Recent progress in rheumatoid arthritis genetics: one step towards improved patient care

At Early Rheumatoid Arthritis Stage, the Infectious Spectrum Is Driven by Non-Familial Factors and Anti-CCP Immunization

Background/Objectives: Patients with rheumatoid arthritis (RA) are prone to develop infections. Methods: Accordingly, 195 untreated early (e)RA patients and 398 healthy controls were selected from women in Tatarstan's cohort to study infectious history in the anamnesis (four criteria) and in the previous year (16 criteria). Information about annual infections was collected face-to-face from year to year by a qualified rheumatologist/general practitioner and included the active use of information from medical records. Results: In the anamnesis, tuberculosis, and pneumonia, and in the previous year, respiratory tract infections, skin infections, and herpes simplex virus reactivation incidence were reported to be increased in eRA patients, as well as the event number and duration of acute and chronic tonsillitis. Moreover, more bacterial-suspected upper respiratory infections and urinary tract infections were retrieved in sporadic eRA patients as compared to familial eRA patients. An elevated immunization against CCP prevented respiratory tract infection in those with HSV exacerbation. Finally, associations were retrieved between infection (event number/delay) and RA indices: (i) chronic tonsillitis exacerbations with disease activity and health assessment (HAQ) in familial eRA; (ii) bacterial-suspected upper respiratory infections with the number of swollen and tender joints in sporadic eRA; and (iii) HSV exacerbation with inflammation in eRA patients with negative/low response against CCP. Here, we demonstrate the complex nature of the interplay of RA with specific infections. Conclusions: For the first time, differences in the patterns of annual trivial infections and their links with RA indices were found in cohorts of familial and sporadic cases of the disease. Additionally, for the first time, we identified a remarkable relationship between early RA and exacerbations of chronic tonsillitis, as well as tuberculosis in the patient's history. Altogether, this study supports the existence of a complex interplay between infections and RA at onset driven by familial status and the presence of anti-CCP Ab at elevated levels.

Single Nucleotide Polymorphisms Associated with Rheumatoid Arthritis in Saudi Patients

Rheumatoid arthritis (RA) is a complex, multifactorial disorder with an autoimmune etiology. RA is highly heritable and is associated with both human leucocyte antigen (HLA) and non-HLA genes. We investigated the associations of 33 single nucleotide polymorphisms (SNPs) with RA in the Saudi population.

METHODS

This study included 105 patients with RA and an equal number of age- and sex-matched controls. The patients with RA attended outpatient clinics at King Khalid University Hospital in Riyadh, Saudi Arabia. Blood samples were collected, and DNA was extracted using Qiagen kits. Primers were designed for the 33 selected SNPs using the MassEXTEND primers program, and samples were genotyped on the Sequenom MassARRAY iPLEX platform. The allele frequencies and genotypes were determined for each SNP, and the results obtained for the patients were compared to those for the controls.

RESULTS

The allele and genotype frequencies of six SNPs were significantly associated with RA: rs1188934, rs10919563, rs3087243, rs1980422, rs10499194, and rs629326. The minor alleles of rs1188934, rs10919563, rs10499194, and rs629326 were protective, with odds ratios of 0.542, 0.597, 0.589, and 0.625, and p-values of 0.002, 0.023, 0.013 and 0.036, respectively. In addition, the heterozygote frequencies of two SNPs (rs6859219 and rs11586238) were significantly higher in the controls than in the patients.

CONCLUSIONS

There is considerable heterogeneity in the genetics of RA in different populations, and the SNPs that are associated with RA in some populations are not in others. We studied 33 SNPs and only eight were associated with RA. The remaining SNPs showed no allelic or genotypic associations with RA.

Current research status of HLA in immune-related diseases

Human leukocyte antigen (HLA), also known as human major histocompatibility complex (MHC), is encoded by the HLA gene complex, and is currently known to have the highest gene density and the most polymorphisms among human chromosomal areas. HLA is divided into class I antigens, class II antigens, and class III antigens according to distribution and function. Classical HLA class I antigens include HLA-A, HLA-B, and HLA-C; HLA class II antigens include HLA-DP, HLA-DQ, and HLA-DR; nonclassical HLA class I and II molecules include HLA-F, E, H, X, DN, DO, and DM; and others, such as complement, are class III antigens. HLA is closely related to the body's immune response, regulation, and surveillance and is of great significance in the study of autoimmune diseases, tumor immunity, organ transplantation, and reproductive immunity. HLA is an important research topic that bridges immunology and clinical diseases. With the development of research methods and technologies, there will be more discoveries and broader prospects.

UBASH3A gene polymorphisms and expression profile in rheumatoid arthritis

OBJECTIVES

Recent evidence has demonstrated that UBASH3A play a pivotal role in multiple autoimmune diseases. In this study, we explored the association between UBASH3A gene single-nucleotide polymorphisms (SNPs) and rheumatoid arthritis (RA) in a Chinese Han population. We also comparatively evaluated the UBASH3A expression profile in peripheral blood mononuclear cells (PBMCs) from patients with RA and healthy controls.

METHODS

Four UBASH3A polymorphisms (rs1893592, rs11203203, rs2277798, and rs3788013) were studied in 553 patients with RA and 587 controls in a Chinese population. Genotyping was performed using the Fluidigm 192.24 Dynamic Array Integrated Fluidic Circuit (IFC). For gene expression study, UBASH3A mRNA levels of 30 RA patients and 31 healthy individuals were assessed by real-time quantitative polymerase chain reaction (RT-qPCR). Data were analyzed by SPSS 19.0 software.

RESULTS

A significant association between rs1893592 polymorphism and RA was found under all genetic models (all p<.05). We also discovered a significant association between rs3788013 polymorphism and RA in the allele and genotype distributions, as well as the recessive model (all p<.05). Moreover, we found the genotype distribution and allele frequency of rs1893592 were significantly associated with RF phenotype in the RA patients (χ² = 6.786, p=.034; χ² = 4.534, p=.033; respectively). We also found the genotype distribution and allele frequency of rs2277798 were significantly associated with anti-CCP phenotype in the RA patients (χ² = 7.873, p=.020; χ² = 4.473, p=.034; respectively). However, we did not detect any significant associations between rs11203203 and RA susceptibility and autoantibody profiles (all p>.05). The mRNA expression of UBASH3A was increased in PBMCs of patients with RA when compared to healthy controls (p=.001).

CONCLUSIONS

Our observations suggested that the dysregulation of UBASH3A might be associated with the pathogenesis of RA, and UBASH3A gene polymorphisms (rs1893592 and rs3788013) might contribute to RA susceptibility in Chinese Han population.

Human Leukocyte Antigen-Disease Associations in Rheumatoid Arthritis

The cause and pathogenesis of rheumatoid arthritis (RA) are influenced by environmental and genetic risk factors. Shared epitope-coding human leukocyte antigen (HLA)-DRB1 alleles increase RA risk and severity; however, the underlying mechanisms of action remain unclear. In contrast, several other DRB1 alleles protect against RA. Additionally, genome-wide association studies suggest that RA associates with other, HLA and non-HLA, genes; but the relative contributions of such risk loci to RA are incompletely understood. Future research challenges include integrating the epidemiologic and genomic data into validated arthritogenic pathways and determining the mechanisms of interaction between RA risk genes and environmental influences.

Association of MICA-129 polymorphism and circulating soluble MICA level with rheumatoid arthritis in a south Indian Tamil population

INTRODUCTION

Rheumatoid arthritis (RA) is a clinically heterogeneous chronic inflammatory disorder characterized by synovitis leading to joint destruction. Both genetic and environmental factors are involved in the pathogenesis of RA. Significant dysregulation of NKG2D, an activating receptor of natural killer and certain autoreactive T cells as well as its ligand major histocompatibility complex class I chain-related gene A (MICA) has been implicated in perpetuating the pathology of RA. Since the genetic polymorphism in MICA gene (MICA-129 met/val polymorphism at codon 129) is known to affect its binding affinity to NKG2D, we explored its influence on RA susceptibility and disease severity.

METHODS

The MICA-129 met/val polymorphism was examined in 270 patients with RA and 232 healthy controls by TaqMan 5'-nuclease assay. Serum soluble MICA (sMICA) was measured in a subset of 89 patients and 80 controls by enzyme-linked immunosorbent assay.

RESULTS

We observed that the frequency of MICA-129 val allele (73% vs. 65%, Pc = 0.006, odds ratio = 1.48, 95% CI = 1.12-1.95) was higher in patients than in controls. sMICA levels were significantly higher in patients with RA than in controls (P < 0.0001). sMICA levels were higher in patients with val/val genotype than in those with met/val or met/met genotype (P = 0.03). The MICA-129 val/val genotype was associated with high titers of sMICA in patients with deforming RA phenotype (P = 0.02), suggesting a role in determination of severity of RA.

CONCLUSION

MICA-129 val/val genotype, associated with higher levels of circulating sMICA, may influence disease susceptibility and associate with increased severity of RA in south Indian Tamils.

NLRP1, PTPN22 and PADI4 gene polymorphisms and rheumatoid arthritis in ACPA-positive Singaporean Chinese

Studies have shown that the genetic risk factors for rheumatoid arthritis (RA) differ substantially between Asian and Caucasian populations. Even among Asian populations, the genetic contributions of NLRP1, PTPN22 and PADI4 have been controversial. Consequently, we sought to address these separate findings and determine whether any of these proposed risk variants are associated with RA susceptibility, onset, DAS activity and erosion in a Singaporean Chinese cohort. We genotyped five SNPs within NLRP1 (rs878329 and rs6502867), PTPN22 (rs2488457 and rs6665194), and PADI4 (rs2240340) in 500 anti-cyclic citrullinated peptide antibody-positive (ACPA) patients with RA and 500 healthy controls using TaqMan assays. The CC genotype of NLRP1 rs878329 and TT genotype of PADI4 rs2240340 were associated with RA susceptibility. The risk association of the T allele of PADI4 rs2240340 with RA was confirmed through a meta-analysis based on previous reports in Asian populations. The GG genotype of PTPN22 rs6665194 (-3508A>G) was associated with significantly reduced risk of RA. No significant association was found for NLRP1 rs6502867 T/C and PTPN22 rs2488457 G/C polymorphisms. None of the five SNPs was associated with RA's clinical features. This work supports the association of the T allele of PADI4 rs2240340 with RA in Asians. The roles of NLRP1 rs878329 G/C and PTPN22 rs6665194 A/G polymorphisms were demonstrated for the first time. We also propose rs6665194 to be a promising candidate for RA risk evaluation between ethnicities.

How Rheumatoid Arthritis Can Result from Provocation of the Immune System by Microorganisms and Viruses

The pathogenesis of rheumatoid arthritis (RA), similar to development of a majority of inflammatory and autoimmune disorders, is largely due to an inappropriate or inadequate immune response to environmental challenges. Among these challenges, infectious agents are the undisputed leaders. Since the 1870s, an impressive list of microorganisms suspected of provoking RA has formed, and the list is still growing. Although a definite causative link between a specific infectious agent and the disease has not been established, several arguments support such a possibility. First, in the absence of a defined pathogen, the spectrum of triggering agents may include polymicrobial communities or the cumulative effect of several bacterial/viral factors. Second, the range of infectious episodes (i.e., clinical manifestations caused by pathogens) may vary in the process of RA development from preclinical to late-stage disease. Third, infectious agents might not trigger RA in all cases, but trigger it in a certain subset of the cases, or the disease onset may arise from an unfortunate combination of infections along with, for example, psychological stress and/or chronic joint tissue microtrauma. Fourth, genetic differences may have a role in the disease onset. In this review, two aspects of the problem of “microorganisms and RA” are debated. First, is there an acquired immune deficiency and, in turn, susceptibility to infections in RA patients due to the too frequent and too lengthy infections, which at last break the tolerance of self antigens? Or, second, is there a congenital deficiency in tolerance and inflammation control, which may occur even with ordinary infection frequency and duration?

A Combination of CD28 (rs1980422) and IRF5 (rs10488631) Polymorphisms Is Associated with Seropositivity in Rheumatoid Arthritis: A Case Control Study

Introduction

The aim of the study was to analyse genetic architecture of RA by utilizing multiparametric statistical methods such as linear discriminant analysis (LDA) and redundancy analysis (RDA).

Methods

A total of 1393 volunteers, 499 patients with RA and 894 healthy controls were included in the study. The presence of shared epitope (SE) in HLA-DRB1 and 11 SNPs (PTPN22 C/T (rs2476601), STAT4 G/T (rs7574865), CTLA4 A/G (rs3087243), TRAF1/C5 A/G (rs3761847), IRF5 T/C (rs10488631), TNFAIP3 C/T (rs5029937), AFF3 A/T (rs11676922), PADI4 C/T (rs2240340), CD28 T/C (rs1980422), CSK G/A (rs34933034) and FCGR3A A/C (rs396991), rheumatoid factor (RF), anti–citrullinated protein antibodies (ACPA) and clinical status was analysed using the LDA and RDA.

Results

HLA-DRB1, PTPN22, STAT4, IRF5 and PADI4 significantly discriminated between RA patients and healthy controls in LDA. The correlation between RA diagnosis and the explanatory variables in the model was 0.328 (Trace = 0.107; F = 13.715; P = 0.0002). The risk variants of IRF5 and CD28 genes were found to be common determinants for seropositivity in RDA, while positivity of RF alone was associated with the CTLA4 risk variant in heterozygous form. The correlation between serologic status and genetic determinants on the 1st ordinal axis was 0.468, and 0.145 on the 2nd one (Trace = 0.179; F = 6.135; P = 0.001). The risk alleles in AFF3 gene together with the presence of ACPA were associated with higher clinical severity of RA.

Conclusions

The association among multiple risk variants related to T cell receptor signalling with seropositivity may play an important role in distinct clinical phenotypes of RA. Our study demonstrates that multiparametric analyses represent a powerful tool for investigation of mutual relationships of potential risk factors in complex diseases such as RA.

Identification of a genetic variant for joint damage progression in autoantibody-positive rheumatoid arthritis

BACKGROUND

Joint destruction is a hallmark of autoantibody-positive rheumatoid arthritis (RA), though the severity is highly variable between patients. The processes underlying these interindividual differences are incompletely understood.

METHODS

We performed a genome-wide association study on the radiological progression rate in 384 autoantibody-positive patients with RA. In stage-II 1557 X-rays of 301 Dutch autoantibody-positive patients with RA were studied and in stage-III 861 X-rays of 742 North American autoantibody-positive patients with RA. Sperm-Associated Antigen 16 (SPAG16) expression in RA synovium and fibroblast-like synoviocytes (FLS) was examined using Real-Time Quantitative Polymerase Chain Reaction (RT-qPCR) and immunohistochemistry. FLS secrete metalloproteinases that degrade cartilage and bone. SPAG16 genotypes were related to matrix metalloproteinase (MMP)-3 and MMP-1 expression by FLS in vitro and MMP-3 production ex vivo.

RESULTS

A cluster of single nucleotide polymorphisms (SNPs) at 2q34, located at SPAG16, associated with the radiological progression rate; rs7607479 reached genome-wide significance. A protective role of rs7607479 was replicated in European and North American patients with RA. Per minor allele, patients had a 0.78-fold (95% CI 0.67 to 0.91) progression rate over 7 years. mRNA and protein expression of SPAG16 in RA synovium and FLS was verified. FLS carrying the minor allele secreted less MMP-3 (p=1.60×10(-2)). Furthermore, patients with RA carrying the minor allele had lower serum levels of MMP-3 (p=4.28×10(-2)). In a multivariate analysis on rs7607479 and MMP-3, only MMP-3 associated with progression (p=2.77×10(-4)), suggesting that the association between SPAG16-rs7607479 and joint damage is mediated via an effect on MMP-3 secretion.

CONCLUSIONS

Genetic and functional analyses indicate that SPAG16 influences MMP-3 regulation and protects against joint destruction in autoantibody-positive RA. These findings could enhance risk stratification in autoantibody-positive RA.

Predicting the risk of rheumatoid arthritis and its age of onset through modelling genetic risk variants with smoking

The improved characterisation of risk factors for rheumatoid arthritis (RA) suggests they could be combined to identify individuals at increased disease risks in whom preventive strategies may be evaluated. We aimed to develop an RA prediction model capable of generating clinically relevant predictive data and to determine if it better predicted younger onset RA (YORA). Our novel modelling approach combined odds ratios for 15 four-digit/10 two-digit HLA-DRB1 alleles, 31 single nucleotide polymorphisms (SNPs) and ever-smoking status in males to determine risk using computer simulation and confidence interval based risk categorisation. Only males were evaluated in our models incorporating smoking as ever-smoking is a significant risk factor for RA in men but not women. We developed multiple models to evaluate each risk factor's impact on prediction. Each model's ability to discriminate anti-citrullinated protein antibody (ACPA)-positive RA from controls was evaluated in two cohorts: Wellcome Trust Case Control Consortium (WTCCC: 1,516 cases; 1,647 controls); UK RA Genetics Group Consortium (UKRAGG: 2,623 cases; 1,500 controls). HLA and smoking provided strongest prediction with good discrimination evidenced by an HLA-smoking model area under the curve (AUC) value of 0.813 in both WTCCC and UKRAGG. SNPs provided minimal prediction (AUC 0.660 WTCCC/0.617 UKRAGG). Whilst high individual risks were identified, with some cases having estimated lifetime risks of 86%, only a minority overall had substantially increased odds for RA. High risks from the HLA model were associated with YORA (P<0.0001); ever-smoking associated with older onset disease. This latter finding suggests smoking's impact on RA risk manifests later in life. Our modelling demonstrates that combining risk factors provides clinically informative RA prediction; additionally HLA and smoking status can be used to predict the risk of younger and older onset RA, respectively.

Rheumatoid arthritis (RA) is a common, incurable disease with major individual and health service costs. Preventing its development is therefore an important goal. Being able to predict who will develop RA would allow researchers to look at ways to prevent it. Many factors have been found that increase someone's risk of RA. These are divided into genetic and environmental (such as smoking) factors. The risk of RA associated with each factor has previously been reported. Here, we demonstrate a method that combines these risk factors in a process called “prediction modelling” to estimate someone's lifetime risk of RA. We show that firstly, our prediction models can identify people with very high-risks of RA and secondly, they can be used to identify people at risk of developing RA at a younger age. Although these findings are an important first step towards preventing RA, as only a minority of people tested had substantially increased disease risks our models could not be used to screen the general population. Instead they need testing in people already at risk of RA such as relatives of affected patients. In this context they could identify enough numbers of high-risk people to allow preventive methods to be evaluated.

Association of rheumatoid arthritis risk alleles with response to anti-TNF biologics: results from the CORRONA registry and meta-analysis

In this study, we investigated whether genetic variants known to be related with susceptibility to rheumatoid arthritis (RA) are also associated with response to therapy with anti-tumor necrosis factor (anti-TNF) biologics; 233 patients enrolled in the Consortium of Rheumatology Researchers of North America (CORRONA) RA registry were studied. Findings were combined with results from an international collaborative study (N = 1,283) in a meta-analysis (N = 1,516). Multivariate models investigating the association between single nucleotide polymorphisms (SNPs) and change in RA disease activity were adjusted for age, gender, concomitant methotrexate, and baseline disease activity. In the CORRONA cohort, nominal associations with disease activity improvement were observed for the rs1980422 SNP of the CD28 gene in multivariate models (coefficient -0.377, p = 0.005) but were not significant after adjustment for multiple comparisons (q = 0.10). In the meta-analysis, the only SNP with nominal associations with change in DAS28 was the rs2812378 SNP of the CCL21 gene (coefficient 1.9195, p = 0.0068). This association was not significant after adjustment for multiple comparisons (q = 0.143). We conclude that the established RA risk alleles studied were not significantly associated with response to anti-TNF biologics in the CORRONA cohort or the meta-analysis.

Presumptive role of 129 strain-derived Sle16 locus in rheumatoid arthritis in a new mouse model with Fcγ receptor type IIb-deficient C57BL/6 genetic background

OBJECTIVE

Fcγ receptor type IIb (FcγRIIb) is a major negative regulator of B cells, and the lack of FcγRIIb expression has been reported to induce systemic lupus erythematosus (SLE) in mice of the C57BL/6 (B6) genetic background. The 129 strain-derived Sle16 locus on the telomeric region of chromosome 1 including polymorphic Fcgr2b confers the predisposition to systemic autoimmunity when present on the B6 background. We undertook this study to examine the effect of the Sle16 locus on autoimmune disease in FcγRIIb-deficient B6 mice.

METHODS

We established 2 lines of FcγRIIb-deficient B6 congenic mouse strains (KO1 and KO2) by selective backcrossing of the originally constructed FcγRIIb-deficient mice on a hybrid (129×B6) background into a B6 background. Although both lack FcγRIIb expression, the KO1 and KO2 strains carry different lengths of the 129 strain-derived telomeric chromosome 1 segment flanked to the null-mutated Fcgr2b gene; the KO1 strain carries a 129 strain-derived ∼6.3-Mb interval distal from the null-mutated Fcgr2b gene within the Sle16 locus, while this interval in the KO2 strain is of B6 origin.

RESULTS

Unexpectedly, both strains failed to develop SLE; instead, the KO1 strain, but not the KO2 strain, spontaneously developed severe rheumatoid arthritis (RA) with an incidence reaching >90% at age 12 months.

CONCLUSION

The current study shows evidence that the epistatic interaction between the Fcgr2b-null mutation and a polymorphic gene(s) in the 129 strain-derived interval located in the distal Sle16 locus contributes to RA susceptibility in a new mouse model with the B6 genetic background, although the participation of other genetic polymorphisms cannot be totally excluded.

Galectins in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a complex and common systemic autoimmune disease characterized by synovial inflammation and hyperplasia. Multiple proteins, cells, and pathways have been identified to contribute to the pathogenesis of RA. Galectins are a group of lectins that bind to β-galactoside carbohydrates on the cell surface and in the extracellular matrix. They are expressed in a wide variety of tissues and organs with the highest expression in the immune system. Galectins are potent immune regulators and modulate a range of pathological processes, such as inflammation, autoimmunity, and cancer. Accumulated evidence shows that several family members of galectins play positive or negative roles in the disease development of RA, through their effects on T and B lymphocytes, myeloid lineage cells, and fibroblast-like synoviocytes. In this review, we will summarize the function of different galectins in immune modulation and their distinct roles in RA pathogenesis.

Identification of the NF-κB activating protein-like locus as a risk locus for rheumatoid arthritis

Objective

To fine-map the NF-κB activating protein-like (NKAPL) locus identified in a prior genome-wide study as a possible rheumatoid arthritis (RA) risk locus and thereby delineate additional variants with stronger and/or independent disease association.

Methods

Genotypes for 101 SNPs across the NKAPL locus on chromosome 6p22.1 were obtained on 1368 Canadian RA cases and 1471 controls. Single marker associations were examined using logistic regression and the most strongly associated NKAPL locus SNPs then typed in another Canadian and a US-based RA case/control cohort.

Results

Fine-mapping analyses identified six NKAPL locus variants in a single haplotype block showing association with p≤5.6×10⁻⁸ in the combined Canadian cohort. Among these SNPs, rs35656932 in the zinc finger 193 gene and rs13208096 in the NKAPL gene remained significant after conditional logistic regression, contributed independently to risk for disease, and were replicated in the US cohort (P_comb=4.24×10⁻¹⁰ and 2.44×10⁻⁹, respectively). These associations remained significant after conditioning on SNPs tagging the HLA-shared epitope (SE) DRB1*0401 allele and were significantly stronger in the HLA-SE negative versus positive subgroup, with a significant negative interaction apparent between HLA-DRB1 SE and NKAPL risk alleles.

Conclusions

By illuminating additional NKAPL variants with highly significant effects on risk that are distinct from, but interactive with those arising from the HLA-DRB1 locus, our data conclusively identify NKAPL as an RA susceptibility locus.

Profiling anti-cyclic citrullinated peptide antibodies in patients with juvenile idiopathic arthritis

BACKGROUND

Anti-citrullinated protein/peptide antibodies (ACPA), have high specificity for rheumatoid arthritis (RA). Some children with juvenile idiopathic arthritis (JIA), phenotypically resemble RA and test positive for rheumatoid factor (RF) a characteristic biomarker of RA. We investigated the prevalence of ACPA and its relationship to other serologic markers associated with RA in a well-characterized JIA cohort.

METHODS

Cases were 334 children with JIA, 30 of whom had RF + polyarticular JIA. Sera from all cases and 50 healthy pediatric controls were investigated by ELISA at a single time point for anti-cyclic citrullinated peptide (anti-CCP) IgG, RF IgM, IgA and IgG, anti-RA33 IgG, and antinuclear antibodies (ANA). Comparisons between cases and controls were made using Chi-square or Fisher exact tests and T-tests.

RESULTS

The prevalence of RF was 8% among controls, and 12% among cases (ns). The prevalence of ACPA was 2% in controls and 14.3% in cases (OR 8.2, p <0.01). Children who were ACPA-positive and RF-negative (n = 23) had a significantly earlier onset-age (4.6 years vs. 12.1 years, p <0.00001) and had fewer HLA-DRB1 shared epitope alleles than those positive for both RF and ACPA (n = 25). Prevalence of anti-RA33 was not different between cases and controls.

CONCLUSIONS

ACPAs are detectable in 14% of children with JIA. Children with positive ACPA but negative RF are frequent, and may define a distinct subset of children with JIA. ACPA testing should be included in the classification of JIA.

Tobacco and other environmental risk factors in rheumatoid arthritis

Many environmental factors have been associated with an increased risk of developing Rheumatoid Arthritis (RA), but so far smoking is the only environmental risk factor that has been extensively studied and widely accepted. Smoking is associated with an increased risk of developing seropositive RA (RF and/or ACPA). Recent studies show that tobacco smoking can influence disease phenotype, with the development of more aggressive disease and greater joint damage; but other studies show contradictory results. Recent data suggests that response to antirheumatic therapy in RA is worse in smokers. In this article we review different environmental factors that have been associated with an increased risk of developing RA, with a special interest in tobacco smoking.

Association of single-nucleotide polymorphisms in CCR6, TAGAP, and TNFAIP3 with rheumatoid arthritis in African Americans

OBJECTIVE

We previously reported an analysis of single-nucleotide polymorphisms (SNPs) in 3 validated European rheumatoid arthritis (RA) susceptibility loci, TAGAP, TNFAIP3, and CCR6, in African American patients with RA. Unexpectedly, the disease-associated alleles were different in African Americans from those in Europeans. In an effort to better define their contribution, we performed additional SNP genotyping in these genes.

METHODS

Seven SNPs were genotyped in 446 African American patients with RA and in 733 African American control subjects. Differences in minor allele frequency between the RA cases and controls were analyzed after controlling for the global proportion of European admixture, and pairwise linkage disequilibrium (LD) was estimated among the SNPs.

RESULTS

Three SNPs were significantly associated with RA: the TNFAIP3 rs719149 A allele (OR 1.22 [95% confidence interval (95% CI) 1.03-1.44], P = 0.02), the TAGAP rs1738074 G allele (OR 0.75 [95% CI 0.63-0.89, P = 0.0012), and the TAGAP rs4709267 G allele (OR 0.74 [95% CI 0.60-0.91], P = 0.004). Pairwise LD between the TAGAP SNPs was low (r(2) = 0.034). The haplotype containing minor alleles for both TAGAP SNPs was uncommon (4.5%). After conditional analysis of each TAGAP SNP, its counterpart remained significantly associated with RA (rs1738074 for rs4709267 P = 0.00001 and rs4709267 for rs1738074 P = 0.00005), suggesting independent effects.

CONCLUSION

SNPs in regulatory regions of TAGAP and an intronic SNP (TNFAIP3) are potential susceptibility loci in African Americans. Pairwise LD, haplotype analysis, and SNP conditioning analysis suggest that these 2 SNPs in TAGAP are independent susceptibility alleles. Additional fine-mapping of this gene and functional genomic studies of these SNPs should provide further insight into the role of these genes in RA.

Systemic Lupus Erythematosus: Recent Concepts in Genomics, Pathogenetic Mechanisms, and Therapies

Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disorder associated with multiple immunological abnormalities and a wide range of clinical manifestations. Recent progress in genetics has expanded the number of the genes associated with SLE to more than 20 in number and has contributed to improvement of understanding of the pathogenesis of the disease. This has enhanced the development of novel therapeutic targets and biomarkers for individualized and tailor-made clinical management of lupus patients. Despite this knowledge, however, it is a challenge to fully understand the genetic pathogenesis of the disease. The present paper describes the current concepts in the mechanisms, genomics, and pathogenesis of SLE and their implications for management of the disorder. The potential role of gene therapy, biological agents, intravenous immunoglobulin, anti-inflammatory cytokines, and cytokine inhibitors is discussed.

A systems genetics approach provides a bridge from discovered genetic variants to biological pathways in rheumatoid arthritis

Genome-wide association studies (GWAS) have yielded novel genetic loci underlying common diseases. We propose a systems genetics approach to utilize these discoveries for better understanding of the genetic architecture of rheumatoid arthritis (RA). Current evidence of genetic associations with RA was sought through PubMed and the NHGRI GWAS catalog. The associations of 15 single nucleotide polymorphisms and HLA-DRB1 alleles were confirmed in 1,287 cases and 1,500 controls of Japanese subjects. Among these, HLA-DRB1 alleles and eight SNPs showed significant associations and all but one of the variants had the same direction of effect as identified in the previous studies, indicating that the genetic risk factors underlying RA are shared across populations. By receiver operating characteristic curve analysis, the area under the curve (AUC) for the genetic risk score based on the selected variants was 68.4%. For seropositive RA patients only, the AUC improved to 70.9%, indicating good but suboptimal predictive ability. A simulation study shows that more than 200 additional loci with similar effect size as recent GWAS findings or 20 rare variants with intermediate effects are needed to achieve AUC = 80.0%. We performed the random walk with restart (RWR) algorithm to prioritize genes for future mapping studies. The performance of the algorithm was confirmed by leave-one-out cross-validation. The RWR algorithm pointed to ZAP70 in the first rank, in which mutation causes RA-like autoimmune arthritis in mice. By applying the hierarchical clustering method to a subnetwork comprising RA-associated genes and top-ranked genes by the RWR, we found three functional modules relevant to RA etiology: "leukocyte activation and differentiation", "pattern-recognition receptor signaling pathway", and "chemokines and their receptors".These results suggest that the systems genetics approach is useful to find directions of future mapping strategies to illuminate biological pathways.

Genetics of rheumatoid arthritis: time for a change!

PURPOSE OF REVIEW

To review recent progress in the genetics of rheumatoid arthritis (RA) and discuss the implications for understanding the pathogenesis of the disease as well as clinical application.

RECENT FINDINGS

Protection against anticitrullinated protein antibody (ACPA) positive RA was shown to be associated wit DRB1*1301. Genome-wide association studies (GWASs) added about 10 new loci to the list of already more than 20 loci associated with RA, so the list is now over 30. Typing for the known risk loci is not helpful for prediction of the risk for RA. It is remarkable how few functional studies have been published.

SUMMARY

Known genetic factors explain 50-60% of the genetic variance for susceptibility to ACPA-positive and 30-50% for ACPA-negative RA. Searching for the remaining missing or hidden heritability is in all probability not going to yield much for prediction and/or targeted intervention. Therefore, I conclude that if you want to find more genes you should have a lot of patience, time and money, stop with convential GWAS and invest in large-scale sequencing of selected patients and controls. I have a better suggestion, however: use the information that is already available to perform functional studies in order to understand the mechanism of the known associations!

Promoter polymorphisms in the chitinase 3-like 1 gene influence the serum concentration of YKL-40 in Danish patients with rheumatoid arthritis and in healthy subjects

Introduction

The present study investigates the association between single nucleotide polymorphisms (SNPs) in the chitinase 3-like 1 (CHI3L1) gene and serum concentrations of YKL-40 in Danish patients with rheumatoid arthritis (RA) and healthy controls as well as the association with RA in the Danish population. The CHI3L1 gene is located on chromosome 1q32.1 and encodes the YKL-40 glycoprotein. YKL-40 concentrations are elevated in the serum of patients with RA compared to healthy subjects, and YKL-40 has been suggested to be an auto-antigen and may play a role in development of RA and in inflammation.

Methods

Eight SNPs in the CHI3L1 gene and promotor were genotyped in 308 patients with RA and 605 controls (healthy blood donors) using TaqMan allele discrimination assays. Serum concentrations of YKL-40 were determined by an enzyme-linked immunosorbent assay (ELISA).

Results

We found significant association between the serum concentrations of YKL-40 and polymorphism in the CHI3L1 gene among both patients with RA and controls. The g.-131(C > G) polymorphism (rs4950928) was most strongly associated with age adjusted serum concentrations of YKL-40 in patients with RA (P < 2.4e-8) and controls (P < 2.2e-16). No significant allelic- or genotypic association with RA was found in this Danish cohort.

Conclusions

We suggest that the g.-131(C > G) promoter polymorphism has a substantial impact on serum concentrations of YKL-40 in patients with RA and healthy subjects. However, the polymorphism does not seem to confer risk to RA itself. The effect of CHI3L1 polymorphism on clinical outcome or the response to treatment in patients with RA remains to be investigated.

Strategies to prevent rheumatoid arthritis in high-risk patients

PURPOSE OF REVIEW

To examine potential interventions, including modification of environmental risk factors and use of pharmacologic agents, in at-risk populations to prevent progression to (or development of) rheumatoid arthritis (RA). This review is timely given the increasing interest in early intervention strategies and new opportunities to identify patients early in the pathogenesis of RA.

RECENT FINDINGS

Despite the growing literature demonstrating a link between anticitrullinated protein antibodies, synovitis, genetic and environmental risk factors such as smoking and RA, there are no studies that have evaluated the effect of modifying environmental risk factors in late preclinical RA. This article describes several studies that have evaluated the ability of pharmacologic interventions to modify outcomes in patients at risk for RA.

SUMMARY

The prevention of RA in at-risk populations is feasible; however, this will necessitate novel efforts to identify patients very early in disease development to examine the effectiveness and cost of preventive interventions.

Genetics of rheumatoid arthritis: what have we learned?

Rheumatoid arthritis (RA) is a chronic autoimmune disease affecting 0.5–1% of the population worldwide. The disease has a heterogeneous character, including clinical subsets of anti-citrullinated protein antibody (ACPA)-positive and APCA-negative disease. Although the pathogenesis of RA is poorly understood, progress has been made in identifying genetic factors that contribute to the disease. The most important genetic risk factor for RA is found in the human leukocyte antigen (HLA) locus. In particular, the HLA molecules carrying the amino acid sequence QKRAA, QRRAA, or RRRAA at positions 70–74 of the DRβ1 chain are associated with the disease. The HLA molecules carrying these “shared epitope” sequences only predispose for ACPA-positive disease. More than two decades after the discovery of HLA-DRB1 as a genetic risk factor, the second genetic risk factor for RA was identified in 2003. The introduction of new techniques, such as methods to perform genome-wide association has led to the identification of more than 20 additional genetic risk factors within the last 4 years, with most of these factors being located near genes implicated in immunological pathways. These findings underscore the role of the immune system in RA pathogenesis and may provide valuable insight into the specific pathways that cause RA.

Mannan Binding Lectin (MBL) genotypes coding for high MBL serum levels are associated with rheumatoid factor negative rheumatoid arthritis in never smokers

Introduction

Previous studies have provided inconsistent results on whether variants in the MBL2 gene, coding for the complement-activating mannan-binding lectin (MBL) protein, associate with rheumatoid arthritis (RA). We re-evaluated this in context of the main environmental and genetic risk factors (smoking, HLA-DRB1 'shared epitope' (SE), PTPN22*620W), which predispose to rheumatoid factor (RF) and/or anti-citrullinated-protein antibody (ACPA)-positive RA.

Methods

In this population-based EIRA study, rheumatoid factor (RF), ACPA, smoking, SE and PTPN22*620W status was determined in incident RA cases and matched controls. MBL-high (n = 1330) and MBL-low (n = 1257) genotypes predicting MBL levels were constructed from four promoter and exon-1 polymorphisms in the MBL2 gene. Odds ratios with 95% confidence interval (OR, 95% CI) were calculated by logistic regression. In extended families (n = 316), previously reported data were re-analyzed, considering RF and smoking.

Results

MBL-high genotypes tended to be associated with RF-negative (OR = 1.20, 95% CI 0.96-1.51) but not RF-positive (OR = 1.00, 95% CI 0.83-1.20) RA. Results divided by ACPA status did not differ. When stratified for smoking, MBL-high genotype was strongly associated with RF-negative RA in never smokers (OR = 1.82, 95% CI 1.24-2.69) but not in ever smokers (OR = 0.96, 95% CI 0.73-1.30). In never smokers, the association was observed in both the RF-negative/ACPA-negative (OR = 1.67, 95% CI 1.10-2.55) and RF-negative/ACPA-positive subgroups (OR = 3.07, 95% CI 1.37-6.89), and remained on an SE/PTPN22*620W negative background. In the extended families, the reported association between high MBL and RA was in fact confined to never smokers.

Conclusions

High MBL may predispose to RF-negative RA but only in individuals who have never smoked. This illustrates the importance of phenotypic subgrouping in genetic studies.

Most common single-nucleotide polymorphisms associated with rheumatoid arthritis in persons of European ancestry confer risk of rheumatoid arthritis in African Americans

OBJECTIVE

Large-scale genetic association studies have identified >20 rheumatoid arthritis (RA) risk alleles among individuals of European ancestry. The influence of these risk alleles has not been comprehensively studied in African Americans. We therefore sought to examine whether these validated RA risk alleles are associated with RA risk in an African American population.

METHODS

Twenty-seven candidate single-nucleotide polymorphisms (SNPs) were genotyped in 556 autoantibody-positive African Americans with RA and 791 healthy African American control subjects. Odds ratios (ORs) and 95% confidence intervals (95% CIs) for each SNP were compared with previously published ORs for RA patients of European ancestry. We then calculated a composite genetic risk score (GRS) for each individual based on the sum of all risk alleles.

RESULTS

Overlap of the ORs and 95% CIs between the European and African American populations was observed for 24 of the 27 candidate SNPs. Conversely, 3 of the 27 SNPs (CCR6 rs3093023, TAGAP rs394581, and TNFAIP3 rs6920220) demonstrated ORs in the opposite direction from those reported for RA patients of European ancestry. The GRS analysis indicated a small but highly significant probability that African American patients relative to control subjects were enriched for the risk alleles validated in European RA patients (P = 0.00005).

CONCLUSION

The majority of RA risk alleles previously validated for RA patients of European ancestry showed similar ORs in our population of African Americans with RA. Furthermore, the aggregate GRS supports the hypothesis that these SNPs are risk alleles for RA in the African American population. Future large-scale genetic studies are needed to validate these risk alleles and identify novel RA risk alleles in African Americans.

Analysis of the workforce and workplace for rheumatology and the research activities of rheumatologists early in their careers

OBJECTIVE

To assess the workforce and workplace in rheumatology, and the research work of early-career rheumatologists.

METHODS

Early-career rheumatologists were defined as practicing physicians who joined the American College of Rheumatology (ACR) in 1991-2005, were 49 years of age or younger when they joined, and reside in North America. This cohort participated in a Web-based survey distributed by the ACR. A total of 247 surveys (21.2% response) were used for this analysis. Survey questions were designed to obtain core insights about the workforce, workplace, research activities, funding, and the demographic profile of respondents.

RESULTS

Respondents from all workplaces-clinical, academic, federal, and industry-engaged in clinical care, teaching, administration, and research. The time devoted to these tasks was employer dependent, and workplaces shaped the scale and scope of research. Patient-oriented research was predominant across all workplaces. Disease, population, and translational research were intermediate, and few respondents pursued basic or prevention-oriented research in any type of workplace. Rheumatologists obtained extramural funds (21.3%) and intramural funds (78.7%) to pay portions of their salaries for time spent on research. Receiving a National Institutes of Health K08/K23 award was associated with receipt of a federal research project grant (P < 0.001). Respondents associated investigative work with reduced earnings, a perception validated by an estimated drop in pre-tax annual earnings of 2.3% for each half-day/week dedicated to research (P < 0.01).

CONCLUSION

The results of this study justify interventions for closing gaps embedded in investigational rheumatology. These include improved funding for clinical research, increasing the number of K08/K23 awards, and recruiting rheumatologists from underrepresented demographic groups.

Patients with early rheumatoid arthritis who smoke are less likely to respond to treatment with methotrexate and tumor necrosis factor inhibitors: observations from the Epidemiological Investigation of Rheumatoid Arthritis and the Swedish Rheumatology Register cohorts

OBJECTIVE

To determine whether cigarette smoking influences the response to treatment in patients with early rheumatoid arthritis (RA).

METHODS

We retrieved clinical information about patients entering the Epidemiological Investigation of Rheumatoid Arthritis (EIRA) early RA cohort from 1996 to 2006 (n=1,998) who were also in the Swedish Rheumatology Register (until 2007). Overall, 1,430 of the 1,621 registered patients were followed up from the time of inclusion in the EIRA cohort. Of these, 873 started methotrexate (MTX) monotherapy at inclusion, and 535 later started treatment with a tumor necrosis factor (TNF) inhibitor as the first biologic agent. The primary outcome was a good response according to the European League Against Rheumatism criteria at the 3-month visit. The influence of cigarette smoking (current or past) on the response to therapy was evaluated by logistic regression, with never smokers as the referent group.

RESULTS

Compared with never smokers, current smokers were less likely to achieve a good response at 3 months following the start of MTX (27% versus 36%; P=0.05) and at 3 months following the start of TNF inhibitors (29% versus 43%; P=0.03). In multivariate analyses in which clinical, serologic, and genetic factors were considered, the inverse associations between current smoking and good response remained (adjusted odds ratio [OR] for MTX response 0.60 [95% CI 0.39-0.94]; adjusted OR for TNF inhibitor response 0.52 [95% CI 0.29-0.96]). The lower likelihood of a good response remained at later followup visits. Evaluating remission or joint counts yielded similar findings. Past smoking did not affect the chance of response to MTX or TNF inhibitors. Evaluating the overall cohort, which reflects all treatments used, current smoking was similarly associated with a lower chance of a good response (adjusted ORs for the 3-month, 6-month, 1-year, and 5-year visits 0.61, 0.65, 0.78, 0.66, and 0.61, respectively).

CONCLUSION

Among patients with early RA, current cigarette smokers are less likely to respond to MTX and TNF inhibitors.

Association analysis of anti-Epstein-Barr nuclear antigen-1 antibodies, anti-cyclic citrullinated peptide antibodies, the shared epitope and smoking status in Brazilian patients with rheumatoid arthritis

INTRODUCTION

Epstein-Barr virus exposure appears to be an environmental trigger for rheumatoid arthritis that interacts with other risk factors. Relationships among anti-cyclic citrullinated peptide antibodies, the shared epitope, and smoking status have been observed in patients with rheumatoid arthritis from different populations.

OBJECTIVE

To perform an association analysis of anti-Epstein-Barr nuclear antigen-1 antibodies, anti-cyclic citrullinated peptide antibodies, the shared epitope, and smoking status in Brazilian patients with rheumatoid arthritis.

METHODS

In a case-control study, 140 rheumatoid arthritis patients and 143 healthy volunteers who were matched for age, sex, and ethnicity were recruited. Anti-Epstein-Barr nuclear antigen-1 antibodies and anti-cyclic citrullinated peptide antibodies were examined using an enzyme-linked immunosorbent assay, and shared epitope alleles were identified by genotyping. Smoking information was collected from all subjects. A comparative analysis of anti-Epstein-Barr nuclear antigen-1 antibodies, anti-cyclic citrullinated peptide antibodies, the shared epitope, and smoking status was performed in the patient group. Logistic regression analysis models were used to analyze the risk of rheumatoid arthritis.

RESULTS

Anti-Epstein-Barr nuclear antigen-1 antibodies were not associated with anti-cyclic citrullinated peptide antibodies, shared epitope alleles, or smoking status. Anti-cyclic citrullinated peptide antibody positivity was significantly higher in smoking patients with shared epitope alleles (OR = 3.82). In a multivariate logistic regression analysis using stepwise selection, only anti-cyclic citrullinated peptide antibodies were found to be independently associated with rheumatoid arthritis (OR = 247.9).

CONCLUSION

Anti-Epstein-Barr nuclear antigen-1 antibodies did not increase the risk of rheumatoid arthritis and were not associated with the rheumatoid arthritis risk factors studied. Smoking and shared epitope alleles were correlated with anti-cyclic citrullinated peptide-antibody-positive rheumatoid arthritis. Of the risk factors, only anticyclic citrullinated peptides antibodies were independently associated with rheumatoid arthritis susceptibility.

What can we learn from genetic studies of systemic lupus erythematosus? Implications of genetic heterogeneity among populations in SLE

Recent progress in genetics has expanded the number of the genes associated with SLE to more than 20 in the past 2 years. One might assign these candidate genetic factors into several pre-existing biological pathways: (i) innate immune response including TLR/interferon signaling pathways (IRF5, STAT4, TNFAIP3, and TREX1); (ii) adaptive immune response (HLA-DR, PTPN22, PDCD1, STAT4, LYN, BLK, and BANK1) including B, T cells, and antigen-presenting cells; and (iii) immune complex clearance mechanism (FCGRs, CRP, and ITGAM). In addition, there are also several genes and loci that could not be assigned into previous known pathways (KIAA1542, PXK, XKR6, ATG5, etc), providing possible novel mechanisms in SLE. It has also been evident that there are similarities and differences in SLE susceptibility loci across ethnic groups. Here we categorize the susceptible genes into four groups. The first group is the consistently associated genes with similar risk allele frequency between multiple ethnic populations such as STAT4, TNFAIP3, BANK1, and IRAK1/MECP2. The second group is the genes that are consistently associated but show marked difference in risk allele frequency (BLK, IRF5). The third group is the genes in which different risk variants exist within a gene or genetic loci (allelic heterogeneity) such as HLA-DR, FCGRs, and IRF5. The fourth group is the genes that show consistently discrepancy between populations such as PTPN22 and possibly ITGAM, PXK, and LYN (genetic heterogeneity). The possible explanations for differences of susceptible genetic factors between populations could be different genetic backgrounds, contribution of gene—gene or gene—environment interaction, and the relation between marker and causal variants. Therefore, efforts to identify ethnic-specific genetic factors or disease causing variants should be necessary for individualized therapy for SLE in future.

Rheumatoid arthritis

Rheumatoid arthritis is characterised by persistent synovitis, systemic inflammation, and autoantibodies (particularly to rheumatoid factor and citrullinated peptide). 50% of the risk for development of rheumatoid arthritis is attributable to genetic factors. Smoking is the main environmental risk. In industrialised countries, rheumatoid arthritis affects 0·5-1·0% of adults, with 5-50 per 100 000 new cases annually. The disorder is most typical in women and elderly people. Uncontrolled active rheumatoid arthritis causes joint damage, disability, decreased quality of life, and cardiovascular and other comorbidities. Disease-modifying antirheumatic drugs (DMARDs), the key therapeutic agents, reduce synovitis and systemic inflammation and improve function. The leading DMARD is methotrexate, which can be combined with other drugs of this type. Biological agents are used when arthritis is uncontrolled or toxic effects arise with DMARDs. Tumour necrosis factor inhibitors were the first biological agents, followed by abatacept, rituximab, and tocilizumab. Infections and high costs restrict prescription of biological agents. Long-term remission induced by intensive, short-term treatment selected by biomarker profiles is the ultimate goal.

Biomarkers for rheumatoid arthritis: making it personal

Effective treatment of rheumatoid arthritis (RA) has been hampered by the heterogeneity of the disease. Although early intervention can result in disease remission, it requires early diagnosis - and current diagnostic tests are not sufficiently accurate or sensitive in the early stages of RA. As a result, RA is typically diagnosed only once damage to the joints has already begun, a time at which the window for optimal treatment may have been missed. Furthermore, a significant proportion of RA patients do not respond to any given therapeutic. Research efforts are increasingly focused on discovery of biomarkers that enable early diagnosis and stratification of RA, and thus the implementation of timely, targeted therapy. Biomarkers have the potential to transform the management of RA by enabling not only early diagnosis, but also assessment and prediction of disease severity, selection of therapy, and monitoring of response to therapy. In this mini review, we discuss the development of molecular biomarkers for RA.

Rheumatoid arthritis risk allele PTPRC is also associated with response to anti-tumor necrosis factor alpha therapy

OBJECTIVE

Anti-tumor necrosis factor alpha (anti-TNF) therapy is a mainstay of treatment in rheumatoid arthritis (RA). The aim of the present study was to test established RA genetic risk factors to determine whether the same alleles also influence the response to anti-TNF therapy.

METHODS

A total of 1,283 RA patients receiving etanercept, infliximab, or adalimumab therapy were studied from among an international collaborative consortium of 9 different RA cohorts. The primary end point compared RA patients with a good treatment response according to the European League Against Rheumatism (EULAR) response criteria (n = 505) with RA patients considered to be nonresponders (n = 316). The secondary end point was the change from baseline in the level of disease activity according to the Disease Activity Score in 28 joints (triangle upDAS28). Clinical factors such as age, sex, and concomitant medications were tested as possible correlates of treatment response. Thirty-one single-nucleotide polymorphisms (SNPs) associated with the risk of RA were genotyped and tested for any association with treatment response, using univariate and multivariate logistic regression models.

RESULTS

Of the 31 RA-associated risk alleles, a SNP at the PTPRC (also known as CD45) gene locus (rs10919563) was associated with the primary end point, a EULAR good response versus no response (odds ratio [OR] 0.55, P = 0.0001 in the multivariate model). Similar results were obtained using the secondary end point, the triangle upDAS28 (P = 0.0002). There was suggestive evidence of a stronger association in autoantibody-positive patients with RA (OR 0.55, 95% confidence interval [95% CI] 0.39-0.76) as compared with autoantibody-negative patients (OR 0.90, 95% CI 0.41-1.99).

CONCLUSION

Statistically significant associations were observed between the response to anti-TNF therapy and an RA risk allele at the PTPRC gene locus. Additional studies will be required to replicate this finding in additional patient collections.

Genome-wide association study meta-analysis identifies seven new rheumatoid arthritis risk loci

To identify new genetic risk factors for rheumatoid arthritis, we conducted a genome-wide association study meta-analysis of 5,539 autoantibody-positive individuals with rheumatoid arthritis (cases) and 20,169 controls of European descent, followed by replication in an independent set of 6,768 rheumatoid arthritis cases and 8,806 controls. Of 34 SNPs selected for replication, 7 new rheumatoid arthritis risk alleles were identified at genome-wide significance (P < 5 x 10(-8)) in an analysis of all 41,282 samples. The associated SNPs are near genes of known immune function, including IL6ST, SPRED2, RBPJ, CCR6, IRF5 and PXK. We also refined associations at two established rheumatoid arthritis risk loci (IL2RA and CCL21) and confirmed the association at AFF3. These new associations bring the total number of confirmed rheumatoid arthritis risk loci to 31 among individuals of European ancestry. An additional 11 SNPs replicated at P < 0.05, many of which are validated autoimmune risk alleles, suggesting that most represent genuine rheumatoid arthritis risk alleles.

GWASs and the age of human as the model organism for autoimmune genetic research

Genetic studies have identified more than 150 autoimmune loci, and next-generation sequencing will identify more. Is it time to make human the model organism for autoimmune research?

Pharmacogenetics of rheumatoid arthritis: Potential targets from susceptibility genes and present therapies

Rheumatoid arthritis (RA) is a chronic heterogeneous autoimmune disorder of unknown etiology resulting in inflammation in the synovium, cartilage, and bone. Genetic factors play an important role in susceptibility to RA as the heritability of RA is between 50% and 60%, with the human leukocyte antigen (HLA) locus accounting for at least 30% of overall genetic risk. Outside the major histocompatibility complex (MHC) region, six additional risk loci have been identified and validated including PTPN22, STAT4, PADI4, CTLA4, TNFAIP3-OLIG3, and TRAF1/C5. Genetic factors are also important in RA pharmacotherapy due to the gene-dependent activity of enzymes involved in the pharmacokinetics and/or pharmacodynamics of RA medications. Indeed, there is great variability in drug efficacy as well as adverse events associated with any anti-rheumatic therapy and genetics is thought to contribute significantly to this inter-individual variability in response. This review will summarize the genetic factors that have been implicated in the pathogenesis of RA, and how these determinants may factor into the potential pharmacogenetics of this disease. We will also review the therapeutic agents that are currently being utilized or presently being evaluated in the treatment of RA, along with potential pharmacogenetic markers that have been proposed for such medications.

Non-synonymous variant (Gly307Ser) in CD226 is associated with susceptibility to multiple autoimmune diseases

OBJECTIVES

Recently, a non-synonymous (Gly307Ser) variant, rs763361, in the CD226 gene was shown to be associated with multiple autoimmune diseases (ADs) in European Caucasian populations. However, shared autoimmunity with CD226 has not been evaluated in non-European populations. The aim of the present study is to assess the association of this single nucleotide polymorphism (SNP) with ADs in non-European populations.

METHODS

To replicate this association in non-European populations, we evaluated case-control association between rs763361 and coeliac disease (CED) samples from Argentina; SLE, RA, type-1 diabetes (T1D) and primary SS (pSS) from Colombia; and SLE samples from China and Japan. We genotyped rs763361 and evaluated its genetic association with multiple ADs, using chi(2)-test. For each association, odds ratio (OR) and 95% CI were calculated.

RESULTS

We show that rs763361 is significantly associated with Argentinean CED (P = 0.0009, OR = 1.60). We also observed a trend of possible association with Chinese SLE (P = 0.01, OR = 1.19), RA (P = 0.047, OR = 1.25), SLE (P = 0.0899, OR = 1.24) and pSS (P = 0.09, OR = 1.33) in Colombians. Meta-analyses for SLE (using our three populations) and T1D (our population and three published populations) yielded significant association with rs763361, P = 0.009 (OR = 1.16) and P = 1.1.46 x 10(-9) (OR = 1.14), respectively.

CONCLUSIONS

Our results demonstrate that the coding variant rs763361 in CD226 gene is associated with multiple ADs in non-European populations.

The pursuit of genome-wide association studies: where are we now?

It is now 5 years since the first genome-wide association studies (GWAS), published in 2005, identified a common risk allele with large effect size for age-related macular degeneration in a small sample set. Following this exciting finding, researchers have become optimistic about the prospect of the genome-wide association approach. However, most of the risk alleles identified in the subsequent GWAS for various complex diseases are common with small effect sizes (odds ratio <1.5). So far, more than 450 GWAS have been published and the associations of greater than 2000 single nucleotide polymorphisms (SNPs) or genetic loci were reported. The aim of this review paper is to give an overview of the evolving field of GWAS, discuss the progress that has been made by GWAS and some of the interesting findings, and summarize what we have learned over the past 5 years about the genetic basis of human complex diseases. This review will focus on GWAS of SNPs association for complex diseases but not studies of copy number variations.