Predominant association of HLA-B*2704 with ankylosing spondylitis in Chinese Han patients

Genetic susceptibility to autoimmunity-Current status and challenges

Autoimmune diseases (ADs) often arise from a combination of genetic and environmental triggers that disrupt the immune system's capability to properly tolerate body self-antigens. Familial studies provided the earliest insights into the risk loci of such diseases, while genome-wide association studies (GWAS) significantly broadened the horizons. A drug targeting a prominent pathological pathway can be applied to multiple indications sharing overlapping mechanisms. Advances in genomic technologies used in genetic studies provide critical insights into future research on gene-environment interactions in autoimmunity. This Review summarizes the history and recent advances in the understanding of genetic susceptibility to ADs and related immune disorders, including coronavirus disease 2019 (COVID-19), and their indications for the development of diagnostic or prognostic markers for translational applications.

The Epidemiology and Treatment of Ankylosing Spondylitis in Korea

Ankylosing spondylitis is a chronic inflammatory disorder characterized by inflammation of the axial skeleton and sacroiliac joints and to a lesser extent by peripheral arthritis and the involvement of some extra-articular organs. It is paramount for the provision of effective health care delivery to be familiar with the epidemiologic studies on prevalence, mortality, and disability. Furthermore, there is no systematic arrangement of studies related to the treatment of ankylosing spondylitis in Korea. In this review, we addressed Korean ankylosing spondylitis epidemiological studies related to prevalence, genetic factor especially human leucocyte antigen-B27, extra-articular manifestations, infections, mortality, radiologic progression, child-birth, and quality of life. Furthermore, we reviewed Korean ankylosing spondylitis treatment researches about treatment trend, patients' registration program called The KOrean College of Rheumatology BIOlogics and targeted therapy (KOBIO) registry project, biologics and biosimiliars, complications especially infections, and issues about bony progression. There would be value to further studying the epidemiology and treatment of Korean ankylosing spondylitis.

Predominant frequency of HLA-B*27 in patients with ankylosing spondylitis in southeastern China

OBJECTIVES

This study was to investigate the polymorphism and distribution of alleles of HLA-B*27 in patients with ankylosing spondylitis (AS) in Han population of southeastern China.

METHODS

A total of 89 peripheral blood samples from southeastern Chinese Han patients with AS that diagnosed according to Modified New York criteria were subtyped using the high-resolution PCR-SSP.Exon 2-3 of HLA-B*27 gene was amplified and sequenced to further confirm the HLA-B*27 subtype.

RESULTS

The frequency of HLA-B*27 was 99.87% in AS patients. Three subtypes, HLA-B*2704, HLA-B*2705, and HLA-B*2706 were identified. The frequencies for these three alleles were HLA-B*2704 in 84/88 (95.46%), HLA-B*2705 in 3/88(3.41%), and HLA-B*2706 in 1/88 (1.13%) of the HLA-B*27 positive patients, respectively.

CONCLUSIONS

Our study shows that HLA-B*2704 has an overwhelming frequency in southeastern Chinese Han AS patients. A combined analysis including previous studies of HLA-B*27-subtype distributions in Chinese Han populations showed that HLA-B*2704 may originate from the southern Han and then migrate and spread to the northern areas, and HLA-B*2705 show the opposite result.

Associations between HLA-B27 subtypes and outcomes in Thai children with enthesitis-related arthritis

OBJECTIVE

Expression of human leukocyte antigen B27 (HLA-B27) has been identified as a predictor of severe disease in enthesitis-related arthritis (ERA) patients. However, the associations between HLA-B27 subtypes and outcomes of this disease are still unclear. Here, we examined the distributions of HLA-B27 subtypes among ERA patients and the associations with disease outcomes.

METHODS

This was a historical cohort study of ERA patients. Patients were followed from diagnosis to the most recent visit. Relationships between outcomes and the HLA-B27 subtype were assessed by mixed-effect regression, Kaplan-Meier survival, and Cox proportional hazards regression analyses.

RESULTS

Of the 66 ERA patients, 50 HLA-B27-positive (86% male) and 16 HLA-B27-negative (69% male) patients were included in this study. Patients with HLA-B27-positive were classified into HLA-B*27:04-positive (84%), including combined HLA-B*27:04 and HLA-B*27:07 (2%), and HLA-B*27:04-negative (16%), including HLA-B*27:05 (10%), HLA-B*27:06 (2%), HLA-B*27:07 (2%), and HLA-B*27:15 (2%). HLA-B*27:04-positive (83.3%) and HLA-B*27:04-negative patients (100%) had refractory disease more than HLA-B27-negative patients (37.5%, p = 0.001). HLA-B*27:04-negative patients (57%, 1.73 years) had relapsing disease more and earlier than HLA-B*27:04-positive (35%, 5.54 years) and HLA-B27-negative patients (40%, 6.92 years; p < 0.001). Furthermore, HLA-B*27:04-negative was predictors of refractory disease (HR 4.56, 95%CI 1.40-14.87; p = 0.012) and relapsing disease (HR 3.80, 95% CI 1.18-12.30; p = 0.026). The duration before anti-tumor necrosis factor treatment initiation > 1 year was also a predictor of refractory disease (HR 116.08, 95% CI 14.67-918.26; p < 0.001).

CONCLUSION

HLA-B*27:04 was the most common HLA-B27 subtype in Thai ERA patients. HLA-B*27:04-negative was associated with more unfavorable outcomes than HLA-B*27:04-positive and HLA-B27-negative patients. Key Points • Most ERA patients in Thailand had HLA-B27-positive, and HLA-B*27:04 was the most common HLA-B27 allele in these patients. • The outcomes of ERA were associated with the presence of HLA-B27 and its subtypes. • HLA-B*27:04-negative patients had unfavorable outcomes, including refractory and relapsing disease, compared to HLA-B*27:04-positive and HLA-B27-negative patients.

Genetics of Ankylosing Spondylitis-Focusing on the Ethnic Difference Between East Asia and Europe

Ankylosing spondylitis (AS) is a common, highly heritable inflammatory arthritis affecting the mainly axial joints in both East Asia and Europe. To date, the pathogenesis of AS is still unknown, although we know that genetics play a vital role in it. The HLA-B27 allele is found in over 85% of AS patients. However, strong evidence suggests that other major histocompatibility complex (MHC) and non-MHC genes are also involved in the pathogenesis. In addition, current data showed that there were significant differences in both genomics and metagenomics among the different ethnic populations. The investigation of the key role of the microbiome in AS pathogenesis also highlighted the host–microbiome genetic interactions. Here, we systematically review current AS genetic research data and further compare genetic differences, especially between East Asian and European groups, which may highlight the challenge in future genetic studies.

HLA-B*27:04 associated with enthesitis and younger age of onset, and HLA-B allele profile in patients with ankylosing spondylitis in Thailand: A cross-sectional study

AIM

The aims of this study were to estimate human leukocyte antigen (HLA)-B allele frequency, to identify alleles associated with ankylosing spondylitis (AS), and to explore manifestations in various HLA-B*27 in Thai AS patients.

METHODS

This was a cross-sectional study. Thai patients older than 18 years with diagnosed AS according to modified New York criteria who visited Siriraj Hospital (Bangkok, Thailand) were consecutively enrolled. HLA-B alleles were determined by reverse sequence-specific oligonucleotide assays, and were assigned at a 4-digit resolution. HLA-B alleles of 334 unrelated healthy Thai donors who participated in a previous phase 2b dengue vaccine clinical trial were included as controls. Odds ratio (OR) and Fisher's exact test were used to estimate association between allele and AS. The P value significance threshold was calculated according to Bonferroni.

RESULTS

Among the 88 patients who were recruited, 34 HLA-B alleles were identified, and all patients were heterozygous. The prevalence of HLA-B*27 was 89.8%, and 4 alleles of HLA-B*27 were identified. HLA-B*27:04 (OR: 39.4, P < .0001) and HLA-B*27:05 (OR: 13.8, P = .0011) were associated with AS. In contrast, HLA-B*27:06 was not found to be associated with AS (OR: 0.4, P = .241). AS patients carrying HLA-B*27:04 were more likely to have enthesitis and younger age at onset than those carrying HLA-B*27:05.

CONCLUSIONS

HLA-B*27:04 and HLA-B*27:05 were both found to be strongly associated with Thai AS. HLA-B*27:06 showed a neutral allele for Thai AS. AS patients with HLA-B*27:04 had more enthesitis and younger age at onset than those with HLA-B*27:05.

The Association of Fecal Microbiota in Ankylosing Spondylitis Cases with C-Reactive Protein and Erythrocyte Sedimentation Rate

The purpose of this work was to identify the features of the gut microbiome in cases of ankylosing spondylitis (AS) testing positive for human leukocyte antigen- (HLA-) B27 and healthy controls (HCs) as well as to determine how bacterial populations were correlated with C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Fecal DNA extracted from fecal samples from 10 AS cases and 12 HCs was subjected to 16S rRNA gene sequencing. The two research groups did not differ significantly regarding alpha diversity. By comparison to HCs, AS cases displayed a lower relative level of Bacteroidetes (P < 0.05), but a higher level of Firmicutes and Verrucomicrobia (P < 0.05). Furthermore, the correlation between the specific gut bacteria and ESR or CRP was investigated. At the phylum level, Firmicutes and Verrucomicrobia had a positive association with ESR and CRP, while Bacteroidetes exhibited an inverse correlation with ESR and CRP. Meanwhile, in terms of genus, Bacteroides had a positive association with ESR and CRP, whereas Ruminococcus and Parasutterella had an inverse correlation with ESR and CRP, and Helicobacter also displayed an inverse correlation with CRP. Such findings indicated dissimilarities between AS cases and HCs regarding the gut microbiome, as well as the existence of correlations between bacterial populations and both ESR and CRP.

The roles of ERAP1 and ERAP2 in autoimmunity and cancer immunity: New insights and perspective

Autoimmunity and cancer affect millions worldwide and both, in principal, result from dysregulated immune responses. There are many well-known molecules involved in immunological process playing as a double-edged sword, by which associating autoimmune diseases and cancer. In this regard, Endoplasmic reticulum aminopeptidases (ERAP) 1, which belongs to the M1 family of aminopeptidases, plays a central role as a "molecular ruler", proteolyzing of N-terminal of the antigenic peptides before their loading onto HLA-I molecules for antigen presentation in the Endoplasmic Reticulum (ER). Several genome-wide association studies (GWAS) highlighted the significance of ERAP1 and ERAP2 in autoimmune diseases, including Ankylosing spondylitis, Psoriasis, Bechet's disease, and Birdshot chorioretinopathy, as well as in cancers. The expression of ERAP1/2 is mostly altered in different cancers compared to normal cells, but how this affects anti-cancer immune responses and cancer growth has been little explored. Recent studies on the immunological outcomes and the catalytic functions of ERAP1 and ERAP2 have provided a better understanding of their potential pathogenetic role in autoimmunity and cancer. In this review, we summarize the role of ERAP1 and ERAP2 in the autoimmune diseases and cancer immunity based on the recent advances in GWAS studies.

Immune checkpoint inhibitor-induced inflammatory arthritis as a model of autoimmune arthritis

The development of inflammatory arthritis in patients receiving immune checkpoint inhibitor therapy is increasingly recognized due to the growing use of these drugs for the treatment of cancer. This represents an important opportunity not only to define the mechanisms responsible for the development of this immune-related adverse event and to ultimately predict or prevent its development, but also to provide a unique window into early events in the development of inflammatory arthritis. Knowledge gained through the study of this patient population, for which the inciting event is known, could shed light into the pathogenesis of autoimmune arthritis. This review will highlight the clinical and immunologic features of these entities to define common elements for future study.

HLA associations in inflammatory arthritis: emerging mechanisms and clinical implications

Our understanding of the mechanisms underlying HLA associations with inflammatory arthritis continues to evolve. Disease associations have been refined, and interactions of HLA genotype with other genes and environmental risk factors in determining disease risk have been identified. This Review provides basic information on the genetics and molecular function of HLA molecules, as well as general features of HLA associations with disease. Evidence is discussed regarding the various peptide-dependent and peptide-independent mechanisms by which HLA alleles might contribute to the pathogenesis of three types of inflammatory arthritis: rheumatoid arthritis, spondyloarthritis and systemic juvenile idiopathic arthritis. Also discussed are HLA allelic associations that shed light on the genetic heterogeneity of inflammatory arthritides and on the relationships between adult and paediatric forms of arthritis. Clinical implications range from improved diagnosis and outcome prediction to the possibility of using HLA associations in developing personalized strategies for the treatment and prevention of these diseases.

MRI compared with low-dose CT scanning in the diagnosis of axial spondyloarthritis

OBJECTIVES

To compare the performance of conventional radiography, ldCT, and MRI in the diagnosis of sacroiliitis in suspected axial spondyloarthritis (axSpA).

METHODS

Patients presenting with > 3 months chronic back pain were assessed by axSpA-experienced rheumatologists and diagnosed as axSpA or not; axSpA patients were then considered nr-axSpA or AS using plain radiography. Non-axSpA patients were recruited as controls, and divided into non-inflammatory and inflammatory groups on the basis of inflammatory back pain and/or CRP/ESR elevation. Clinical variables, pelvic radiography, sacroiliac joint (SIJ) ldCT, and SIJ MRI were obtained.

RESULTS

A total of 121 patients were included and had SIJ radiography and ldCT, of whom 71 additionally had an SIJ MRI. These included 23 non-inflammatory controls, 21 inflammatory controls, 32 nr-axSpA cases, and 45 AS cases. Fourteen of 32 (44%) nr-axSpA patients had positive ldCT scans, 21/24 (88%) had MRI-BMO, and 11/24 (46%) had MRI-structural lesions. ldCT had high specificity with only 1/23 (4%) non-inflammatory controls being positive. MRI-BMO had the highest sensitivity for nr-axSpA, but compared with ldCT lower specificity, with 5/15 (33%) of non-inflammatory controls being positive, and similar sensitivity for AS (20/22 (91%) vs 44/44 for ldCT).

CONCLUSIONS

ldCT identifies evidence of radiographic change in a significant proportion of nr-axSpA cases and is highly specific for axSpA. MRI-BMO lesions are more sensitive than either conventional radiography or MRI-structural assessment for axSpA. The relative position of these imaging modalities in screening for axSpA needs to be reconsidered, also taking into account the costs involved.Key Points• ldCT is more sensitive for erosions or sclerosis in axSpA than plain radiography, with 44% of patients with nr-axSpA having evidence of AS-related sacroiliac joint changes on ldCT.• MRI-structural lesions are no more sensitive but are less specific for AS than ldCT.• MRI-BMO is the most sensitive test for nr-axSpA of the modalities tested but is less specific for axSpA than for ldCT.

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.

HLA-B27 testing: A journey from flow cytometry to molecular subtyping

BACKGROUND

Determination of HLA-B27 status plays an important role as adjuvant in suspected cases for diagnosis of Ankylosing Spondilytis (AS). Objectives of this study were to evaluate (i) flow cytometry method in comparison with DNA microarray for HLA-B27 typing and (ii) EUROArray HLA-B27 Direct assay for HLA-B27 allele detection along with discrimination of AS/non-AS subtypes in Indian population.

METHODS

A total of 7543 patients with a presumptive clinical diagnosis of AS were referred for screening of HLA-B27. All samples were initially tested by flow cytometry, and based on its findings, 1560 samples were analyzed for the presence of HLA-B27 allele by microarray technology. A subset of samples (n = 200) were further tested by DNA sequencing for identification of HLA-B27 subtypes.

RESULTS

Screening of HLA-B27 by flow cytometry reported 1551 positive (20.56%) and 5556 negative (73.65%) cases. Remaining 436 (5.78%) samples were identified within equivocal zone. Of cases (n = 1560) analyzed by microarray method, 1333 (85.44%) and 227 (14.55%) were detected microarray positive and negative, respectively. DNA sequencing identified HLA-B*27:07 as the predominant subtype among cases showing ex2 positivity by microarray method. Of 200 cases, 20 cases (14 of HLA-B*07 and 6 of HLA-B*37) of HLA-B27 cross-reactive subtypes were also identified.

CONCLUSION

We recommend DNA typing as a complementary tool along with flow cytometry to accomplish successful HLA-B27 phenotype determination. This is the first study among Indian population to evaluate efficacy of EUROArray to detect B27 allele and its potential to indicate the presence of nondisease-associated alleles in Indian population.

Polymorphisms of human leukocyte antigen B*27 on clinical phenotype of spondyloarthritis in Chinese

BACKGROUND

In recent years, an ever-increasing number of alleles of human leukocyte antigen B*27 (HLA-B*27) have been identified. This study aimed to establish an updated method for HLA-B*27 subtyping, and to investigate the impact of HLA-B*27 polymorphisms on the clinical phenotype of spondyloarthritis (SpA).

METHODS

Overall, 184 SpA patients were recruited for analyzing diversity of HLA-B*27 via an updated high-resolution polymerase chain reaction amplification with sequence specific primers (PCR-SSP).

RESULTS

The prevalence of HLA-B*27 was 94.0%, and four subtypes were identified including HLA-B*2704 (77.5%), B*2705 (20.2%), B*2707 (1.7%), and B*2724 (0.6%). There was an obvious male predominance (P=.05) and markedly elevated C-reaction protein (CRP) in B*27 positive SpA (P<.01). In multivariate linear regression analysis, the elevated CRP was positively associated with HLA-B*27 positivity (regression coefficient B=46.1, P=.0003), grade of sacroiliitis (B=47.5, P=.0032), and male gender (B=20.4, P=.0041). Notably, a male predilection was also found in B*2705 positive SpA while B*2707 was associated with older age, higher positive family history, and higher prevalence of extra-articular features (all P<.05).

CONCLUSIONS

In this study, an updated PCR-SSP technique to identify increasing alleles of HLA-B*27 was developed and their different effects on clinical manifestations of SpA were demonstrated. Genotyping of HLA-B*27 would shed light on our understanding of the pathogenesis of SpA.

Mice expressing human ERAP1 variants associated with ankylosing spondylitis have altered T-cell repertoires and NK cell functions, as well as increased in utero and perinatal mortality

Specific variants of endoplasmic reticulum-associated aminopeptidase 1 (ERAP1) identified by genome-wide association study modify the risk for developing ankylosing spondylitis. We previously confirmed that disease-associated ERAP1 variants have altered enzymatic abilities that can impact upon the production of pro-inflammatory cytokines from cells expressing the same ERAP1 variants. To determine if these ERAP1 variants also impacted immune responses in vivo, we generated two strains of transgenic mice expressing human ERAP1 genes containing non-synonymous single-nucleotide polymorphisms associated with an increased (ERAP1-High) or decreased (ERAP1-Low) risk for developing autoimmune disease. After vaccination with foreign antigens, ERAP1-High mice generated unique populations of antigen-specific T-cell clones. The expression of ERAP1-High also reduced MHC-I expression on the surface of multiple cell types, demonstrating a global impact on the MHC-I peptidome. ERAP1 variants also affected the innate immune system, because NK cells from murine ERAP1 (mERAP1) knockout mice and ERAP1-High/mERAP1-/- mice had decreased surface expression of the activating receptor NKG2D on their NK and T cells, and NK cells derived from mERAP1-/- mice or ERAP1-Low mice demonstrated more active NK cell killing than NK cells derived from wild-type or ERAP1-High mice. Finally, these studies were conducted in female mice, as all male ERAP1-High mice died in utero or shortly after birth, making ERAP1-High one of the only dominant lethal autosomal genes known in mammals. Together, these results present the first direct evidence that human disease-associated ERAP1 variants can greatly alter survival, as well as antigen presentation, T-cell repertoire and NK cell responses in vivo.

HLA-B27

Possession of the human leukocyte antigen (HLA) class I molecule B27 is strongly associated with ankylosing spondylitis (AS), but the pathogenic role of HLA-B27 is unknown. Two broad theories most likely explain the role of HLA-B27 in AS pathogenesis. The first is based on the natural immunological function of HLA-B27 of presenting antigenic peptides to cytotoxic T cells. Thus, HLA-B27-restricted immune responses to self-antigens, or arthritogenic peptides, might drive immunopathology. B27 can also "behave badly," misfolding during assembly and leading to endoplasmic reticulum stress and autophagy responses. β2m-free B27 heavy chain structures including homodimers (B272) can also be expressed at the cell surface following endosomal recycling of cell surface heterotrimers. Cell surface free heavy chains and B272 bind to innate immune receptors on T, NK, and myeloid cells with proinflammatory effects. This review describes the natural function of HLA-B27, its disease associations, and the current theories as to its pathogenic role.

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.

Association of HLA-B27 genetic polymorphisms with ankylosing spondylitis susceptibility worldwide: a meta-analysis

OBJECTIVES

Many publications have evaluated the correlation between HLA-B27 polymorphisms and ankylosing spondylitis (AS), with conflicting results. We carried out this new meta-analysis in order to collect all the relevant studies to further clarify the association of HLA-B27 polymorphisms with AS susceptibility.

METHODS

Relevant published data were retrieved through Medline, PubMed, Web of Science, CNKI, and the Chinese BioMedical Literature Database on disc. The statistical analysis was conducted using Review Manager Version 5.0 and STATA 11.0. From these data, the odds ratio (OR) with a 95 % confidence interval (95 % CI) was calculated.

RESULTS

(1) A total of 38 studies, including 3,410 AS cases and 1,735 healthy controls, were collected in this meta-analysis. (2) Our results showed that B2704 was a risk factor but B2703, B2706, B2707, B2727, B2729, and B2747 may be protective factors for AS worldwide. (3) These subtypes, such as B2701, B2702, B2705, B2708-15, B2717-20, B2723-24, B2733, B2735, B2740, B2746, B2749, and B2767, showed no association with susceptibility to AS. There was a huge difference with previous reports for B2702 and B2705. (4) The B2702, B2704 and B2705 subtypes have existed high heterogeneity but no publication bias.

CONCLUSIONS

This meta-analysis in our study suggested that B2704 might be a potential risk factor, however, B2703, B2706, and B2707 might be potential protective factors of AS, especially in Asia.

Ankylosing spondylitis in iran; late diagnosis and its causes

Background:

Ankylosing spondylitis (AS) is a chronic destructive and inflammatory disease of the axial skeleton manifested by back pain and progressive stiffness of the spine.

Objectives:

The aim of the present cross-sectional study was to evaluate and identify factors leading to delayed diagnosis of AS in Iranian patients.

Patients and Methods:

Sixty patients, (53 males, 7 females) with a diagnosis of AS according to the modified New York criteria were recruited. Diagnosis delay was defined as the interval between a patient’s first spondyloarthritic symptoms [inflammatory back pain (IBP), inflammatory arthritis, enthesopathy and uveitis] and a correct diagnosis of AS.

Results:

The average age of patients at diagnosis of AS was 36.4 ± 4.5 years and the average of delay in diagnosis was 6.2 ± 3.5 years. The most common diagnosis at the first visit was disc herniation (68.3%). Delay in diagnosis of Human Leukocyte Antigen (HLA-B27) positive and negative patients were 4.6 ± 2.2 years and 10.1 ± 3.2 years, respectively (P = 0.0001). Diagnosis delay in patients with morning stiffness and IBP were significantly shorter than that of patients without these symptoms (P = 0.0001 and P = 0.001, respectively). Patients with uveitis had the shortest diagnosis delay (P = 0.02). The Bath Ankylosing spondylitis disease activity index (BASDAI) was not significantly different in early (< 3years) and late (> 3years) diagnosis (3.3 ± 0.9 and 3.6 ± 0.7, respectively) (P = 0.18), but the Both ankylosing spondylitis functional index (BASFI) was significantly different between them (3.3 ± 1.0 and 4.1 ± 0.7 respectively) (P = 0.001).

Conclusions:

In this study, delay in diagnosis was similar to other studies. Educating physicians to careful history taking especially in the case of IBP, non-musculoskeletal symptoms such as uveitis and precise physical examination are important in early diagnosis.

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.

Endoplasmic reticulum aminopeptidase-1 alleles associated with increased risk of ankylosing spondylitis reduce HLA-B27 mediated presentation of multiple antigens

Ankylosing spondylitis (AS) is a chronic systemic arthritic disease that leads to significant disability and loss of quality of life in the ∼0.5% of the worldwide human population it affects. There is currently no cure for AS and mechanisms underlying its pathogenesis remain unclear. AS is highly genetic, with over 70% of the genetic risk being associated with the presence of HLA-B27 and endoplasmic reticulum aminopeptidase-1 (ERAP1) alleles. Furthermore, gene-gene interactions between HLA-B27 and ERAP1 AS risk alleles have recently been confirmed. Here, we demonstrate that various ERAP1 alleles can differentially mediate surface expression of antigens presented by HLA-B27 on human cells. Specifically, for all peptides tested, we found that an ERAP1 variant containing high AS risk SNPs reduced the amount of the peptide presented by HLA-B27, relative to low AS risk ERAP1 variants. These results were further validated using peptide catalysis assays in vitro, suggesting that high AS risk alleles have an enhanced catalytic activity that more rapidly destroys many HLA-B27-destined peptides, a result that correlated with decreased HLA-B27 presentation of the same peptides. These findings suggest that one mechanism underlying AS pathogenesis may involve an altered ability for AS patients harboring both HLA-B27 and high AS risk ERAP1 alleles to correctly display a variety of peptides to the adaptive arm of the immune system, potentially exposing such individuals to higher AS risk due to abnormal display of pathogen or self-derived peptides by the adaptive immune system.

Brief report: high-throughput sequencing of IL23R reveals a low-frequency, nonsynonymous single-nucleotide polymorphism that is associated with ankylosing spondylitis in a Han Chinese population

OBJECTIVE

Ankylosing spondylitis (AS) is a highly heritable common inflammatory arthritis that targets the spine and sacroiliac joints of the pelvis, causing pain and stiffness and leading eventually to joint fusion. Although previous studies have shown a strong association of IL23R with AS in white Europeans, similar studies in East Asian populations have shown no association with common variants of IL23R, suggesting either that IL23R variants have no role or that rare genetic variants contribute. The present study was undertaken to screen IL23R to identify rare variants associated with AS in Han Chinese.

METHODS

A 170-kb region containing IL23R and its flanking regions was sequenced in 50 patients with AS and 50 ethnically matched healthy control subjects from a Han Chinese population. In addition, the 30-kb region of peak association in white Europeans was sequenced in 650 patients with AS and 1,300 healthy controls. Validation genotyping was undertaken in 846 patients with AS and 1,308 healthy controls.

RESULTS

We identified 1,047 variants, of which 729 were not found in the dbSNP genomic build 130. Several potentially functional rare variants in IL23R were identified, including one nonsynonomous single-nucleotide polymorphism (nsSNP), Gly(149) Arg (position 67421184 GA on chromosome 1). Validation genotyping showed that the Gly(149) Arg variant was associated with AS (odds ratio 0.61, P = 0.0054).

CONCLUSION

This is the first study to implicate rare IL23R variants in the pathogenesis of AS. The results identified a low-frequency nsSNP with predicted loss-of-function effects that was protectively associated with AS in Han Chinese, suggesting that decreased function of the interleukin-23 (IL-23) receptor protects against AS. These findings further support the notion that IL-23 signaling has an important role in the pathogenesis of AS.

Profiling of hla-B alleles for association studies with ankylosing spondylitis in the chinese population

Human leucocyte antigen (HLA) B*27 is a susceptibility allele to ankylosing spondylitis (AS). However, major AS-associated subtypes of HLA-B*27 and other HLA-B alleles vary in different ethnic populations. Herein, we examined HLA-B alleles in a total of 360 AS patients and 350 controls of Chinese Han ancestry. The HLA-B genotyping was performed with sequence-based typing (SBT) method. Six HLA-B*27 subtypes B*27:04, B*27:05, B*27:07, B*27:08, B*27:10 and B*27:15 were observed in the cohorts. HLA-B*27:04:01 and -B*27:05:02 appeared significantly increased in AS patients, which indicated as two major susceptibility alleles to AS. Homozygous B*27 was observed only in AS patients. There are 30 HLA-B alleles identified in the studies. HLA-B*15, especially B*15:01:01:01, appeared as the major allele type in the Chinese controls. Some common HLA-B alleles such as HLA-B*15, B*13, B*46 and B*51 were significantly reduced in Chinese AS patients. In conclusion, the studies profiled the HLA-B alleles, and identified major susceptibility subtypes of B27 to AS in Han Chinese population

A polymorphism in ERAP1 is associated with susceptibility to ankylosing spondylitis in a Turkish population

We assessed the role played by the ERAP1 gene in Turkish patients with ankylosing spondylitis (AS) in terms of disease susceptibility, clinical manifestations, and disease severity. We included 150 consecutive AS patients who met the modified New York classification criteria and 150 healthy controls. We documented the presence of 10 ERAP1 single-nucleotide polymorphisms (SNPs) and HLA-B27 in these patients. ERAP1 SNPs were genotyped using competitive allele-specific polymerase chain reaction. Differences between genotype and allele frequencies were compared using the Pearson's Chi-square test. The associations between ERAP1 SNPs, on the one hand, and with disease severity and clinical findings, on the other, were determined. One SNP, rs26653, was significantly associated with AS susceptibility (OR 1.609, 95% CI 1.163-2.226; p = 0.004). The population-attributable risk of possession of the rs26653 SNP allele was 23.4%. No relationship was noted between HLA-B27 positivity and the distribution of rs26653 genotype frequency. No associations were seen between disease severity measures and clinical manifestations of AS. In summary, an ERAP1 polymorphism was associated with AS in a Turkish population. The contributions of HLA-B27 and the rs26653 SNP to AS pathogenesis appear to be independent.

Identification of a novel HLA-B*27 allele, B*27:79 and the B*27 subtype polymorphism in the Hunan ethnic Han population of China

This article describes a novel HLA-B*27 allele, HLA-B*27:79, which was identified in a Hunan Han ethnic individual of China by a PCR sequence-based typing method. The new sequence has one nucleotide mutation at position 437(A→T) compared with the allele B*27:04:01. This nucleotide change causes an amino acid substitution from Aspartate (Asp) to Valine (Val) at codon 122. This is the first report of mutation at this position in the HLA-B locus. Then, we investigated the HLA-B*27 subtype polymorphism of the Hunan Han population, and the results showed that B*27:04, B*27:05 and B*27:06 are the predominant subtypes with the allele frequencies 0.97%, 0.26% and 0.10% respectively.

Immunogenetic study in Chinese population with ankylosing spondylitis: are there specific genes recently disclosed?

Purpose. Ankylosing spondylitis (AS) is a systemic, autoimmune disease resulting in the destruction of the affected joints. Over the past 5 years, several new genes or genetic regions associated with AS have been identified in the Chinese population. This paper aims to discuss the major findings and related potential mechanisms of these studies in our population. Recent Findings. In recent years, due to the rapid advances in computational genetics and technology, there has been an increasing list of well-validated genes or genetic regions associated with AS susceptibility. So far, several genes or genetic regions have now been reported in the Han ethnic Chinese population, containing the major histocompatibility complex (MHC), ERAP1, IL-23R, 12q12, 2p15, 5q14.3, and so on. Different hypotheses for disease mechanisms have been investigated on the basis of the functional studies of these genes or genetic regions. Summary. This paper tries to summarize the association of several candidate genes with risk for AS in the Han ethnic Chinese population and aims to identify the novel inflammatory pathways and provide potential strategies for better therapies.

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.

A genome-wide association study in Han Chinese identifies new susceptibility loci for ankylosing spondylitis

To identify susceptibility loci for ankylosing spondylitis, we performed a two-stage genome-wide association study in Han Chinese. In the discovery stage, we analyzed 1,356,350 autosomal SNPs in 1,837 individuals with ankylosing spondylitis and 4,231 controls; in the validation stage, we analyzed 30 suggestive SNPs in an additional 2,100 affected individuals and 3,496 controls. We identified two new susceptibility loci between EDIL3 and HAPLN1 at 5q14.3 (rs4552569; P = 8.77 × 10(-10)) and within ANO6 at 12q12 (rs17095830; P = 1.63 × 10(-8)). We also confirmed previously reported associations in Europeans within the major histocompatibility complex (MHC) region (top SNP, rs13202464; P < 5 × 10(-324)) and at 2p15 (rs10865331; P = 1.98 × 10(-8)). We show that rs13202464 within the MHC region mainly represents the risk effect of HLA-B*27 variants (including HLA-B*2704, HLA-B*2705 and HLA-B*2715) in Chinese. The two newly discovered loci implicate genes related to bone formation and cartilage development, suggesting their potential involvement in the etiology of ankylosing spondylitis.

Rapid and reliable genotyping of HLA-B*27 in the Chinese Han population using a duplex real-time TaqMan PCR assay

OBJECTIVES

To develop a duplex real-time TaqMan PCR assay for genotyping HLA-B*27 in the Chinese Han population.

DESIGN AND METHODS

A standard curve was constituted to deduce amplification efficiency, dynamic range and detection limit of the duplex real-time TaqMan PCR assay, whereas PCR-SBT (PCR with sequence-based typing) was used to evaluate the accuracy of the assay.

RESULTS

A linear standard curve for determining HLA-B*27 was obtained within the range of 10(1)-10(9) copies per reaction with the correlation coefficient of 0.99 and amplification efficiency of 98.30%. The detection limit was 3.09 copies per reaction. Complete concordance was found between the results obtained by the duplex real-time TaqMan PCR assay and PCR-SBT. Fifty-nine of the 178 genomic samples were HLA-B*27 positive and the other 119 were HLA-B*27 negative.

CONCLUSIONS

The duplex real-time TaqMan PCR approach appears to be a reliable, sensitive, rapid and high-throughput method to genotype HLA-B*27 in the Chinese Han population.

Does HLA-B*2706 protect against ankylosing spondylitis? A meta-analysis

The human leukocyte antigen (HLA)-B*2706 is a relatively rare subtype of HLA-B27. In contrast to most HLA-B27 subtypes, some studies have reported HLA-B*2706 to be protective against ankylosing spondylitis (AS). A systematic review and a meta-analysis of available studies was performed to investigate the association of HLA-B*2706 with AS. After literature review a random effect meta-analysis was performed. No studies were found comparing the frequency of HLA-B*2706 in AS patients and controls. Meta-analysis of seven studies using HLA-B27-positive AS patients and controls showed a protective effect of HLA-B*2706 on development of AS in HLA-B27 individuals (odds ratio = 0.128, 95% CI = 0.043-0.378, P < 0.001). The results of the meta-analysis of HLA-B*2706 in HLA-B27-positive patients and controls is preliminary evidence of a protective effect of HLA-B*2706 against AS in the population. There is a clear need for additional studies on HLA-B*2706 in AS. Due to the fact that HLA-B*2706 is more or less restricted to Southeast Asia, researchers in this part of the world may have an essential role in performing these studies.

Current controversies in spondyloarthritis: SPARTAN

The Spondyloarthritis Research and Therapy Network (SPARTAN), founded in 2003 to promote research, education, and treatment of ankylosing spondylitis (AS) and related forms of spondyloarthritis (SpA), held its 7th Annual Research and Education Meeting in July 2009 in Houston, Texas. Current controversies in SpA discussed during the meeting included an update on the epidemiology of AS, axial SpA, and inflammatory back pain; the adequacy of the mSASS to assess radiographic involvement; the helpfulness of magnetic resonance imaging in assessing disease progression; the reliability of metrology in assessing damage; and whether biologic agents alter the course of AS. Presentations also were made on psoriasis in the SCID mouse model; the challenges and opportunities of SpA in China; a discussion of the special needs in managing SpA in Ibero-America, and the SPARK Survey in Europe and North America.

Association of STAT3 and TNFRSF1A with ankylosing spondylitis in Han Chinese

OBJECTIVES

Recent association studies by the Australo-Anglo-American Spondyloarthritis Consortium (TASC) in Caucasian European populations from Australia, North America and the UK have identified a number of genes as being associated with ankylosing spondylitis (AS). A candidate gene study in a Han Chinese population was performed based on these findings to identify associated genes in this population.

METHODS

A case-control study was performed in a Han Chinese population of patients with AS (n = 775) and controls (n = 1587) from Shanghai and Nanjing. All patients met the modified New York criteria for AS. The cases and controls were genotyped for 115 single nucleotide polymorphisms (SNPs) tagging IL23R, ERAP1, STAT3, JAK2, TNFRSF1A and TRADD, as well as other confirmation SNPs from the TASC study, using the Sequenom iPlex and the ABI OpenArray platforms. Statistical analysis of genotyped SNPs was performed using the Cochran-Armitage test for trend and meta-analysis was performed using METAL. SNPs in AS-associated genes in this study were then imputed using MaCH, and association with AS tested by logistic regression.

RESULTS

SNPs in TNFRSF1A (rs4149577, p = 8.2 × 10⁻⁴), STAT3 (rs2293152, p = 0.0015; rs1053005, p = 0.017) and ERAP1 (rs27038, p = 0.0091; rs27037, p = 0.0092) were significantly associated with AS in Han Chinese. Association was also observed between AS and the intergenic region 2p15 (rs10865331, p = 0.023). The lack of association between AS and IL23R in Han Chinese was confirmed (all SNPs p > 0.1).

CONCLUSIONS

The study results demonstrate for the first time that genetic polymorphisms in STAT3, TNFRSF1A and 2p15 are associated with AS in Han Chinese, suggesting common pathogenic mechanisms for the disease in Chinese and Caucasian European populations. Furthermore, previous findings demonstrating that ERAP1, but not IL23R, is associated with AS in Chinese patients were confirmed.

Remarkable polymorphism of HLA-B27: an ongoing saga

Histocompatibility antigen HLA-B27 is a normal gene that is distributed worldwide with variable prevalence and shows a remarkable association with ankylosing spondylitis and related spondyloarthropathies. The precise biological explanation for this remarkable association remains elusive. HLA-B27 represents a family of closely related proteins encoded by an ever-increasing number of alleles; there are 75 alleles of HLA-B27 known thus far, based on nucleotide sequence differences, but at the translated protein level, there are 62 known subtypes of HLA-B27. Not all subtypes are disease associated. Moreover, existence of a possible hierarchical ranking among some of the subtypes for their disease association has been observed.

The Role of HLA-B27 in Spondyloarthritis

This article summarizes the proceedings of a one-day international workshop held in July 2009 on the role of HLA-B27 in the pathogenesis of ankylosing spondylitis (AS) and related disorders. HLA-B27 is found in about 90% of patients with AS, with an odds ratio of about 100, but the mechanism underlying this association is not known. There are currently 3 major mechanistic hypotheses for this association: (1) T cell recognition of one or more B27 presented peptides; (2) B27 heavy-chain misfolding that induces an unfolded protein response; and (3) innate immune recognition of cell-surface expressed B27 heavy-chain dimers. None of these hypotheses accounts for the tissue specificity of the inflammation characteristic of AS. These hypotheses were discussed in the context of known epidemiologic, biochemical, structural, and immunologic differences among HLA-B27 subtypes; data from the HLA-B27 transgenic rat model of spondyloarthritis; the growing list of other genes that have been found to be associated with AS; and other data on the pathogenesis of spondyloarthritis. Proposed directions for future research include expanded efforts to define similarities and differences among the B27 subtypes; further development of animal models; identifying the interactions of B27 with the products of other genes associated with AS; and continued investigation into the pathogenesis of spondyloarthritis.

HLA-B27 and ankylosing spondylitis: tales from China

The two most frequent HLA-B27 subtypes worldwide are B*2704 and B*2705. In the Han population of China B*2704 and, to a lower extent, B*2705 are found with significant frequency, and both are associated to ankylosing spondylitis (AS). Two articles in this issue report that the association to AS in this ethnic group is stronger for B*2704 than for B*2705. Thus, at least among the Han, B*2704 would be the strongest known susceptibility factor for AS.