Two susceptibility loci to Takayasu arteritis reveal a synergistic role of the IL12B and HLA-B regions in a Japanese population

Multiple occlusions in extracranial arteries in patients with aortic arch syndrome: is minimally invasive treatment still possible? Technical aspects of the treatment based on our own experience and a review of the literature

Takayasu arteritis is a large vessel vasculitis of granulomatous nature and unknown aetiology affecting predominantly the aorta and its major branches, which may lead to ischaemic symptoms of many organs including the central nervous system. To decrease the risk of neurological complications and improve the quality of life, an arterial revascularisation may be necessary. The treatment options include pharmacotherapy as well as both open surgical and endovascular procedures, which has to be carefully chosen to obtain clinical success. There is an ongoing debate on the advantages, possibilities, and indications for implementing endovascular and open surgical methods, especially in high-risk patients. In this article we present our own experience in the treatment of an unusually complex and high-risk patient with multiple occlusion of supra-aortic branches, focusing on the technical aspects of the procedures and the decision-making process, as well as to confront with contemporary medical knowledge.

Childhood-onset Takayasu Arteritis

Childhood-onset Takayasu Arteritis (cTAK) is a rare, large-vessel type of vasculitis seen in children, mainly affecting the aorta and its major branches. Clinical manifestations are often severe and arise as a result of systemic and local inflammation, along with end-organ ischemia. Disease flares are common and the disease burden is high, with a significant rate of morbidity and mortality. Recent advances in understanding the underlying disease pathobiology resulted in the use of pathway-targeting agents, such as TNF- or IL-6 inhibitors with improved disease control. Nonetheless, the prognosis often remains guarded and the accrued damage is significant. This review aims at summarizing the recent evidence and observations regarding this condition, with a focus on pediatric publications.

Current State of Precision Medicine in Primary Systemic Vasculitides

Precision medicine (PM) is an emerging data-driven health care approach that integrates phenotypic, genomic, epigenetic, and environmental factors unique to an individual. The goal of PM is to facilitate diagnosis, predict effective therapy, and avoid adverse reactions specific for each patient. The forefront of PM is in oncology; nonetheless, it is developing in other fields of medicine, including rheumatology. Recent studies on elucidating the genetic architecture of polygenic and monogenic rheumatological diseases have made PM possible by enabling physicians to customize medical treatment through the incorporation of clinical features and genetic data. For complex inflammatory disorders, the prevailing paradigm is that disease susceptibility is due to additive effects of common reduced-penetrance gene variants and environmental factors. Efforts have been made to calculate cumulative genetic risk score (GRS) and to relate specific susceptibility alleles for use of target therapies. The discovery of rare patients with single-gene high-penetrance mutations informed our understanding of pathways driving systemic inflammation. Here, we review the advances in practicing PM in patients with primary systemic vasculitides (PSVs). We summarize recent genetic studies and discuss current knowledge on the contribution of epigenetic factors and extracellular vesicles (EVs) in disease progression and treatment response. Implementation of PM in PSVs is a developing field that will require analysis of a large cohort of patients to validate data from genomics, transcriptomics, metabolomics, proteomics, and epigenomics studies for accurate disease profiling. This multi-omics approach to study disease pathogeneses should ultimately provide a powerful tool for stratification of patients to receive tailored optimal therapies and for monitoring their disease activity.

Single-Nucleotide Polymorphism of the MLX Gene Is Associated With Takayasu Arteritis

BACKGROUND

Takayasu arteritis (TAK) is an autoimmune systemic arteritis of unknown pathogenesis. Genome-wide association studies revealed that single-nucleotide polymorphisms in the MLX gene encoding the MLX (Max-like protein X) transcription factor are significantly associated with TAK in Japanese patients. MLX single-nucleotide polymorphism rs665268 is a missense mutation causing the Q139R substitution in the DNA-binding site of MLX.

METHODS

To elucidate the hypothesis that the single-nucleotide polymorphism of the MLX gene plays a critical role in the development of TAK, we conducted clinical and laboratory analyses.

RESULTS

We show that rs665268 significantly correlated with the severity of TAK, including the number of arterial lesions and morbidity of aortic regurgitation; the latter may be attributed to the fact that MLX mRNA expression was mostly detected in the aortic valve. Furthermore, the Q139R mutation caused structural changes in MLX, which resulted in enhanced formation of a heterodimer with MondoA, upregulation of TXNIP (thioredoxin-interacting protein) expression, and increase in the activity of the NLRP3 (NACHT, LRR, and PYD domains-containing protein 3) inflammasome and cellular oxidative stress. Furthermore, autophagy, which negatively regulates inflammasome activation, was suppressed by the Q139R mutation in MLX. The MLX-Q139R mutant significantly induced macrophage proliferation and macrophage-endothelium interaction, which was abolished by the treatment with SBI-477, an inhibitor of MondoA nuclear translocation. Our findings suggest that the Q139R substitution in MLX plays a crucial role in the pathogenesis of TAK.

CONCLUSIONS

MLX-Q139R mutation plays a crucial role in the pathogenesis of TAK through promoting inflammasome formation.

Leveraging Genetic Findings for Precision Medicine in Vasculitis

Vasculitides are a heterogeneous group of low frequent disorders, mainly characterized by the inflammation of blood vessels that narrows or occlude the lumen and limits the blood flow, leading eventually to significant tissue and organ damage. These disorders are classified depending on the size of the affected blood vessels in large, medium, and small vessel vasculitis. Currently, it is known that these syndromes show a complex etiology in which both environmental and genetic factors play a major role in their development. So far, these conditions are not curable and the therapeutic approaches are mainly symptomatic. Moreover, a percentage of the patients do not adequately respond to standard treatments. Over the last years, numerous genetic studies have been carried out to identify susceptibility loci and biological pathways involved in vasculitis pathogenesis as well as potential genetic predictors of treatment response. The ultimate goal of these studies is to identify new therapeutic targets and to improve the use of existing drugs to achieve more effective treatments. This review will focus on the main advances made in the field of genetics and pharmacogenetics of vasculitis and their potential application for ameliorating long-term outcomes in patient management and in the development of precision medicine.

Takayasu arteritis risk locus in IL6 represses the anti-inflammatory gene GPNMB through chromatin looping and recruiting MEF2-HDAC complex

OBJECTIVE

Previous work has revealed a genetic association between Takayasu arteritis and a non-coding genetic variant in an enhancer region within IL6 (rs2069837 A/G). The risk allele in this variant (allele A) has a protective effect against chronic viral infection and cancer. The goal of this study was to characterise the functional consequences of this disease-associated risk locus.

METHODS

A combination of experimental and bioinformatics tools were used to mechanistically understand the effects of the disease-associated genetic locus in IL6. These included electrophoretic mobility shift assay, DNA affinity precipitation assays followed by mass spectrometry and western blotting, luciferase reporter assays and chromosome conformation capture (3C) to identify chromatin looping in the IL6 locus. Both cell lines and peripheral blood primary monocyte-derived macrophages were used.

RESULTS

We identified the monocyte/macrophage anti-inflammatory gene GPNMB,~520 kb from IL6, as a target gene regulated by rs2069837. We revealed preferential recruitment of myocyte enhancer factor 2-histone deacetylase (MEF2-HDAC) repressive complex to the Takayasu arteritis risk allele. Further, we demonstrated suppression of GPNMB expression in monocyte-derived macrophages from healthy individuals with AA compared with AG genotype, which was reversed by histone deacetylase inhibition. Our data show that the risk allele in rs2069837 represses the expression of GPNMB by recruiting MEF2-HDAC complex, enabled through a long-range intrachromatin looping. Suppression of this anti-inflammatory gene might mediate increased susceptibility in Takayasu arteritis and enhance protective immune responses in chronic infection and cancer.

CONCLUSIONS

Takayasu arteritis risk locus in IL6 might increase disease susceptibility by suppression of the anti-inflammatory gene GPNMB through chromatin looping and recruitment of MEF2-HDAC epigenetic repressive complex. Our data highlight long-range chromatin interactions in functional genomic and epigenomic studies in autoimmunity.

Genetic overlap of chronic obstructive pulmonary disease and cardiovascular disease-related traits: a large-scale genome-wide cross-trait analysis

BACKGROUND

A growing number of studies clearly demonstrate a substantial association between chronic obstructive pulmonary disease (COPD) and cardiovascular diseases (CVD), although little is known about the shared genetics that contribute to this association.

METHODS

We conducted a large-scale cross-trait genome-wide association study to investigate genetic overlap between COPD (Ncase = 12,550, Ncontrol = 46,368) from the International COPD Genetics Consortium and four primary cardiac traits: resting heart rate (RHR) (N = 458,969), high blood pressure (HBP) (Ncase = 144,793, Ncontrol = 313,761), coronary artery disease (CAD)(Ncase = 60,801, Ncontrol = 123,504), and stroke (Ncase = 40,585, Ncontrol = 406,111) from UK Biobank, CARDIoGRAMplusC4D Consortium, and International Stroke Genetics Consortium data.

RESULTS

RHR and HBP had modest genetic correlation, and CAD had borderline evidence with COPD at a genome-wide level. We found evidence of local genetic correlation with particular regions of the genome. Cross-trait meta-analysis of COPD identified 21 loci jointly associated with RHR, 22 loci with HBP, and 3 loci with CAD. Functional analysis revealed that shared genes were enriched in smoking-related pathways and in cardiovascular, nervous, and immune system tissues. An examination of smoking-related genetic variants identified SNPs located in 15q25.1 region associated with cigarettes per day, with effects on RHR and CAD. A Mendelian randomization analysis showed a significant positive causal effect of COPD on RHR (causal estimate = 0.1374, P = 0.008).

CONCLUSION

In a set of large-scale GWAS, we identify evidence of shared genetics between COPD and cardiac traits.

Vasculitis: Decade in Review

BACKGROUND

In the last decade, we have come to better understand and manage the vasculitides. The classification of vasculitides has been revised. Genome- wide association studies and linkage analyses have been undertaken in hope of better understanding the pathogenesis of vasculitides. Comprehensive genetic studies have highlighted new pathways that may guide us in more targeted therapies. Description of the monogenic forms of vasculitis, such as deficiency of adenosine deaminase type 2 (DADA2), Haploinsufficiency of A20 (HA20), have introduced a new perspective to vasculopathies, and introduced alternative treatments for these diseases.

CONCLUSION

In this review, the important discoveries in pathogenesis and consensus treatment recommendations from the past decade will be summarized.

Childhood-Onset Takayasu Arteritis (c-TA): Current and Future Drug Therapy

Childhood-onset Takayasu arteritis (c-TA) is the third most common systemic vasculitic disorder in children. Vascular stenosis is the main complication, and aneurysms are reported in 19-65% of cases, often in combination with stenotic lesions. Management of patients with c-TA is largely based on studies involving predominantly patients with adult-onset TA (a-TA). More widely used criteria for patients with c-TA have been devised by the joint European League Against Rheumatism, Pediatric Rheumatology International Trials Organization, and Pediatric Rheumatology European Society. Of the available imaging modalities, those that do not use radiation (color Doppler ultrasound and magnetic resonance angiogram) are preferred over ¹⁸F-labeled fluoro-2-deoxyglucose (¹⁸F-FDG) positron-emission tomography, computed tomography (CT), and CT angiogram in children. Remission rates have been reported to be lower in c-TA than in a-TA, and published mortality rates in c-TA range from 16 to 40%, which is much higher than reported in patients with a-TA. The usual drug therapy options include steroids plus steroid-sparing second-line immunosuppressants, such as mycophenolate, azathioprine, methotrexate, cyclophosphamide, and cyclosporine, along with antiplatelet agents. Interleukin-6 inhibitors such as tocilizumab, as well as the tumor necrosis factor inhibitors, are other aggressive therapeutic options. As yet, no randomized controlled trials have been conducted in c-TA.

Genetic Basis of Vasculitides with Neurologic Involvement

"Vasculitides are a heterogeneous group of inflammatory diseases of blood vessels in which genetic variation plays an important role in their susceptibility and clinical spectrum. Because of the use of novel technologies and the increase of the sample size of the study cohorts, the knowledge of the genetic background of vasculitides has considerably expanded during the last years. However, few insights have been obtained regarding the genetics underlying severe clinical phenotypes, such as those related to the nervous system. In this review the authors provide an updated overview of the genetic landscape behind vasculitis predisposition and development of neurologic manifestations."

Takayasu arteritis - epidemiology, pathogenesis, diagnosis and treatment

Takayasu disease belongs to the group of autoimmune vasculitis which most often affects the aorta and its branches. It is rare, and it mainly affects young women. Recent epidemiologic studies suggest that Takayasu arteritis is being increasingly recognized in Europe. The first symptoms are non-specific and an early diagnosis is difficult and requires clinical awareness and suspicion. Patients with Takayasu arteritis often present increased inflammatory markers, including C-reactive protein and erythrocyte sedimentation rate, but systemic inflammatory response does not always show a positive correlation with inflammatory activity in the vessel wall. Therefore, imaging studies play a principal role in diagnosis and control of the disease. Glucocorticoids remain the most effective and serve as a cornerstone first line treatment. Immunosuppressive drugs play an important role as well, and biological therapy is increasingly being included in the treatment. This article describes the epidemiology, pathophysiology, diagnostics and treatment of this rare disease, so as to alert clinicians because disease left untreated can lead to narrowing and even closure of vital blood vessels. The most common Takayasu arteritis complications include pulmonary thrombosis, aortic regurgitation, congestive heart failure, cerebrovascular events, vision degeneration or blindness, and hearing problems.

Pathophysiology of large vessel vasculitis and utility of interleukin-6 inhibition therapy

Takayasu arteritis (TAK) and giant cell arteritis (GCA) affect mainly large- and medium-sized arteries. In refractory cases, vascular remodeling progresses and leads to serious outcomes. Studies have demonstrated that cytokines such as interleukin (IL)-6 play crucial roles in the pathophysiology of TAK and GCA. Recently, randomized controlled trials on IL-6 inhibition therapy using tocilizumab (TCZ) were performed, and significant effects were exhibited. The purposes of conventional treatments have been to improve symptoms and decrease the levels of inflammatory markers. Arterial changes have been considered as damages. However, after TCZ came into practical use, establishment of treat to target is desired to prevent vascular remodeling. In contrast, a combination therapy of glucocorticoids (GCs) and TCZ notably increases the risk of infections. When TCZ is used, careful attention must be paid to possible infections, and dose of GC should be tapered as much as possible. Future tasks are to establish indication and dosage of TCZ, indication for discontinuation of TCZ due to remission, efficacy of TCZ monotherapy, and protocols of TCZ for pediatric cases.

Hemoptysis Originating from the Bronchial Artery in Takayasu Arteritis with Ulcerative Colitis

Takayasu arteritis (TAK) is a large-vessel vasculitis affecting the aorta and its main branches. Hemoptysis can be experienced as the respiratory manifestation, but origination from a bronchial artery is rare. Ulcerative colitis (UC) shares genetic similarities with TAK; HLA-B52*01 is associated with TAK and UC. We herein report a patient who presented with hemoptysis from the right bronchial artery and was diagnosed with TAK during the follow-up of UC. Transcatheter embolization was performed, and prednisolone and tocilizumab induced remission. Complication of TAK should be considered in the clinical course of HLA-B52-positive UC patients, and tocilizumab may be a treatment option.

Genetic determinants and an epistasis of LILRA3 and HLA-B*52 in Takayasu arteritis

Takayasu arteritis (TAK) is a systemic vasculitis with severe complications that affects the aorta and its large branches. HLA-B*52 is an established susceptibility locus to TAK. To date, there are still only a limited number of reports concerning non-HLA susceptibility loci to TAK. We conducted a genome-wide association study (GWAS) and a follow-up study in a total of 633 TAK cases and 5,928 controls. A total of 510,879 SNPs were genotyped, and 5,875,450 SNPs were imputed together with HLA-B*52. Functional annotation of significant loci, enhancer enrichment, and pathway analyses were conducted. We identified four unreported significant loci, namely rs2322599, rs103294, rs17133698, and rs1713450, in PTK2B, LILRA3/LILRB2, DUSP22, and KLHL33, respectively. Two additional significant loci unreported in non-European GWAS were identified, namely HSPA6/FCGR3A and chr21q.22. We found that a single variant associated with the expression of MICB, a ligand for natural killer (NK) cell receptor, could explain the entire association with the HLA-B region. Rs2322599 is strongly associated with the expression of PTK2B Rs103294 risk allele in LILRA3/LILRB2 is known to be a tagging SNP for the deletion of LILRA3, a soluble receptor of HLA class I molecules. We found a significant epistasis effect between HLA-B*52 and rs103294 (P = 1.2 × 10^-3). Enhancer enrichment analysis and pathway analysis suggested the involvement of NK cells (P = 8.8 × 10^-5, enhancer enrichment). In conclusion, four unreported TAK susceptibility loci and an epistasis effect between LILRA3 and HLA-B*52 were identified. HLA and non-HLA regions suggested a critical role for NK cells in TAK.

Vasculitis Pathogenesis: Can We Talk About Precision Medicine?

Precision medicine is designing the medical care by taking into account the individual variability for each person. We have tried to address whether the existing data may guide precision medicine in primary systemic vasculitides (PSV). We have reviewed genome-wide association studies (GWAS) data, lessons from monogenic mimics of these diseases, and biomarker studies in immunoglobulin A vasculitis/Henoch–Schönlein purpura, Kawasaki disease, anti-neutrophil cytoplasmic antibody-associated vasculitis, polyarteritis nodosa (PAN), Takayasu arteritis, and Behçet’s disease (BD). GWAS provide insights about the pathogenesis of PSV while whole exome sequencing studies lead to discovery of monogenic vasculitides, phenotype of which could mimic other types of vasculitis such as PAN and BD. Monogenic vasculitides form a subgroup of vasculitis which are caused by single gene alterations and discovery of these diseases has enabled more specific therapies in these patients. With increasing number of studies on biomarkers, new targets for treatment appear and better and structured follow-up of PSV patients will become possible. Proteomics and metabolomics studies are required to better categorize our patients with PSV so that we can manage them appropriately and offer more targeted therapy.

Takayasu Arteritis Coexisting with Sclerosing Osteomyelitis

We report a rare case of a 27-year-old woman with Takayasu arteritis (TAK) complicated by diffuse sclerosing osteomyelitis. She first presented with sclerosing osteomyelitis of the right mandible without evidence of arteritis in the carotid arteries. Eight months later, she complained of left neck pain, and imaging studies revealed the presence of arteritis in the left carotid artery. She was diagnosed with TAK, and immunosuppressive treatment was initiated, which was effective for both the arteritis and the osteomyelitis. Osteomyelitis is an important complication of TAK and bone scintigraphy is useful for its detection.

A case of ankylosing spondylitis with concurrent Takayasu arteritis

We herein report a case involving a 56-year-old man who had experienced neck and lower back pain since the age of 23 years. Ankylosing spondylitis (AS) was diagnosed at 41 years of age, and treatment with sulfasalazine was initiated. At 44 years of age, the patient developed respiratory distress on exertion and chest pain. Aortic regurgitation (AR) was diagnosed via echocardiography, and the patient presented to our hospital for close examination and treatment. Coronary computed tomography angiography revealed no lesions in the coronary artery; however, magnetic resonance angiography revealed stenotic lesions in the left common carotid artery and left subclavian artery. Based on the findings of a physical examination, fundus examination, and blood tests, the patient was diagnosed with AS with concurrent Takayasu arteritis (TA). Upon administration of steroids to alleviate inflammation caused by an autoimmune mechanism, the patient’s chest symptoms and inflammatory findings improved. AR was treated with aortic valve replacement and prosthetic blood vessel replacement, after which the patient progressed well. Intraoperative aortic biopsy revealed findings pathologically consistent with TA. Although AS with concurrent AR is well described, AS with concurrent TA, as in the present case, is rare.

How to conduct research of rare autoimmune diseases

Rare autoimmune diseases are difficult to conduct researches in spite of present era with advanced scientific progress. Research using genetic approach is a promising way since genetic findings implicate causality of diseases. Still, there are multiple obstacles preventing genetic studies of rare diseases. Here, we list up the problems and propose solutions for them with detailed examples. The biggest problem is that it is difficult to collect a substantial number of DNA samples from patients with rare diseases. We propose to collaborate not only with academic institutions and hospitals but with patients' groups. Detailed examples include studies about Takayasu arteritis (TAK), relapsing polychondritis, and systemic sclerosis. In TAK, we identified IL12B, a key gene which seems to play a central role in the disease. After getting evidence of IL12p40 encoded by IL12B as a possible therapeutic target by showing similarities of the genetic background between TAK and ulcerative colitis, we performed a pilot clinical study of ustekinumab, a monoclonal antibody against IL12p40 for patients with refractory TAK and obtained good response. This is a good example of how genetic findings in a rare disease lead to development of new therapeutic option.

Biological treatments in giant cell arteritis & Takayasu arteritis

Giant cell arteritis (GCA) and Takayasu arteritis (TAK) are the two main large vessel vasculitides. They share some similarities regarding their clinical, radiological and histological presentations but some pathogenic processes in GCA and TAK are activated differently, thus explaining their different sensitivity to biological therapies. The treatment of GCA and TAK essentially relies on glucocorticoids. However, thanks to major progress in our understanding of their pathogenesis, the role of biological therapies in the treatment of these two vasculitides is expanding, especially in relapsing or refractory diseases. In this review, the efficacy, the safety and the limits of the main biological therapies ever tested in GCA and TAK are discussed. Briefly, anti TNF-α agents appear to be effective in treating TAK but not GCA. Recent randomized placebo-controlled trials have reported on the efficacy and safety of abatacept and mostly tocilizumab in inducing and maintaining remission of GCA. Abatacept was not effective in TAK and robust data are still lacking to draw any conclusions concerning the use of tocilizumab in TAK. Furthermore, ustekinumab appears promising in relapsing/refractory GCA whereas rituximab has been reported to be effective in only a few cases of refractory TAK patients. If a biological therapy is indicated, and in light of the data discussed in this review, the first choice would be tocilizumab in GCA and anti-TNF-α agents (mainly infliximab) in TAK.

Takayasu Arteritis

Takayasu arteritis is an idiopathic granulomatous vasculitis of the aorta and its main branches and it constitutes one of the more common vasculitides in children. Inflammation and intimal proliferation lead to wall thickening, stenotic or occlusive lesions, and thrombosis, while destruction of the elastica and muscularis layers originates aneurysms and dissection. Carotid artery tenderness, claudication, ocular disturbances, central nervous system abnormalities, and weakening of pulses are the most frequent clinical features. The diagnosis is usually confirmed by the observation of large vessel wall abnormalities: stenosis, aneurysms, occlusion, and evidence of increased collateral circulation in angiography, MRA or CTA imaging. The purpose of this revision is to address the current knowledge on pathogenesis, investigations, classification, outcome measures and management, and to emphasize the need for timely diagnosis, effective therapeutic intervention, and close monitoring of this severe condition.

A novel susceptibility locus in the IL12B region is associated with the pathophysiology of Takayasu arteritis through IL-12p40 and IL-12p70 production

BACKGROUND

A previous study revealed the association between susceptibility to Takayasu arteritis (TAK) and a single nucleotide polymorphism (SNP) rs6871626 located in IL12B, which encodes interleukin (IL)-12p40, a common component of IL-12p70 and IL-23. We investigated the expression of these cytokines in patients with TAK, stratifying them into those with or without the risk allele at the rs6871626 SNP.

METHODS

Plasma levels of IL-12p40, IL-12p70, and IL-23 were quantified in 44 patients with TAK and 19 healthy controls (HCs) by enzyme-linked immunosorbent assays. Monocytes were obtained from 20 patients with TAK and 14 HCs, treated with interferon-γ (IFN-γ) and lipopolysaccharide, and then supernatant cytokines were quantified. In addition, the ratio of IFN-γ⁺ or IL-17A⁺ cells to CD4⁺ T cells was measured by flow cytometric analysis of peripheral blood mononuclear cells.

RESULTS

The levels of plasma IL-12p40, plasma IL-12p70, and supernatant IL-12p70 were significantly higher in patients with TAK than in HCs, whereas there were no significant differences in the levels of plasma IL-23, supernatant IL-23, or supernatant IL-12p40. The levels of plasma IL-12p70, supernatant IL-12p40, and supernatant IL-12p70 were significantly higher in patients with the risk allele than in those without. The ratio of CD4⁺IFN-γ⁺ cells was significantly higher in patients with the risk allele, whereas CD4⁺IL-17A⁺ cells showed no differences.

CONCLUSIONS

The rs6871626 SNP in IL12B may influence the increased expression of IL-12p40 and IL-12p70. These enhanced cytokines might play roles in the pathophysiology of TAK.

Association of FCGR2A/FCGR3A variant rs2099684 with Takayasu arteritis in the Han Chinese population

Takayasu arteritis (TA) is a chronic large-vessel vasculitis of unclear pathogenesis. A recent genome-wide association study (GWAS) has revealed that the FCGR2A/FCGR3A, EEFSEC, RPS9/LILRB3, RIPPLY2 and MLX genes confer susceptibility to TA. We investigated the linkage between presumptive TA-related genes (FCGR2A/FCGR3A, EEFSEC, RPS9/LILRB3, RIPPLY2 and MLX) and TA in the Han Chinese population.We performed a large case-control multi-center study of 412 Han Chinese TA patients and 597 ethnically matched healthy controls. Five single nucleotide polymorphisms (SNPs) were assessed and genotyped using Sequenom MassArray system (iPLEX assay, Sequenom, San Diego, CA, USA).The frequency of the rs2099684 variant G allele in the FCGR2A/FCGR3A gene was significantly higher in the TA patients than in the controls (37.5% compared with 25.4%, OR =1.77, 95% CI: 1.46-2.14, Pc =1.5×10-8). Similar results were observed in genotype distribution analysis and logistic regression analyses conducted using three genetic models. The allele and genotype distributions for the other polymorphisms were not significantly associated with TA among the Han Chinese patients.The SNP rs2099684 in FCGR2A/FCGR3A can be considered a genetic risk factor for TA in the Chinese Han population. These findings provide further insights into the etiopathogenesis of TA.

What is new in management of Takayasu arteritis?

Management of Takayasu arteritis (TAK) is challenging mostly due to difficulties in assessing actual disease activity. The rational of medical treatment is to suppress both vascular and systemic inflammation with appropriate systemic immunosuppression, including corticosteroids and conventional immunosuppressive (IS) agents. In case of refractory disease activity, biologic agents such as TNF inhibitors and tocilizumab may be tried. In selected cases, endovascular interventions and surgical procedures may be indicated and should be performed during inactive disease. Among conventional IS agents, new data is available for leflunomide. On the other hand, most of the new information in the management of TAK arises from the growing experience with biologic agents used in resistant cases. Besides, there are potential new therapeutic targets which may be promising in the future for medical treatment of TAK. Finally, new trends in endovascular interventions for management of TAK deserve attention.

The genetics of Takayasu arteritis

Takayasu arteritis (TAK) is a rare systemic vasculitis that is characterized by granulomatous inflammation of the aorta and its major branches. The cellular and biochemical processes involved in the pathogenesis of TAK are beginning to be elucidated, and implicate both cell and antibody-mediated autoimmune mechanisms. In addition, the underlying etiology to TAK may be explained, at least in part, by a complex genetic contribution. The most well-recognized genetic susceptibility locus for the disease is the classical HLA allele, HLA-B*52, which has been confirmed in several ethnicities. The genetic susceptibility with HLA-B*52, as well as additional classical alleles and loci, implicate both HLA class I and class II involvement in TAK. Furthermore, genetic associations with genes encoding immune response regulators, pro-inflammatory cytokines and mediators of humoral immunity may directly relate to disease mechanisms. Non-HLA susceptibility loci that have been recently established for TAK with a genome-wide level of significance include FCGR2A/FCGR3A, IL12B, IL6, RPS9/LILRB3, and a locus on chromosome 21 near PSMG1. In this review, we present the complex genetic predisposition to TAK and discuss how recent findings identified potential targets in the pathogenesis and treatment of the disease.

Endoscopic features and genetic background of inflammatory bowel disease complicated with Takayasu arteritis

BACKGROUND AND AIM

Takayasu arteritis (TA) is occasionally complicated with inflammatory bowel disease (IBD). This study assessed the endoscopic and genetic features of IBD complicated with TA (IBD-TA).

METHODS

This study retrospectively reviewed the clinical charts of 142 TA patients (14 men and 128 women; median age 48.5 years [range, 18-97 years]). Human lymphocyte antigen (HLA) types and a single-nucleotide polymorphism rs6871626 in the IL12B gene were assessed in 101 and 81 patients with TA, respectively.

RESULTS

Inflammatory bowel disease was diagnosed in 13 (9.2%) of the 142 patients. The endoscopic features of IBD-TA at initial diagnosis (n = 8) showed discontinuous and focal mucosal inflammations (n = 7, 87.5%), and only one case was diagnosed as ulcerative colitis (UC) at the first colonoscopy. In the genetic comparison of HLA class I between TA patients with IBD and those without IBD, HLA-B*52:01 and C*12:02 were more frequent in the IBD-TA group (P = 0.001 and P = 0.009, respectively). Meanwhile, HLA-DRB-1*15:02, DQA-1*01:03, DQB-1*06:01, and DPB-1*09:01 as HLA class II were positively associated with IBD-TA (P = 0.004, P = 0.019, P = 0.019, and P = 0.002, respectively). IL12B rs6871626 did not show an association with IBD-TA compared with that with TA without IBD.

CONCLUSIONS

The endoscopic findings of IBD-TA at initial diagnosis were atypical for UC or Crohn's disease. IBD-TA possessed the HLA haplotype, which had a susceptible effect on UC.

Interleukin-17F and interleukin-6 gene polymorphisms in Asian Indian patients with Takayasu arteritis

OBJECTIVES

To assess genetic association between single nucleotide polymorphisms (SNPs) in genes encoding T-helper cytokines and Takayasu Arteritis (TA) susceptibility in Asian Indian population.

METHODS

In Phase-1, the genomic DNA of 120 TA patients and 119 healthy controls were genotyped for SNPs rs1800795 (interleukin (IL)-6), rs763780 (IL-17F), rs1800871, rs1800872, rs1800896 (IL-10) and rs1800468, rs1800469, rs1800470 (transforming growth factor-β). Allele frequencies between cases and controls were compared using chi-squared test and also reassessed empirically (p_e) by 10,000 permutations. In Phase-2, additional 98 TA patients and 101 controls were genotyped for replicating the significant associations noted in Phase-1 of the study.

RESULTS

All 8 SNPs in Phase 1 were in Hardy-Weinberg proportions. The G allele at rs763780 (IL-17F) was significantly associated with TA (p=0.014). We also found that rs1800795 (IL-6) was associated with tuberculosis (p=0.001) under a dominant model. In Phase-2 replication part of the study, the rs763780 showed a trend towards association with TA (p=0.08), and the magnitude and direction of the odds ratio (OR) also were consistent with results of Phase-1. In the combined analysis, protective association of the G allele of rs763780 with TA was again significant [OR (95% CI)=0.44 (0.25-0.77); p=0.0029]. The G allele was also significantly associated (p<0.05) with underlying tuberculosis (TB) and occurrence of syncope in TA.

CONCLUSION

G allele of rs763780 in IL-17F gene was protectively associated against susceptibility to TA. GG genotypes of rs1800795 in IL-6 was also associated with occurrence of tuberculosis in our patients with TA.

Transethnic meta-analysis identifies GSDMA and PRDM1 as susceptibility genes to systemic sclerosis

OBJECTIVES

Systemic sclerosis (SSc) is an autoimmune disease characterised by skin and systemic fibrosis culminating in organ damage. Previous genetic studies including genome-wide association studies (GWAS) have identified 12 susceptibility loci satisfying genome-wide significance. Transethnic meta-analyses have successfully expanded the list of susceptibility genes and deepened biological insights for other autoimmune diseases.

METHODS

We performed transethnic meta-analysis of GWAS in the Japanese and European populations, followed by a two-staged replication study comprising a total of 4436 cases and 14 751 controls. Associations between significant single nuclear polymorphisms (SNPs) and neighbouring genes were evaluated. Enrichment analysis of H3K4Me3, a representative histone mark for active promoter was conducted with an expanded list of SSc susceptibility genes.

RESULTS

We identified two significant SNP in two loci, GSDMA and PRDM1, both of which are related to immune functions and associated with other autoimmune diseases (p=1.4×10^-10 and 6.6×10^-10, respectively). GSDMA also showed a significant association with limited cutaneous SSc. We also replicated the associations of previously reported loci including a non-GWAS locus, TNFAIP3. PRDM1 encodes BLIMP1, a transcription factor regulating T-cell proliferation and plasma cell differentiation. The top SNP in GSDMA was a missense variant and correlated with gene expression of neighbouring genes, and this could explain the association in this locus. We found different human leukocyte antigen (HLA) association patterns between the two populations. Enrichment analysis suggested the importance of CD4-naïve primary T cell.

CONCLUSIONS

GSDMA and PRDM1 are associated with SSc. These findings provide enhanced insight into the genetic and biological basis of SSc.

Analysis of the common genetic component of large-vessel vasculitides through a meta-Immunochip strategy

Giant cell arteritis (GCA) and Takayasu’s arteritis (TAK) are major forms of large-vessel vasculitis (LVV) that share clinical features. To evaluate their genetic similarities, we analysed Immunochip genotyping data from 1,434 LVV patients and 3,814 unaffected controls. Genetic pleiotropy was also estimated. The HLA region harboured the main disease-specific associations. GCA was mostly associated with class II genes (HLA-DRB1/HLA-DQA1) whereas TAK was mostly associated with class I genes (HLA-B/MICA). Both the statistical significance and effect size of the HLA signals were considerably reduced in the cross-disease meta-analysis in comparison with the analysis of GCA and TAK separately. Consequently, no significant genetic correlation between these two diseases was observed when HLA variants were tested. Outside the HLA region, only one polymorphism located nearby the IL12B gene surpassed the study-wide significance threshold in the meta-analysis of the discovery datasets (rs755374, P = 7.54E-07; OR_GCA = 1.19, OR_TAK = 1.50). This marker was confirmed as novel GCA risk factor using four additional cohorts (P_GCA = 5.52E-04, OR_GCA = 1.16). Taken together, our results provide evidence of strong genetic differences between GCA and TAK in the HLA. Outside this region, common susceptibility factors were suggested, especially within the IL12B locus.

Single nucleotide polymorphisms of IL12B are associated with Takayasu arteritis in Chinese Han population

Takayasu arteritis (TA) is a rare autoimmune disease of unknown etiology. Genome-wide association studies (GWAS) have demonstrated association between genetic variants of IL12B and IL6 and TA. Since TA has been reported with ethnic heterogeneity, we sought to investigate whether the single-nucleotide-polymorphisms (SNPs) reported in these studies are associated with TA in the Chinese Han population. A multi-center study involving 412 patients with TA and 597 healthy controls was conducted. Sequenom MassArray iPLEX platform was used to determine the frequencies of SNPs in the IL12B and IL6 region. We demonstrated a allele association between the four SNPs of IL12B and TA (rs6871626: OR 1.52, 95% CI 1.26-1.83; rs4921492: OR 1.46, 95% CI 1.21-1.75; rs60689680: OR 1.41, 95% CI 1.17-1.69; rs4921493: OR 1.45, 95% CI 1.21-1.75, all P _c  < 10^- 3 ). A meta-analysis consist of four populations showed rs6871626 was a susceptible locus of TA. Its OR was 1.51, and 95% CI was 1.31-1.74. The four SNPs were in strong linkage disequilibrium and two haplotypes were significantly different between patients and controls. Conditional analysis shows that these SNPs were not independent factors contributing to TA. Nevertheless, neither genotype nor allele frequencies of rs2069837 in IL6 showed significant between-group differences. Thus SNP of IL12B may be considered a high-risk factor for TA in Chinese Han population and provide further clues for research into the pathogenesis of TA.

Single Nucleotide Polymorphism rs10919543 in FCGR2A/FCGR3A Region Confers Susceptibility to Takayasu Arteritis in Chinese Population

Background:

Takayasu arteritis (TA) is a rare inflammatory arteriopathy of unknown etiology. The aim of this study was to investigate the genetic susceptibility to TA in a Chinese population.

Methods:

Four single nucleotide polymorphisms (SNPs) those locate in the IL12B region (rs56167332), the MLX region (rs665268), the FCGR2A/FCGR3A locus (rs10919543), and the HLA-B/MICA locus (rs12524487), associated with TA in different population, were genotyped in 123 Chinese TA patients and 147 healthy controls from January 2013 to August 2014. A Chi-square test was used to test for genotype/allele frequencies variants.

Results:

Among the four SNPs, rs10919543 was found to be significantly associated with TA in the studied population. The GG genotype of rs10919543 at the FCGR2A/FCGR3A locus is a high risk factor (odds ratio [OR] = 6.532, 95% confidence interval [CI] = 2.402 − 17.763, P < 0.001) for TA. Among TA patients, the level of eosinophil granulocytes (Eos) in the peripheral blood was observed to be higher in the GG group of rs10919543 (n = 23, Eos = 0.11 [0.08, 0.17] ×10⁹/L) than the GA + AA group (n = 100, Eos = 0.08 [0.05, 0.13] ×10⁹/L, P = 0.028). No correlation between the genotypes of the other three SNPs and TA patients was observed.

Conclusions:

Our findings revealed unique genetic pattern in Chinese TA patients that may be partly responsible for the higher risk of TA in this population. FCGR2A/FCGR3A-related immune disorder might contribute to the etiology of TA.

Genome-wide association analysis identifies variation in vitamin D receptor and other host factors influencing the gut microbiota

Human gut microbiota is an important determinant for health and disease, and recent studies emphasize the numerous factors shaping its diversity. Here we performed a genome-wide association study (GWAS) of the gut microbiota using two cohorts from northern Germany totaling 1,812 individuals. Comprehensively controlling for diet and non-genetic parameters, we identify genome-wide significant associations for overall microbial variation and individual taxa at multiple genetic loci, including the VDR gene (encoding vitamin D receptor). We observe significant shifts in the microbiota of Vdr^-/- mice relative to control mice and correlations between the microbiota and serum measurements of selected bile and fatty acids in humans, including known ligands and downstream metabolites of VDR. Genome-wide significant (P < 5 × 10^-8) associations at multiple additional loci identify other important points of host-microbe intersection, notably several disease susceptibility genes and sterol metabolism pathway components. Non-genetic and genetic factors each account for approximately 10% of the variation in gut microbiota, whereby individual effects are relatively small.

Updates in Pathophysiology, Diagnosis and Management of Takayasu Arteritis

BACKGROUND

Takayasu arteritis (TA) is a rare, systemic, inflammatory vasculitis of granulomatous nature, and still of unknown etiology. It mainly involves the aorta and its major branches and is more commonly seen in women of childbearing age and Asians. TA leads to stenosis, occlusion, or aneurysmal degeneration of large arteries, and its pathogenesis seems to be mainly due to an abnormal cell-mediated immunity, although other molecular and genetic abnormalities may contribute. The diagnosis and treatments lie on clinical and arteriographic findings. Because of its fluctuating course, both clinical scores and biomarkers are currently evaluated. The aim of this review is to report a comprehensive and methodologically robust state of the art about Takayasu arteritis, including the latest data and evidences in the definition, epidemiology, pathogenesis and etiology, clinical manifestations and classification, diagnosis, assessment of disease activity and progression, biomarkers, and treatment.

METHODS

We searched all publications addressing definition, epidemiology, pathogenesis, etiology, classification, diagnosis, biomarkers, and treatment of TA. Randomized trials, cohort studies, and reviews were contemplated to give a breadth of clinical data. PubMed and Scopus were searched from August 2010 to November 2015.

RESULTS

Of the 3,056 records found, 267 matched our inclusion criteria. After reading the full-text articles, we decided to exclude 169 articles because of the following reasons: (1) no innovative or important content; (2) no multivariable analysis; (3) insufficient data; (4) no clear potential biases or strategies to solve them; (5) no clear end-points; and (6) inconsistent or arbitrary conclusions. The final set included 98 articles.

CONCLUSIONS

This review presents the last updates in all fields of Takayasu arteritis. Still today, large areas of TA pathogenesis and disease-activity assessment need to be further investigated to better treat patients with TA.

Lack of association between polymorphisms in interleukin (IL)-12, IL-12R, IL-23, IL-23R genes and Takayasu arteritis in a Chinese population

OBJECTIVE

The goal of this study was to investigate the relationship between polymorphisms in interleukin (IL)-12, IL-12R, IL-23, and IL-23R genes and Takayasu arteritis (TA) in a Chinese population.

METHODS

A case-control study was performed to investigate the associations of 19 single nucleotide polymorphisms (SNPs) mapping to IL12A, IL12B, IL12RB1, IL12RB2 and IL23R with susceptibility to TA in 145 Chinese TA patients and 300 healthy controls. Genotype identification was performed with the MassARRAY system from Sequenom. The statistical analysis was conducted by Chi square test and unconditional logistic regression with plink.

RESULTS

No significant differences were found for the distribution of allele and genotype frequencies of these SNPs between TA patients and healthy controls. However, a trend for IL12A rs582054 and IL23R rs1004819 in association with the TA phenotype was detected. TA patients carrying the rs582054/rs568408 haplotype (P' = 0.019) appeared less likely to progress to a more severe form of disease. And the C allele (P' = 0.082) of IL23R rs1004819 appeared to be a protective factor to refractory disease.

CONCLUSIONS

These findings suggest that the polymorphisms of IL12A, IL12B, IL12RB1, IL12RB2 and IL23R might make no contribution to the susceptibility of TA in the Chinese population.

Epigenomic functional characterization of genetic susceptibility variants in systemic vasculitis

Systemic vasculitides are poorly understood inflammatory diseases of the blood vessels that are frequently associated with significant organ damage. Genetic risk variants contribute to the susceptibility of vasculitis, but functional consequences of these genetic variants are largely unknown. Most genetic risk variants in immune-mediated diseases, including systemic vasculitis, are localized to non-coding genetic regions suggesting they might increase disease risk by influencing regulatory elements within the genome. Long range regulatory interactions pose an additional obstacle in localizing functional consequences associated with risk variants to specific genes or cell types. We used cell-type specific enrichment patterns of histone changes that mark poised, primed, and active enhancers, and DNase hypersensitivity to identify specific immune cells mediating genetic risk in vasculitis. Our data suggest that genetic risk variants in ANCA-associated vasculitis are significantly enriched in enhancer elements in Th17 cells, supporting a role for Th17 cells in this disease. Primed and active enhancer elements in B cells can be potentially affected by genetic risk variants associated with Kawasaki disease. Genetic risk in Behçet's disease and Takayasu arteritis might affect enhancer elements in multiple cell types, possibly explained by influencing enhancers in hematopoietic stem cells. Interestingly, our analyses indicate a role for B cells in Kawasaki disease, Behçet's disease, and Takayasu arteritis, and suggest that further work to characterize the involvement of B cells in these diseases is warranted.