Role of rs1343151 IL23R and rs3790567 IL12RB2 Polymorphisms in Biopsy-proven Giant Cell Arteritis

Genetics of vasculitis

Systemic vasculitis encompasses a wide range of conditions characterized by varying degrees of inflammation in blood vessels. Although the etiology of vasculitis remains unclear, accumulated data suggest that it is triggered in genetically predisposed individuals by the concurrence of certain environmental factors. The importance of the genetic component has been consistently supported by evidence of familial aggregation, differential prevalence by ethnicity, and multiple genetic associations with disease susceptibility and severity reported in recent years. The strongest association signals in most vasculitides correspond to genetic variants within the HLA region, suggesting an important role of the immune system in its pathophysiology. However, each type of vasculitis has distinct defining HLA association markers, likely due to disease-specific differences in antigenic drivers. Furthermore, other genetic polymorphisms located outside the HLA region play an important role in susceptibility to different vasculitides. More recent research has assessed the shared genetic susceptibility evident across different vasculitides. Future studies should focus on the identification of genetic markers that can serve as reliable biomarkers for early diagnosis, prognosis, and treatment response in systemic vasculitis.

Current Insights into Tissue Injury of Giant Cell Arteritis: From Acute Inflammatory Responses towards Inappropriate Tissue Remodeling

Giant cell arteritis (GCA) is an autoimmune disease affecting large vessels in patients over 50 years old. It is an exemplary model of a classic inflammatory disorder with IL-6 playing the leading role. The main comorbidities that may appear acutely or chronically are vascular occlusion leading to blindness and thoracic aorta aneurysm formation, respectively. The tissue inflammatory bulk is expressed as acute or chronic delayed-type hypersensitivity reactions, the latter being apparent by giant cell formation. The activated monocytes/macrophages are associated with pronounced Th1 and Th17 responses. B-cells and neutrophils also participate in the inflammatory lesion. However, the exact order of appearance and mechanistic interactions between cells are hindered by the lack of cellular and molecular information from early disease stages and accurate experimental models. Recently, senescent cells and neutrophil extracellular traps have been described in tissue lesions. These structures can remain in tissues for a prolonged period, potentially favoring inflammatory responses and tissue remodeling. In this review, current advances in GCA pathogenesis are discussed in different inflammatory phases. Through the description of these-often overlapping-phases, cells, molecules, and small lipid mediators with pathogenetic potential are described.

New insights into the pathogenesis of giant cell arteritis: are they relevant for precision medicine?

Giant cell arteritis is a primary granulomatous vasculitis characterised by a strict tissue tropism for large and medium-size vessels, occurring in people older than 50 years. Although considerable progress in understanding some of the pathophysiological mechanisms involved in the pathogenesis of giant cell arteritis has been made in the past 10 years, specific triggers of disease and mechanisms of chronic damage have not yet been identified. The definition of a specific pro-inflammatory hierarchy between the multiple cell types and the different cytokines or chemokines involved in the inflammatory process are still unexplored areas of study. The overall goal of precision medicine is to identify the best possible therapeutic approach for an individual or group of individuals with a given disease. The fundamental prerequisite of this approach is the identification, at baseline, of clinical and imaging findings and of molecular biomarkers that allow a precise stratification of patients and an adequate prediction of the therapeutic response. In this regard, the possibility of obtaining temporal artery biopsies for diagnostic purposes offers incredible exploratory possibilities to define different disease pathotypes potentially susceptible to different therapeutic interventions. In this Series paper, we will describe the most recent evidence relating to the pathogenesis of giant cell arteritis, trying to define, if possible, a new pathogenetic-centred approach to patients with giant cell arteritis.

Genetic Predispositions of Glucocorticoid Resistance and Therapeutic Outcomes in Polymyalgia Rheumatica and Giant Cell Arteritis

Polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) are closely related chronic inflammatory diseases. Glucocorticoids (GCs) are first-choice drugs for PMR and GCA, although some patients show poor responsiveness to the initial GC regimen or experience flares after GC tapering. To date, no valid biomarkers have been found to predict which patients are at most risk for developing GC resistance. In this review, we summarize PMR- and GCA-related gene polymorphisms and we associate these gene variants with GC resistance and therapeutic outcomes. A limited number of GC resistance associated-polymorphisms have been published so far, mostly related to HLA-DRB1*04 allele. Other genes such ICAM-1, TLR4 and 9, VEGF, and INFG may play a role, although discrepancies are often found among different populations. We conclude that more studies are required to identify reliable biomarkers of GC resistance. Such biomarkers could help distinguish non-responders from responders to GC treatment, with concomitant consequences for therapeutic strategy.

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.

Autoimmune risk loci of IL12RB2, IKZF1, XKR6, TMEM39A and CSK in Chinese patients with systemic lupus erythematosus

Recent genome-wide or follow-up studies conducted in European or Caucasian populations have identified single nucleotide polymorphisms (SNPs) conferring increased risk to autoimmune diseases. It is unclear whether these observations can apply to systemic lupus erythematosus (SLE) in China. An association study was performed on 395 SLE patients and 378 healthy controls recruited from the Chinese population, in which the IL12RB2 rs3790567, IKZF1 rs2366293, XKR6 rs4240671, TMEM39A rs1132200 and CSK rs34933034 polymorphisms were examined by Matrix Assisted Laser Desorption Time of Flight Mass Spectrometry. The frequency of the A allele of IL12RB2 rs3790567 was lower in the cases compared with the controls (24.8% vs 30.2%, P = 0.018) and significant difference among the AA, AG and GG genotypes of rs3790567 was detected between the SLE patients and healthy controls (P = 0.020). We also found a statistically significant difference in the dominant model (GG+AG vs AA, P = 0.008). There was no correlation between the genotypes and specific sub-phenotypes in the current cohort. Associations with IKZF1 rs2366293, XKR6 rs4240671, TMEM39A rs1132200 and CSK rs34933034 were also lacking (P > 0.05). The results supported the theory that IL12RB2 is associated with SLE in the Chinese population.

Functional analysis of differences in transcriptional activity conferred by genetic variants in the 5' flanking region of the IL12RB2 gene

Interleukin 12 receptor β chain (IL12RB2) is a crucial regulatory factor involved in cell-mediated immune responses, and genetic variants of the gene encoding IL12RB2 are associated with susceptibility to various immune-related diseases. We previously demonstrated that haplotypes with single nucleotide polymorphisms (SNPs) in the 5' flanking region of IL12RB2, including -1035A>G (rs3762315) and -1023A>G (rs3762316), affect the expression of IL12RB2, thereby altering susceptibility to leprosy and periodontal diseases. In the present study, we identified transcription factors associated with the haplotype-specific transcriptional activity of IL12RB2 in T cells and NK cells. The -1023G polymorphism was found to create a consensus binding site for the transcription factor activating protein (AP)-1, and enzyme-linked immunosorbent assay (ELISA)-based binding assays showed that these SNPs enhanced AP-1 binding to this region. In reporter assays, suppression of JunB expression using siRNA eliminated differences in the -1035G/-1023G and -1035A/-1023A regions containing IL12RB2 promoter activity in Jurkat T cells and NK3.3 cells. These results suggested that the -1035/-1023 polymorphisms created differential binding affinities for JunB that could lead to differential IL12RB2 expression. Moreover, the -1035G and -1035A alleles formed binding sites for GATA-3 and myocyte enhancer factor-2 (MEF-2), respectively. Our data indicated that in addition to JunB, the SNP at -1035/-1023 influenced GATA-3 and MEF-2 binding affinity, potentially altering IL12RB2 transcriptional activity. These findings confirm the effects of rs3762315 and rs3762316 on IL12RB2 transcription. These genetic variants may alter cellular activation of T cells and NK cells and modify cell-mediated immune responses.

Differential expression and function of human IL-12Rβ2 polymorphic variants

The receptor for interleukin-12, formed by IL-12Rβ1 and IL-12Rβ2, mediates the type I immune responses of various types of lymphocytes. Polymorphisms in IL12RB2, the gene encoding IL-12Rβ2, were reported to be associated with several immune related diseases, such as Crohn's disease. Because the IL23R and IL12RB2 genes are located in close proximity on the genome, the reported associations might also be attributable to linked polymorphisms in IL23R, which were found to be associated with immune related diseases as well. To clarify the role of IL-12Rβ2 in immune diseases, we investigated the functional consequences of thirteen amino acid substitutions in IL-12Rβ2. We developed a model with retroviral expression of IL-12Rβ2 in B cell lines. With the use of this model the expression and function of the variants was compared within the same genetic background. Four of the IL-12Rβ2 variants, N271Y, R313G, A604V and L808R showed reduced IL-12 responses compared to the wild type variant. Two of these are relatively common in some populations and may be used in future association studies to reveal a role for IL-12 in infectious and/or immune related diseases.

A patient and physician survey of fibromyalgia across Latin America and Europe

Background

Patients and physicians from three Latin American (LA) and six European countries were surveyed in order to describe differences in journey to diagnosis, impact, and management of fibromyalgia (FM).

Methods

900 patients (300 LA; 600 Europe) and 1824 physicians (604 LA; 1220 Europe) were surveyed between October-December 2010 (LA) and February-April 2008 (Europe). Patients and physicians (GP or specialists) completed separate questionnaires, on symptoms, impact, and FM management. Interviews were conducted in local languages. Appropriate rating scales were used throughout. Data were analyzed using cross-tabulations and descriptive statistics. Significance was determined at P < 0.05 (indicated by *).

Results

In LA versus Europe, patients reported having FM symptoms for longer (100.8 vs. 83.7* months), and taking longer to be diagnosed (42.3 vs. 31.1* months). FM was characterized by multiple symptoms (11.2 vs. 6.9), but more LA patients reported 14 common symptoms*, and rated pain higher on 11-point scale (8.0 vs. 7.2*). LA patients were taking fewer medications (3.3 vs. 4.0). Patients from both regions found common symptoms very/extremely disruptive to their quality of life, but symptoms impacted daily living and ability to work more significantly in LA. Physicians (GPs or specialists) from LA more often considered problems sleeping*, difficulty concentrating*, anxiety*, depression*, numbness/tingling*, and leg cramps* very/extremely disruptive vs. European physicians. Despite headache, heightened sensitivity to touch, difficulty concentrating, and joint pain being experienced by ≥50% of patients from both regions, <15% of PCPs or specialists considered these typical FM symptoms. Patients also considered 12/14 symptoms more disruptive than PCPs or specialists in the same region. However, a higher proportion of PCPs or specialists considered FM to have a strong/very strong impact on aspects of daily living vs. patients within the same region.

Conclusions

Patient- and physician-rated disease perception and impact was often higher in LA than in Europe. Patient and physician perspective concerning FM impact and disruption were often misaligned within the same region. Our observations may be representative of cultural differences in stoicism, expression, beliefs, and attitudes to pain perception and management. Better understanding of these complexities could help targeted educational/training programs incorporating cultural differences, to improve chronic care.

Impact of cytokine and cytokine receptor gene polymorphisms on cellular immunity after smallpox vaccination

We explored associations between SNPs in cytokine/cytokine receptor genes and cellular immunity in subjects following primary smallpox vaccination. We also analyzed the genotype-phenotype associations discovered in the Caucasian subjects among a cohort of African-Americans. In Caucasians we found 277 associations (p<0.05) between gene SNPs and inter-individual variations in IFN-α, IL-12p40, IL-1β, IL-2, and TNF-α secretion levels. A collection of SNPs in the IL1RN, IL2RB, IL4R, IL6, IL10RB, IL12A, and IL12RB2 genes had consistent associations among both Caucasians and African-Americans. A regulatory SNP (rs452204) in the IL1RN gene was significantly associated with higher levels of IL-2 secretion in an allele dose-dependent manner in both race groups (p=0.05 for Caucasians and p=0.002 for African-Americans). IL12RB2 polymorphism rs3790567 was associated with a dose-related decrease in IL-1β secretion (p=0.009 for Caucasians and p=0.01 for African-Americans). Our results demonstrate that variations in smallpox vaccine-induced cytokine responses are modulated by genetic polymorphisms in cytokine and cytokine receptor genes.

A GWAS follow-up study reveals the association of the IL12RB2 gene with systemic sclerosis in Caucasian populations

A single-nucleotide polymorphism (SNP) at the IL12RB2 locus showed a suggestive association signal in a previously published genome-wide association study (GWAS) in systemic sclerosis (SSc). Aiming to reveal the possible implication of the IL12RB2 gene in SSc, we conducted a follow-up study of this locus in different Caucasian cohorts. We analyzed 10 GWAS-genotyped SNPs in the IL12RB2 region (2309 SSc patients and 5161 controls). We then selected three SNPs (rs3790567, rs3790566 and rs924080) based on their significance level in the GWAS, for follow-up in an independent European cohort comprising 3344 SSc and 3848 controls. The most-associated SNP (rs3790567) was further tested in an independent cohort comprising 597 SSc patients and 1139 controls from the USA. After conditional logistic regression analysis of the GWAS data, we selected rs3790567 [P(MH)= 1.92 × 10(-5) odds ratio (OR) = 1.19] as the genetic variant with the firmest independent association observed in the analyzed GWAS peak of association. After the first follow-up phase, only the association of rs3790567 was consistent (P(MH)= 4.84 × 10(-3) OR = 1.12). The second follow-up phase confirmed this finding (P(χ2) = 2.82 × 10(-4) OR = 1.34). After performing overall pooled-analysis of all the cohorts included in the present study, the association found for the rs3790567 SNP in the IL12RB2 gene region reached GWAS-level significant association (P(MH)= 2.82 × 10(-9) OR = 1.17). Our data clearly support the IL12RB2 genetic association with SSc, and suggest a relevant role of the interleukin 12 signaling pathway in SSc pathogenesis.