HLA-B60 and B61 are strongly associated with ankylosing spondylitis in HLA-B27-negative Taiwan Chinese patients

Updates on ankylosing spondylitis: pathogenesis and therapeutic agents

Ankylosing spondylitis (AS) is an autoinflammatory disease that manifests with the unique feature of enthesitis. Gut microbiota, HLA-B*27, and biomechanical stress mutually influence and interact resulting in setting off a flame of inflammation. In the HLA-B*27 positive group, dysbiosis in the gut environment disrupts the barrier to exogenous bacteria or viruses. Additionally, biomechanical stress induces inflammation through enthesial resident or gut-origin immune cells. On this basis, innate and adaptive immunity can propagate inflammation and lead to chronic disease. Finally, bone homeostasis is regulated by cytokines, by which the inflamed region is substituted into new bone. Agents that block cytokines are constantly being developed to provide diverse therapeutic options for preventing the progression of inflammation. In addition, some antibodies have been shown to distinguish disease selectively, which support the involvement of autoimmune immunity in AS. In this review, we critically analyze the complexity and uniqueness of the pathogenesis with updates on the findings of immunity and provide new information about biologics and biomarkers.

A multicentre study of clinical features and HLA typing in Japanese patients with ankylosing spondylitis

OBJECTIVES

Due to the low prevalence of HLA-B27 and ankylosing spondylitis (AS) in Japan, rheumatologists have little experience with AS. We conducted a multicentre study to identify the characteristics and frequency of HLA-B types.

METHODS

We analysed epidemiological and clinical data, blood tests, spine radiographs, and HLA-B types in Japanese AS patients.

RESULTS

We evaluated 111 AS patients, predominantly men (82.9%). The mean age, disease onset, diagnosis, and time from onset to diagnosis were 43.7, 24.2, 36.0, and 11.6 years, respectively. Inflammatory low back pain was found in 96 cases (86.5%); peripheral arthritis in 59 (53.2%), enthesitis in 35 (31.5%), and dactylitis in 6 (5.4%). Extra-articular symptoms included uveitis, psoriasis, and inflammatory bowel disease in 41 (36.9%), 1 (0.9%), and 5 (4.5%) cases, respectively. HLA-B27 was positive in 83 cases (74.8%; odds ratio, 1146.0); and HLA-B48 in 9 (8.1%; odds ratio, 3.0). HLA-B27-positive patients were younger at onset and had a shorter diagnostic delay.

CONCLUSIONS

AS clinical symptoms were almost the same as other countries except for the low coexistence of psoriasis. HLA-B27 positivity in Japanese patients was 78%. HLA-B27-positive patients were younger and diagnosed earlier. In addition to HLA-B27, a relationship with HLA-B48 was suggested.

No Evidence to Support a Causal Relationship between Circulating Adiponectin Levels and Ankylosing Spondylitis: A Bidirectional Two-Sample Mendelian Randomization Study

Based on previous observational studies, the causal association between circulating adiponectin (CA) levels and ankylosing spondylitis (AS) risk remains unclear. Therefore, this study aims to investigate whether CA levels are related to the risk of AS. We carried out a bidirectional two-sample Mendelian randomization (MR) analysis to examine the causal correlation between CA levels and AS via published genome-wide association study (GWAS) datasets. Single-nucleotide polymorphisms (SNPs) related to CA levels were derived from a large GWAS that included 39,883 individuals of European descent. SNPs related to AS were obtained from the FinnGen consortium (2252 cases and 227,338 controls). The random-effects inverse variance weighted (IVW) method was the primary method utilized in our research. We also used four complementary approaches to improve the dependability of this study (MR-Egger regression, Weighted median, Weighted mode, and Simple mode). Random-effects IVW (odds ratio [OR], 1.00; 95% confidence interval [CI], 0.79-1.27, p = 0.984) and four complementary methods all indicated that genetically predicted CA levels were not causally related to the risk of AS. In reverse MR analysis, there is little evidence to support the genetic causality between the risk of AS and CA levels.

MHC associations of ankylosing spondylitis in East Asians are complex and involve non-HLA-B27 HLA contributions

BACKGROUND

The association of HLA-B*27 with AS is amongst the strongest of any known association of a common variant with any human disease. Nonetheless, there is strong evidence indicating that other HLA-B alleles are involved in the disease. European ethnicity studies have demonstrated risk associations with HLA-B*40 and multiple other HLA-B, HLA-A, and HLA class II alleles, and demonstrated that in that ethnic group, the amino acid sequence at position 97 in HLA-B is the key determinant of HLA associations with AS. A recent study in Korean AS cases and controls additionally identified association at HLA-C*15:02. In the current study, we examined the MHC associations of AS in an expanded East Asian cohort.

METHODS

A total of 1637 Chinese, Taiwanese, and Korean AS cases meeting the modified New York Criteria for AS, and 1589 ethnically matched controls, were genotyped with the Illumina Immunochip, including a dense coverage of the MHC region. HLA genotypes and amino acid composition were imputed using the SNP2HLA programme using the Han-MHC reference panel based on the data of Han Chinese subjects (n = 9689), and association tested using logistic regression controlling for population stratification effects.

RESULTS

A strong association was seen with HLA-B*27 (odds ratio (OR) = 205.3, P = 5.76 × 10^-244). Controlling for this association, the strongest risk association is seen with HLA-C*15 at genome-wide significant level (OR = 7.62, P = 9.30 × 10^-19), and confirmed association is also seen with HLA-B*40 at suggestive level (OR = 1.65, P = 2.54 × 10^-4). At amino acid level, the strongest association seen in uncontrolled analysis was with histidine at position 114 in HLA-B (P = 7.24 × 10^-241), but conditional analyses suggest that the primary amino acid associations are with lysine at position 70 and asparagine at position 97. Restriction of the ERAP1 association with HLA-B27-positive AS, previously reported in European subjects, was confirmed in East Asians.

CONCLUSIONS

This study confirms in East Asians that the HLA associations of AS are multiple, including previously reported associations at HLA-B*27, HLA-B*40, and HLA-C*15, as well as novel association with HLA-DQB1*04. The HLA-B associations are driven by the amino acids at positions 70 and 97, in the B pocket of HLA-B.

The Pathogenesis of Ankylosing Spondylitis: an Update

PURPOSE OF REVIEW

Ankylosing spondyloarthritis (AS) is a chronic inflammatory disease that involves the axial joints and entheses. Extra-spinal manifestations such as anterior uveitis, psoriasis, and colitis also occur frequently. This review on the pathogenesis of AS includes an update on the recent discoveries within the field.

RECENT FINDINGS

HLA-B*27 is still considered of major importance in the pathogenesis, and it has recently been shown to profoundly affect the gut microbiome and its metabolites and the handling of bacteria during infection. Biochemical and biophysical properties of HLA-B*27 influence its ability to misfold, to induce an endoplasmic reticulum stress response, and to promote autophagy/unfolded protein responses (UPR). HLA-B*27 free heavy chains may induce inflammation through T cells, NK cells, and myeloid cells. Induction of UPR genes results in release of tumor necrosis factor-α (TNF-α), interleukin-17 (IL-17), IL-23, and interferon-γ and increase in T helper (Th) 17 cells. Several other HLA-B and non-B molecules have been associated with AS, although their role in the pathogenesis is unknown. Genotypes of endoplasmic reticulum aminopeptidases (ERAP) 1 and 2 have been associated with alterations in the antigenic pool expressed by HLA-B*27 molecules. In the gut, innate immune cells type 3 (ILC3) influence T cell expression of IL-17 and IL-22. Gamma-delta (γ/δ) T cells are induced by IL-23 to produce IL-17. IL-7 induces mucosa-associated invariant T (MAIT) cells to produce IL-17. Besides the microbiome, zonulin may be important through its effects on the permeability of tight junctions in the intestinal epithelial barrier.

Ankylosing spondylitis presenting with enthesitis at an uncommon site and fever of unknown origin

A 58-year-old man presented with a 2-month history of arthralgia and bilateral temporal region pain, and a 1-month history of fever. He had had refractory neck pain since his 20s. Reduced cervical and lumbar mobility was observed. Radiographs of cervical and thoracic vertebrae disclosed syndesmophytes. Pelvic radiographs showed sclerosis in the right sacroiliac joint and ankylosis in the left sacroiliac joint. MRI with contrast enhancement showed enthesitis in the upper extremities and enhancement in the bilateral temporal muscle, which indicated enthesitis of temporal muscle. He was diagnosed with ankylosing spondylitis based on the limitation in mobility of the lumbar spine and radiographic findings. To the best of our knowledge, this is the first report describing enthesitis of the temporal muscle. This case highlights that ankylosing spondylitis can be accompanied with enthesitis at the temporal muscle and fever of unknown origin at the initial presentation.

Ankylosing spondylitis: etiology, pathogenesis, and treatments

Ankylosing spondylitis (AS), a common type of spondyloarthropathy, is a chronic inflammatory autoimmune disease that mainly affects spine joints, causing severe, chronic pain; additionally, in more advanced cases, it can cause spine fusion. Significant progress in its pathophysiology and treatment has been achieved in the last decade. Immune cells and innate cytokines have been suggested to be crucial in the pathogenesis of AS, especially human leukocyte antigen (HLA)‑B27 and the interleukin‑23/17 axis. However, the pathogenesis of AS remains unclear. The current study reviewed the etiology and pathogenesis of AS, including genome-wide association studies and cytokine pathways. This study also summarized the current pharmaceutical and surgical treatment with a discussion of future potential therapies.

Beyond the TNF-α Inhibitors: New and Emerging Targeted Therapies for Patients with Axial Spondyloarthritis and their Relation to Pathophysiology

Axial spondyloarthritis (axSpA) is a complex disease that affects the joints and entheses of axial and peripheral joints, and is associated with inflammation in extra-articular sites such as the gut. Improved knowledge on genetics and immunology has improved treatment options with the availability of treatments targeting tumor necrosis factor-α (TNF-α) and interleukin (IL)-17. However, these agents do not provide clinical benefit for about 40% of patients, and additional therapeutic options are necessary. Theories on pathogenesis includes misfolding of HLA-B*27 during its assembly leading to endoplasmic reticulum stress and autophagy/unfolded protein response (UPR). HLA-B*27 may express free heavy chain on the cell surface, which activates innate immune receptors on T, natural killer, and myeloid cells with pro-inflammatory effects. Activation of UPR genes is associated with increased TNF-α, interleukin-23 (IL-23), IL-17, interferon-γ expression, and expansion of T helper (Th)-17 cells. Certain genotypes of endoplasmic reticulum aminopeptidase (ERAP) 1 and 2 are associated with ankylosing spondylitis (AS) and functionally interact with the HLA-B27 peptidome. Innate immune cells type 3, which express RORγt, regulate expression of IL-17 and IL-22 in T cells. Stimulation of gamma-delta T cells with IL-23 also induces IL-17. Mucosa-associated invariant T cells residing in the gut mucosa express IL-17 in AS patients after stimulation with IL-7. Prostaglandin E2 induces IL-17A independent of IL-23 via IL-1β and IL-6. The pathogenic role of gut inflammation, zonulin and microbiota, which has a different composition in AS patients, remains to be elucidated. This article also includes a comprehensive review on the mechanism of action and efficacy of the biological treatments currently approved for axSpA (TNF-α inhibitors and IL-17 inhibitors) and future targets for treatment (other IL-17 family member (s), Janus kinase, IL-23, and phosphodiesterase 4).

Ankylosing spondylitis: analysis of gene-gene interactions between IL-12β, JAK2, and STAT3 in Han Chinese and Algerian cohorts

Introduction

Association studies have recently identified the importance of new genetic variants for ankylosing spondylitis (AS) in several populations. Our aim was to confirm associations of variants within genes involved in the IL-23 signalling pathway with AS in two ethnically different populations: Han Chinese and Algerian.

Material and methods

Two case-control studies were performed in separate cohorts: Han Chinese (430 AS patients and 580 controls) and Algerian (130 AS patients and 120 controls). We genotyped four single nucleotide polymorphisms (SNPs): rs3212227 (or +1188A/C) and rs6887695 in IL-12β, rs7857730 in JAK2, and rs2293152 in STAT3, using TaqMan SNP genotyping assays. Gene-gene interaction analyses were also tested by logistic regression and multifactor dimensionality reduction (MDR).

Results

Statistical analysis revealed a difference in allele frequencies between AS patients and controls for rs321222 in the IL-12β gene in both the Han Chinese (p = 0.005) and the Algerian (p = 0.031) cohorts. Two other associations were reported with JAK2 rs7857730 in the Han Chinese (allelic p = 0.014) cohort and STAT3 rs2293152 in the Algerian (allelic p = 0.006) cohort. Moreover, logistic regression analyses showed a number of significant combinations within the two populations, and the gene-gene epistasis effects in AS were also confirmed by MDR.

Conclusions

Our findings have confirmed the association between genes in IL-23 signalling pathway and the pathogenesis of AS. This association was particularly novel in both Han Chinese and Algerian populations with the 3’ untranslated region (3’UTR) variant rs3212227 (or +1188A/C) of IL-12β. The gene-gene interaction models in this pathway may thus increase the risk of AS in these populations.

Progress of genome-wide association studies of ankylosing spondylitis

Ankylosing spondylitis (AS) is an immune-mediated arthritis which primarily affects the spine and sacroiliac joints. Significant progress has been made in discovery of genetic associations with AS by genome-wide association studies (GWAS) over past decade. These findings have uncovered novel pathways involved pathogenesis of the disease and have led to introduction of novel therapeutic treatments for AS. In this Review, we discuss the genetic variations associated with AS identified by GWAS, the major pathways revealed by these AS-associated variations and critical cell types involved in AS development.

rs657075 (CSF2) Is Associated with the Disease Phenotype (BAS-G) of Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a systemic autoimmune disease mainly affecting the lumbar spine and sacroiliac joints, and exhibits peripheral inflammatory arthropathy. More than 25 loci have been identified as associated with AS. Because both AS and rheumatoid arthritis (RA) are autoimmune diseases that may share some common genetic factors, we therefore examined if the newly identified RA genetic polymorphisms were associated with AS in a Taiwanese population. In this study, we enrolled 475 AS patients and 11,301 healthy subjects from a Taiwanese biobank as controls. Although none of single-nucleotide polymorphisms (SNPs) were associated with the susceptibility to AS, the AS disease index Bath AS Global (BAS-G) clinical phenotype was observed as significantly correlated to the AA genotype of rs657075 (CSF2). The significance remains after gender/age/disease duration adjustment and after group categorization by human leukocyte antigen-B 27 (HLA-B27) genotype. We further investigated the possible functions of rs657075 through bioinformatics approaches. Results revealed that polymorphism of rs657075 is able to influence the expression of acyl-CoA synthetase long-chain family member 6 (ACSL6). In conclusion, our study indicated that rs657075 (CSF2) is strongly associated with the AS disease index Bath AS Global (BAS-G) clinical phenotype.

Association of human leukocyte A, B, and DR antigens in Colombian patients with diagnosis of spondyloarthritis

There is substantial evidence that non-B27 major histocompatibility complex (MHC) genes are associated with spondyloarthritis (SpA). Studies in Mexican and Tunisian populations demonstrated the association of SpA and human leukocyte antigen (HLA) B15. The purpose of this study was to evaluate the association of HLA-A, B, and DR antigens in a group of Colombian patients with a diagnosis of SpA. A total of 189 patients and 100 healthy subjects were included in the present study. All subjects underwent a complete characterization of HLA alleles A, B, and DR. Of the 189 studied patients, 35 were reactive arthritis (ReA), 87 were ankylosing spondylitis (AS), and 67 undifferentiated SpA (uSpA). According to the Assessment of Spondyloarthritis International Society (ASAS) criteria, 167 were axial SpA (axSpA) and 171 were peripheral SpA (pSpA). 63.8% were men, with a mean age of 35.9 ± 12.7 years. 40.7% (77/189) of patients were HLA-B27 positive of which 52.9% had AS and 42.5% axSpA. 23.2% (44/189) of patients were HLA-B15 positive: 23.8% were uSpA, 12.57% were axSpA, and 11.7% were pSpA. In addition, HLA-DRB1*01 was associated with AS (58.6%) and axSpA (42.5%). Also, HLA-DRB1*04 was present in 62 patients with AS (71.2%) and in 26 with axSpA (15.5%). In this population, we found a strong association between the presence of HLA-B27 and the diagnosis of axSpA and AS, but the HLA-B15 is also significantly associated with all subtypes of the disease, predominantly with pSpA. Additionally, HLA-DR1 and DR4 were associated in a cohort of patients with SpA from Colombia.

New insights toward the pathogenesis of ankylosing spondylitis; genetic variations and epigenetic modifications

Ankylosing spondylitis (AS) is a chronic inflammatory autoimmune disease, characterized by typically an axial arthritis. AS is the prototype of a group of disorders called spondyloarthropathies, which is believed to have common clinical manifestations and genetic predisposition. To date, the exact etiology of AS remains unclear. Over the past few years, however, the role of genetic susceptibility and epigenetic modifications caused through environmental factors have been extensively surveyed with respect to the pathogenesis of AS, resulted in important advances. This review article focuses on the recent advances in the field of AS research, including HLA and non-HLA susceptibility genes identified in genome-wide association studies (GWAS), and aberrant epigenetic modifications of gene loci associated with AS. HLA genes most significantly linked with AS susceptibility include HLA-B27 and its subtypes. Numerous non-HLA genes such as those in ubiquitination, aminopeptidases and MHC class I presentation molecules like ERAP-1 were also reported. Moreover, epigenetic modifications occurred in AS has been summarized. Taken together, the findings presented in this review attempt to explain the circumstance by which both genetic variations and epigenetic modifications are involved in triggering and development of AS. Nonetheless, several unanswered dark sides continue to clog our exhaustive understanding of AS. Future researches in the field of epigenetics should be carried out to extend our vision of AS etiopathogenesis.

Interaction between HLA-B60 and HLA-B27 as a Better Predictor of Ankylosing Spondylitis in a Taiwanese Population

Objective

Ankylosing spondylitis (AS) is a form of chronic inflammatory spondyloarthritis (SpA) that causes pain and stiffness in spines or joints. Human leukocyte antigen B27 (HLA-B27) and B60 (HLA-B60) have been reported as major genetic risk factors of AS. In addition, rs13202464, located on major histocompatibility complex (MHC) region, showed high sensitivity (98.7%) and specificity (98.0%) for HLA-B27.

Design

The aim of our study is to test whether the interaction between HLA-B60 and HLA-B27 (rs13202464) can serve as a better predictor of AS. We have genotyped HLA-B60 and rs13202464 among 471 patients with AS and 557 healthy subjects. Combined risk factors were investigated to test the biological interaction.

Results

Our results indicated that the relative risk (RR) for HLA-B27+/HLA-B60− was 152 (95% CI 91 to 255) and it increased to 201 (95% CI 85 to 475) in HLA-B27+/HLA-B60+ patients (with HLA-B27−/HLA-B60− as reference). Combinational analysis of two risk factors (HLA-B27+/HLA-B60+) showed a relative excess risk due to interaction (RERI) of 46.79 (95% CI: -117.58 to 211.16), attributable proportion (AP) of 0.23 (95% CI: -0.41 to 0.88) and a synergy index (S) of 1.31 (95% CI: 0.56 to 3.04).

Conclusion

In conclusion, genetic interaction analysis revealed that the interaction between HLA-B60 and HLA-B27 is a better marker for the risk of AS susceptibility in a Taiwanese population.

[REITER'S SYNDROME FOLLOWING INTRAVASICAL BCG THERAPY FOR UROTHELIAL CARCINOMA. SUMMARY OF CASE REPORTS OVER THE PAST 13 YEARS IN JAPAN, INCLUDING OUR CURRENT 6 CASES]

Reiter's syndrome is one of the rare complications following intravesical bovis Bacillus Calmette-Guerin (BCG) treatment. In this study we have reviewed and discussed 101 cases including our own 6 cases over the past 13 years in Japan (2000-2013). The patients comprised 70 males and 25 females (6 cases were unknown), mean age of 63.1 (range 42 - 91). Arthritis occured 4-5 days after conjunctivitis. Thirty five (55%) of 68 patients needed corticosteroid treatment to control their arthritis. HLA-B27 is known as a risk factor of Reiter's syndrome, however, positive rate was only 2.4% (n = 41).

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.

Major histocompatibility complex associations of ankylosing spondylitis are complex and involve further epistasis with ERAP1

Ankylosing spondylitis (AS) is a common, highly heritable, inflammatory arthritis for which HLA-B*27 is the major genetic risk factor, although its role in the aetiology of AS remains elusive. To better understand the genetic basis of the MHC susceptibility loci, we genotyped 7,264 MHC SNPs in 22,647 AS cases and controls of European descent. We impute SNPs, classical HLA alleles and amino-acid residues within HLA proteins, and tested these for association to AS status. Here we show that in addition to effects due to HLA-B*27 alleles, several other HLA-B alleles also affect susceptibility. After controlling for the associated haplotypes in HLA-B, we observe independent associations with variants in the HLA-A, HLA-DPB1 and HLA-DRB1 loci. We also demonstrate that the ERAP1 SNP rs30187 association is not restricted only to carriers of HLA-B*27 but also found in HLA-B*40:01 carriers independently of HLA-B*27 genotype.

Ankylosing spondylitis is a common, highly inheritable inflammatory arthritis with poorly understood biology. Here Brown, Cortes and colleagues use fine mapping of the major histocompatibility complex and identify novel associations, and identify other HLA alleles that like HLA-B27 interact with ERAP1 variants to influence disease risk.

Identification of Disease-Promoting HLA Class I and Protective Class II Modifiers in Japanese Patients with Familial Mediterranean Fever

Objectives

The genotype-phenotype correlation of MEFV remains unclear for the familial Mediterranean fever (FMF) patients, especially without canonical MEFV mutations in exon 10. The risk of FMF appeared to be under the influence of other factors in this case. The contribution of HLA polymorphisms to the risk of FMF was examined as strong candidates of modifier genes.

Methods

Genotypes of HLA-B and -DRB1 loci were determined for 258 mutually unrelated Japanese FMF patients, who satisfied modified Tel-Hashomer criteria, and 299 healthy controls. The effects of carrier status were evaluated for the risk of FMF by odds ratio (OR). The HLA effects were also assessed for clinical forms of FMF, subsets of FMF with certain MEFV genotypes and responsiveness to colchicine treatment.

Results

The carriers of B*39:01 were increased in the patients (OR = 3.25, p = 0.0012), whereas those of DRB1*15:02 were decreased (OR = 0.45, p = 0.00050), satisfying Bonferroni’s correction for multiple statistical tests (n = 28, p<0.00179). The protective effect of DRB1*15:02 was completely disappeared in the co-existence of B*40:01. The HLA effects were generally augmented in the patients without a canonical MEFV variant allele M694I, in accordance with the notion that the lower penetrance of the mutations is owing to the larger contribution of modifier genes in the pathogenesis, with a few exceptions. Further, 42.9% of 14 colchicine-resistant patients and 13.5% of 156 colchicine-responders possessed B*35:01 allele, giving OR of 4.82 (p = 0.0041).

Conclusions

The differential effects of HLA class I and class II polymorphisms were identified for Japanese FMF even in those with high-penetrance MEFV mutations.

Suppression subtractive hybridization reveals differentially expressed genes in supraspinous ligaments of patients with ankylosing spondylitis

Ankylosing spondylitis (AS) is a severe chronic inflammatory disease that may ultimately result in the development of a 'bamboo‑like' spine. Although the pathological changes that occur in AS have been extensively investigated, the mechanism underlying spinal fusion during AS remains elusive. Differentially expressed genes (DEGs) in paraspinal tissues from patients with AS compared with those from healthy controls were therefore investigated. Polymerase chain reaction (PCR)‑based suppression subtractive hybridization was performed using total mRNA from the supraspinal ligaments of three patients with AS and three patients with spinal fractures as controls. From this, 27 genes were identified in all of the three independent forward libraries, which were defined as DEGs associated with AS. Reverse transcription‑quantitative PCR demonstrated that six DEGs were overexpressed in the tissues from patients with AS compared with those from individuals in the control group, including those encoding transforming growth factor β types I and III receptor, vascular endothelial growth factor, matrix metalloproteinase‑3, core‑binding factor α1 and bone morphogenetic protein 2. Western blot analysis showed increased expression in all six of these proteins in the samples from patients with AS compared with those in the control groups. These findings suggested that changes in the expression of these genes and proteins are associated with the development of spinal fusion during the pathogenesis of AS. Furthermore, these genes may be novel markers of the risk of developing AS, in addition to being targets for the treatment of this disease.

rs10865331 associated with susceptibility and disease severity of ankylosing spondylitis in a Taiwanese population

Ankylosing spondylitis (AS) is a highly familial rheumatic disorder and is considered as a chronic inflammatory disease. Genetic factors are involved in the pathogenesis of AS. To identify genes which render people susceptible to AS in a Taiwanese population, we selected six single-nucleotide polymorphisms (SNPs) from previous genome-wide association studies (GWASs) which were associated with AS in European descendants and Han Chinese. To assess whether the six SNPs contributed to AS susceptibility and severity in Taiwanese population, 475 AS patients fulfilling the modified New York Criteria and 527 healthy subjects were recruited. We found that rs10865331 was significantly associated with AS susceptibility and with Bath AS Function Index (BASFI). The AA and AG genotypes of rs10865331 were also significantly associated with a higher erythrocyte sedimentation rate. Our findings provided evidence that rs10865331 is associated AS susceptibility and with disease activity (BASFI) in a Taiwanese population.

Mutations in the B30.2 domain of pyrin and the risk of ankylosing spondylitis in the Chinese Han population: a case-control study

Ankylosing spondylitis (AS) and familial Mediterranean fever (FMF) are a common autoimmune disease and a classic autoinflammatory disease, respectively. Mediterranean fever (MEFV) encodes the pyrin protein and is the causal disease gene in FMF. This protein is an important regulator of innate immunity and may play a key role in the development of AS. To identify the mutations in the B30.2 domain of pyrin and to uncover the relationships between these mutations and AS risk in the Chinese Han population, we extracted genomic DNA from the peripheral blood of 200 AS patients and 200 matched controls and performed polymerase chain reactions (PCRs) and direct sequencing on those samples. Statistical analysis indicated that only Met694Val (rs61752717) in the B30.2 domain of pyrin could affect the risk of AS (P = 0.042; odds ratio [OR] = 5.103; 95% confidence interval [CI] = 1.111-23.437 for the model of Met (M) vs. Val (V), P = 0.040; OR = 5.211; 95% CI = 1.127-24.091 for the model of MM vs. MV+VV). Moreover, M694V is significantly associated with a higher level of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) in AS patients. Our results are the first to suggest that the M694V allele of the pyrin was associated with AS risk in the Chinese Han population and that this mutation may be associated with the inflammatory response in the development of AS.

An update on the contribution of the MHC to AS susceptibility

The 40-year-old association of HLA-B27 with ankylosing spondylitis is one of the best examples of disease association with a hereditary marker. Genomewide association and family studies suggest that other important major histocompatibility complex (MHC) influences are operative in ankylosing spondylitis (AS) susceptibility. HLA-B27 positive hepatitis C individuals are immunologically more efficient in combating viral infections such as HIV-1, hepatitis C, and influenza and less efficient in combating against certain bacteria (and perhaps other organisms) capable of surviving intracellularly. A recent representative population survey of the frequency of HLA-B27 in the USA found a lower frequency of HLA-B27 in older US adults, perhaps reflecting this. Other HLA class I and class II alleles have been implicated in AS susceptibility, the most consistent being HLA-B*40/B60 (B*40:01) but also B14, B15, A*0201, DRB1*04:04, and certain DPA1 and DPB1 alleles. Non-HLA MHC alleles have also been implicated, although many such studies have been inconsistent, likely due to power issues related to the low number of HLA-B27-negative AS patients examined. The best evidence is for major histocompatibility complex class I chain-related gene A (MICA) whose recognition by intestinal epithelial T cells expressing different V-delta-1 gamma/delta TCR further implicates the gut in AS pathogenesis. The HLA class I and class II and other non-HLA allelic associations underscore the importance of T cells in AS pathogenesis.

Role of hla-B alleles and clinical presentation of b27 negative spondyloarthritis patients from mumbai, Western India

Seronegative spondyloarthritis (SpA) are variably associated with HLA-B∗27 antigen. HLA-B∗27 negative SpA has also been reported from different parts of the world. There is paucity of data on this entity from Indian subcontinent. We studied 100 consecutively diagnosed HLA-B27 negative spondyloarthritis patients from a tertiary care center in India. Modified New York Criteria for ankylosing spondylitis (AS) and ESSG criteria for SpA were used for diagnosing patients. HLA-B∗27 typing was done by an in-house PCR-SSP technique in SpA patients to exclude B∗27 positive patients and PCR-SSOP technique was used to type 100 B∗27 negative SpA patients and 100 controls from the same ethnicity. Frequency of B∗07 was significantly increased (B∗07: % PF 54 versus 18; OR 5.348; 95% CI 2.808-10.186; P value 1.14E - 07), whereas frequency of B∗40 was significantly decreased (B∗40: % PF 17 versus 32; OR 0.435; 95% CI 0.222-0.850; P value 0.013) when compared with B∗27 negative controls. Among 100 SpA patients, 47 were undifferentiated spondyloarthritis and 33 patients were reactive arthritis patients. 40% of the patients were suffering from polyarticular arthritis, 35% had pauciarticular arthritis with knee joint, hip joint, ankle joint, and SI joint involvement. We conclude that B∗07 was significantly associated with B27 negative spondyloarthropathy from Western India and majority of B∗27 negative patients were uSpA.

Polymorphism of HLA-B27: 105 subtypes currently known

HLA-B27 has a high degree of genetic polymorphism, with 105 known subtypes, named HLA-B*27:01 to HLA-B*27:106, encoded by 132 alleles. The most common subtypes associated with ankylosing spondylitis are HLA-B*27:05 (Caucasians), HLA-B*27:04 (Chinese), and HLA-B*27:02 (Mediterranean populations). For Chinese populations, HLA-B*27:04 is associated with a greater ankylosing spondylitis risk than HLA-B*27:05. Two subtypes, HLA-B27*06 and HLA-B27*09, seem to have no disease association. These differential disease associations of HLA-B27 subtypes, and the recent discovery that ERAP1 is associated with ankylosing spondylitis for patients with HLA-B27, have increased attempts to determine the function of HLA-B27 in disease pathogenesis by studying hemodynamic features of its protein structure, alterations of its peptidome, aberrant peptide handling, and associated molecular events. However, after 40 years we still do not fully know how HLA-B27 predisposes to ankylosing spondylitis and related spondyloarthritis.

Genetics of ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory arthritis that affects the spine and sacroiliac joints. It causes significant disability and is associated with a number of other features including peripheral arthritis, anterior uveitis, psoriasis and inflammatory bowel disease (IBD). Significant progress has been made in the genetics of AS have in the last five years, leading to new treatments in trial, and major leaps in understanding of the aetiopathogenesis of the disease.

Fine mapping of a major histocompatibility complex in ankylosing spondylitis: association of the HLA-DPA1 and HLA-DPB1 regions

OBJECTIVE

To investigate the potential association of major histocompatibility complex (MHC) markers other than HLA-B27 with ankylosing spondylitis (AS).

METHODS

A total of 603 patients with AS and 542 healthy control subjects, all of whom were HLA-B27 positive, were selected for this study based on clinical criteria. First, high-density genotyping across the MHC region (2,360 single-nucleotide polymorphisms [SNPs]) was performed in a cohort of 191 patients and 241 control subjects. After a fine-mapping study, 5 SNPs from the HLA-DPA1/DPB1 region were validated in a second cohort of 412 patients with AS and 301 healthy control subjects.

RESULTS

Seventeen SNPs located within or near the HLA-DPA1 and HLA-DPB1 loci showed association with AS (P = 1.38 × 10⁻⁵ to 0.05). In addition, multimarker tests, both linkage disequilibrium and sliding windows, showed association of some groups of adjacent SNPs within the HLA-DPA1/DPB1 region with AS (P = 1.0 × 10⁻⁴ to 3.96 × 10⁻⁷). We validated the association by genotyping 5 SNPs from the DPA1/DPB1 region in an additional cohort and obtained P values from 6.42 × 10⁻⁵ to 0.01 in the analysis of the combined cohorts. Subtyping analysis of HLA-DPA1 and HLA-DPB1 showed that HLA-DPA1*01:03, A1*02:01, and B1*13:01 were the subtypes most susceptible to AS.

CONCLUSION

HLA markers and linkage disequilibrium blocks near HLA-DPA1 and HLA-DPB1 are statistically associated with AS. We identified a region located around the HLA-DPA1 and HLA-DPB1 loci associated with AS, another region within the MHC that is different from HLA-B27.

Association study of polymorphisms rs4552569 and rs17095830 and the risk of ankylosing spondylitis in a Taiwanese population

Ankylosing spondylitis (AS) is a chronic inflammation of the sacroiliac joints, spine and peripheral joints. However, the development of anklosing spondylitis is unclear. Human leukocyte antigens HLA-B27 and ERAP1 have been widely reported to be associated with AS susceptibility. A recent genome-wide association study (GWAS) showed that two new susceptibility loci between EDIL3 and HAPLN1 at 5q14.3 (rs4552569) and within ANO6 at 12q12 (rs17095830) contribute to the risk of AS in Han Chinese. In this study, we enrolled 475 AS patients and 475 healthy subjects to assess whether these genetic variations contribute to the susceptibility and the severity of AS in the Taiwanese population. The correlation between genetic polymorphisms, AS activity indexes, (namely, BASDAI, BASFI and BAS-G) and AS complications (uveitis and inflammatory bowel disease) were tested using the markers, rs4552569 and rs17095830. Although no association between rs4552569/rs17095830 genetic polymorphisms and AS susceptibility/severity was found, a significant association between rs17095830 and inflammatory bowel disease was observed in a Taiwanese population.

Genetic polymorphisms of stromal interaction molecule 1 associated with the erythrocyte sedimentation rate and C-reactive protein in HLA-B27 positive ankylosing spondylitis patients

Ankylosing spondylitis (AS) is a chronic inflammation of the sacroiliac joints, spine and peripheral joints. The development of ankylosing spondylitis is still unclear. Genetics factors such as human leukocyte antigen HLA-B27 and ERAP1 have been widely reported to associate to AS susceptibility. In this study, we enrolled 361 AS patients and selected four tagging single nucleotides polymorphisms (tSNPs) at STIM1 gene. The correlation between STIM1 genetic polymorphisms and AS activity index (BASDAI, BASFI, BAS-G) as well as laboratory parameters of inflammation (erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)) were tested. Our results indicated that HLA-B27 positive AS patients who are carrying the minor allele homozygous G/G genotype of SNP rs3750996 significantly associated with a higher level of ESR in serum. Furthermore, rs3750996/rs3750994 pairwise allele analysis indicated that G-C haplotypes also significantly correlated with higher level of ESR as well as CRP. These findings provide a better understanding of STIM1 genetic contribution to the pathogenesis of AS.

Old and new HLA associations with ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory rheumatic disease that primarily involves the axial skeleton and the sacroiliac joint, but may also affect peripheral joints and entheses. AS susceptibility is clearly attributable to genetic factors and the link between human leukocyte antigen (HLA)-B27 and AS is the strongest association between an HLA class I molecule and a disease. However, there is evidence for the involvement of other, non-B27 factors within the major histocompatibility complex (MHC) in AS susceptibility. MHC class I is clearly the most significant genetic region for the disease, although most of the genetic association of this region is driven by HLA-B27. Moreover, several studies have investigated the MHC class II region and its association with AS. This review summarizes the current findings concerning the MHC genetics of the disease, focusing in particular on the associations of HLA with AS found in different ethnic populations throughout the world, and the possible mechanisms underlying them.

The genetics of ankylosing spondylitis and axial spondyloarthritis

Ankylosing spondylitis (AS) and spondyloarthritis are strongly genetically determined. The long-standing association with HLA-B27 is well described, although the mechanism by which that association induces AS remains uncertain. Recent developments include the description of HLA-B27 tag single nucleotide polymorphisms in European and Asian populations. An increasing number of non-MHC genetic associations have been reported, which provided amongst other things the first evidence of the involvement of the IL-23 pathway in AS. The association with ERAP1 is now known to be restricted to HLA-B27 positive disease. Preliminary studies on the genetics of axial spondyloarthritis demonstrate a lower HLA-B27 carriage rate compared with AS. Studies with larger samples and including non-European ethnic groups are likely to further advance the understanding of the genetics of AS and spondyloarthritis.

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.

Distribution of HLA class I and II genes in ankylosing spondylitis patients from Morocco

OBJECTIVES

In Morocco, the patients affected by ankylosing spondylitis (AS) presents a high frequency of coxitis. Our study reports, for the first time, the polymorphism of Human Leukocyte Antigen (HLA) class I and class II molecules in the Moroccan patients.

METHODS

Forty-six patients diagnosed with an AS and coxitis were compared to a group of 183 healthy controls matched by age, sex and ethnic origin. The HLA typing was performed using microlymphocytotoxicity for the class I (-A, -B) and PCR-SSP for the class II (-DR, -DQ).

RESULTS

We found a significant increase of the HLA-B27 antigen frequency (P<0.0001, RR=20.9) in AS patients (29.3%) compared to the controls (3.2%) and a significant decrease in the frequency of HLA-B12 and HLA-B18 antigens. Examination of HLA class II distribution shows a significant increase of the HLA-DRB1*11 allele frequency in patients (P<0.0001). Concerning HLA-DQB1* alleles, no significant difference between patients and controls was appreciable.

CONCLUSIONS

The HLA-B27 antigen is involved in the predisposition to the AS with coxitis in the Moroccan population. However, the low frequency observed in our population suggests the existence of other genetic and/or environmental factors. Other HLA genes seem to confer a predisposing effect (DRB*11) or a protective effect (B12 and B18) against the disease.

Association of ORAI1 haplotypes with the risk of HLA-B27 positive ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammation of the sacroiliac joints, spine and peripheral joints. The aetiology of ankylosing spondylitis is still unclear. Previous studies have indicated that genetics factors such as human leukocyte antigen HLA-B27 associates to AS susceptibility. We carried out a case-control study to determine whether the genetic polymorphisms of ORAI1 gene, a major component of store-operated calcium channels that involved the regulation of immune system, is a susceptibility factor to AS in a Taiwanese population. We enrolled 361 AS patients fulfilled the modified New York criteria and 379 controls from community. Five tagging single nucleotides polymorphisms (tSNPs) at ORAI1 were selected from the data of Han Chinese population in HapMap project. Clinical statuses of AS were assessed by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), and Bath Ankylosing Spondylitis Global Index (BAS-G). Our results indicated that subjects carrying the minor allele homozygote (CC) of the promoter SNP rs12313273 or TT homozygote of the SNP rs7135617 had an increased risk of HLA-B27 positive AS. The minor allele C of 3′UTR SNP rs712853 exerted a protective effect to HLA-B27 positive AS. Furthermore, the rs12313273/rs7135617 pairwise allele analysis found that C-G (OR 1.69, 95% CI 1.27, 2.25; p = 0.0003) and T-T (OR 1.75, 95% CI 1.36, 2.27; p<0.0001) haplotypes had a significantly association with the risk of HLA-B27-positive AS in comparison with the T-G carriers. This is the first study that indicate haplotypes of ORAI1 (rs12313273 and rs7135617) are associated with the risk of HLA-B27 positive AS.

Genetics of ankylosing spondylitis

PURPOSE OF REVIEW

Over the past 3 years, several new genes and gene deserts have been identified that are associated with ankylosing spondylitis (AS). The purpose of this review is to discuss the major findings of these studies, and the answers they provide and questions they raise about the pathogenesis of this common condition.

RECENT FINDINGS

Five genes/genetic regions have now definitively been associated with AS [the major histocompatibility complex (MHC), IL23R, ERAP1, 2p15 and 21q22]. Strong evidence to support association with the disease has been demonstrated for the genes IL1R2, ANTXR2, TNFSF15, TNFR1 and a region on chromosome 16q including the gene TRADD. There is an overrepresentation of genes involved in Th17 lymphocyte differentiation/activation among genes associated with AS and the related diseases inflammatory bowel disease and psoriasis, pointing strongly to this pathway as playing a major causative role in the disease. Increasing information about differential association of HLA-B27 subtypes with disease suggests a hierarchy of strength of association of those alleles with AS, providing a useful test as to the validity of different potential mechanisms of association of HLA-B27 with AS. The mechanism underlying the association of the gene deserts, 2p15 and 21q22, suggests the involvement of noncoding RNA in AS etiopathogenesis.

SUMMARY

The increasing list of genes identified as being definitely involved in AS provides a useful platform for hypothesis-driven research in the field, providing a potential alternative route to determining the underlying mechanisms involved in the disease to research focusing on HLA-B27 alone.

Association of ERAP1, but not IL23R, with ankylosing spondylitis in a Han Chinese population

OBJECTIVE

The results of a recent genome-wide association study have shown that ERAP1 and IL23R are associated with ankylosing spondylitis (AS) in Caucasian populations from North America and the UK. Based on these findings, we undertook the current study to investigate whether single-nucleotide polymorphisms (SNPs) covering the genes ERAP1 and IL23R are associated with AS in a Han Chinese population.

METHODS

A case-control study was performed in Han Chinese patients with AS (n = 527) and controls (n = 945) from Shanghai and Nanjing. All patients met the modified New York criteria for AS. The Sequenom iPlex platform was used to genotype cases and controls for 21 tag SNPs covering IL23R and 38 tag SNPs covering ERAP1. Statistical analysis was performed using the Cochran-Armitage test for trend.

RESULTS

Multiple SNPs in ERAP1 were significantly associated with AS (for rs27980, P = 0.0048; for rs7711564, P = 0.0081). However, no association was observed between IL23R and AS (for all SNPs, P > 0.1). The nonsynonymous SNP in IL23R, rs11209026, widely thought to be the primary AS-associated SNP in IL23R in Europeans, was found not to be polymorphic in Chinese.

CONCLUSION

Our results demonstrate that genetic polymorphisms in ERAP1 are associated with AS in Han Chinese, suggesting a common pathogenic mechanism for the disease in Chinese and Caucasian populations, and that IL23R is not associated with AS in Chinese, indicating a difference in the mechanism of disease pathogenesis between Chinese and Caucasian populations. This may result from the fact that rs11209026, the nonsynonymous SNP in IL23R, is not polymorphic in Chinese patients, providing further evidence that rs11209026 is the key polymorphism associated with AS (and likely inflammatory bowel disease and psoriasis) in this gene.

Polymorphisms of cytotoxic T lymphocyte-associated antigen-4 and cytokine genes in Taiwanese patients with ankylosing spondylitis

Cytokines, costimulatory and counter-regulatory molecules play important roles in the regulation of inflammatory response, and are good candidates involved in the development of ankylosing spondylitis (AS). This study investigated the genotypic distribution of proinflammatory cytokines and T-cell negative regulator cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) in healthy subjects and AS patients. Genomic DNA was extracted from 143 AS patients and 166 ethnic-matched healthy subjects. Nine polymorphisms within the genes of interleukin-4 (IL-4) (-34T>C, -81A>G, -285C>T and -589T>C), interleukin-6 (IL-6) (-174G>C), interleukin-10 (IL-10) (-592A>C and -819T>C) and CTLA-4 (-318C>T and +49A>G) were examined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Significantly less AS patients carried the CTLA-4 high-expressing -318 T allele (P = 0.040). The CTLA-4 +49A>G genotypes were associated with circulatory levels of the inflammatory marker C-reactive protein (CRP) (P = 0.022). Our study documented the most complete genetic information of Taiwanese AS patients. The observations that CTLA-4 +49A>G genotypes are associated with circulatory CRP levels and significantly less AS subjects carrying CTLA-4 higher-secretor -318 T allele suggest the level and regulation of inflammation in AS subjects may be pre-determined by and associated with CTLA-4 genotypes.

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.

Mucosal lesions may be a minor complication of SAPHO syndrome: a study of 11 Japanese patients with SAPHO syndrome

Since the term synovitis-acne-pustulosis-hyperostosis-osteitis (SAPHO) syndrome was proposed by Chamot et al. (Rev Rhum Mal Osteoartic 54:187-196, 1987), clinical reviews concerning this syndrome have been mainly reported from Europe. We carried out a retrospective analysis of 11 Japanese patients with SAPHO syndrome, and reviewed the clinical features of our series in comparison with those in a European large case study. In this study the major features of SAPHO syndrome were chronic osteitis of the anterior chest wall and pustulotic arthro-ostitis with middle age onset, and mucosal lesions seemed to be a minor complication of SAPHO syndrome. The non-erosive peripheral large joints arthritis and the particular HLA types (HLA-B51, B52, or A26), which had been reported to be increased in Behcet's disease, were frequently seen in SAPHO syndrome with mucosal lesions. This study also suggests that SAPHO syndrome with mucosal lesions may be part of a broader disease spectrum including Behcet's disease.