Early monitoring of anti-infliximab antibodies by drug-tolerant assay predicts later immunogenicity and drug survival in rheumatic diseases.

OBJECTIVES: To investigate the appearance of anti-drug antibodies (ADA) against infliximab (IFX) determined by drug-sensitive and drug-tolerant assays and their relationship with drug levels and drug survival. METHODS: This longitudinal observational study included 45 patients with rheumatoid arthritis (RA) and 61 with spondyloarthritis (SpA). Serum samples were obtained at weeks 2, 6, 12, 24, and 52. Serum IFX levels were measured by a capture enzyme-linked immunosorbent assay (ELISA) and ADA by an in-house drug-sensitive two-site (bridging) enzyme-linked immunosorbent assay (bELISA) and a commercially available drug-tolerant ELISA (IDK, Immundiagnostik, Germany). RESULTS: Anti-drug antibodies were detected earlier by IDK than by bELISA. Once ADA appeared, positivity persisted throughout the study period. Patients who were bELISA ADA+ had higher IDK ADA levels (than bELISA ADA- patients). Circulating IFX levels were detected in all patients except those found to be bELISA ADA+. Serum IFX levels were lower in IDK ADA+ than in IDK ADA-patients.Most patients (64%) discontinued due to inefficacy. The early onset of immunogenicity was related to IFX survival. Both in RA and SpA, the median survival (years) was shorter in patients with earlier development of ADA (IDK+ before or at week 24) than those who became IDK+ later (after week 24) or never developed ADA. CONCLUSION: A drug-tolerant assay detects ADA during IFX therapy earlier and more frequently than a drug-sensitive assay. The onset of immunogenicity detected by drug-tolerant assays is related to the subsequent detection of ADA by drug-sensitive assays and drug survival.

Influence of rheumatoid factor on serum drug levels of TNF inhibitors with different structures in rheumatoid arthritis.

OBJECTIVES: Certolizumab pegol (CZP), an Fc-free antibody fragment, has shown stable serum levels and steady efficacy in the treatment of RA patients, irrespective of RF levels at baseline. Here, we examine, in clinical practice, the effect of baseline RF and ACPA levels on serum drug levels of IFX, ADL and CZP an Fc-free antibody fragment. METHODS: This is a retrospective study performed in real-world patients. We assessed 170 patients with RA: 90 (53%) received IFX, 48 (28%) ADL and 32 (19%) CZP. Demographic and clinical variables, RF and ACPA levels were obtained at the baseline visit (T0), and patients were stratified based on negative, low, medium, or high levels. After 6 months (T6) serum drug levels and anti-drug antibodies (ADAb), were computed. RESULTS: While CZP serum levels did not differ across RF groups at T6, high baseline RF was linked to lower serum drug levels compared to RF negative status in treatment with complete monoclonal antibodies IFX and ADL. No differences in disease activity measured by DAS28 at baseline were observed across RF quartiles in patients treated with IFX or ADL. ADAb was observed in 26 patients with IFX, 3 with ADL and 1 with CZP, following 6 months of treatment. Patients with high baseline RF levels dropped out more frequently by secondary non-response in IFX or ADL than CZP (80% vs. 75% vs. 33%, p=0.002). CONCLUSIONS: In this real word data evaluation, CZP serum levels were independent of RF levels in patients however patients with high baseline RF levels who obtained IFX or ADL had lower serum drug levels at 6 months than baseline RF-negative patients. In addition, secondary non-response was more frequent in patients with high RF levels treated with IFX and ADL.

Optimal concentration range of golimumab in patients with axial spondyloarthritis.

OBJECTIVES: To investigate the association between serum golimumab (GLM) trough levels, clinical disease activity and treatment response during the first year of therapy in patients with axial spondyloarthritis (axSpA), as well as determining an optimal concentration range of GLM in axSpA. METHODS: This was an observational prospective study including 49 patients with axSpA monitored during 52 weeks (W52). Serum GLM trough levels were measured by capture ELISA and antidrug antibodies by bridging ELISA at baseline, W24 and W52. Disease activity was assessed by the Ankylosing Spondylitis Disease Activity Score (ASDAS) and clinical improvement by ΔASDAS. The association between serum GLM trough levels and disease activity was assessed using univariable and multivariable regression. In case of drop-out or missing data before W52, the last observation carried forward (LOCF) was performed. ASDAS values and GLM levels at W24 were available for 42 patients and 38 patients at W52. RESULTS: In the univariable analyses, serum GLM trough levels were inversely associated with ASDAS at W24 (n=42, r =-0.445; p<0.01), at W52 (n=38, r=-0.330; p<0.05) and W52LOCF (n=49, r=-0.309; p<0.05). In the multivariable analysis, this significant association remained. Serum trough GLM levels above the 0.7-1.4mg/L range did not contribute to additional clinical improvement. CONCLUSIONS: In patients with axSpA, serum GLM trough levels are associated with disease activity during the first year of treatment. A concentration range of 0.7-1.4mg/L appears to be useful to achieve clinical response to GLM.

Infusion reactions during infliximab treatment are not associated with IgE anti-infliximab antibodies.

OBJECTIVES: Controversy exists on the role of IgE antidrug antibodies (IgE-ADA) in infusion reactions (IR) on infliximab treatment, partly due to the lack of a positive control used for assay validation. We sought to (1) develop a robust assay to measure IgE-ADA, including a positive control, (2) determine the association between IgE-ADA and IR and (3) determine the incidence of IgE-ADA in infliximab treated patients. METHODS: A recombinant human IgE anti-infliximab monoclonal antibody was developed as standard and positive control. With this antibody, we set up a novel robust assay to measure IgE-ADA. IgE-ADA was determined in three retrospective cohorts (n=159) containing IR+ (n=37) and IR- (n=39), and longitudinal sera of 83 spondyloarthritis. RESULTS: IgE-ADA was found in 0/39 IR-, whereas 4/37 (11%) IR+ showed low levels (0.1-0.3 IU/mL, below the 0.35 IU/mL threshold associated with elevated risk of allergic symptoms). All patients who were IgE-ADA positive also had (very) high IgG-ADA levels. The incidence of IgE-ADA in patients with infliximab-treated spondyloarthritis was estimated at less than approximately 1%. CONCLUSIONS: IgE-ADA is rarely detected in infliximab-treated patients. Moreover, the absence of IgE-ADA in the majority of IR+ patients suggests that IgE-ADA is not associated with infusion reactions.

Current Practices for Therapeutic Drug Monitoring of Biopharmaceuticals in Pediatrics.

Biopharmaceuticals have recently emerged as effective treatments for refractory pediatric autoimmune conditions. Several reports have shown a relationship between drug concentration, antidrug antibodies, and clinical response in these patients, strongly suggesting the potential interest, usefulness, and reliability of therapeutic drug monitoring (TDM) in children. This article reviews the current state of research in juvenile idiopathic arthritis, pediatric inflammatory bowel disease, and pediatric psoriasis from a TDM point of view. There is a remarkable lack of evidence-based data in pediatric patients, which is reflected throughout the article. Most investigations of TDM are focused on research of tumor necrosis factor alpha antagonists in inflammatory bowel disease, albeit preliminary publications are emerging from pediatric rheumatologists and dermatologists. To date, immunogenicity has been a primary concern, particularly regarding infliximab and adalimumab therapy in children, as it may lead to a loss of therapeutic response. Preliminary investigations show that adjusting the dose according to blood drug concentrations improves disease outcomes by overcoming antidrug antibodies, suggesting a crucial role for TDM. Patients who receive other drugs, such as etanercept, abatacept, or tocilizumab, could benefit from TDM because dosage can be optimized by adjusting it to the minimum effective dose.

Rationale for Therapeutic Drug Monitoring of Biopharmaceuticals in Inflammatory Diseases.

Biopharmaceuticals bring together a number of specific characteristics as compared with other drugs. However, as it is done for most drugs, an individual adjustment of their dose may be necessary. Similar to "chemical" drugs, biopharmaceuticals used in immunoinflammatory diseases have a rather narrow therapeutic range, lack good early clinical or biological marker of response, have variable pharmacokinetics, and their serum concentrations are most often related with response. Monoclonal antibodies have additional specific sources of pharmacokinetic variability. Low concentrations may increase the risks of immunization, plasmapheresis may increase their elimination, and subcutaneous formulations may be associated with decreased adherence. For all these reasons, pharmacokinetic therapeutic drug monitoring may be useful. However, few randomized controlled therapeutic drug monitoring studies have been published. For monoclonal antibodies, a precise definition of the therapeutic concentrations is challenging because of the interindividual variability in their concentration-effect relationship.

Antibodies to infliximab in Remicade-treated rheumatic patients show identical reactivity towards biosimilars.

OBJECTIVES: The aim of this study was to determine whether antibodies to infliximab (IFX) in Remicade-treated patients cross-react with the biosimilar CT-P13. METHODS: 250 consecutive patients with rheumatic diseases under Remicade and 77 controls were retrospectively selected for the study. Anti-IFX antibodies at drug through levels were measured in parallel with three different bridging ELISA assays: Promonitor-ANTI-IFX kit, which uses Remicade to detect antibodies, and two more assays that use either Inflectra or Remsima with the same format. Correlation and association between each assay was studied. RESULTS: 50.4% of patients were tested positive with Promonitor-ANTI-IFX. All were antibodies to IFX (ATI)-positive when either Inflectra or Remsima assays were used. In all comparisons positive and negative percentage agreements were 100%, and correlation coefficients were ≥0.995. No differences between rheumatoid arthritis and spondyloarthritis, or between concomitant immunosuppressives, were observed. CONCLUSIONS: Anti-IFX antibodies of Remicade-treated patients cross-react with either Inflectra or Remsima. Although additional epitopes may be present in the biosimilar, results suggest that epitopes influencing the immune response to IFX are also present in the biosimilar. Antibody-positive patients treated with Remicade should not be switched to the biosimilar, since antibodies will interact with the new drug and potentially lead to loss of response. This finding supports the utility for therapeutic drug monitoring before a switching strategy is considered.

Comparing a tapering strategy to the standard dosing regimen of TNF inhibitors in rheumatoid arthritis patients with low disease activity.

OBJECTIVES: The aim of this study is to compare clinical outcomes, incidence of flares and administered drug reduction between rheumatoid arthritis (RA) patients under TNF inhibitors (TNFi) tapering strategy and RA patients on standard regimen. METHODS: Two groups of RA patients on TNFi with DAS28<3.2 were compared: the tapering group (TG: 67 pts from Spain) and the control group with standard therapy regimen (CG: 77 pts from the Netherlands). DAS28 was measured at different time points: visit 0 (prior starting TNFi), visit 1 (prior to start tapering in TG and with DAS28<3.2 in TG and CG), visit 2 (6 months after visit 1), visit 3 (1 year after visit 1), visit 4 (the last visit available after visit 1) and visit-flare (visit with the worst flare between visit 1 and visit 4). RESULTS: Despite the reduction of administered drug at visit 4 in the TG (interval elongation of 32.8% in infliximab, 52.9% in adalimumab and 52.6% in etanercept), the DAS28 remained similar between groups at the end of the study (DAS28: 2.7±0.9 in TG vs. 2.5±1 in CG, p=0.1). No differences were seen in the number of patients with flares [26/67 (38.9%) in the TG vs. 30/77 (39%) in the CG, p=0.324] and only nineteen out of 136 patients (14%) had anti-drug antibodies at the end of the study. CONCLUSIONS: The tapering strategy of TNFi in RA patients result in a reduction of the drug administered, while the disease control is not worse than patients on the standard regimen.

Confirmation of -174G/C interleukin-6 gene promoter polymorphism as a genetic marker predicting antitumor necrosis factor treatment outcome.

BACKGROUND: The IL-6 -174G/C genetic variant has recently been associated with the clinical response to etanercept therapy in rheumatoid arthritis (RA) patients. Considering previous results, the aim of our study was to validate the role of this polymorphism as a predictor of the antitumor necrosis factor (anti-TNF) treatment outcome in RA. MATERIALS AND METHODS: Our study population was composed of 199 Spanish patients with RA receiving anti-TNF therapy. The IL-6 -174G/C (rs1800795) genetic variant was genotyped using the TaqMan allelic discrimination technology. Patients were classified, according to the European League Against Rheumatism (EULAR) criteria, as responders (good and moderate response) and nonresponders at 6, 12, 18, and 24 months after the first infusion. RESULTS: The -174*G allele was significantly associated with a good or moderate EULAR response at 12 [P=0.015, odds ratio (OR)=2.93, 95% confidence interval (CI) 1.29-6.70], 18 (P=4.54E-03, OR=5.17, 95% CI 1.80-14.85), and 24 months (P=4.54E-03, OR=14.86, 95% CI 2.91-75.91). A meta-analysis combining these data with the results from a previous study confirmed this association (P=1.89E-02, OR=1.80, 95% CI 1.13-2.87, at 12 months). CONCLUSION: Our results support the role of the -174G/C IL-6 polymorphism as a genetic marker of responsiveness to anti-TNF therapy.

Lack of association between ABO, PPAP2B, ADAMST7, PIK3CG, and EDNRA and carotid intima-media thickness, carotid plaques, and cardiovascular disease in patients with rheumatoid arthritis.

INTRODUCTION: Rheumatoid arthritis (RA) is a polygenic disease associated with accelerated atherosclerosis and increased cardiovascular (CV) mortality. Recent studies have identified the ABO rs579459, PPAP2B rs17114036, and ADAMTS7 rs3825807 polymorphisms as genetic variants associated with coronary artery disease and the PIK3CG rs17398575 and EDNRA rs1878406 polymorphisms as the most significant signals related to the presence of carotid plaque in nonrheumatic Caucasian individuals. Accordingly, we evaluated the potential relationship between these 5 polymorphisms and subclinical atherosclerosis (assessed by carotid intima-media thickness (cIMT) and presence/absence of carotid plaques) and CV disease in RA. MATERIAL AND METHODS: 2140 Spanish RA patients were genotyped for the 5 polymorphisms by TaqMan assays. Subclinical atherosclerosis was evaluated in 620 of these patients by carotid ultrasonography technology. RESULTS: No statistically significant differences were found when each polymorphism was assessed according to cIMT values and presence/absence of carotid plaques in RA, after adjusting the results for potential confounders. Moreover, no significant differences were obtained when RA patients were stratified according to the presence/absence of CV disease after adjusting for potential confounders. CONCLUSION: Our results do not confirm association between ABO rs579459, PPAP2B rs17114036, ADAMTS7 rs3825807, PIK3CG rs17398575, and EDNRA rs1878406 and subclinical atherosclerosis and CV disease in RA.

Translation and cross-cultural adaptation of the mSQUASH into Spanish.

BACKGROUND: There is a lack of outcome measures for the assessment of physical activity in patients with axial spondyloarthritis (axSpA). For this matter, the modified Short QUestionnaire to Assess Health (mSQUASH) was developed and validated, originally in Dutch. OBJECTIVE: To translate and cross-culturally adapt the mSQUASH into Spanish and to evaluate the equivalence of the translated version in patients with axSpA. METHODS: The mSQUASH was translated following forward-backward procedure according to the protocol of Beaton. Two bi-lingual translators produced independent forward translations of the mSQUASH into Spanish, and the versions were harmonized in a consensual version. Another translator back translated the synthesized version into Dutch. A scientific committee reached consensus on discrepancies and developed a pre-final version of the questionnaire. The field test with cognitive debriefing involved 10 patients with axSpA with different gender, age, disease duration, educational level and working status. RESULTS: The translation process of the mSQUASH was completed without major issues. The first translation needed several iterations due to small discrepancies in the wording. Back-translation was performed without difficulties, and the scientific committee agreed upon a final version of the questionnaire. Cognitive debriefing showed the Spanish questionnaire to be clear, relevant, understandable and comprehensive. The preliminary version was accepted with minor modifications. CONCLUSIONS: The resulting Spanish version of the mSQUASH showed good linguistic and face validity according to the field test, revealing potential for use in clinical practice and research. In order to conclude the cross-cultural adaptation of the mSQUASH into Spanish, the next step is the assessment of psychometric properties of the Spanish version.

Coping with rheumatic stressors (CORS) questionnaire: Spanish translation and cross-cultural adaptation.

BACKGROUND: Rheumatic and Musculoskeletal Diseases (RMDs) substantially impact the lives of patients, with complex associations between disease severity and self-perceived health status. In this regard, the Coping with Rheumatic Stressors (CORS) questionnaire was developed to measure how patients with RMDs cope with stressors such as pain, limitations or dependency. The CORS is not currently available in Spanish, and therefore the adaptation of this instrument is needed. OBJECTIVE: First, to cross-culturally adapt the CORS into Spanish for Spain. Secondly, to test the conceptual equivalence of the translated version in patients with axial spondyloarthritis (axSpA). METHODS: A translation of the CORS into Spanish was performed adhering to the forward-backward procedure described by Beaton. Two translators produced independent forward translations of the item content, response options, and instructions of the CORS into Spanish. Both versions were harmonized in a consensual version. Another translator back-translated the synthesized version into Dutch. A scientific committee including all the translators, one methodologist and a rheumatologist, held a meeting and reached consensus on discrepancies to develop a final draft version of the Spanish CORS. Then, a field test with cognitive debriefing was conducted, involving a sample of 10 patients with axSpA. RESULTS: The translation process of the CORS was completed after the discussion of some discrepancies throughout the process. The first translation was done without major complications. Back-translation presented some discrepancies. These led to minor modifications in the wording in one response option and 15 questionnaire items. The scientific committee agreed upon a final version of the questionnaire. Cognitive debriefing, led to minor modifications; for example, three respondents indicated that one of the statements in the instructions was syntactically complex ("indique cuán a menudo usted ha llevado a cabo dicho comportamiento") which led to its adjustment. The process indicated that the final CORS Spanish questionnaire was clear and understandable to all patients. CONCLUSIONS: The Spanish version of the CORS showed good cross-cultural validity and good face validity according to the field test. Before the Spanish CORS is implemented, further validation is in progress to test the psychometric properties of the instrument in patients with axSpA.

Influence of immunogenicity on the efficacy of longterm treatment of spondyloarthritis with infliximab.

BACKGROUND: Infliximab (IFX) is a monoclonal antibody against tumour necrosis factor α that is effective for treating spondyloarthritis (SpA). However, after initial success of the drug some patients lose responsiveness or develop infusion reactions, which may be related to the development of antibodies against the drug. OBJECTIVE: To investigate the clinical relevance of antibodies to infliximab (ATI) formation in patients with SpA undergoing IFX treatment over a prolonged period. METHODS: 94 patients with SpA treated with IFX from 1999 to 2010 were studied. Their clinical characteristics, serum trough IFX levels and ATI status were evaluated for a mean of 6.99 (95% CI:6.28 to 7.7) years. Clinical activity and improvement were measured using the Ankylosing Spondylitis Disease Activity Score (ASDAS): inactive <1.3, moderate ≥1.3 and <2.1, high ≥2.1-≤3.5, and very high >3.5 at three time points (6 months, 12 months and >4 years). RESULTS: ATI were detected in 24 (25.5%) patients. The patients with ATI had higher ASDAS scores than those without ATI (2.55±0.89 vs 1.79±1.04, p=0.038 at 6 months; 1.95±0.67 vs 1.67±0.71, p=0.042 at 1 year; 2.52±0.99 vs 1.53±0.81, p=0.024 at >4 years). Eleven patients (12%) developed infusion-related reactions, and of these, ATI were present in eight patients (73%). The patients with infusion-related reactions had higher ATI titres (median 12 931 AU/ml, IQR 853-82 437) vs median 2454 AU/ml, IQR 449-7718, p=0.028) and shorter survival (4.25 years vs 8.19 years, p<0.001). ATI development occurred more frequently in the patients not receiving methotrexate (20/58 (34.5%) vs 4/36 (11.1%), p=0.011). CONCLUSION: In patients with SpA treated with IFX, ATI formation is associated with a poor clinical response, the appearance of infusion reactions and the discontinuation of treatment.

The PTPN22 R263Q polymorphism is a risk factor for rheumatoid arthritis in Caucasian case-control samples.

OBJECTIVE: Recently, a functional PTPN22 variant (R263Q; rs33996649) was found to be associated with systemic lupus erythematosus (SLE). This study was undertaken to analyze the influence of this polymorphism on the risk of rheumatoid arthritis (RA). METHODS: RA patients (n = 5,579) were recruited from outpatient clinics from 6 different countries (Spain, New Zealand, the UK, Norway, The Netherlands, and Germany). Healthy controls (n = 5,392) were recruited from the same areas. There was 100% power to detect an effect equivalent to that observed in SLE. Samples were genotyped for the PTPN22 R263Q (rs33996649) and PTPN22 R620W (rs2476601) polymorphisms using a TaqMan 5'-allele discrimination assay. The effect of the R263Q variant was analyzed in isolation and in combination with the effect of R620W, using Unphased and Stata 10 software. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were determined. RESULTS: The minor allele A of PTPN22 R263Q was significantly associated with a lower risk of RA in the pooled analysis of the 6 populations (P = 0.016, Mantel-Haenszel pooled OR 0.80 [95% CI 0.67-0.96]), independent of the effect of the R620W polymorphism. Both polymorphisms had an additive effect. The more RA risk alleles carried (R263Q G allele, R620W T allele), the higher the RA risk (for 2 versus 1 risk allele P = 0.014, OR 1.28 [95% CI 1.05-1.55], for 3 versus 1 risk allele P = 6.67 × 10(-11) , OR 2.01 [1.63-2.48], and for 4 versus 1 risk allele P = 6.50 × 10(-11) , OR 3.55 [2.42-5.20]). CONCLUSION: Our findings indicate that the minor allele of the PTPN22 R263Q polymorphism is associated with a lower risk of RA. This association is independent of the well-established association between PTPN22 R620W and RA. Both polymorphisms have an additive effect on the risk of RA.

Low Serum BAFF Concentration Is Associated with Response to TNF Inhibitors in Seropositive Patients with Rheumatoid Arthritis.

We investigated B-cell-activating factor (BAFF) in relation to response to treatment with TNF inhibitors (TNFis) in rheumatoid arthritis (RA). This was a longitudinal study including 158 patients with RA treated with TNFis and followed up for 6 months. Clinical response at 6 months of treatment was defined according to the EULAR criteria for good responders (GRs). BAFF concentration was measured in serum samples, collected at baseline and at 6 months. Associations with EULAR response were evaluated using univariable and multivariable logistic regression models. ROC analysis was performed to determine the optimal threshold of serum BAFF concentration associated with good EULAR response to treatment. After 6 months of TNFi treatment, 24% of patients were GRs. They had a lower BMI, lower baseline DAS28 and lower baseline serum BAFF concentration than non-responders. After 6 months of TNFi treatment, autoantibody-positive patients who attained GR had significantly lower serum BAFF concentrations compared with patients who did not. Serum BAFF < 968 pg/mL at 6 months represented the concentration likely to best discriminate between GR and non-GR at 6 months of TNFi treatment. Autoantibody-seropositive patients who had serum BAFF < 968 pg/mL at 6 months demonstrated a more than four-fold increased probability to be GRs compared with patients with higher BAFF concentrations. In conclusion, serum BAFF concentrations were associated with response to TNFis in seropositive RA patients, corroborating the importance of the B-cell compartment in RA.

Influence of immunogenicity on the efficacy of long-term treatment with infliximab in rheumatoid arthritis.

OBJECTIVE: To analyse the clinical relevance of the production of anti-infliximab antibodies (anti-infliximab Abs) in patients with RA undergoing infliximab treatment over a prolonged period of time. METHODS: Clinical characteristics, serum trough infliximab and antibody levels were evaluated in 85 RA patients treated with infliximab for a median of 4.42 (interval 0.4-10.2) years. DAS in 28 joints (DAS-28), EULAR response criteria and survival of treatment were assessed at 3 time points (6 months, 12 months and >4 years). RESULTS: Antibodies against infliximab were detected in 28 (32.9%) patients and were present in all EULAR non-responder patients. Antibody levels were higher in EULAR non-responders throughout the study period (P = 0.05 at 6 months, P = 0.02 at 1 year, P = 0.003 at >4 years) compared with EULAR (good and moderate) responders. Nine (10.5%) patients, all of them with high-serum anti-infliximab Ab levels, developed infusion-related reactions. Patients with anti-infliximab Abs more often required increased infliximab doses (51.7%) (P = 0.032) and median survival time on treatment was shorter (4.15 vs 8.89 years) (P = 0.0006). MTX co-therapy was not associated with lower proportion of anti-infliximab Ab-positive patients, but those receiving both infliximab and MTX had lower levels of anti-infliximab Abs (P = 0.073) and longer survival (P = 0.015) on treatment. CONCLUSION: The formation of anti-infliximab Abs during treatment with infliximab is associated with a loss of clinical response, the appearance of infusion reactions and discontinuation of treatment.

Evidence of epistasis between TNFRSF14 and TNFRSF6B polymorphisms in patients with rheumatoid arthritis.

OBJECTIVE: Genetic variants located close to 2 genes codifying for members of the tumor necrosis factor receptor superfamily (TNFRSF), TNFRSF14 and TNFRSF6B, have recently been associated with rheumatoid arthritis (RA) and with inflammatory bowel disease susceptibility, respectively. The TNFRSF6B protein has been related to osteoclastic activity, apoptosis inhibition, and modulation of T cell activation and differentiation. Interestingly, peptides encoded by both genes bind a common ligand called LIGHT, which is overexpressed in RA synovium. The aim of this study was to investigate the combined effect of the TNFRSF14 rs6684865 and TNFRSF6B rs4809330 polymorphisms in RA predisposition. METHODS: TaqMan genotyping of these polymorphisms was conducted in 649 patients with RA and 553 ethnically matched control subjects (first study). To validate the results, an independent replication cohort with 211 patients and 255 control subjects was additionally studied (replication study). RESULTS: The frequency of the rs6684865 G allele in the RA subgroup with the rs4809330 GG susceptibility genotype was significantly higher than that in the other patients with RA (74% versus 65%; P = 0.002) or in control subjects (74% versus 67%; P = 0.003). Because no significant differences between the control and patient groups in the first and replication studies were observed, the data were pooled. When compared with control subjects overall, the effect of the rs6684865 G allele in the group with the rs4809330 GG genotype (odds ratio [OR] 1.49) was significantly different from the effect observed in the group carrying the rs4809330 A allele (OR 0.97; P = 0.0015 by Breslow-Day test of homogeneity). CONCLUSION: We have identified and replicated a novel gene-gene interaction between 2 polymorphisms of TNFRSF members in Spanish patients with RA, based on the hypothesis of shared pathogenic pathways in complex diseases.

Identification of the oxidative stress-related gene MSRA as a rheumatoid arthritis susceptibility locus by genome-wide pathway analysis.

OBJECTIVE: Genome-wide association studies carried out in rheumatoid arthritis (RA) have led to the discovery of several genetic associations with this disease. Still, the current associated genetic variations can explain only part of the genetic risk involved in RA, and it is well recognized that these genome-wide association studies are likely underpowered to detect all common disease variants. This study was undertaken to explore the genomic regions showing low-significance associations in previous genome-wide association studies of RA. METHODS: To reduce the false-positive signal fraction, we exploited pathway analysis to prioritize regions containing genes most likely to be implicated in RA. We hypothesized that true disease genes would be in a similar pathway. Therefore, genes from similar pathways but located in different regions were prioritized for replication using Prioritizer software. A total of 384 genetic variants selected from previous RA genome-wide association studies were tested in a Spanish case-control discovery cohort comprising 376 RA patients and 478 healthy controls for replication. Statistically significant associations were further validated in replication cohorts from Spain and The Netherlands. The study consisted of a total of 1,818 RA patients and 2,498 controls. RESULTS: We detected a novel genetic association between RA and the MSRA gene (rs10903323) in the Spanish combined population (P = 2.91 × 10(-5) , odds ratio [OR] 1.51). This association was further tested in our independent Dutch replication cohort. Combined analysis showed an overall association of MSRA with RA (P = 3.19 × 10(-4) , OR 1.28). CONCLUSION: Our findings indicate that a novel association in the MSRA gene is related to oxidative stress and support the notion of a major role for this process in RA.