The interleukin 1 gene cluster contains a major susceptibility locus for ankylosing spondylitis

Using genetic association data to guide drug discovery and development: Review of methods and applications

Evidence on the validity of drug targets from randomized trials is reliable but typically expensive and slow to obtain. In contrast, evidence from conventional observational epidemiological studies is less reliable because of the potential for bias from confounding and reverse causation. Mendelian randomization is a quasi-experimental approach analogous to a randomized trial that exploits naturally occurring randomization in the transmission of genetic variants. In Mendelian randomization, genetic variants that can be regarded as proxies for an intervention on the proposed drug target are leveraged as instrumental variables to investigate potential effects on biomarkers and disease outcomes in large-scale observational datasets. This approach can be implemented rapidly for a range of drug targets to provide evidence on their effects and thus inform on their priority for further investigation. In this review, we present statistical methods and their applications to showcase the diverse opportunities for applying Mendelian randomization in guiding clinical development efforts, thus enabling interventions to target the right mechanism in the right population group at the right time. These methods can inform investigators on the mechanisms underlying drug effects, their related biomarkers, implications for the timing of interventions, and the population subgroups that stand to gain the most benefit. Most methods can be implemented with publicly available data on summarized genetic associations with traits and diseases, meaning that the only major limitations to their usage are the availability of appropriately powered studies for the exposure and outcome and the existence of a suitable genetic proxy for the proposed intervention.

Disentangling the effects of traits with shared clustered genetic predictors using multivariable Mendelian randomization

When genetic variants in a gene cluster are associated with a disease outcome, the causal pathway from the variants to the outcome can be difficult to disentangle. For example, the chemokine receptor gene cluster contains genetic variants associated with various cytokines. Associations between variants in this cluster and stroke risk may be driven by any of these cytokines. Multivariable Mendelian randomization is an extension of standard univariable Mendelian randomization to estimate the direct effects of related exposures with shared genetic predictors. However, when genetic variants are clustered, due to being located in a single genetic region, a Goldilocks dilemma arises: including too many highly-correlated variants in the analysis can lead to ill-conditioning, but pruning variants too aggressively can lead to imprecise estimates or even lack of identification. We propose multivariable methods that use principal component analysis to reduce many correlated genetic variants into a smaller number of orthogonal components that are used as instrumental variables. We show in simulations that these methods result in more precise estimates that are less sensitive to numerical instability due to both strong correlations and small changes in the input data. We apply the methods to demonstrate the most likely causal risk factor for stroke at the chemokine gene cluster is monocyte chemoattractant protein-1.

Relationship Between IL1 Gene Polymorphism and Susceptibility to Ankylosing Spondylitis: An Updated and Supplemented Meta-Analysis

The literature has provided inconsistent findings on the relationship between interleukin IL-1 gene polymorphisms and susceptibility to ankylosing spondylitis (AS). Therefore, a systematic review and meta-analysis were conducted. Online electronic database searches were performed for relevant research published as of May 2021. Meta-analysis was performed to compare alleles and multiple genetic models (including dominant, recessive, heterozygous, and homozygous models) using random-effects models to reduce the impact of heterogeneity. A 95% confidence interval (95% CI) odds ratio (OR) was used to assess potential relationships. Nineteen studies including 6235 patients with AS and 5919 healthy controls were recruited. IL-1A-889 (rs1800587) had statistical significance in the allelic model (OR 1.38, 95% CI 1.08-1.77, P = 0.010) (I² = 51%.1, P = 0.0001); homozygous model (OR 1.92, 95% CI 1.27-2.89, P = 0.002); heterozygous model (OR 1.49, 95% CI 1.02-2.17, P = 0.163); dominant genetic model (OR 1.53, 95% CI 1.05-2.24, P = 0.026); and recessive model (OR 1.54, 95% CI 1.04-2.28, P = 0.031). Further stratified analysis showed that the allele model (OR 1.35, 95% CI 1.08-1.69, P = 0.008), heterozygous model (OR 1.45, 95% CI 1.07-1.96, P = 0.017), and dominant model (OR 1.49, 95% CI 1.11-1.99, P = 0.007) in the English population and allele model (OR 2.21, 95% CI 1.45-3.37, P = 0.0001), homozygous model (OR 3.85, 95% CI 1.38-10.76, P = 0.010), heterozygous model (OR 3.42, 95% CI 1.85-6.32, P = 0.0001), and dominant model (OR 3.49, 95% CI 1.93-6.30, P = 0.001) in Tunis were significantly associated with susceptibility to AS. Analysis of the IL1F7 exon 2 (rs3811047) showed that the G allele frequency was higher in the normal population than in the AS population (OR 0.76, 95% CI (0.64, 0.91)). Further stratified analysis concluded that the allele model was significantly associated with AS susceptibility in Canadian (OR 0.76, 95% CI 0.61-0.94, P = 0.011) and Chinese patients (OR 0.64, 95% CI 0.41-0.98, P = 0.041). The meta-analysis showed that the IL-1 gene polymorphism IL-1A-889 (rs1800587) increases the risk of AS in English and Tunisian populations. IL1F7 exon 2 (rs3811047) is negatively correlated with susceptibility to AS in Canadian and Chinese populations, but additional studies are needed for further exploration.

Female with Ankylosing Spondylitis from the 7th–6th century BCE Lori Berd burial (Armenia)

A female skeleton from the Lori Berd archaeological cemetery, located near the city of Stepanavan (Lori Province of Armenia) is described. Palaeopathological analysis revealed a variety pathology (ankylosis of the sacroiliac joints, ankylosis of the vertebrae, syndesmophytes, ankylosed of the costovertebral and costotransverse joint fusions, kyphosis, lordosis, fracture of the anterior inferior iliac spine and traumatic lesions). This paper reports a new case of ankylosing spondylitis in a skeleton and a differential diagnosis performed to determine the etiology of the condition. The vertebral bodies remodel and together with the associated syndesmophytes form a continuous, smooth bone surface that is sometimes referred to as “bamboo spine”. In this skeleton changes in the spine, ribs, the sacrum, acetabulum, head of the femur and greater trochanter, as well as the anterior inferior iliac spine are typical of ankylosing spondylitis in advanced stage. Addtionally, there were signs of a traumatic death with injuries sustained to the scapula and vertebra. Using osteological markers in combination with the reconstruction of the archaeological context, the burial pattern suggests that the pathology the female suffered was likely due to her physical deficiencies.

Cytokine "fine tuning" of enthesis tissue homeostasis as a pointer to spondyloarthritis pathogenesis with a focus on relevant TNF and IL-17 targeted therapies

A curious feature of axial disease in ankylosing spondylitis (AS) and related non-radiographic axial spondyloarthropathy (nrAxSpA) is that spinal inflammation may ultimately be associated with excessive entheseal tissue repair with new bone formation. Other SpA associated target tissues including the gut and the skin have well established paradigms on how local tissue immune responses and proven disease relevant cytokines including TNF and the IL-23/17 axis contribute to tissue repair. Normal skeletal homeostasis including the highly mechanically stressed entheseal sites is subject to tissue microdamage, micro-inflammation and ultimately repair. Like the skin and gut, healthy enthesis has resident immune cells including ILCs, γδ T cells, conventional CD4+ and CD8+ T cells and myeloid lineage cells capable of cytokine induction involving prostaglandins, growth factors and cytokines including TNF and IL-17 that regulate these responses. We discuss how human genetic studies, animal models and translational human immunology around TNF and IL-17 suggest a largely redundant role for these pathways in physiological tissue repair and homeostasis. However, disease associated immune system overactivity of these cytokines with loss of tissue repair “fine tuning” is eventually associated with exuberant tissue repair responses in AS. Conversely, excessive biomechanical stress at spinal enthesis or peripheral enthesis with mechanically related or degenerative conditions is associated with a normal immune system attempts at cytokine fine tuning, but in this setting, it is commensurate to sustained abnormal biomechanical stressing. Unlike SpA, where restoration of aberrant and excessive cytokine “fine tuning” is efficacious, antagonism of these pathways in biomechanically related disease may be of limited or even no value.

Identification of RELN variant p.(Ser2486Gly) in an Iranian family with ankylosing spondylitis; the first association of RELN and AS

Ankylosing spondylitis (AS) is a common complex inflammatory disease; however, up to now distinct genes with monogenic pattern have not been reported for this disease. In the present study, we report a large Iranian family with several affected members with AS. DNAs of the three affected and two healthy cases were chosen for performing whole-exome sequencing (WES). After several filtering steps, candidate variants in the following genes were detected: RELN, DNMT1, TAF4β, MUC16, DLG2, and FAM208. However, segregation analysis confirmed the association of only one variant, c.7456A>G; p.(Ser2486Gly) in the RELN gene with AS in this family. In addition, in silico predictions supported the probable pathogenicity of this variant. In this study, for the first time, we report a novel variant in the RELN gene, c.7456A>G; p.(Ser2486Gly), which completely co-segregates with AS. This association suggests potential insights into the pathophysiological bases of AS and it could broaden horizons toward new therapeutic strategies.

Associations of the IL-1B level, IL-1A and IL-1B gene polymorphisms and ankylosing spondylitis risk in a Chinese Han population

INTRODUCTION

The aim of this study was to investigate the effect of interleukin (IL)-1A and IL-1B gene polymorphisms on ankylosing spondylitis (AS) susceptibility in a Chinese population. Additionally, we examined the association of IL-1B level with different genotype of rs2853550 polymorphism and clinicopathological features of AS patients.

MATERIALS AND METHODS

The IL-1B concentration in plasma was determined by an enzyme-linked immunosorbent assay. The IL-1A rs3783546, IL-1A rs3783550 and IL-1B rs2853550 gene polymorphisms were determined by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

RESULTS

Our data indicated that the average plasma IL-1B concentration in the AS patients was markedly higher than in the control samples. Subgroup analyses suggested that there was no significant association between plasma IL-1B concentration and sex, age, HLA-B27, C-reactive protein (CRP), or grade of the sacroiliac joint in AS patients. We also found that the IL-1B rs2853550 AG genotype showed significantly correlation with an increased risk of AS. In comparing AS patients to control participants, elevated plasma concentrations were observed in AS patients while significant differences were found between the IL-1B rs2853550 AA genotypes. There is a negative correlation between the IL-1A rs3783550 and IL-1A rs3783546 polymorphisms in the AS patients in relation to controls.

CONCLUSIONS

The IL-1B concentration in plasma was markedly higher in cases and AA genotype carriers. Furthermore, IL-1B rs2853550 AG was a genetic contributor to AS risk in a Chinese population.

Genetic polymorphisms in IL1B predict susceptibility to steroid-induced osteonecrosis of the femoral head in Chinese Han population

The purpose of this research was to examine if the IL1B gene polymorphism has impact on the risk of steroid-induced ONFH in Chinese population. We found that IL1B rs1143630 decreased the SANFH's risk and IL1B rs2853550 increased the risk of steroid-induced ONFH. So, we guess that IL1B gene influences the genetic susceptibility of steroid-induced ONFH.

INTRODUCTION

Genetic polymorphisms in IL1B gene could be related in the pathogenesis of osteonecrosis. Discusses on the relationship between the IL1B gene and steroid-induced osteonecrosis of the femoral head (steroid-induced ONFH) is still less in Chinese Han population. So, in this research, we want to examine whether the IL1B gene polymorphism has impact on the risk of steroid-induced ONFH in Chinese population.

METHODS

A total of 286 steroid-induced ONFH patients and 441 controls were recruited, and seven SNPs (rs2853550, rs1143643, rs3136558, rs1143630, rs1143627, rs16944, and rs1143623) in IL1B gene were selected; unconditional logistic regression analysis was used to research the influence on the risk of steroid-induced ONFH. Functional annotations of IL1B variants were performed by RegulomeDB and HaploReg.

RESULTS

rs1143630 (A>C) in the IL1B gene decreased the risk of steroid-induced ONFH in the allele model (OR = 0.69, 95%CI 0.51-0.93, p = 0.014). Further genetic model analyses found that IL1B rs2853550 AG genotype increased the risk of steroid-induced ONFH compared with the people who are carriers of the IL1B rs2853550 GG genotype (OR = 1.69, 95%CI 1.16-2.46, p = 0.012). In the dominant model, IL1B rs1143630 GG-GT genotype decreased the risk of steroid-induced ONFH (OR = 0.62, 95%CI 0.44-0.87, p = 0.0051). And further haplotype analysis was performed, while the result was not significant. Using RegulomeDB and HaploReg, rs2853550 is likely to affect TF binding, any motif and DNase peak.

CONCLUSIONS

We guess that IL1B gene influences the genetic susceptibility of steroid-induced ONFH.

IL-1A gene variation in relation to cytokine levels and clinical characteristics in ankylosing spondylitis

Objective

Variations in the IL-1 alpha (IL-A) gene increase the risk for ankylosing spondylitis (AS), but the pathway underlying this association is not fully understood. As IL-1A is primarily a regulatory cytokine, we investigated the influence of IL-1A gene variation on disease severity and cytokine expression in AS.

Methods

This was a cross sectional study of tumor necrosis factor inhibitors (TNFi)-naïve AS patients (n=334, 90% B27 +, age 45 years) fulfilling the modified New York criteria. We recorded demographics, clinical findings, spinal mobility, Bath AS Functional Index (BASFI), and routine lab findings. IL-1A genotyping for three AS-associated single nucleotide polymorphism (SNP; rs2856836, rs17561 and rs1894399) was performed using Taqman RT-PCR, with TNF, IL-6, IL-17A, and IL-23 levels measured using ELISA. Genotypic associations included logistic regression analysis for genotype (codominant model) and global haplotype (threshold 5%) associations with cytokine levels and clinical features.

Results

The three variants were in near complete linkage disequilibrium and formed two only common haplotypes (ACC 67%, GAT 33%). The levels for TNF, IL-6, IL-17A, IL-23, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were similar across genotypes and haplotypes (all p-values >0.4) as were the measures for spinal mobility and BASFI. The TAQ haplotype showed a borderline significant trend with reduced heart disease and mortality during follow-up.

Conclusion

IL-1A gene cluster variations do not have an impact on the clinical disease measures or cytokine levels in AS, suggesting that IL-1A has no direct role in AS.

Association of IL-1A and IL-1B polymorphisms with ankylosing spondylitis among the Chinese Han population: a case-control study

Ankylosing spondylitis (AS) is a complex and chronic inflammatory disease with a high heritage. Previous study has shown that IL-1A and IL-1B involved in inflammatory reaction. But little is known about single nucleotide polymorphisms (SNPs) of IL-1A and IL-1B associated with AS. We conducted a case-control study among 267 AS cases and 297 healthy controls from China. In the genetic model analysis, we found the “T” genotype of rs3783550 was associated with decreased AS risk in the dominant model (p = 0.044) and log-additive model (p = 0.023); the “C” genotype of rs3783546 was significantly associated with decreased AS risk based in the dominant model (p = 0.044) and log-additive model (p = 0.023). Additionally, the minor allele “A” of rs2853550 may also reduce the risk of AS in dominant (p = 0.025) and log-additive model (p = 0.024). Our results suggested that the polymorphisms of IL-1A and IL-1B are associated with the AS susceptibility in the Chinese Han population. Further studies are needed to characterize the functional sequences that cause AS.

In vivo anti-inflammatory activities of novel cytokine IL-38 in Murphy Roths Large (MRL)/lpr mice

The newly named interleukin (IL)-36 subfamily member IL-38 has been shown to exert anti-inflammatory activity. However, the in vivo immunomodulatory activity of IL-38 was poorly investigated in systemic lupus erythematosus (SLE). We have investigated the expression of CD4⁺IL-17⁺ Th17, CD4⁺IFN-γ⁺ Th1 and CD3⁺CD4^-CD8^- double negative (DN) T cells and the related immunopathological mechanisms in female MRL/lpr mice model of spontaneous lupus-like disease, with or without IL-38 treatment. Intravenous administration of murine recombinant IL-38 into MRL/lpr mice can ameliorate the lupus-like clinical symptoms including proteinuria, leukocyteuria and skin lesions. A remission of histopathology characteristics of skin and nephritis was also observed upon IL-38 treatment. Accordingly, IL-38 receptor was expressed on the cell surface of both CD4⁺ Th and CD19⁺ B lymphocytes. The splenic Th17 and DN T lymphocytes, the average mRNA level of epigenetically regulated gene expression of Th17 cells, and serum concentrations of IL-17 and IL-22 were significantly decreased upon the treatment of IL-38 (all p<0.05). The in vivo results suggest that IL-38 can ameliorate skin inflammation and nephritis in SLE mice probably via suppressing the formation of inflammatory cytokines such as IL-17 and IL-22, and pathogenic DN T cells. These findings may provide a biochemical basis for further investigation of the therapeutic mechanisms of IL-38 for the treatment of autoimmune-mediated inflammation.

Interleukin-1 Gene Cluster Polymorphisms and Their Association with Coronary Artery Disease: Separate Evidences from the Largest Case-Control Study amongst North Indians and an Updated Meta-Analysis

Several researchers have reported significant association of numerous single nucleotide polymorphisms (SNPs) residing in the interleukin-1 (IL-1) gene cluster with coronary artery disease (CAD). However, their association status amongst North Indian ancestry (NIA) have never been systematically assessed. Despite a published meta-analysis on this subject, their association status worldwide as well as amongst different major ancestral subgroups still remains unclear. We therefore decided to prospectively test the association of 11 IL-1 gene cluster SNPs with CAD, vide a case-control study amongst a cohort of NIA and attempted to validate our results with the help of an updated meta-analysis of all relevant published association studies. Included studies were segregated into ancestral subgroups and association statuses for each subgroup were determined. A total of 323 cases and 400 healthy, age and sex matched controls belonging to NIA were prospectively enrolled and subsequently genotyped for 11 selected IL-1 gene cluster SNPs. Although results for none of the evaluated IL-1 gene cluster SNPs reached the adjusted level of significance (p<0.0045), clear trends of association were seen for IL1B -511 C>T and IL1RN 86bp VNTR in several of the constructed genetic models (p range = 0.01–0.044 and 0.005–0.034 respectively). The presence of >1, ‘T’ (minor) allele of IL1B -511 C>T in a genotype seemed to provide protection against CAD (OR = 0.62, p = 0.044), while the presence of >1, ‘C’ (major) allele seemed to increase the risk of CAD (OR = 1.36, p = 0.041). The minor allele (allele 2) of IL1RN 86bp VNTR and its homozygous genotype (2/2 genotype) also seemed to carry an increased risk for CAD (OR = 1.62, p = 0.005 and OR = 2.25, p = 0.031 respectively). On the other hand, several haplotype combinations constructed out of IL1B and IL1RN gene variants clearly showed statistically significant associations with CAD (p<0.0045). Our meta-analysis was conducted for 8 previously assessed IL-1 SNPs. We included 53 different studies which involved a total sample of 26,210 (13,982 cases and 12,228 controls). Our pooled results concurred with the findings of our case-control study and was not able to deduce any statistically significant associations for any of the 8 studied SNPs (p>0.05). Subgroup analysis, however, yielded interesting results, where significant differences in association statuses were seen for IL1A +4845 G>T, IL1B -511 C>T, IL1RN 86bp VNTR and IL1RN +8006 T>C for select ancestral subgroups. The hints of associations deduced for subjects belonging to NIA in our case-control study for both IL1B -511 C>T and IL1RN 86bp VNTR were duly validated vide significant p values seen for NIA in all three genetic models (OR range = 0.62–0.76, p range = 0.01–0.04 and OR range = 1.51–2.25, p range = 0.004–0.04 respectively). On the other hand, Mixed Ancestry (MA) subgroup carrying IL1B -511 C>T, IL1RN 86bp VNTR or IL1RN +8006 T>C polymorphisms seemed to enjoy significant protection against CAD. A few other ancestral subgroups also demonstrated significant associations for a few of the studied SNPs vide one of the three genetic models. Clinical interpretation of derived results is however recommended.

Association of rs11209032 and rs1004819 Polymorphisms in Interleukin-23 Receptor Gene With Ankylosing Spondylitis

Objectives

This study aims to investigate the distribution of human leukocyte antigen B27 (HLA-B27) alleles (+/-) and interleukin-23 receptor (IL-23R) gene rs11209032 and rs1004819 polymorphisms among ankylosing spondylitis (AS) patients in a Turkish cohort.

Patients and methods

The study sample comprised 106 AS patients (89 males, 18 females; mean age 38.9±10 years; range 19 to 65 years) and 82 healthy controls (70 males, 12 females; mean age 32.15±7.07 years; range 19 to 51 years). Distribution of HLA-B27 alleles (+)/(-) in AS patients were observed by reverse hybridization technique. Genotyping of IL-23R rs11209032 and rs1004819 polymorphisms of AS patients and healthy controls were performed by real time polymerase chain reaction.

Results

Of the AS patients, 69 (65.1%) were HLA-B27 positive. Distribution of rs11209032 genotype frequencies in AS group were 31.1% for GG, 50.9% for GA, and 17.9% for AA; while in control group, it was 34.1% for GG, 53.7% for GA, and 12.2% for AA. Distribution of rs1004819 genotype frequencies in AS group were 30.2% for CC, 52.8% for CT, and 17.0% for TT; while in control group, it was 42.7% for CC, 46.3% for CT, and 11.0% for TT. There was no significant difference between AS patients and controls in terms of genotype frequencies of IL-23R gene rs11209032 and rs1004819 polymorphisms.

Conclusion

No association was found between AS and IL23R rs11209032 and rs1004819 polymorphisms in this Turkish AS cohort.

Polymorphism of IL37 gene as a protective factor for autoimmune thyroid disease

Autoimmune thyroid disease (AITD) comprises Graves' disease (GD) and Hashimoto's thyroiditis (HT). IL37 has been recently proved to be a natural suppressor for innate immunity and acquired immunity. Therefore, this study was conducted to identify the association of IL37 genetic polymorphisms with AITD in Chinese Han population. Polymorphisms of rs3811046/rs3811047/rs2723176/rs272186 in the IL37 gene were assessed in a case-control study comprising 701 GD patients, 301 HT patients and 939 controls. Genetic variants were genotyped by multiplex polymerase chain reaction and ligase detection reaction. The frequencies of the minor allele A of rs2723176 and A of rs2723186 were significantly lower in the GD patients than in the controls (P=0.014, OR=0.774; P=0.014, OR=0.777). After gender stratification, the rs3811046 G allele and the rs3811047/rs2723186 A allele were both significantly associated with a decreased risk of GD in female patients (P=0.030, OR=0.777; P=0.023, OR=0.774; P=0.029, OR=0.761). However, none of the four single nucleotide polymorphisms of IL37 gene showed any significant association with HT. Moreover, haplotype analysis revealed the GCG haplotype conferred increased risk for GD as a whole and in female GD patients (OR=1.213; OR=1.320). The ACG haplotype was associated with an increased risk of HT as a whole (OR=1.567) and in male GD patients (OR=1.820). In contrast, the AAA haplotype showed a protective role for GD as a whole (OR=0.760) and in female GD patients (OR=0.765). Our study strongly supports that the IL37 gene variants are associated with the susceptibility to AITD.

The effect of IL-4 and MTHFR gene variants in ankylosing spondylitis

PURPOSE

Ankylosing Spondylitis (AS) is a chronic inflammatory rheumatic disease that characteristically affects the sacroiliac joints and the spine. The exact pathogenesis of AS remains poorly understood, but genetic factors play a key role in disease development. Several genes have been consistently associated with susceptibility to AS. This study was conducted in Turkish AS patients to determine the frequency of the methylenetetrahydrofolate reductase (MTHFR) gene C677T and interleukin-4 (IL-4) gene 70 bp variable number of tandem repeats (VNTR) variants, as well as their association with clinical characteristics.

METHODS

Genomic DNA obtained from 272 persons (122 AS patients and 150 healthy controls) was used in this study. Genomic DNA was isolated and genotyped using a polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) assay for the MTHFR C677T and IL-4 70 bp VNTR gene variants, which were determined using specific PCR primers.

RESULTS

There was statistically significant difference between the groups with respect to MTHFR genotype distribution (p = 0.02) and allele frequencies (p < 0.001). When we examined MTHFR and IL-4 genotype frequencies according to clinical characteristics, we found an association between the homozygous MTHFR TT genotype and ocular involvement, although this did not reach statistical significance (p = 0.02). However, we did not find any difference between the groups with respect to IL-4 genotype distribution or allele frequencies and clinical characteristics (p > 0.05).

CONCLUSION

Our findings suggest that there is an association of the MTHFR gene C677T polymorphism with the susceptibility of a person for development of AS. However, the IL-4 gene is not associated with AS within the same population.

Ankylosing spondylitis: A state of the art factual backbone

Ankylosing spondylitis (AS) is a chronic inflammatory disease that affects 1% of the general population. As one of the most severe types of spondyloarthropathy, AS affects the spinal vertebrae and sacroiliac joints, causing debilitating pain and loss of mobility. The goal of this review is to provide an overview of AS, from the pathophysiological changes that occur as the disease progresses, to genetic factors that are involved with its onset. Considering the high prevalence in the population, and the debilitating life changes that occur as a result of the disease, a strong emphasis is placed on the diagnostic imaging methods that are used to detect this condition, as well as several treatment methods that could improve the health of individuals diagnosed with AS.

Cytokine production associated with smallpox vaccine responses

Smallpox was eradicated 34 years ago due to the success of the smallpox vaccine; yet, the vaccine continues to be studied because of its importance in responding to potential biological warfare and the adverse events associated with current smallpox vaccines. Interindividual variations in vaccine response are observed and are, in part, due to genetic variation. In some cases, these varying responses lead to adverse events, which occur at a relatively high rate for the smallpox vaccine compared with other vaccines. Here, we aim to summarize the cytokine responses associated with smallpox vaccine response to date. Along with a description of each of these cytokines, we describe the genetic and adverse event data associated with cytokine responses to smallpox vaccination.

Mechanisms of unconventional secretion of IL-1 family cytokines

One of the most poorly understood processes in cell biology is the peculiar ability of specific leaderless proteins to be secreted via ER/Golgi-independent mechanisms ('unconventional protein secretion'). One such leaderless protein is the major immune-activating cytokine, interleukin-1β (IL-1β). Unusual amongst cytokines, IL-1β is expressed in the cytosol as an inactive precursor protein. It requires maturation by the caspase-1 protease, which itself requires activation upon immune cell sensing of infection or cell stress. Despite 25 years of intensive research into IL-1β secretory mechanisms, how it exits the cell is still not well understood. Here we will review the various mechanisms by which macrophages have been proposed to secrete IL-1 family cytokines, and the potential involvement of caspase-1 therein. Since aberrant IL-1β production drives inherited and acquired human diseases (e.g. autoinflammatory diseases, arthritic diseases, gout, Alzheimer's disease), elucidation of the IL-1β secretory pathway may offer new therapeutic opportunities for treatment across this wide range of human conditions.

Interleukin-1 gene cluster variants in hemodialysis patients with end stage renal disease: An association and meta-analysis

We evaluated whether polymorphisms in interleukin (IL-1) gene cluster (IL-1 alpha [IL-1A], IL-1 beta [IL-1B], and IL-1 receptor antagonist [IL-1RN]) are associated with end stage renal disease (ESRD). A total of 258 ESRD patients and 569 ethnicity matched controls were examined for IL-1 gene cluster. These were genotyped for five single-nucleotide gene polymorphisms in the IL-1A, IL-1B and IL-1RN genes and a variable number of tandem repeats (VNTR) in the IL-1RN. The IL-1B − 3953 and IL-1RN + 8006 polymorphism frequencies were significantly different between the two groups. At IL-1B, the T allele of − 3953C/T was increased among ESRD (P = 0.0001). A logistic regression model demonstrated that two repeat (240 base pair [bp]) of the IL-1Ra VNTR polymorphism was associated with ESRD (P = 0.0001). The C/C/C/C/C/1 haplotype was more prevalent in ESRD = 0.007). No linkage disequilibrium (LD) was observed between six loci of IL-1 gene. We further conducted a meta-analysis of existing studies and found that there is a strong association of IL-1 RN VNTR 86 bp repeat polymorphism with susceptibility to ESRD (odds ratio = 2.04, 95% confidence interval = 1.48-2.82; P = 0.000). IL-1B − 5887, +8006 and the IL-1RN VNTR polymorphisms have been implicated as potential risk factors for ESRD. The meta-analysis showed a strong association of IL-1RN 86 bp VNTR polymorphism with susceptibility to ESRD.

Genetic variants in the IL1A gene region contribute to intestinal-type gastric carcinoma susceptibility in European populations

The most studied genetic susceptibility factors involved in gastric carcinoma (GC) risk are polymorphisms in the inflammation-linked genes interleukin 1 (IL1) B and IL1RN. Despite the evidence pointing to the IL1 region, definite functional variants reproducible across populations of different genetic background have not been discovered so far. A high density linkage disequilibrium (LD) map of the IL1 gene cluster was established using HapMap to identify haplotype tagSNPs. Eighty-seven SNPs were genotyped in a Portuguese case-control study (358 cases, 1,485 controls) for the discovery analysis. A replication study, including a subset of those tagSNPs (43), was performed in an independent analysis (EPIC-EurGast) containing individuals from 10 European countries (365 cases, 1284 controls). Single SNP and haplotype block associations were determined for GC overall and anatomopathological subtypes. The most robust association was observed for SNP rs17042407, 16Kb upstream of the IL1A gene. Although several other SNP associations were observed, only the inverse association of rs17042407 allele C with GC of the intestinal type was observed in both studies, retaining significance after multiple testing correction (p = 0.0042) in the combined analysis. The haplotype analysis of the IL1A LD block in the combined dataset revealed the association between a common haplotype carrying the rs17042407 variant and GC, particularly of the intestinal type (p = 3.1 × 10(-5) ) and non cardia localisation (p = 4.6 × 10(-3) ). These results confirm the association of IL1 gene variants with GC and reveal a novel SNP and haplotypes in the IL1A region associated with intestinal type GC in European populations.

The genetic basis of ankylosing spondylitis: new insights into disease pathogenesis

Ankylosing spondylitis (AS) is a complex disease involving multiple risk factors, both genetic and environmental. AS patients are predominantly young men, and the disease is characterized by inflammation and ankylosis, mainly at the cartilage–bone interface and enthesis. HLA-B27 has been known to be the major AS-susceptibility gene for more than 40 years. Despite advances made in the past few years, progress in the search for non-human leukocyte antigen susceptibility genes has been hampered by the heterogeneity of the disease. Compared to other complex diseases, such as inflammatory bowel disease (IBD), fewer susceptibility loci have been identified in AS. Furthermore, non-major histocompatibility-complex susceptibility loci discovered, such as ERAP1 and IL23R, are likely contributors to joint inflammation. Identification and confirmation of functional variants remains a significant challenge of investigations involving genome-wide association studies (GWAS). It remains unclear why none of the AS-susceptibility genes identified in GWAS appear to be directly involved in the ankylosing process. Numerous reviews have recently been published on the genetics of AS. Therefore, aside from a brief summary of what AS GWAS has successfully achieved thus far, this review will focus on directions that could address unanswered questions raised by GWAS.

Distribution of the IL-1RN, IL-6, IL-10, INF-γ, and TNF-α Gene Polymorphisms in the Mexican Population

BACKGROUND

Cytokines are a group of polypeptides with an important role in the inflammatory response. It has been suggested that certain polymorphisms located in several cytokine genes are associated with different diseases. The aim of the present study was to establish the gene frequency of 13 polymorphisms of the IL-1RN, IL-6, IL-10, INF-γ, and TNF-α genes in a Mexican population. These polymorphisms have been reported in several populations, with important variation in frequency according to the studied population.

METHODS

Thirteen polymorphisms (rs419598, rs315951, rs2234663, rs3811058, rs1800796, rs2069827, rs1800896, rs1800871, rs1800872, rs1800629, rs2069709, rs2069710, and rs361525) were analyzed by 5' exonuclease TaqMan genotyping assays in a group of 248 healthy unrelated Mexican individuals.

RESULTS

The results obtained showed that the studied Mexican population presents significant differences (p<0.05) in the distribution of the IL1RN (rs419598, rs315951, and and rs2234663), IL1F10 (rs3811058), IL6 (rs1800796, rs2069827), IL10 (rs1800896, rs1800871, and rs1800872), and TNF-α (rs1800629) polymorphisms when compared to Caucasian, Asian, and African populations.

CONCLUSIONS

In summary, the distribution of the IL-1RN, IL-6, IL-10, and TNF-α cytokine gene polymorphisms distinguishes the studied Mexican population from other groups. Since the alleles of these cytokines are associated with the development of several inflammatory diseases, knowledge of the distribution of these alleles in the studied Mexican population could be helpful to understand their true role as a genetic susceptibility marker in this population.

Genetics of spondyloarthritis--beyond the MHC

Ankylosing spondylitis (AS), psoriasis and inflammatory bowel disease (IBD) often coexist in the same patient and in their families. In AS, genes within the MHC region, in particular HLA-B27, account for nearly 25% of disease hereditability, with additional small contributions from genes outside of the MHC locus, including those involved in intracellular antigen processing (that is, ERAP1, which interacts with HLA-B27) and cytokine genes such as those involved in the IL-17-IL-23 pathway. Similar to AS, the strongest genetic signal of susceptibility to psoriasis and psoriatic arthritis also emanates from the MHC region (attributable mostly to HLA-C(*)06:02 although other genes have been implicated), and gene-gene interaction of HLA-C with ERAP1. The remaining hereditary load is from genes involved in cytokine production, specifically genes in the IL-17-IL-23 pathway, the NFκB pathway and the type 2 T-helper pathway. In IBD, similar genetic influences are operative. Indeed, genes important in the regulation of the IL-17-IL-23 pathway and, in Crohn's disease, genes important for autophagy (that is, NOD2 and ATG16L1 and IRGM) have a role in conferring susceptibility of individuals to these diseases. Thus, AS, psoriasis and IBD seem to share similar pathogenic mechanisms of aberrant intracellular antigen processing or elimination of intracellular bacteria and cytokine production, especially in the IL-17-IL-23 pathway.

Interleukin-1 gene cluster variants and recurrent pregnancy loss among North Indian women: retrospective study and meta-analysis

The aim of this study was to determine whether or not interleukin-1 alpha (IL-1a), interleukin-1 beta (IL-1b) and IL-1 receptor antagonist (IL-1RA) polymorphisms are associated with risk of unexplained recurrent pregnancy loss (RPL) among North Indian women. This retrospective case–control study examine 200 well-characterized RPL cases for IL-1 gene cluster variants, determined by restriction fragment length polymorphism-PCR. The observed allele, genotype and haplotype distributions were compared with those obtained from 300 ethnically matched negative controls. Invariant distribution of IL-1 gene cluster single-nucleotide polymorphisms was observed among RPL cases and controls. Meta-analysis of IL-1b _511, +3953 and IL-1RN 86-bp variable number tandem repeat from the reported literature and this study did not reveal any significant association with the risk of RPL. In conclusion, no significant difference between RPL and control groups was observed at the allele, genotype or haplotype levels when tested for association using the dominant, recessive and additive models of inheritance for IL-1 gene cluster variants. As far as is known, this is the first report from India pertaining to IL-1 gene cluster variants’ association with the risk of RPL from North India.

IL1 gene polymorphisms in enthesitis related arthritis category of juvenile idiopathic arthritis (ERA-JIA)

Cytokine gene loci are one of the potential susceptibility factors in immuno-inflammatory diseases. Interleukin1 (IL-1) is a major monocyte derived proinflammatory cytokine that mediates tissue damage and cartilage loss in chronic arthritis. IL-1 locus has been linked to various autoimmune diseases, but data on juvenile idiopathic arthritis (JIA) is limited. Ninety-four patients with enthesitis related arthritis (ERA) category of JIA (ILAR criteria) were included in the study. One hundred eighty-five healthy blood donors were used as controls. IL-1Ra VNTR polymorphism was done by PCR using specific primers, and allele assignment was done on product size obtained on 2% agarose gel. IL-1α-889 and IL-β-511 polymorphism was done using PCR-RFLP method. Among 94 patients, 87 were males, and the mean age at onset of disease was 11.8 + 1.8 years; 17 had history of uveitis, and 13 had positive family history. Forty-two had enthesitis, and 51 had inflammatory back pain; all had arthritis. Seventy-six were HLA B27 positive. All three loci genotypes were in the Hardy-Weinberg equilibrium in controls. There was no difference in genotype frequency among patients and controls for IL-1Ra, IL-1α-889 and IL-β-511. IL1*RN2 homozygosity was more common in patients, whereas carriage rate for IL1*RN1 was less frequent in patients. Haplotype frequencies were also similar in both groups. IL-1 gene cluster is not a susceptibility locus for ERA.

Interactions of the innate and adaptive arms of the immune system in the pathogenesis of spondyloarthritis

The immune system can be divided into the innate and adaptive arms. Historically, most of the research into the pathogenesis of spondyloarthritis (SpA) and other types of chronic arthritis focused on the adaptive immune system. Recently, the pendulum has shifted, and much current work in SpA focuses on innate immunity. Herein, I summarise evidence demonstrating that both the innate and the adaptive arms of the immune system are involved in the pathogenesis of SpA, propose a mechanism in which both arms interact to maintain chronic arthritis, and discuss potential research directions.

Regulatory T cells increased while IL-1β decreased during antidepressant therapy

BACKGROUND

Regulatory T cells (Tregs, CD4(+)CD25(hi)) are specialized in steering the immune response and cytokine release to maintain tolerance to self-antigens. As cytokines such as interleukin (IL)-1β, IL-6 and interferon (IFN)-α have been shown to be involved in the pathophysiology of depression and cytokine levels have been shown to change during successful antidepressant treatment, we tested the involvement CD4(+)CD25(hi) Tregs in these immunological processes during antidepressant therapy.

METHODS

16 patients suffering from a depressive episode were included into the study and treated with antidepressants according to their doctor's choice. Blood samples were collected during the first week after admission and after 6 weeks of treatment. Therein, we determined plasma levels of IL-1β, and measured IL-1β, IL-6 and IFN-α levels in the stimulated blood by performing a whole blood assay. We distinguished lymphocytes and identified CD4(+)CD25(hi) Tregs by multiparameter flow cytometry. The psychopathological status was assessed using the Hamilton Depression Rating Scale (HAMD-21).

RESULTS

HAMD-21 score, IL-1β serum levels as well as LPS-stimulated IL-1β and IL-6 production had decreased significantly at the end of treatment. In contrast, the amount of CD4(+)CD25(hi) cells increased significantly from 2.74% ± 0.88 (mean value ± standard deviation) to 3.54% ± 1.21; p = 0.007. No significant changes in virus-induced IFN-α production was observed.

CONCLUSIONS

The increase in CD4(+)CD25(hi) Tregs during antidepressant therapy may be the reason for the decrease in cytokine production and the recovery from depression.

Association of the intergenic single-nucleotide polymorphism rs10865331 (2p15) with ankylosing spondylitis in a Spanish population

OBJECTIVE

A recent genome-wide association study has identified 2 single-nucleotide polymorphisms (SNP) associated with ankylosing spondylitis (AS), rs10865331 (2p15) and rs2242944 (21q22). We assessed the association of these SNP with AS in a Spanish population.

METHODS

Four hundred fifty-six patients with AS fulfilling the modified New York Criteria and 300 healthy donors were analyzed. Result. SNP rs10865331 (allele A: p = 0.039; genotype: p = 0.016) was significantly associated with AS, while no association was found for rs2242944.

CONCLUSION

This is the first study that replicates in an independent cohort the association of the intergenic SNP rs10865331 with susceptibility to AS.

The genetic background of ankylosing spondylitis

It has long been known that the major histocompatibility complex (MHC) is essentially involved in genetic susceptibility to ankylosing spondylitis (AS). The HLA-B27 antigen has been accounted for 20 to 50% of the total genetic risk for this disease. However, susceptibility to AS cannot be fully explained by associations with the MHC. Recent studies including linkage analyses as well as candidate gene and, most recently, genome-wide association studies indicate significant associations of the interleukin-1 gene cluster, interleukin-23 receptor and ARTS1 genes as well as other possible loci with AS. In the murine model of proteoglycan-induced spondylitis, two susceptibility loci termed Pgis1 and Pgis2 were identified. Thus, AS is not a single-gene disease and the involvement of multiple non-MHC genes may account for the individual as well as geographical differences seen in AS.

Association ofARTS1Gene Polymorphisms with Ankylosing Spondylitis in the Hungarian Population: The rs27044 Variant Is Associated with HLA-B*2705 Subtype in Hungarian Patients with Ankylosing Spondylitis

Objective.

Associations have been found between ankylosing spondylitis (AS) and polymorphisms in the aminopeptidase regulator of TNFR1 shedding (ARTS1) gene. We studied the association of 5 polymorphisms within theARTS1gene with AS in Hungarian patients. We also investigated the prevalence of HLA-B27 subtypes in the Hungarian population.

Methods.

A case-control study including 297 patients with AS and 200 sex and ethnically matched healthy controls was performed. Patients and controls were genotyped for rs27044, rs17482078, rs10050860, rs30187, and rs2287987 single-nucleotide polymorphisms using real-time polymerase chain reaction (PCR) allelic discrimination. HLA-B27 subtypes were determined with PCR sequence-specific primer (PCR-SSP) technique.

Results.

We observed a significant increase in the minor allele frequency of rs27044 (p = 0.001) in the AS group compared to controls. The minor allele frequencies of rs10050860 (p = 0.006) and rs2287987 (p = 0.002) showed a significant decrease in AS patients compared to controls. Haplotype analysis revealed association of 2 ARTS1 haplotypes with AS in the Hungarian population. We found that HLA-B*2705 was the predominant subtype in Hungarians with AS. Carriage of the G allele of rs27044 was significantly associated with the HLA-B*2705 subtype (p = 0.009) in AS patients.

Conclusion.

We confirmed reported associations ofARTS1gene polymorphisms with AS in a Hungarian cohort study. We found HLA-B*2705 as the predominant subtype in Hungarian AS patients in accord with other studies on Caucasian populations. Our results suggest that theARTS1gene variants together with HLA-B27 strongly contribute to disease susceptibility in patients with AS.

Association of IL-1 gene complex members with ankylosing spondylitis in Chinese Han population

There are reports of IL-1 complex gene polymorphisms in ankylosing spondylitis (AS; MIM 106300), but the results have been inconsistent among populations. Moreover, few studies examine the association between IL-1 complex gene polymorphisms and clinical symptoms of AS patients. We investigated polymorphisms of IL-1 complex with AS in the Chinese Han population in this study. Chinese Han AS patients and ethnically matched healthy controls were genotyped for five single nucleotide polymorphisms (IL1beta+3953, beta-511, F10.3, RN.4, RN.6/1) and the IL1RN.VNTR of IL-1 gene cluster. Allele, Genotype and haplotype frequencies were compared between cases and controls by SHEsis software. The frequency of allele C of the marker IL1F10.3 was significantly increased in AS patients versus controls [p = 0.001, odds ratio (OR) = 1.54, 95% confidence interval (CI) = 1.19-1.20; p = 0.002, respectively]. Strong linkage disequilibrium was identified between IL1B-511, IL1B+3953 and RN4 in both patients and healthy controls (D' > 0.95). Haplotypes of pairs of these markers (6) were also significantly associated with AS. The strongest associations observed was between allele combination B-511-T/B+3953-C/F10.3-C/RN4-T/RN2VNTR-1/RN6.1-C and AS (p = 3.32 x 10(-5), OR = 4.41, 95% CI=2.1-9.3). Clinical manifestation showed week association between RN2VNTR A2 allele and risk of peripheral arthritis (OR = 0.2, 95% CI = 0.07-0.91). The IL-1 gene cluster is associated with AS in Chinese population. This finding provides strong statistical support for the previously observed relationship and indicates possible association between clinical manifestation and genetic factor.

Progress in spondylarthritis. Progress in studies of the genetics of ankylosing spondylitis

The advent of high-throughput SNP genotyping methods has advanced research into the genetics of common complex genetic diseases such as ankylosing spondylitis (AS) rapidly in recent times. The identification of associations with the genes IL23R and ERAP1 have been robustly replicated, and advances have been made in studies of the major histocompatibility complex genetics of AS, and of KIR gene variants and the disease. The findings are already being translated into increased understanding of the immunological pathways involved in AS, and raising novel potential therapies. The current studies in AS remain underpowered, and no full genomewide association study has yet been reported in AS; such studies are likely to add to the significant advances that have already been made.

Comprehensive linkage and association analyses identify haplotype, near to the TNFSF15 gene, significantly associated with spondyloarthritis

Spondyloarthritis (SpA) is a chronic inflammatory disorder with a strong genetic predisposition dominated by the role of HLA-B27. However, the contribution of other genes to the disease susceptibility has been clearly demonstrated. We previously reported significant evidence of linkage of SpA to chromosome 9q31–34. The current study aimed to characterize this locus, named SPA2. First, we performed a fine linkage mapping of SPA2 (24 cM) with 28 microsatellite markers in 149 multiplex families, which allowed us to reduce the area of investigation to an 18 cM (13 Mb) locus delimited by the markers D9S279 and D9S112. Second, we constructed a linkage disequilibrium (LD) map of this region with 1,536 tag single-nucleotide polymorphisms (SNPs) in 136 families (263 patients). The association was assessed using a transmission disequilibrium test. One tag SNP, rs4979459, yielded a significant P-value (4.9×10⁻⁵). Third, we performed an extension association study with rs4979459 and 30 surrounding SNPs in LD with it, in 287 families (668 patients), and in a sample of 139 cases and 163 controls. Strong association was observed in both familial and case/control datasets for several SNPs. In the replication study, carried with 8 SNPs in an independent sample of 232 cases and 149 controls, one SNP, rs6478105, yielded a nominal P-value<3×10⁻². Pooled case/control study (371 cases and 312 controls) as well as combined analysis of extension and replication data showed very significant association (P<5×10⁻⁴) for 6 of the 8 latter markers (rs7849556, rs10817669, rs10759734, rs6478105, rs10982396, and rs10733612). Finally, haplotype association investigations identified a strongly associated haplotype (P<8.8×10⁻⁵) consisting of these 6 SNPs and located in the direct vicinity of the TNFSF15 gene. In conclusion, we have identified within the SPA2 locus a haplotype strongly associated with predisposition to SpA which is located near to TNFSF15, one of the major candidate genes in this region.

Spondyloarthritis (SpA) is a common variety of articular inflammatory disorder characterized by axial and/or peripheral arthritis, frequently associated with extra-articular manifestations such as psoriasis, uveitis, and inflammatory bowel diseases (ulcerative colitis or Crohn's disease (CD)). SpA is a complex disorder with high heritability. The MHC class I HLA-B27 allele is a very strong risk factor for its development, but other genetic factors located outside the MHC also play a role in disease susceptibility. By a previous whole-genome linkage investigation, we have demonstrated that a region located on the chromosome 9q31–34 was involved in SpA susceptibility. The present study aimed to further characterize this locus. Using a stepwise linkage and association approach, we identified a haplotype spanning 6 single-nucleotide polymorphisms strongly associated with SpA and located in a genomic region paralogous to the MHC, near to the TNFSF15 gene. Interestingly, polymorphisms of this gene have previously been shown to be associated with CD. This original finding offers a new research track for the understanding of SpA pathophysiology, which is still poorly understood, as well as new hope for diagnostic and therapeutic innovation.

An autoinflammatory disease with deficiency of the interleukin-1-receptor antagonist

BACKGROUND

Autoinflammatory diseases manifest inflammation without evidence of infection, high-titer autoantibodies, or autoreactive T cells. We report a disorder caused by mutations of IL1RN, which encodes the interleukin-1-receptor antagonist, with prominent involvement of skin and bone.

METHODS

We studied nine children from six families who had neonatal onset of sterile multifocal osteomyelitis, periostitis, and pustulosis. Response to empirical treatment with the recombinant interleukin-1-receptor antagonist anakinra in the first patient prompted us to test for the presence of mutations and changes in proteins and their function in interleukin-1-pathway genes including IL1RN.

RESULTS

We identified homozygous mutations of IL1RN in nine affected children, from one family from Newfoundland, Canada, three families from The Netherlands, and one consanguineous family from Lebanon. A nonconsanguineous patient from Puerto Rico was homozygous for a genomic deletion that includes IL1RN and five other interleukin-1-family members. At least three of the mutations are founder mutations; heterozygous carriers were asymptomatic, with no cytokine abnormalities in vitro. The IL1RN mutations resulted in a truncated protein that is not secreted, thereby rendering cells hyperresponsive to interleukin-1beta stimulation. Patients treated with anakinra responded rapidly.

CONCLUSIONS

We propose the term deficiency of the interleukin-1-receptor antagonist, or DIRA, to denote this autosomal recessive autoinflammatory disease caused by mutations affecting IL1RN. The absence of interleukin-1-receptor antagonist allows unopposed action of interleukin-1, resulting in life-threatening systemic inflammation with skin and bone involvement. (ClinicalTrials.gov number, NCT00059748.)