HLA-B27 polymorphism and worldwide susceptibility to ankylosing spondylitis

HLA-B27 and its role of the pathogenesis of psoriatic arthritis

The literature review presents the characteristics of the human leukocyte antigen (HLA)-B27 as a factor contributing to the development of psoriatic arthritis. HLA-B27 is a class I surface antigen encoded by the major histocompatibility complex (MHC) B locus located on chromosome 6. The main function is to present antigenic peptides to the CD8+ T-cells. HLA-B27 is the most important genetic biomarker for psoriatic arthritis, as it provides phenotypic differentiation in the patient population. The prevalence of HLA-B27 in various population groups are presented. The structural features of the HLA-B27 molecule are described. The characteristics of methods for detecting HLA-B27 status and determining its subtypes are given. The main mechanisms of the HLA-B27 polymorphism influence on the development of psoriatic arthritis are considered, and hypotheses are analyzed that explain the pathogenic effect of HLA-B27: the arthritogenic peptide hypothesis, the misfolding hypothesis, the HLA-B27 heavy chain homodimer formation hypothesis. The features of the clinical manifestations and course of HLA-B27-positive psoriatic arthritis are presented, allowing the use of HLA-B27 to predict the development of psoriatic joint damage.

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.

A proposed HLA-B*27 screening method for ankylosing spondylitis detection based on tag-single nucleotide polymorphisms: a preliminary study

BACKGROUND

Ankylosing spondylitis (AS) is a type of inflammatory arthritis that affects primarily the spine. There is a strong association of the HLA-B*27 allele with AS pathogenesis, but recent studies have demonstrated the participation of ERAP1 gene in the genetic susceptibility. The aim of this study was to determine whether HLA-B tag-single nucleotide polymorphisms (SNPs) and ERAP1-related genetic variations associated with AS have equal or similarly performance in patients´ screening compared to HLA-B*27 standard genotyping in Mexican population.

METHODS AND RESULTS

Genomic DNA from patients with AS and population-based controls from Mexico City was analyzed for five single nucleotide polymorphisms (SNPs): rs4349859, rs13202464, rs116488202, tagging HLA-B*27; and rs30187 and rs27044 in ERAP1 gene. TaqMan genotype assay method was used for SNPs genotyping. We found a significant association between AS and the heterozygote genotypes and minor alleles of the HLA-B*27 tag-SNPs, as well as for their haplotypes. With respect to ERAP1 polymorphisms, no significant associations were observed (p > 0.05). The sensitivity and specificity analysis showed values of 0.96 and 1.00 for the rs4349859 SNP, and 0.96 and 0.94 for the rs116488202 SNP, respectively, in detecting HLA-B*27 compared to the B27 test as the gold standard.

CONCLUSIONS

HLA-B*27 tag-SNPs are associated with AS susceptibility; furthermore, the rs4349859 SNP by its own have an outstanding performance in detecting HLA-B*27 and therefore can be proposed as screening marker in the identification of HLA-B*27 in our population.

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.

Prevalence of HLA-B*27 subtypes in the Tamil population of India with Ankylosing spondylitis and its correlation with clinical features

INTRODUCTION

HLA-B*27 is strongly associated with Ankylosing spondylitis (AS). Its subtypes show considerable geographic and ethnic difference. The main aim of this study was to assess the frequency of subtypes of HLA-B*27 in the Indian Tamil AS patients.

METHODS AND MATERIALS

Adult AS patients positive for HLA-B*27 were considered for the study. The high-resolution typing to define HLA-B*27 subtypes were done using Invitrogen B kits from One Lambda (SeCore® Sequencing Kits, Thermo Fisher, United States).

RESULTS AND CONCLUSION

Prevalence of subtypes identified were HLA-B*27:04 (52.2%), HLA-B*27:05 (41.6%), HLA-B*27:07 (3.5%) and HLA-B*27:02 (2.7%). All subtypes showed disease predisposition for males. The most common extra articular manifestation seen was enthesitis in HLA-B*27:04 and HLA-B*27:05. Uveitis was mainly associated with HLA-B*27:05 and dactylitis with HLA-B*27:04. A significant peripheral joints involvement for female and axial joint involvement for males was seen in HLA-B*27:04. Our study establishes the prevalence of HLA-B*27 subtypes and the associated clinical phenotypes among the Indian Tamil population. Considering the variability of presentation, organ involvement, and disease course in different subtypes and across ethnicities it is critical to define these associations in the ethnic populations we treat for their appropriate care considering the significant negative health and socioeconomic effects of AS.

Potential implications of six American Indian patients with myopathy, statin exposure and anti-HMGCR antibodies

OBJECTIVES

Statin-associated autoimmune myopathy is a rare condition associated with the formation of autoantibodies to 3-hydroxy-3-methylglutaryl-coenzyme A reductase. Underlying environmental and genetic risk factors remain poorly understood. American Indians have high rates of cardiovascular disease and associated co-morbidities that require lipid-lowering therapies. We observed this autoimmune myopathy in a series of American Indian statin users in rural Arizona.

METHODS

We reviewed the charts of six American Indian patients with statin-associated autoimmune myopathy. We provide an illustrative case in addition to summaries of clinical presentations and treatment courses.

RESULTS

This is the first report of statin-associated autoimmune myopathy in American Indians. These cases were all identified at the same geographically isolated hospital that exclusively serves an American Indian population with only 1800 statin users. There is relatively low migration. Each case was consistent with the previously described classical presentations for the disease. All six of our cases had diabetes and developed myopathy on high-dose atorvastatin, often with a recent change in statin type or dose.

CONCLUSION

Providers serving American Indians need to be aware of the possibility of statin-associated autoimmune myopathy and familiar with its presentation. Larger, inclusive, population-based investigations are needed to elucidate risk factors for this condition, in particular the potential interactions between predisposing HLA alleles, diabetes and specific statin exposures. This is necessary to identify effective and safe lipid-lowering medications.

Spondyloarthritis in African Populations Compared to Europeans Living in the United Kingdom

Background:

With the aim to study Spondyloarthritis in patients originating from Africa and compare the disease with the way it is manifested in Europeans, data was analysed from 62 African patients and compared with 56 Europeans living in the same geographical area (north East London, United Kingdom) and treated under the same health system (NHS). Data analysed were demographic, social and clinical characteristics.

Results:

Comparisons showed differences in prevalence of psoriasis (more in Caucasians), uveitis (more in Africans), smoking (more in Europeans), and significantly fewer patients of African origin declared family history of SpA. African patients have less disease activity (but not significantly better measured by BASDAI), and statistically significant better functional ability (BASFI) compared to Europeans. No difference has been noted in gender distribution, age of disease onset, disease duration, delay in diagnosis, disease associations with IBD, night pain, or overall wellbeing.

Conclusions:

SpA is different in Africans in that it shows to be milder in terms of disease activity and functional ability with more uveitis less psoriasis and less family history of SpAs.

The Genetics of Spondyloarthritis

The term spondyloarthritis (SpA) encompasses a group of chronic inflammatory diseases with common features in terms of clinical presentation and genetic predisposition. SpA is characterized by inflammation of the spine and peripheral joints, and is also be associated with extra-articular inflammatory manifestations such as psoriasis, uveitis, or inflammatory bowel disease (IBD). The etiology of SpA is not completely understood, but it is known to have a strong genetic component dominated by the human leukocyte antigen (HLA)-B27. In the last few years, our understanding of genetic susceptibility to SpA, particularly ankylosing spondylitis (AS), has greatly improved thanks to the findings derived from powered genome-wide association studies (GWAS) based on single nucleotide polymorphism (SNP) arrays. These studies have identified many candidate genes, therefore providing new potential directions in the exploration of disease mechanisms, especially with regard to the key role of the immune system in the pathogenesis of SpA. SpA is a complex disease where genetic variability, environmental factors, and random events interact to trigger pathological pathways. The aim of this review is to summarize current findings on the genetics of SpA, some of which might help to study new treatment approaches.

Allelic association with ankylosing spondylitis fails to correlate with human leukocyte antigen B27 homodimer formation

Expression of human leukocyte antigen (HLA)-B27 is strongly associated with predisposition toward ankylosing spondylitis (AS) and other spondyloarthropathies. However, the exact involvement of HLA-B27 in disease initiation and progression remains unclear. The homodimer theory, which proposes that HLA-B27 heavy chains aberrantly form homodimers, is a central hypothesis that attempts to explain the role of HLA-B27 in disease pathogenesis. Here, we examined the ability of the eight most prevalent HLA-B27 allotypes (HLA-B*27:02 to HLA-B*27:09) to form homodimers. We observed that HLA-B*27:03, a disease-associated HLA-B27 subtype, showed a significantly reduced ability to form homodimers compared with all other allotypes, including the non-disease-associated/protective allotypes HLA-B*27:06 and HLA-B*27:09. We used X-ray crystallography and site-directed mutagenesis to unravel the molecular and structural mechanisms in HLA-B*27:03 that are responsible for its compromised ability to form homodimers. We show that polymorphism at position 59, which differentiates HLA-B*27:03 from all other allotypes, is responsible for its compromised ability to form homodimers. Indeed, histidine 59 in HLA-B*27:03 leads to a series of local conformational changes that act in concert to reduce the accessibility of the nearby cysteine 67, an essential amino acid residue for the formation of HLA-B27 homodimers. Considered together, the ability of both protective and disease-associated HLA-B27 allotypes to form homodimers and the failure of HLA-B*27:03 to form homodimers challenge the role of HLA-B27 homodimers in AS pathoetiology. Rather, this work implicates other features, such as peptide binding and antigen presentation, as pivotal mechanisms for disease pathogenesis.

Comparison of HLA-B*27 subtypes between Chinese patients with ankylosing spondylitis and non-ankylosing spondylitis carriers

Objective

To investigate the distribution of subtypes between HLA-B*27 (+) patients with ankylosing spondylitis (AS) and carriers.

Methods

This case–control study recruited Chinese Han patients with HLA-B*27 (+) AS from six hospitals in Zhejiang Province, China between 2013 and 2018. Patients who were examined for HLA-B*27 because of back pain or arthralgia but who did not have AS or arthritis were recruited as controls. HLA-B*27 target DNA was amplified by amplification refractory mutation systems and HLA-B*27 subtypes were determined by sequencing.

Results

The positive rate of HLA-B*27 was significantly higher in the AS group than in the control group. In AS patients, HLA-B*2704 was predominant at 86.4%, followed by HLA-B*2705 at 12.6%; HLA-B*2704 and HLA-B*2705 were found in 70.0% and 10.0% of controls, respectively. HLA-B*2702 and HLA-B*2706 were detected at low frequencies in the control group, while the rare subtype HLA-B*2715 was only observed in two (1.0%) patients with AS. HLA-B*2707 was not detected in AS or control groups.

Conclusion

HLA-B*2704 is the predominant subtype among patients with AS and carriers in southeast China.

The clinical utility of human leucocyte antigen B27 in axial spondyloarthritis

The association between HLA-B27 and AS was first established in the early 1970s. Since then, our understanding of this disease has changed, such that we now recognize AS to be the extreme of the clinical phenotype within a disease spectrum known as axial SpA (axSpA). Recent advances in therapeutic options have driven the need for earlier diagnosis and many screening strategies have been proposed to facilitate this. In parallel, our understanding of axSpA genetics, and especially the contribution of HLA-B27, has expanded. In this article we will present and discuss the evidence supporting the use of HLA-B27 in clinical practice. We will briefly summarize the evolution of the concept of axSpA, the prevalence of HLA-B27 and axSpA and the potential role of HLA-B27 in the aetiopathogenesis of axSpA and focus on the utility of HLA-B27 in everyday clinical practice.

Association of the HLA-B27 antigen and the CTLA4 gene CT60/rs3087243 polymorphism with ankylosing spondylitis in Algerian population: A case-control study

Ankylosing spondylitis (AS) is a complex inflammatory disease that represents a major health problem both in Algeria and worldwide. Several lines of evidence support that genetic risk factors play a role in AS etiology and the CTLA4 gene has attracted a considerable attention. In this study, we were interested in evaluating the HLA-B27 frequency and in exploring the CTLA4 gene in a sample of the North African population. The dataset of the current study is composed of 81 patients with AS and 123 healthy controls. All samples were genotyped by TaqMan^® allelic discrimination assay. The genetic risk of the HLA-B27 specificity and the CTLA4/CT60 polymorphism were assessed by odds ratios (OR) with 95% confidence intervals (CI). High spondylitis risk was detected for HLA-B27 allele (OR= 14.62, p = 10^-6 ) in addition to a significant association of the CT60*G allele (OR= 1.89, p = .002). After gender and age stratifications, the association of the CT60*G allele was still significant in females sample (OR= 2.10, p = .001) and when age up to 30 years (OR = 2.21, p = .008). Interestingly, the CT60*G allele revealed an increased spondylitis risk in the B27 negative group (OR= 2.81, p = .006). The present work showed in West Algerian population that the HLA-B27 antigen and the variation in the CTLA4 3'UTR region played an important role in the ankylosing spondylitis susceptibility. The heterogeneity of this disease is deduced by genetic difference found between B27+ and B27- groups.

Genetic association between TAP1 and TAP2 polymorphisms and ankylosing spondylitis: a systematic review and meta-analysis

OBJECTIVES

Ankylosing spondylitis (AS) is a chronic inflammatory joint disease. The transporter associated with antigen processing (TAP) has been identified to play an important role in immune response as well as the HLA-associated diseases. The aim of our meta-analysis was to investigate the contribution of TAP (TAP1 and TAP2) polymorphisms to the risk of AS.

METHODS

Meta-analyses were performed between 2 polymorphisms in TAP1 (TAP1-333, -637) and 3 polymorphisms in TAP2 (TAP2-379, -565, and -665) and AS.

RESULTS

The meta-analyses were involved with 6 studies with 415 cases and 659 controls. Significant association was found between TAP1-333Val, TAP1-637Gly, and TAP2-565Thr and AS compared with combined control group (TAP1-333Val: p = 0.009, OR = 1.40, 95% CI 1.09-1.80; TAP1-637Gly: p = 0.002, OR = 1.48, 95% CI 1.15-1.91; p = 0.03, OR = 1.38, 95% CI 1.04-1.84). Subgroup analysis shown that significant association was only found in AS when compared with HLA-B27-negative controls (TAP1-333Val: p = 0.004, OR = 1.53, 95% CI 1.14-2.06; TAP1-637Gly: p = 0.004, OR = 1.52, 95% CI 1.15-2.02; p = 0.02, OR = 1.56, 95% CI 1.09-2.24), but not in AS when compared with HLA-B27-positive controls (p > 0.05). Moreover, no significant associations were found between haplotypes in TAP1 and TAP2 in both the combined and the subgroup analyses (p > 0.05).

CONCLUSIONS

TAP1-333Val, TAP1-637Gly, and TAP2-565Thr were likely to be associated with AS.

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.

Analysis of HLA-B15 and HLA-B27 in spondyloarthritis with peripheral and axial clinical patterns

OBJECTIVE

Human leucocyte antigen (HLA) B27 and HLA-B15 are associated with spondyloarthritis (SpA). Recent Assessment of SpondyloArthritis international Society (ASAS) criteria emphasise a distinction between SpA with axial and peripheral patterns. We analysed whether HLA-A, HLA-B and HLA-DRB1 alleles could associate with these patterns.

METHODS

We studied 100 healthy individuals and 178 patients with SpA according to European Spondyloarthropathy Study Group (ESSG) criteria. Patients were then classified according to ASAS criteria, the axial spondyloarthritis pattern (axSpA) being defined by ascertained sacroiliitis and the peripheral pattern (pSpA) by enthesitis and/or arthritis in extremities. A combined ax/p pattern was also considered.

RESULTS

Only HLA-B27 and HLA-B15 alleles were associated with SpA. ASAS criteria for axSpA were met in 152 patients (12 with isolated axSpA and 140 with a combined ax/p patterns). When the ASAS peripheral criteria were applied, 161 patients met these criteria (13 with isolated pSpA and 148 with a combined ax/p pattern). HLA-B27 was found in 83% of patients with axSpA and 43% of ax/pSpA patients according to axASAS. HLA-B27 occurred in 7% controls but not in any patient with isolated pSpA. HLA-B15 was encountered in 31% of patients with isolated pSpA and 20% of ax/pSpA patients according to pASAS criteria. Moreover, 2 healthy controls, but none of our patients with isolated axSpA were positive for HLA-B15.

CONCLUSIONS

Our data suggest that the presence of HLA-B15 favours the development of isolated/combined peripheral rather than isolated axSpA, while HLA-B27 promotes an isolated/combined axial disease and excludes a peripheral pattern. HLA-B15 should be considered in addition to HLA-B27 when diagnosing patients with SpA according to ASAS criteria.

Polymorphisms of HLA-A, -B, -Cw and DRB1 antigens in Moroccan patients with ankylosing spondylitis and a comparison of clinical features with frequencies of HLA-B*27

Ankylosing spondylitis (AS) is very often associated with human leukocyte antigen (HLA), particularly HLA-B*27. However, the strength of this association and clinical features may vary in different ethnic groups. Our study aims to assess the distribution of HLA-A, -B, -Cw and DRB1 alleles in Moroccan patients with AS and to compare the clinical features of AS and the frequencies of HLA-B27 in patients from Morocco with other series. Seventy-five patients diagnosed with AS and assessed for clinical manifestations were selected and compared to 100 healthy controls. HLA class I and II antigens were typed by polymerase chain reaction sequence-specific oligonucleotide. HLA-B27 subtypes were studied by polymerase chain reaction amplification with sequence-specific primers. HLA-B27 was found in 64% of patients. It was positively associated with younger age at disease onset, family history, and uveitis while it had a negative association with late onset. Six B*27 subtypes were identified in the AS group. HLA-B*2705 and B*2702 were the most common observed subtypes. Among other HLA genes, a significant increase in the prevalence of HLA-Cw*02 and HLA-DRB*15 was found in AS patients. HLA-B27 is involved in the predisposition of AS in the Moroccan population. HLA-B*2705 and B*2702 were the predominant subtypes supporting previous reports in Caucasian spondyloarthropathies. Other HLA genes, HLA-Cw*02 and HLA-DRB1*15, seem to confer predisposing effect to the disease. However, the lower frequency of HLA-B27 compared to the literature in our study suggests the existence of different genetic and/or environmental factors in Morocco.

Activating killer immunoglobulin-like receptors genes are associated with increased susceptibility to ankylosing spondylitis

The aim of this study was to analyse the association of specific killer cell immunoglobulin-like receptors (KIR) genes and haplotypes with susceptibility to ankylosing spondylitis (AS) and its different clinical manifestations in a Spanish population. The presence or absence of all KIR genes was studied for their association with AS. A total of 176 patients with AS and 435 healthy control subjects were selected for this study based on clinical criteria. The commercial KIR-sequence-specific oligonucleotides (SSO) typing kit was used to investigate KIR typing. Frequencies of KIR2DS1 and KIR3DS1 genes were increased significantly in patients compared with healthy controls [52·8 versus 38·2%, PBonf < 0·01, odds ratio (OR) = 1·81 (1·28-2·59); 51·7 versus 37·5%, PBonf < 0·01, OR = 1·79 (1·25-2·54)]. Moreover, the frequency of activating genotypes in the AS patient group was significantly higher than in the healthy control group (P < 0·05). KIR2DS1 and KIR3DS1, in addition to human leucocyte antigen (HLA)-B27, may play an important role in the pathogenesis of AS. However, we show that the contribution of the KIR genes to AS susceptibility extends beyond the association with individual KIRs, with an imbalance between activating and inhibitory KIR genes seeming to influence the susceptibility to AS.

Raised incidence of ankylosing spondylitis among Inuit populations could be due to high HLA-B27 association and starch consumption

Ankylosing spondylitis (AS) is a chronic inflammatory arthritis mainly affecting the spinal joints. It would appear that the most likely causative agent in the development of AS is an environmental factor in the genetically susceptible, HLA-B27 positive, individuals. Extensive data from several countries support the notion that Klebsiella pneumonia bacteria are the most likely culprit in the causation of AS. These microbes possess antigens which resemble HLA-B27 and spinal collagens. Increased intake of high-starch diet is directly proportional to the gut-associated bacterial load, especially in the large intestine, and among these microbial agents, Klebsiella is considered as one of the main constituting components. Therefore, a low-starch diet intake alongside the currently used medical therapeutic modalities could be beneficial in the management of patients with early AS. It is suggested that a change in the dietary habits from high protein, low-starch marine components to the Westernized high-starch diet among the Inuit peoples of Alaska and Canada could be considered as one of the main contributing factors in the increased prevalence of AS during the last few decades within this genetically unmixed native population.

Genome-wide copy number variation analysis identifies deletion variants associated with ankylosing spondylitis

OBJECTIVE

To identify ankylosing spondylitis (AS)-associated copy number variations (CNVs) in Korean subjects and their synergistic roles in the development of AS.

METHODS

A genome-wide association study (GWAS) was performed in 309 patients with AS and 309 control subjects, using a copy number variant (CNV) microarray. AS-associated CNV regions were replicated in 2 independent sets (625 patients and 891 control subjects) by quantitative polymerase chain reaction (PCR) and deletion-typing PCR.

RESULTS

In the CNV GWAS, 227 CNV regions were shown to be significantly associated with the risk of AS. Of the candidate CNV regions, 9 were successfully replicated in the first replication analysis: 1q32.2 (HHAT), 1p34.2 (BMP8A), 2q31.2 (PRKRA), 6p21.32 (HLA-DPB1), 11q22.1 (CNTN5), 13q13.1 (EEF1DP3), 14q24.2 (RGS6), 16p13.3, and 22q11.1 (IL17RA). The 5 deletion-type CNV regions, in 1q32.2, 2q31.2, 6p21.32, 13q13.1, and 16p13.3, were associated with an increased risk of AS, and the other 4 CNV regions were protective. In the second replication analysis, 4 CNV regions in 1q32.2, 2q31.2, 6p21.32, and 16p13.3 were replicated. Among patients with CNV regions in ≥4 risk-increasing loci, the risk was 18.0 times higher than that in patients without any deletions (odds ratio [OR] 17.98, P = 2.3 × 10(-7) ). Among patients with CNV regions in ≥2 protective loci, the risk was 5.2 times lower than that in those without any deletions (OR 0.19, P = 4.0 × 10(-10) ). The additive effects of simultaneous events were shown to be dependent on the frequency of CNV regions. Through deletion-typing PCR and sequencing, the exact sizes and breakpoint sequences were defined in 4 CNV regions. The mechanism of all 3 deletions was shown to be microhomology-based nonhomologous end joining.

CONCLUSION

The results of this study can help to identify pathogenic mechanisms of AS and can easily be applied in the development of algorithms estimating the risk of AS.

TNF receptor-associated factor 5 gene confers genetic predisposition to acute anterior uveitis and pediatric uveitis

Introduction

TNF Receptor-Associated Factor 5 (TRAF5) has been shown to be associated with autoimmune disease. The current study sought to investigate the potential association of TRAF5 with acute anterior uveitis (AAU) and pediatric uveitis in Han Chinese.

Methods

Three TRAF5 SNPs were analyzed in 450 AAU patients with or without ankylosing spondylitis (AS), 458 pediatric uveitis patients, and 1,601 healthy controls by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or TaqMan SNP Genotyping Assay. Numerous variables were evaluated, including age, sex distribution, and clinical and laboratory observations.

Results

Two SNPs (rs6540679, rs12569232) of TRAF5 were associated with pediatric uveitis, and rs12569232 also showed a relation with the presence of microvascular leakage. No significant associations were found when patients were subdivided according to their rheumatoid factor (RF) or anti-nuclear antibody (ANA) status or whether they had juvenile idiopathic arthritis (JIA). Rs12569232 predisposed to AAU and its subgroups (with ankylosing spondylitis (AS) or HLA-B27 positive). No association was found between rs10863888 and either pediatric uveitis or AAU.

Conclusion

This study revealed that TRAF5 is involved in the development of AAU and pediatric uveitis. Further stratified analysis according to the clinical and laboratory observations suggested that rs12569232/TRAF5 may play a role in the development of retinal vasculitis.

Application of a Simple In-House PCR-SSP Technique for HLA-B* 27 Typing in Spondyloarthritis Patients

Background. Microlymphocytotoxicity (MLCT) and flowcytometry (FC) are the conventional serological methods to detect HLA-B* 27. Due to some disadvantages in these methods, most of the HLA laboratories have now switched over to molecular methods. Molecular techniques based on commercial kits are expensive; as such many laboratories with limited funds in developing countries cannot afford these techniques. Aims. Our main aim was to standardize a simple inexpensive in-house PCR-SSP technique for HLA-B* 27 typing. Materials and Methods. Sequence Specific primers were designed to amplify all the subtypes of B* 27 using IMGT-HLA sequence database. Accuracy was checked by retyping of 90 PCR-SSOP typed controls. Results. The presence of 149 bp specific band with control band on 2% agarose gel showed B* 27 positivity. No discrepancies were found when compared with PCR-SSOP results. The frequency of HLA-B* 27 was found to be significantly increased (68.75% versus 4.40%, O.R 46.909: P value 6.62E − 32) among 700 SpA patients as compared to controls. Clinically, 54% of patients had polyarticular arthritis with SI joints involvement (68%) and restricted spine flexion (60%). Conclusion. In-house PCR-SSP technique is very simple and inexpensive technique to detect B* 27 allele, which was strongly associated with SpA patients from Western India.

Prevalence of HLA-B27 in the New Zealand population: effect of age and ethnicity

INTRODUCTION

HLA-B27 genotyping is commonly used to support a diagnosis of ankylosing spondylitis (AS). A recent study has suggested that HLA-B27 may adversely affect longevity. The objectives of this study were to determine, for the first time, the prevalence of HLA-B27 in the New Zealand population, and to test whether HLA-B27 prevalence declines with age.

METHODS

117 Caucasian controls, 111 New Zealand Māori controls, and 176 AS patients were directly genotyped for HLA-B27 using PCR-SSP. These participants and a further 1103 Caucasian controls were genotyped for the HLA-B27 tagging single nucleotide polymorphisms (SNPs) rs4349859 and rs116488202. All AS patients testing positive for HLA-B27 of New Zealand Māori ancestry underwent high resolution typing to determine sub-allele status.

RESULTS

HLA-B27 prevalence was 9.2% in New Zealand Caucasian controls and 6.5% in Māori controls. No decline in HLA-B27 prevalence with age was detected in Caucasian controls (p = 0.92). Concordance between HLA-B27 and SNP genotypes was 98.7-99.3% in Caucasians and 76.9-86% in Māori. Of the 14 AS patients of Māori ancestry, 1 was negative for HLA-B27, 10 were positive for HLAB*2705, and 3 positive for HLAB*2704. All cases of genotype discordance were explained by the presence of HLAB*2704.

CONCLUSIONS

HLA-B27 prevalence in New Zealand Caucasians is consistent with that of Northern European populations and did not decline with increasing age. In Māori with AS who were HLA-B27 positive, 76.9% were positive for HLA-B*2705, suggesting that genetic susceptibility to AS in Māori is primarily due to admixture with Caucasians.

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.

HLA-B27 homozygosity has no influence on radiographic damage in ankylosing spondylitis: Observation Study of Korean spondyloArthropathy Registry (OSKAR) data

OBJECTIVES

To evaluate the influence of homozygosity for HLA-B27 on the radiographic damage in ankylosing spondylitis (AS).

METHODS

A total of 368 AS patients with positive HLA-B27 status from the Observation Study of Korean spondyloArthropathy Registry (OSKAR) cohort were recruited for this study. HLA-B27 positive patients out of all AS patients were assessed for whether they had homozygosity or heterozygosity for HLA-B27. First, all data were stratified in relation to the carrier state of positive HLA-B27 for cross-sectional survey. Then we compared the radiographic damage score between groups. Second, we evaluated collected clinical and radiographic parameters at two different time points. Then we compared radiographic progression between groups. To use the mSASSS, cervical and lumbar spinal radiographs were examined by two experienced bone and joint radiologists (S. Lee, K.B. Joo).

RESULTS

The agreement between the two readers regarding mSASSS was very good: ICC coefficient 0.70 (95% CI 0.60-0.81). The mean age (SD) of the AS patients was 37.0 (9.2) years, and the mean disease duration (SD) was 15.6 (9.1) years. Of these patients, 34.5% (127 patients) had HLA-B27 homozygosity. The mean mSASSS unit (SEM) was not significantly different between groups (homozygosity 28.57±4.12 vs heterozygosity 23.34±3.44, P=0.344) on cross-sectional survey. When it comes to radiographic progression between groups over 5 years, there was no significant difference in spite of adjusting for confounding variable (homozygosity 4.98±0.98 vs heterozygosity 4.21±0.82, P=0.562).

CONCLUSION

The carrier state of positive HLA-B27 plays no role in determining the radiographic progression in AS.

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.

Interaction pattern of Arg 62 in the A-pocket of differentially disease-associated HLA-B27 subtypes suggests distinct TCR binding modes

The single amino acid replacement Asp116His distinguishes the two subtypes HLA-B*2705 and HLA-B*2709 which are, respectively, associated and non-associated with Ankylosing Spondylitis, an autoimmune chronic inflammatory disease. The reason for this differential association is so far poorly understood and might be related to subtype-specific HLA:peptide conformations as well as to subtype/peptide-dependent dynamical properties on the nanoscale. Here, we combine functional experiments with extensive molecular dynamics simulations to investigate the molecular dynamics and function of the conserved Arg62 of the α1-helix for both B27 subtypes in complex with the self-peptides pVIPR (RRKWRRWHL) and TIS (RRLPIFSRL), and the viral peptides pLMP2 (RRRWRRLTV) and NPflu (SRYWAIRTR). Simulations of HLA:peptide systems suggest that peptide-stabilizing interactions of the Arg62 residue observed in crystal structures are metastable for both B27 subtypes under physiological conditions, rendering this arginine solvent-exposed and, probably, a key residue for TCR interaction more than peptide-binding. This view is supported by functional experiments with conservative (R62K) and non-conservative (R62A) B*2705 and B*2709 mutants that showed an overall reduction in their capability to present peptides to CD8+ T cells. Moreover, major subtype-dependent differences in the peptide recognition suggest distinct TCR binding modes for the B*2705 versus the B*2709 subtype.

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.

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.

KIR3DL1+HLA-B Bw4Ile80 and KIR2DS1+HLA-C2 combinations are both associated with ankylosing spondylitis in the Iranian population

Contribution of killer cell immunoglobulin-like receptors (KIR) and their human leucocyte antigen (HLA) class I ligands in the pathogenesis of autoimmune diseases has been shown in several studies. In this study, the possible association of KIR genes, their known HLA ligands and compound KIR/HLA genotypes with ankylosing spondylitis (AS) was assessed. Combined KIR/HLA ligand genotyping was performed by a polymerase chain reaction-sequence-specific primers assay in 35 Iranian patients with AS, and genotypes were compared to those in 200 healthy individuals. The frequencies of telomeric cluster genes KIR2DL5A, KIR2DS1 and KIR3DS1 were significantly increased in AS patient group (P(c) = 0.0082, P(c) = 0.0195 and P(c) = 0.0328, respectively). Conversely, HLA-Bw4 ligand (the presence of one or more -B Bw4(Ile80) , -B Bw4(Thr80) and -A Bw4 epitopes) (P(c) = 0.0004) and HLA-B Bw4(Ile80) (P(c) = 0.053) were less frequent in these patients. Meanwhile, compound KIR/HLA genotype analyses revealed lower frequency of KIR3DL1+HLA-B Bw4(Ile80) (P(c)  = 0.0343) and higher frequency of KIR2DS1+HLA-C2 (P(c) = 0.0308) combinations in patients with AS than in controls. In addition, the genotypes iKIR+HLA > aKIR+HLA (P(c) = .0308) and iKIR+HLA > aKIR (P(c) = 0.0258) were statistically less common, and genotypes iKIR+HLA = aKIR+HLA (P(c) = 0.0081) and iKIR+HLA < aKIR (P(c) = 0.077) were more common in patient group. Our findings suggest a role for excessive or inappropriate NK cell activation through 'KIR/HLA' system in AS disease.

Association and frequency of HLA-A, B and HLA-DR genes in south Tunisian patients with spondyloarthritis (SpA)

The aim of this study is to investigate the association of HLA-A, B and HLA-DR gene expression and to assess an association of additional HLA antigens besides HLA-B27 in south Tunisian patients with spondyloarthritis (SpA). Eighty-five patients diagnosed with ankylosing spondylitis (AS, n=68) and reactive arthrithis (ReA, n=17) were selected and compared with 100 healthy controls (HC). HLA class I antigens were typed serologically using microlymphocytotoxicity technique. HLA-DRB1* alleles were studied by polymerase chain reaction amplification with sequence-specific primers. The significance of differences between patients and controls was tested by chi-square analysis. We found significantly increased frequencies of HLA-A3 (30.6%; pC=0.04; OR=2.95), HLA-B27 (62.35%; pC=4.10(-17), OR=53.55), and HLA-DRB1*15 (17.2%; pC=0.026; RR=2.58) alleles in SpA patients compared to HC. The most frequent and strongest association was observed for HLA-B27 in AS (pC=6.6 ×10(-16), OR=52.23). When AS and ReA patients were analysed separately, HLA-DRB1*15 and HLA-A3 were increased only in AS (pC=0.01, OR=2.99 and pC=0.03, OR=3.14, respectively). In ReA patients, HLA-DRB1*04 (p=0.033, pC=NS, OR=2.89) was found to be the most common allele. By analysing the HLA-B27-negative subgroup, HLA-A3 and HLA-DRB1*15 expression was found to be dependent on the presence of HLA-B27. HLA-B27 expression was higher in male (45/53; 85%) as compared to female (8/53; 15%) patients (p=0.03). Apart from HLA-B27, HLA-A3 and HLA-DRB1*15 are the MHC class I and II alleles found most frequent in Tunisian patients with AS, whereas HLA-DRB1*04 was found most frequent in ReA patients. HLA-B27 is more frequent in male than in female patients.

HLA genes in Amerindian immigrants to Madrid (Spain): epidemiology and a virtual transplantation waiting list: Amerindians in Madrid (Spain)

Amerindians immigrated to Madrid (Spain) region are about 10% of the present day population. Amerindians are believed to be the first American inhabitants, before Na-Dene speakers, Aleuts and Eskimo. They may initially have arrived to America from Siberia and also from other parts of Pacific Sea (South Asia, Polynesia and Australia). Nowadays, they populate America from Canada to Tierra del Fuego (South America tip South). Most Amerindian immigrants to Madrid have come from Andean Countries in the last 10 years (mainly Ecuador, Bolivia, Peru and Colombia). They show an HLA profile with "quasi-specific alleles", which makes them different to the rest of the World. In the present work, we have aimed to determine the immigrants HLA profile in order to establish a virtual transplantation waiting list which may be useful for their therapeutic transplants, particularly bone marrow transplantation. This would be carried out together with Amerindian immigrants to other parts of Spain and with their own countries in order to build up transplantation programs. Specific epidemiology programs on HLA linked disease will also be established. Immigrant volunteer unrelated blood donors contributed to the present study. HLA typing was performed by standard methods and their HLA profile obtained and obtained and compared with 15,108 HLA chromosomes from the rest of the World, including Spaniards. The immigrants showed a typical Amerindian profile similar to isolated Amerindian ethnic groups and altogether different to other World inhabitants (including Spaniards). These are the first bases to set up transplantation and epidemiology studies in collaboration with their original population in America. Finally, the HLA profile found in these Amerindians does not indicate their American specific original area, as it is expected from previous studies, i.e.: they do not relate more with Andean than with other Amerindians in Neighbour Joining dendrograms or correspondence analyses.

Better short-term clinical response to etanercept in Chinese than Caucasian patients with active ankylosing spondylitis

Tumor necrosis factor-alpha (TNF-α) inhibitors including etanercept have been demonstrated to be very effective in severe ankylosing spondylitis (AS) in Caucasian patients. However, clinical efficacy of etanercept to treat active AS in Chinese patients has not been reported. In this study, a prospective, open-label trial of etanercept (25 mg BIW), involving 46 AS patients from 16 medical centers of Taiwan, was conducted. Questionnaire was utilized to record demographic data and clinical parameters, including Bath AS Disease Activity Index (BASDAI), Bath AS Functional Index (BASFI), Bath AS Global Index (BASGI), Assessment in Ankylosing Spondylitis (ASAS) 20, 50, and 70, and others, before and at different time intervals after etanercept treatment. Laboratory tests including blood chemistry, hematology, urine analysis, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were done at baseline and at weeks 4, 8, and 12. In this 12-week study, etanercept demonstrated rapid and significant improvement in the ASAS20 response criteria (91.3%), at as early as 2 weeks of therapy (71.3%). Partial remission of AS was achieved in 49.3% of patients after 12 weeks of treatment. Disease activity (BASDAI) and function (BASFI) were also significantly improved after 12 weeks etanercept treatment (p < 0.0001 and p < 0.0001, respectively). In addition, significant increase of chest expansion (2.77 ± 1.69 cm versus 3.56 ± 1.82 cm, p = 0.0004) and lumbar flexion (2.11 ± 2.76 cm versus 2.58 ± 3.42 cm, p = 0.0075) and significant reduction of occiput-to-wall distance (6.59 ± 7.14 cm versus 5.32 ± 6.65 cm, p = 0.0006) were also demonstrated. Both ESR and CRP declined significantly after patients were treated with etanercept. There were no severe adverse effects during the treatment period. Etanercept is generally safe, well tolerated, and effective in Chinese patients with severe AS. Clinical efficacy, including partial remission and BASDAI, is even better in Chinese than in Caucasian patients. Further study is required to assess long-term efficacy and safety in Chinese patients with AS.

Association of the KIR3DS1*013 and KIR3DL1*004 alleles with susceptibility to ankylosing spondylitis

OBJECTIVE

The killer cell immunoglobulin-like receptors (KIRs) form a group of regulatory molecules that specifically recognize HLA class I molecules. The aim of this study was to analyze the possible contribution of the KIR3DL1 and KIR3DS1 alleles, in addition to HLA-B27, in the susceptibility to ankylosing spondylitis (AS) in a population of individuals from Spain.

METHODS

We genotyped the KIR3DS1 and KIR3DL1 alleles in 2 cohorts of patients with AS and healthy control subjects. In total, 270 patients with AS and 435 healthy, HLA-B27-positive matched control subjects from Spain were enrolled. The KIR3DS1 and KIR3DL1 alleles were genotyped by sequence-specific oligonucleotide probe-polymerase chain reaction, and their association with AS was analyzed. All individuals were typed for HLA-B.

RESULTS

The KIR3DS1*013 allele was solely responsible for the increased frequency of the activator receptor KIR3DS1 in patients with AS compared with healthy HLA-B27-positive control subjects (35.7% versus 22.6% [P = 10(-6)], odds ratio 1.90, 95% confidence interval 1.50-2.40). The increased frequency of the KIR3DS1*013 allele in patients with AS was independent of the presence or absence of the HLA-Bw4I80 epitope. Moreover, the null allele KIR3DL1*004 was a unique inhibitory KIR3DL1 allele that showed a negative association with AS in the presence of HLA-Bw4I80.

CONCLUSION

The increased frequency of the KIR3DS1*013 allele in patients with AS is clearly independent of the presence of the HLA-Bw4I80 epitope, whereas the presence of inhibitory allotypes such as KIR3DL1*004 demonstrated a negative association in patients with AS in the presence of HLA-Bw4I80. As a consequence, the influence of KIR genotypes on AS susceptibility would be mediated by a general imbalance between protective/inhibitory and risk/activating allotypes.

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.

CD8+ T-cell mediated self-reactivity in HLA-B27 context as a consequence of dual peptide conformation

HLA-B2709 does not predispose for Ankylosing Spondylitis although it differs from B2705, the most common and AS-associated subtype in different ethnic groups, only for the substitution His116Asp. Therefore, a productive approach to elucidate the molecular mechanisms of the disease could be the comparison of these alleles. B2705 has been shown to display certain self-peptides enriched in basic residues i.e., pVIPR and pGR, in a dual conformation and this is accompanied by the presence of specific cytotoxic T cells in patients with AS. In this study, we convalidate our previous observation that B2709 healthy subjects do not possess primary reactivity towards pVIPR while showing a prompt CD8+ T cell response driven by pGR. Notably, in the B2709 context of presentation, pVIPR assumes only a single conformation in contrast with pGR which is dimorphic. These results suggest a possible general connection between the occurrence of double peptide conformation and the property of inducing specific autoimmune responses.