Autoantibodies to RuvBL1 and RuvBL2: a novel systemic sclerosis-related antibody associated with diffuse cutaneous and skeletal muscle involvement.

OBJECTIVE: To identify and characterize a novel systemic sclerosis (SSc)-related autoantibody directed against a complex consisting of RuvBL1 and RuvBL2 (RuvBL1/2) and to assess its clinical correlations. METHODS: We first analyzed 316 consecutive patients with SSc who were evaluated at Kanazawa University Hospital. Controls included 290 patients with other connective tissue diseases, interstitial lung disease alone, or autoimmune hepatitis, and 50 healthy subjects. Autoantibody specificities were analyzed using RNA and protein immunoprecipitation assays. Autoimmune targets were affinity purified using patients' sera and subjected to liquid chromatography mass spectrometry. SSc patients in another institution in Japan and the University of Pittsburgh cohort were also included in analysis for evaluating clinical correlations. RESULTS: By protein immunoprecipitation assay, 6 SSc sera (1.9%) reacted with doublets with molecular weights of ∼50 kd. Liquid chromatography mass spectrometry of the partially purified autoantigen and additional immunoblot-based analyses revealed that this antibody specificity recognized RuvBL1/2. Anti-RuvBL1/2 antibody was exclusively detected in SSc patients. SSc patients with anti-RuvBL1/2 in both the Japanese and Pittsburgh cohorts consistently had higher frequencies of SSc in overlap with myositis and diffuse skin thickening than those without anti-RuvBL1/2. Compared with other autoantibodies related to SSc/myositis overlap (anti-PM-Scl and anti-Ku), anti-RuvBL1/2 was distinctive in terms of its associations with older age at SSc onset, male sex, and a high frequency of diffuse cutaneous involvement. CONCLUSION: Anti-RuvBL1/2 antibody is a novel SSc-related autoantibody associated with a unique combination of clinical features, including myositis overlap and diffuse cutaneous involvement.

Association of hepatocyte growth factor promoter polymorphism with severity of interstitial lung disease in Japanese patients with systemic sclerosis.

OBJECTIVE: To examine associations of single-nucleotide polymorphisms (SNPs) within genes for hepatocyte growth factor (HGF) and its receptor c-met with disease susceptibility and organ involvement in Japanese patients with systemic sclerosis (SSc). METHODS: Four SNPs (HGF -1652 C/T, +44222 C/T, and +63555 G/T, and c-met -980 T/A) were analyzed in 159 SSc patients and 103 healthy control subjects with the use of a polymerase chain reaction-based assay. The influence of the HGF -1652 SNP on transcription activity was evaluated with a luciferase reporter assay and an electrophoretic mobility shift assay (EMSA). RESULTS: There was no difference in the distribution of HGF/c-met SNPs between SSc patients and controls. HGF -1652 TT was found much more frequently in SSc patients with end-stage lung disease (ESLD) than in those without (41% versus 8%; P = 0.0004). This association was confirmed by a replication study involving a separate cohort of 155 SSc patients. Kaplan-Meyer analysis revealed that HGF -1652 TT carriers had a higher probability of developing ESLD than did CT or CC carriers. The HGF promoter carrying the HGF -1652 T allele had lower transcription activity than did the promoter carrying the C allele. EMSA showed the presence of a potential negative transcription regulator that binds specifically to the HGF promoter carrying a T allele at position -1652. Finally, TT carriers had a relative inability to increase circulating HGF levels even in the presence of advanced interstitial lung disease. CONCLUSION: A SNP in the HGF promoter region may modulate the severity of interstitial lung disease by controlling the transcriptional efficiency of the HGF gene.

Clinical correlations with dermatomyositis-specific autoantibodies in adult Japanese patients with dermatomyositis: a multicenter cross-sectional study.

OBJECTIVE: To clarify the association of clinical and prognostic features with dermatomyositis (DM)-specific autoantibodies (Abs) in adult Japanese patients with DM. DESIGN: Retrospective study. SETTING: Kanazawa University Graduate School of Medical Science Department of Dermatology and collaborating medical centers. Patients A total of 376 consecutive adult Japanese patients with DM who visited our hospital or collaborating medical centers between 2003 and 2008. MAIN OUTCOME MEASURES: Clinical and laboratory characteristics of adult Japanese patients with DM and DM-specific Abs that include Abs against Mi-2, 155/140, and CADM-140. RESULTS: In patients with DM, anti-Mi-2, anti-155/140, and anti-CADM-140 were detected in 9 (2%), 25 (7%), and 43 (11%), respectively. These DM-specific Abs were mutually exclusive and were detected in none of 34 patients with polymyositis, 326 with systemic sclerosis, and 97 with systemic lupus erythematosus. Anti-Mi-2 was associated with classical DM without interstitial lung disease or malignancy, whereas anti-155/140 was associated with malignancy. Patients with anti-CADM-140 frequently had clinically amyopathic DM and rapidly progressive interstitial lung disease. Cumulative survival rates were more favorable in patients with anti-Mi-2 compared with those with anti-155/140 or anti-CADM-140 (P < .01 for both comparisons). Nearly all deaths occurred within 1 year after diagnosis in patients with anti-CADM-140. Conclusion Dermatomyositis-specific Abs define clinically distinct subsets and are useful for predicting clinical outcomes in patients with DM.

RNA helicase encoded by melanoma differentiation-associated gene 5 is a major autoantigen in patients with clinically amyopathic dermatomyositis: Association with rapidly progressive interstitial lung disease.

OBJECTIVE: To identify the autoantigen recognized by the autoantibody that is associated with clinically amyopathic dermatomyositis (C-ADM) and rapidly progressive interstitial lung disease (ILD). METHODS: An anti-CADM-140 antibody-positive prototype serum sample was used to screen a HeLa cell-derived complementary DNA (cDNA) library. Selected cDNA clones were further evaluated by immunoprecipitation of their in vitro-transcribed and in vitro-translated products using anti-CADM-140 antibody-positive and anti-CADM-140 antibody-negative sera. The lysates of COS-7 cells transfected with the putative antigen were similarly tested. An enzyme-linked immunosorbent assay (ELISA) to detect the anti-CADM-140 antibody was established using a recombinant CADM-140 antigen, and its specificity and sensitivity for C-ADM and rapidly progressive ILD were assessed in 294 patients with various connective tissue diseases. RESULTS: By cDNA library screening and immunoprecipitation of in vitro-transcribed and in vitro-translated products, we obtained a cDNA clone encoding melanoma differentiation-associated gene 5 (MDA-5). The anti-CADM-140 antibodies in patients' sera specifically reacted with MDA-5 protein expressed in cells transfected with full-length MDA-5 cDNA, confirming the identity of MDA-5 as the CADM-140 autoantigen. The ELISA, using recombinant MDA-5 protein as the antigen, showed an analytical sensitivity of 85% and analytical specificity of 100%, in comparison with the "gold standard" immunoprecipitation assay, and was useful for identifying patients with C-ADM and/or rapidly progressive ILD. CONCLUSION: Given that RNA helicase encoded by MDA-5 is a critical molecule involved in the innate immune defense against viruses, viral infection may play an important role in the pathogenesis of C-ADM and rapidly progressive ILD. Moreover, our ELISA using recombinant MDA-5 protein makes detection of the anti-CADM-140 antibody routinely available.