoding a critical regulator of immune responses, the alpha chain of the interleukin-2 receptor, harbors variants that differentially confer risk to MS and T1D. In addition, several independent variants correlate with levels of soluble interleukin-2 receptor in the serum. This finding has critical implications for the field of complex disease genetics as it emphasizes the caution that must be taken when interpreting results for such a complex region with multiple susceptibility alleles.

The T244I variant of the interleukin-7 receptor-alpha gene and multiple sclerosis

Several but not all studies have provided evidence for the association between multiple sclerosis (MS) and the T244I variant of the interleukin-7 receptor-alpha gene (IL7RA), rs6897932. We performed a new replication case-control study in 599 MS patients and 594 healthy controls, all Caucasians from the south of Spain. The genotype and allele frequencies differed between MS cases and controls. The IL7RA rs6897932 C allele and the CC genotype were found to be factors for disease susceptibility [per allele odds ratio (OR) 1.32, 95% CI 1.1-1.6, P=0.0031; per CC genotype vs TT + TC genotypes, OR 1.5, 95% CI 1.18-1.87, P=0.0007]. The combined data analysis included 3324 cases and 5032 controls of Europeans and Americans of European origin resulting in stronger association with similar OR (P=1.9 x 10E-9). These findings in our sample support previous reported association studies between IL7RA rs6897932 and MS.

Replication of KIAA0350, IL2RA, RPL5 and CD58 as multiple sclerosis susceptibility genes in Australians

A recent genome-wide association study (GWAS) conducted by the International Multiple Sclerosis Genetics Consortium (IMSGC) identified a number of putative MS susceptibility genes. Here we have performed a replication study in 1134 Australian MS cases and 1265 controls for 17 risk-associated single nucleotide polymorphisms (SNPs) reported by the IMSGC. Of 16 SNPs that passed quality control filters, four, each corresponding to a different non-human leukocyte antigen (HLA) gene, were associated with disease susceptibility: KIAA0350 (rs6498169) P=0.001, IL2RA (rs2104286) P=0.033, RPL5 (rs6604026) P=0.041 and CD58 (rs12044852) P=0.042. There was no association (P=0.58) between rs6897932 in the IL7R gene and the risk of MS. No interactions were detected between the replicated IMSGC SNPs and HLA-DRB1*15, gender, disease course, disease progression or age-at-onset. We used a novel Bayesian approach to estimate the extent to which our data increased or decreased evidence for association with the six most-associated IMSGC loci. These analyses indicated that even modest P-values, such as those reported here, can contribute markedly to the posterior probability of 'true' association in replication studies. In conclusion, these data provide support for the involvement of four non-HLA genes in the pathogenesis of MS, and combined with previous data, increase to genome-wide significance (P=3 x 10(-8)) evidence of an association between KIAA0350 and risk of disease.

Pharmacogenetics: potential role in the treatment of diabetes and obesity

BACKGROUND

Common genetic variation is associated with increased risk of common metabolic diseases such as type 1 and type 2 diabetes, and obesity. Increasing experience with genetic association studies has led to an understanding of the large sample sizes required to detect a weak to moderate genetic predisposition to disease, the need to reproduce such associations in independent cohorts, and the statistical criteria required to detect a true association. This approach has been used successfully to identify disease-associated gene variation usually in representative populations of large numbers.

OBJECTIVE

To review the current understanding of how common genetic variation influences predisposition to, and treatment of, metabolic disease.

METHODOLOGY

Review of scientific literature.

RESULTS

While there has been progress in understanding how genetic variation predisposes to diabetes and obesity, and how candidate genes may alter drug response, several caveats limit the interpretation and significance of pharmacogenetic studies published to date: those caveats typically include relatively small numbers of participants and choice of endpoints in determining gene-associated differences in response, which may not be clinically significant or relevant as a biomarker or predictor of a desired clinical effect. The genetic variants studied at a given locus are often limited in number and may not represent a comprehensive map of the region under study.

CONCLUSIONS

The pharmacogenetic associations in diabetes and obesity that have been reported to date have had limited impact on the choice of individual treatments. We perceive, however, that this field is in its infancy in these multifactorial metabolic diseases, and with further advances and future drug intervention trials designed in a way that allows a more clear interpretation of the impact of genetic variation on differences in drug response in obesity and diabetes, it is anticipated that pharmacogenetics will have a significant impact on individualizing medical care.

Interferon regulatory factor 5 (IRF5) gene variants are associated with multiple sclerosis in three distinct populations

Background:

IRF5 is a transcription factor involved both in the type I interferon and the toll-like receptor signalling pathways. Previously, IRF5 has been found to be associated with systemic lupus erythematosus, rheumatoid arthritis and inflammatory bowel diseases. Here we investigated whether polymorphisms in the IRF5 gene would be associated with yet another disease with features of autoimmunity, multiple sclerosis (MS).

Methods:

We genotyped nine single nucleotide polymorphisms and one insertion-deletion polymorphism in the IRF5 gene in a collection of 2337 patients with MS and 2813 controls from three populations: two case–control cohorts from Spain and Sweden, and a set of MS trio families from Finland.

Results:

Two single nucleotide polymorphism (SNPs) (rs4728142, rs3807306), and a 5 bp insertion-deletion polymorphism located in the promoter and first intron of the IRF5 gene, showed association signals with values of p<0.001 when the data from all cohorts were combined. The predisposing alleles were present on the same common haplotype in all populations. Using electrophoretic mobility shift assays we observed allele specific differences in protein binding for the SNP rs4728142 and the 5 bp indel, and by a proximity ligation assay we demonstrated increased binding of the transcription factor SP1 to the risk allele of the 5 bp indel.

Conclusion:

These findings add IRF5 to the short list of genes shown to be associated with MS in more than one population. Our study adds to the evidence that there might be genes or pathways that are common in multiple autoimmune diseases, and that the type I interferon system is likely to be involved in the development of these diseases.

Risk alleles for multiple sclerosis identified by a genomewide study

BACKGROUND

Multiple sclerosis has a clinically significant heritable component. We conducted a genomewide association study to identify alleles associated with the risk of multiple sclerosis.

METHODS

We used DNA microarray technology to identify common DNA sequence variants in 931 family trios (consisting of an affected child and both parents) and tested them for association. For replication, we genotyped another 609 family trios, 2322 case subjects, and 789 control subjects and used genotyping data from two external control data sets. A joint analysis of data from 12,360 subjects was performed to estimate the overall significance and effect size of associations between alleles and the risk of multiple sclerosis.

RESULTS

A transmission disequilibrium test of 334,923 single-nucleotide polymorphisms (SNPs) in 931 family trios revealed 49 SNPs having an association with multiple sclerosis (P<1x10(-4)); of these SNPs, 38 were selected for the second-stage analysis. A comparison between the 931 case subjects from the family trios and 2431 control subjects identified an additional nonoverlapping 32 SNPs (P<0.001). An additional 40 SNPs with less stringent P values (<0.01) were also selected, for a total of 110 SNPs for the second-stage analysis. Of these SNPs, two within the interleukin-2 receptor alpha gene (IL2RA) were strongly associated with multiple sclerosis (P=2.96x10(-8)), as were a nonsynonymous SNP in the interleukin-7 receptor alpha gene (IL7RA) (P=2.94x10(-7)) and multiple SNPs in the HLA-DRA locus (P=8.94x10(-81)).

CONCLUSIONS

Alleles of IL2RA and IL7RA and those in the HLA locus are identified as heritable risk factors for multiple sclerosis.