Tsuneyo Mimori

Genetics of rheumatoid arthritis contributes to biology and drug discovery

A major challenge in human genetics is to devise a systematic strategy to integrate disease-associated variants with diverse genomic and biological data sets to provide insight into disease pathogenesis and guide drug discovery for complex traits such as rheumatoid arthritis (RA). Here we performed a genome-wide association study meta-analysis in a total of >100,000 subjects of European and Asian ancestries (29,880 RA cases and 73,758 controls), by evaluating ∼10 million single-nucleotide polymorphisms. We discovered 42 novel RA risk loci at a genome-wide level of significance, bringing the total to 101 (refs 2, 3, 4). We devised an in silico pipeline using established bioinformatics methods based on functional annotation, cis-acting expression quantitative trait loci and pathway analyses—as well as novel methods based on genetic overlap with human primary immunodeficiency, haematological cancer somatic mutations and knockout mouse phenotypes—to identify 98 biological candidate genes at these 101 risk loci. We demonstrate that these genes are the targets of approved therapies for RA, and further suggest that drugs approved for other indications may be repurposed for the treatment of RA. Together, this comprehensive genetic study sheds light on fundamental genes, pathways and cell types that contribute to RA pathogenesis, and provides empirical evidence that the genetics of RA can provide important information for drug discovery.

A novel clinical entity, IgG4-related disease (IgG4RD): general concept and details

IgG4-related disease (IgG4RD) is a novel clinical disease entity characterized by elevated serum IgG4 concentration and tumefaction or tissue infiltration by IgG4-positive plasma cells. IgG4RD may be present in a certain proportion of patients with a wide variety of diseases, including Mikulicz’s disease, autoimmune pancreatitis, hypophysitis, Riedel thyroiditis, interstitial pneumonitis, interstitial nephritis, prostatitis, lymphadenopathy, retroperitoneal fibrosis, inflammatory aortic aneurysm, and inflammatory pseudotumor. Although IgG4RD forms a distinct, clinically independent disease category and is attracting strong attention as a new clinical entity, many questions and problems still remain to be elucidated, including its pathogenesis, the establishment of diagnostic criteria, and the role of IgG4. Here we describe the concept of IgG4RD and up-to-date information on this emerging disease entity.

Efficacy of rituximab (anti-CD20) for refractory systemic lupus erythematosus involving the central nervous system

Aim: Neuropsychiatric systemic lupus erythematosus (NPSLE) is a serious treatment-resistant phenotype of systemic lupus erythematosus. A standard treatment for NPSLE is not available. This report describes the clinical and laboratory tests of 10 patients with NPSLE before and after rituximab treatment, including changes in lymphocyte phenotypes. Methods: Rituximab was administered at different doses in 10 patients with refractory NPSLE, despite intensive treatment. Results: Treatment with rituximab resulted in rapid improvement of central nervous system-related manifestations, particularly acute confusional state. Rituximab also improved cognitive dysfunction, psychosis and seizure, and reduced the SLE Disease Activity Index Score at day 28 in all 10 patients. These effects lasted for >1 year in five patients. Flow cytometric analysis showed that rituximab down regulated CD40 and CD80 on B cells and CD40L, CD69 and inducible costimulator on CD4+ T cells. Conclusions: Rituximab rapidly improved refractory NPSLE, as evident by resolution of various clinical signs and symptoms and improvement of radiographic findings. The down regulation of functional molecules on B and T cells suggests that rituximab modulates the interaction of activated B and T cells through costimulatory molecules. These results warrant further analysis of rituximab as treatment for NPSLE.

International consensus guidance statement on the management and treatment of IgG4-related disease

A. Khosroshahi, Z. S. Wallace, J. L. Crowe, T. Akamizu, A. Azumi, M. N. Carruthers, S. T. Chari, E. Della-Torre, L. Frulloni, H. Goto, P. A. Hart, T. Kamisawa, S. Kawa, M. Kawano, M. H. Kim, Y. Kodama, K. Kubota, M. M. Lerch, M. L€ ohr, Y. Masaki, S. Matsui, T. Mimori, S. Nakamura, T. Nakazawa, H. Ohara, K. Okazaki, J. H. Ryu, T. Saeki, N. Schleinitz, A. Shimatsu, T. Shimosegawa, H. Takahashi, M. Takahira, A. Tanaka, M. Topazian, H. Umehara, G. J. Webster, T. E. Witzig, M. Yamamoto, W. Zhang, T. Chiba, and J. H. Stone

Discontinuation of infliximab after attaining low disease activity in patients with rheumatoid arthritis: RRR (remission induction by Remicade in RA) study

Background Tumour necrosis factor (TNF) inhibitors enable tight control of disease activity in patients with rheumatoid arthritis (RA). Discontinuation of TNF inhibitors after acquisition of low disease activity (LDA) is important for safety and economic reasons. Objective To determine whether infliximab might be discontinued after achievement of LDA in patients with RA and to evaluate progression of articular destruction during the discontinuation. Methods 114 patients with RA who had received infliximab treatment, and whose Disease Activity Score, including a 28-joint count (DAS28) was <3.2 (LDA) for 24 weeks, were studied. Results The mean disease duration of the 114 patients was 5.9 years, mean DAS28 5.5 and mean modified total Sharp score (mTSS) 63.3. After maintaining LDA for >24 weeks by infliximab treatment, the drug was discontinued and DAS28 in 102 patients was evaluated at year 1. Fifty-six patients (55%) continued to have DAS28<3.2 and 43% reached DAS<2.6 at 1 year after discontinuing infliximab. For 46 patients remission induction by Remicade in RA (RRR) failed: disease in 29 patients flared within 1 year and DAS28 was >3.2 at year 1 in 17 patients. Yearly progression of mTSS (ΔTSS) remained <0.5 in 67% and 44% of the RRR-achieved and RRR-failed groups, respectively. The estimated ΔmTSS was 0.3 and 1.6 and Health Assessment Questionnaire-Disability Index was 0.174 and 0.614 in the RRR-achieved and RRR-failed groups, respectively, 1 year after the discontinuation. Conclusion After attaining LDA by infliximab, 56 (55%) of the 102 patients with RA were able to discontinue infliximab for >1 year without progression of radiological articular destruction.

Proteasome assembly defect due to a proteasome subunit beta type 8 (PSMB8) mutation causes the autoinflammatory disorder, Nakajo-Nishimura syndrome

Nakajo-Nishimura syndrome (NNS) is a disorder that segregates in an autosomal recessive fashion. Symptoms include periodic fever, skin rash, partial lipomuscular atrophy, and joint contracture. Here, we report a mutation in the human proteasome subunit beta type 8 gene (PSMB8) that encodes the immunoproteasome subunit β5i in patients with NNS. This G201V mutation disrupts the β-sheet structure, protrudes from the loop that interfaces with the β4 subunit, and is in close proximity to the catalytic threonine residue. The β5i mutant is not efficiently incorporated during immunoproteasome biogenesis, resulting in reduced proteasome activity and accumulation of ubiquitinated and oxidized proteins within cells expressing immunoproteasomes. As a result, the level of interleukin (IL)-6 and IFN-γ inducible protein (IP)-10 in patient sera is markedly increased. Nuclear phosphorylated p38 and the secretion of IL-6 are increased in patient cells both in vitro and in vivo, which may account for the inflammatory response and periodic fever observed in these patients. These results show that a mutation within a proteasome subunit is the direct cause of a human disease and suggest that decreased proteasome activity can cause inflammation.

High diagnostic performance of ELISA detection of antibodies to citrullinated antigens in rheumatoid arthritis.

Objective: We investigated the rheumatoid arthritis (RA) diagnostic performances of anti‐cyclic citrullinated peptide antibody (anti‐CCP) and antifilaggrin antibody (AFA) in comparison with RF and matrix metalloproteinase‐3 (MMP‐3). Methods: We used a second generation enzyme‐linked immunosorbent assay (ELISA) kit for the detection of anti‐CCP. We constructed recombinant human filaggrin, which was citrullinated in vitro by human peptidylarginine deiminase, and subsequently used it as the coating antigen for AFA‐ELISA. A total of 549 RA patients and 208 other rheumatic disease patients were included in the study. Results: The specificities of anti‐CCP (88.9%) and AFA (94.7%) were superior to those of RF (81.7%) and MMP‐3 (49.5%). The sensitivity of anti‐CCP (87.6%) was superior to all others. However, the sensitivity of AFA (68.7%) was inferior to those of RF (69.8%) and MMP‐3 (75.7%). Furthermore, receiver operating characteristic curves of anti‐CCP and AFA passed closer to the upper left corner than those of RF and MMP‐3, and the areas under the curves (AUC) of AFA and anti‐CCP were significantly larger. In addition, the AUC of anti‐CCP was significantly larger than that of AFA. Conclusion: ELISA detection of antibodies to citrullinated antigens, especially a second generation anti‐CCP, showed higher discriminative ability than other assays, including RF, and would be useful to aid the diagnosis of RA in clinical practice.

The RIG-I-like receptor IFIH1/MDA5 is a dermatomyositis-specific autoantigen identified by the anti-CADM-140 antibody

OBJECTIVES Various autoantibodies are detected in the sera of PM/DM patients. Some of them are specific to PM/DM patients and closely associated with clinical manifestations of the diseases. Recently, the anti-CADM-140 antibody was reported to be found specifically in clinically amyopathic DM (C-ADM) patients and to be associated with acute interstitial lung disease (ILD). We assessed the clinical significance of the anti-CADM-140 antibody and then investigated the autoantigen recognized by the anti-CADM-140 antibody. METHODS Autoantibodies were screened in 192 patients with various CTDs and 21 healthy controls using immunoprecipitation with [(35)S]methionine-labelled HeLa cells. Immunoabsorbent column chromatography was used to purify an autoantigen that was subsequently subjected to peptide mass fingerprinting. RESULTS The anti-CADM-140 antibody was revealed to be specific to DM. Most of the anti-CADM-140-positive patients were C-ADM although some of them showed apparent myositis. The anti-CADM-140-positive patients frequently showed hyperferritinaemia and acute progressive ILD with poor prognosis. The anti-CADM-140 antibody was shown to recognize IFN induced with helicase C domain protein 1 (IFIH1), also known as the melanoma differentiation-associated gene 5 (MDA5), which is one of the RIG-I-like receptors and plays a role in innate immune responses. CONCLUSION The anti-CADM-140 antibody was a marker of DM and intractable ILD and recognized IFIH1/MDA5, which is involved in innate immunity. These findings may give a new insight into the pathogenesis of DM.

Anti-MDA5 and anti-TIF1-γ antibodies have clinical significance for patients with dermatomyositis

OBJECTIVES Myositis-specific autoantibodies are useful for diagnosing PM/DM. Recently, two new myositis-specific autoantibodies against melanoma differentiation-associated gene 5 (MDA5) and transcriptional intermediary factor 1-gamma (TIF1-gamma) were identified in DM. Here, we detected these autoantibodies in patient sera using new assays with recombinant MDA5 and TIF1-gamma, and associated clinical features with the presence of anti-MDA5 or anti-TIF1-gamma antibodies. METHODS We screened 135 Japanese patients with various CTDs, including 82 with DM. DM patients were classified as clinically amyopathic DM (CADM), cancer-associated DM or classical DM without cancer. Anti-MDA5 and anti-TIF1-gamma antibodies were detected by their ability to immunoprecipitate biotinylated recombinant proteins. RESULTS Sera from 21 (26%) of 82 DM patients immunoprecipitated MDA5, and every anti-MDA5-positive patient had DM (except one patient with SSc). Sera from 20 (65%) of 31 CADM patients reacted with MDA5. Notably, anti-MDA5-positive DM patients had significantly more interstitial lung disease than anti-MDA5-negative DM patients (95 vs 32%, P < 0.001). Sera from 12 (15%) of 82 DM patients immunoprecipitated TIF1-gamma, and anti-TIF1-gamma antibodies were only detected in DM patients. Strikingly, 7 (58%) of 12 patients with cancer-associated DM had sera that reacted with TIF1-gamma. Anti-TIF1-gamma-positive DM patients had significantly more internal malignancies than anti-TIF1-gamma-negative DM patients (58 vs 9%, P < 0.001). CONCLUSIONS Anti-MDA5 and anti-TIF1-gamma antibodies were confirmed to be serological DM subset markers. Anti-MDA5 and anti-TIF1-gamma antibodies were detected based on their ability to immunoprecipitate biotinylated recombinant MDA5 and TIF1-gamma, and were closely associated with life-threatening complications in DM.

Complement drives Th17 cell differentiation and triggers autoimmune arthritis

Activation of serum complement triggers Th17 cell–dependent spontaneous autoimmune disease in an animal model. In genetically autoimmune-prone SKG mice, administration of mannan or β-glucan, both of which activate serum complement, evoked Th17 cell–mediated chronic autoimmune arthritis. C5a, a chief component of complement activation produced via all three complement pathways (i.e., lectin, classical, and alternative), stimulated tissue-resident macrophages, but not dendritic cells, to produce inflammatory cytokines including IL-6, in synergy with Toll-like receptor signaling or, notably, granulocyte/macrophage colony-stimulating factor (GM-CSF). GM-CSF secreted by activated T cells indeed enhanced in vitro IL-6 production by C5a-stimulated macrophages. In vivo, C5a receptor (C5aR) deficiency in SKG mice inhibited the differentiation/expansion of Th17 cells after mannan or β-glucan treatment, and consequently suppressed the development of arthritis. Transfer of SKG T cells induced Th17 cell differentiation/expansion and produced arthritis in C5aR-sufficient recombination activating gene (RAG)−/− mice but not in C5aR-deficient RAG−/− recipients. In vivo macrophage depletion also inhibited disease development in SKG mice. Collectively, the data suggest that complement activation by exogenous or endogenous stimulation can initiate Th17 cell differentiation and expansion in certain autoimmune diseases and presumably in microbial infections. Blockade of C5aR may thus be beneficial for controlling Th17-mediated inflammation and autoimmune disease.