Identification of connective tissue disease autoantibodies and a novel autoantibody anti-annexin A11 in patients with "idiopathic" interstitial lung disease.

BACKGROUND: Autoantibodies are a hallmark feature of Connective Tissue Diseases (CTD). Their presence in patients with idiopathic interstitial lung disease (ILD) may suggest covert CTD. We aimed to determine the prevalence of CTD autoantibodies in patients diagnosed with idiopathic ILD. METHODS: 499 patient sera were analysed: 251 idiopathic pulmonary fibrosis (IPF), 206 idiopathic non-specific interstitial pneumonia (iNSIP) and 42 cryptogenic organising pneumonia (COP). Autoantibody status was determined by immunoprecipitation. RESULTS: 2.4% of IPF sera had a CTD-autoantibody compared to 10.2% of iNSIP and 7.3% of COP. 45% of autoantibodies were anti-synthetases. A novel autoantibody targeting an unknown 56 kDa protein was found in seven IPF patients (2.8%) and two NSIP (1%) patients. This was characterised as anti-annexin A11. CONCLUSION: Specific guidance on autoantibody testing and interpretation in patients with ILD could improve diagnostic accuracy. Further work is required to determine the clinical significance of anti-annexin A11.

The reliability of immunoassays to detect autoantibodies in patients with myositis is dependent on autoantibody specificity.

OBJECTIVES: In order to address the reliability of commercial assays to identify myositis-specific and -associated autoantibodies, we aimed to compare the results of two commercial immunoassays with the results obtained by protein immunoprecipitation. METHODS: Autoantibody status was determined using radio-labelled protein immunoprecipitation for patients referred to our laboratory for myositis autoantibody characterization. For each autoantibody of interest, the sera from 25 different patients were analysed by line blot (Euroline Myositis Antigen Profile 4, EuroImmun, Lübeck, Germany) and dot blot (D-Tek BlueDiver, Diagnostic Technology, Belrose, NSW, Australia). Sera from 134 adult healthy controls were analysed. RESULTS: Overall commercial assays performed reasonably well, with high agreement (Cohen's κ >0.8). Notable exceptions were the detection of rarer anti-synthetases with κ < 0.2 and detection of anti-TIF1γ, where κ was 0.70 for the line blot and 0.31 for dot blot. Further analysis suggested that the proportion of patients with anti-TIF1γ may recognize a conformational epitope, limiting the ability of blotting-based assays that utilize denatured antigen to detect this clinically important autoantibody. A false-positive result occurred in 13.7% of samples analysed by line blot and 12.1% analysed by dot blot. CONCLUSION: The assays analysed do not perform well for all myositis-specific and -associated autoantibodies and overall false positives are relatively common. It is crucial that clinicians are aware of the limitations of the methods used by their local laboratory. Results must be interpreted within the clinical context and immunoprecipitation should still be considered in selected cases, such as apparently autoantibody-negative patients where anti-synthetase syndrome is suspected.

Focused HLA analysis in Caucasians with myositis identifies significant associations with autoantibody subgroups.

OBJECTIVES: Idiopathic inflammatory myopathies (IIM) are a spectrum of rare autoimmune diseases characterised clinically by muscle weakness and heterogeneous systemic organ involvement. The strongest genetic risk is within the major histocompatibility complex (MHC). Since autoantibody presence defines specific clinical subgroups of IIM, we aimed to correlate serotype and genotype, to identify novel risk variants in the MHC region that co-occur with IIM autoantibodies. METHODS: We collected available autoantibody data in our cohort of 2582 Caucasian patients with IIM. High resolution human leucocyte antigen (HLA) alleles and corresponding amino acid sequences were imputed using SNP2HLA from existing genotyping data and tested for association with 12 autoantibody subgroups. RESULTS: We report associations with eight autoantibodies reaching our study-wide significance level of p<2.9×10-5. Associations with the 8.1 ancestral haplotype were found with anti-Jo-1 (HLA-B*08:01, p=2.28×10-53 and HLA-DRB1*03:01, p=3.25×10-9), anti-PM/Scl (HLA-DQB1*02:01, p=1.47×10-26) and anti-cN1A autoantibodies (HLA-DRB1*03:01, p=1.40×10-11). Associations independent of this haplotype were found with anti-Mi-2 (HLA-DRB1*07:01, p=4.92×10-13) and anti-HMGCR autoantibodies (HLA-DRB1*11, p=5.09×10-6). Amino acid positions may be more strongly associated than classical HLA associations; for example with anti-Jo-1 autoantibodies and position 74 of HLA-DRB1 (p=3.47×10-64) and position 9 of HLA-B (p=7.03×10-11). We report novel genetic associations with HLA-DQB1 anti-TIF1 autoantibodies and identify haplotypes that may differ between adult-onset and juvenile-onset patients with these autoantibodies. CONCLUSIONS: These findings provide new insights regarding the functional consequences of genetic polymorphisms within the MHC. As autoantibodies in IIM correlate with specific clinical features of disease, understanding genetic risk underlying development of autoantibody profiles has implications for future research.

The performance of the European League Against Rheumatism/American College of Rheumatology idiopathic inflammatory myopathies classification criteria in an expert-defined 10 year incident cohort.

OBJECTIVES: To assess the performance of the EULAR/ACR idiopathic inflammatory myopathies (IIMs) classification criteria in a cohort of incident IIM cases and examine how criteria-assigned IIM subtype correlates with expert opinion. METHODS: Adults with newly diagnosed IIM attending Salford Royal NHS Foundation Trust were identified over a 10 year period. A retrospective review of all putative cases was performed and those fulfilling a consensus expert opinion diagnosis of IIM were included. Clinical, serological and histological data were collected and each case was assigned a single IIM subtype. The EULAR/ACR classification criteria were then applied and sensitivity, specificity and positive and negative predictive values were calculated, presented with 95% CIs. RESULTS: A total of 1637 cases were screened, with 255 consensus expert opinion IIM cases ultimately identified. Applying the EULAR/ACR classification criteria, the sensitivity to diagnose an IIM was 99.6% (95% CI 97.2, 100) and 80.9% (95% CI 76.0, 85.8) for the criteria cut-points of probable and definite diagnoses, respectively. In 94/255 cases the IIM subtype differed between consensus expert opinion and classification criteria, most strikingly in the group subtyped as PM by the EULAR/ACR criteria, where there was discrepancy in the majority (i.e. in 87/161). CONCLUSION: The EULAR/ACR criteria performed with high sensitivity in identifying IIM in this external cohort of incident IIM. However, substantial disagreements arose between consensus expert opinion and the criteria regarding IIM subtype assignments, resulting in a large proportion of criteria-assigned cases of PM having heterogeneous features. These results may have important implications for future use of these criteria in subsequent research.

Investigation of myositis and scleroderma specific autoantibodies in patients with lung cancer.

BACKGROUND: The close temporal association between onset of some connective tissue diseases and cancer suggests a paraneoplastic association. Adult patients with scleroderma with anti-RNA polymerase III autoantibodies and adult patients with dermatomyositis with anti-transcriptional intermediary factor 1 (anti-TIF1) or anti-nuclear matrix protein 2 (anti-NXP2) autoantibodies have a significantly increased risk of developing cancer. Autoantibodies may serve as biomarkers for early detection of cancer and also could be relevant for prediction of responses to immune therapies. We aimed to test whether myositis and scleroderma specific or associated autoantibodies are detectable in individuals with lung cancer. METHODS: Serum from 60 Caucasian patients with lung cancer (30 with small cell lung cancer, 30 with non-small cell lung cancer) was screened for myositis and scleroderma specific and associated autoantibodies by radiolabelled immunoprecipitation. RESULTS: Anti-TIF1, anti-NXP2 or anti-RNA polymerase III autoantibodies were not detected in any of the 60 patients with lung cancer. Anti-glycyl-transfer RNA (tRNA) synthetase (anti-EJ) autoantibodies were detected in one patient with non-small cell lung cancer. No other known myositis or scleroderma autoantibodies were identified. CONCLUSIONS: Myositis and scleroderma specific autoantibodies, including anti-TIF1, anti-NXP2 and anti-RNA polymerase III, are rare in patients with lung cancer without an autoimmune disease. We report here the first case of anti-EJ autoantibodies being detected in a patient with lung cancer without clinical or radiographic evidence of the anti-synthetase syndrome.

Presence of anti-eukaryotic initiation factor-2B, anti-RuvBL1/2 and anti-synthetase antibodies in patients with anti-nuclear antibody negative systemic sclerosis.

Objectives: Autoantibodies targeting ubiquitously expressed nuclear antigens can be identified in most patients with SSc. Cytoplasmic autoantibodies (in otherwise ANA-negative sera) targeting eukaryotic initiation factor-2B (anti-eIF2B) have recently been identified in SSc with clinical associations to dcSSc disease and interstitial lung disease (ILD), although the majority of samples originated from a tertiary SSc-ILD centre. We investigated the prevalence and clinical associations of recently described SSc-specific (including anti-eIF2B) and other cytoplasmic autoantibodies in ANA-negative sera obtained from a large representative SSc cohort. Methods: ANA-negative sera from the Scleroderma Family Registry and DNA Repository underwent indirect immunofluorescence, radiolabelled protein immunoprecipitation (± immunodepletion) to identify anti-eIF2B and other CTD-related autoantibodies. The clinical phenotype of positive samples was evaluated. Results: Immunoprecipitation was performed on 128 ANA-negative samples (obtained from 3249 SSc patients). Anti-eIF2B antibodies were present in nine patients (7%), the majority of whom had dcSSc (8/9). SSc-ILD was present in all anti-eIF2B patients for whom chest imaging was available (7/9). Anti-synthetase autoantibodies (targeting PL12, PL7, OJ and Zo) were identified in seven patients (5.5%), all of whom fulfilled the 2013 ACR/EULAR classification criteria for SSc and had evidence of SSc-ILD where relevant outcomes were available for evaluation. Anti-RuvBL1/2 antibodies were identified in two patients with SSc-overlap syndromes. Conclusion: Anti-eIF2B antibodies are cytoplasmic SSc-specific autoantibodies with strong clinical associations with dcSSc and SSc-ILD found in ANA-negative sera. Anti-synthetase autoantibodies, and other recently discovered SSc-specific antibodies such as anti-RuvBL1/2, can also be identified in ANA-negative SSc.

The EuroMyositis registry: an international collaborative tool to facilitate myositis research.

AIMS: The EuroMyositis Registry facilitates collaboration across the idiopathic inflammatory myopathy (IIM) research community. This inaugural report examines pooled Registry data. METHODS: Cross-sectional analysis of IIM cases from 11 countries was performed. Associations between clinical subtypes, extramuscular involvement, environmental exposures and medications were investigated. RESULTS: Of 3067 IIM cases, 69% were female. The most common IIM subtype was dermatomyositis (DM) (31%). Smoking was more frequent in connective tissue disease overlap cases (45%, OR 1.44, 95% CI 1.09 to 1.90, p=0.012). Smoking was associated with interstitial lung disease (ILD) (OR 1.32, 95% CI 1.06 to 1.65, p=0.013), dysphagia (OR 1.43, 95% CI 1.16 to 1.77, p=0.001), malignancy ever (OR 1.78, 95% CI 1.36 to 2.33, p<0.001) and cardiac involvement (OR 2.40, 95% CI 1.60 to 3.60, p<0.001).Dysphagia occurred in 39% and cardiac involvement in 9%; either occurrence was associated with higher Health Assessment Questionnaire (HAQ) scores (adjusted OR 1.79, 95% CI 1.43 to 2.23, p<0.001). HAQ scores were also higher in inclusion body myositis cases (adjusted OR 3.85, 95% CI 2.52 to 5.90, p<0.001). Malignancy (ever) occurred in 13%, most commonly in DM (20%, OR 2.06, 95% CI 1.65 to 2.57, p<0.001).ILD occurred in 30%, most frequently in antisynthetase syndrome (71%, OR 10.7, 95% CI 8.6 to 13.4, p<0.001). Rash characteristics differed between adult-onset and juvenile-onset DM cases ('V' sign: 56% DM vs 16% juvenile-DM, OR 0.16, 95% CI 0.07 to 0.36, p<0.001). Glucocorticoids were used in 98% of cases, methotrexate in 71% and azathioprine in 51%. CONCLUSION: This large multicentre cohort demonstrates the importance of extramuscular involvement in patients with IIM, its association with smoking and its influence on disease severity. Our findings emphasise that IIM is a multisystem inflammatory disease and will help inform prognosis and clinical management of patients.

Autoantibodies in juvenile-onset myositis: Their diagnostic value and associated clinical phenotype in a large UK cohort.

OBJECTIVES: Juvenile myositis is a rare and heterogeneous disease. Diagnosis is often difficult but early treatment is important in reducing the risk of associated morbidity and poor outcomes. Myositis specific autoantibodies have been described in both juvenile and adult patients with myositis and can be helpful in dividing patients into clinically homogenous groups. We aimed to explore the utility of myositis specific autoantibodies as diagnostic and prognostic biomarkers in patients with juvenile-onset disease. METHODS: Using radio-labelled immunoprecipitation and previously validated ELISAs we examined the presence of myositis specific autoantibodies in 380 patients with juvenile-onset myositis in addition to, 318 patients with juvenile idiopathic arthritis, 21 patients with juvenile-onset SLE, 27 patients with muscular dystrophies, and 48 healthy children. RESULTS: An autoantibody was identified in 60% of juvenile-onset myositis patients. Myositis specific autoantibodies (49% patients) were exclusively found in patients with myositis and with the exception of one case were mutually exclusive and not found in conjunction with another autoantibody. Autoantibody subtypes were associated with age at disease onset, key clinical disease features and treatment received. CONCLUSIONS: In juvenile patients the identification of a myositis specific autoantibody is highly suggestive of myositis. Autoantibodies can be identified in the majority of affected children and provide useful prognostic information. There is evidence of a differential treatment approach and patients with anti-TIF1γ autoantibodies are significantly more likely to receive aggressive treatment with IV cyclophosphamide and/or biologic drugs, clear trends are also visible in other autoantibody subgroups.

Anti-HMGCR Autoantibodies in Juvenile Idiopathic Inflammatory Myopathies Identify a Rare but Clinically Important Subset of Patients.

OBJECTIVE: We aimed to establish the prevalence and clinical associations of anti-HMG-CoA-reductase (anti-HMGCR) in a large UK cohort with juvenile myositis. METHODS: There were 381 patients investigated for anti-HMGCR using ELISA. RESULTS: Anti-HMGCR autoantibodies were detected in 4 patients (1%). These children had no or minimal rash and significant muscle disease. Muscle biopsies were considered distinctive, with widespread variation in fiber size, necrotic fibers, and chronic inflammatory cell infiltrates; all had prolonged elevation of creatine kinase and all ultimately received biologic therapies. CONCLUSION: Anti-HMGCR in UK children with myositis are associated with severe disease that is poorly responsive to standard treatment.

Systematic protein-protein interaction and pathway analyses in the idiopathic inflammatory myopathies.

BACKGROUND: The idiopathic inflammatory myopathies (IIM) are autoimmune diseases characterised by acquired proximal muscle weakness, inflammatory cell infiltrates in muscle and myositis-specific/associated autoantibodies. It is unclear which pathways are involved in IIM, and the functional relationship between autoantibody targets has not been systematically explored. Protein-protein interaction and pathway analyses were conducted to identify pathways relevant to disease, using autoantibody targets and gene products of IIM-associated single nucleotide polymorphism (SNP) loci. METHODS: Protein-protein interactions were analysed using Disease Association Protein-Protein Link Evaluator (DAPPLE). Gene ontology and pathway analyses were conducted using Database for Annotation Visualisation and Integrated Discovery (DAVID) and Gene Relationships Across Implicated Loci (GRAIL). Analyses were undertaken including the targets of published autoantibodies, significant and suggestive SNPs from an IIM association study and autoantibody targets plus SNPs combined. RESULTS: The protein-protein interaction networks formed by autoantibody targets and associated SNPs showed significant direct and/or indirect connectivity (p < 0.05). Autoantibody targets plus associated SNPs combined resulted in more significant indirect and common interactor connectivity, suggesting autoantibody targets and proteins encoded by IIM-associated loci may be involved in common pathways. Tumour necrosis factor receptor-associated factor 6 (TRAF6) was identified as a hub protein, and UBE3B, HSPA1A, HSPA1B and PSMD3 also were identified as genes with significant connectivity. Pathway analysis identified that autoantibody targets and associated SNP regions are significantly interconnected (p < 0.01), and confirmed autoantibody target involvement in translational and post-translational processes. 'Ubiquitin' was the only keyword strongly linking significant genes across regions in all three GRAIL analyses of autoantibody targets and IIM-associated SNPs. CONCLUSIONS: Autoantibody targets and IIM-associated loci show significant connectivity and inter-relatedness, and identify several key genes and pathways in IIM pathogenesis, possibly mediated via the ubiquitination pathway.

Brief Report: Anti-Eukaryotic Initiation Factor 2B Autoantibodies Are Associated With Interstitial Lung Disease in Patients With Systemic Sclerosis.

OBJECTIVE: To investigate novel systemic sclerosis (SSc) autoantibodies in autoantibody-negative patients and establish clinical associations. METHODS: Serum samples and clinical data for 548 patients with SSc were collected. Routine serologic techniques were used to test the serum samples for known SSc autoantibodies, and samples with negative results were further investigated by radiolabeled-protein immunoprecipitation assay. Sera that immunoprecipitated a novel 30-kd band were analyzed by indirect immunofluorescence and immunoprecipitation, using depleted cell extracts to establish a common reactivity. Mass spectrometry was performed to identify the novel autoantigen, and the results were confirmed using commercial antibodies. Sera from 426 patients with other forms of connective tissue disease, 103 with rheumatoid arthritis, 114 with idiopathic interstitial lung disease (ILD), and 150 healthy subjects were serotyped as controls. RESULTS: A novel autoantigen with a molecular weight of ∼30 kd was recognized by 7 sera from patients with SSc, 6 of whom had ILD, and by no controls. Six of the patients had diffuse cutaneous involvement, and 4 had overlap features with other autoimmune diseases. Immunodepletion experiments indicated that all samples targeted the same autoantigen, and mass spectrometry identified the novel autoantigen as eukaryotic initiation factor 2B (eIF2B). CONCLUSION: We report the identification of a novel autoantibody (anti-eIF2B) in a small number of patients with SSc (∼1%); this autoantibody is closely associated with diffuse cutaneous manifestations and the presence of ILD.

Muscle Biopsy Findings in Combination With Myositis-Specific Autoantibodies Aid Prediction of Outcomes in Juvenile Dermatomyositis.

OBJECTIVE: Juvenile dermatomyositis (DM) is a rare and severe autoimmune condition characterized by rash and proximal muscle weakness. While some patients respond to standard treatment, others do not. This study was carried out to investigate whether histopathologic findings and myositis-specific autoantibodies (MSAs) have prognostic significance in juvenile DM. METHODS: Muscle biopsy samples (n = 101) from patients in the UK Juvenile Dermatomyositis Cohort and Biomarker Study were stained, analyzed, and scored for severity of histopathologic features. In addition, autoantibodies were measured in the serum or plasma of patients (n = 90) and longitudinal clinical data were collected (median duration of follow-up 4.9 years). Long-term treatment status (on or off medication over time) was modeled using generalized estimating equations. RESULTS: Muscle biopsy scores differed according to MSA subgroup. When the effects of MSA subgroup were accounted for, increased severity of muscle histopathologic features was predictive of an increased risk of remaining on treatment over time: for the global pathology score (histopathologist's visual analog scale [hVAS] score), 1.48-fold higher odds (95% confidence interval [95% CI] 1.12-1.96; P = 0.0058), and for the total biopsy score (determined with the standardized score tool), 1.10-fold higher odds (95% CI 1.01-1.21; P = 0.038). A protective effect was identified in patients with anti-Mi-2 autoantibodies, in whom the odds of remaining on treatment were 7.06-fold lower (95% CI 1.41-35.36; P = 0.018) despite muscle biopsy scores indicating more severe disease. In patients with anti-nuclear matrix protein 2 autoantibodies, anti-transcription intermediary factor 1γ autoantibodies, or no detectable autoantibody, increased histopathologic severity alone, without adjustment for the effect of MSA subtype, was predictive of the risk of remaining on treatment: for the hVAS global pathology score, 1.61-fold higher odds (95% CI 1.16-2.22; P = 0.004), and for the total biopsy score, 1.13-fold higher odds (95% CI 1.03-1.24; P = 0.013). CONCLUSION: Histopathologic severity, in combination with MSA subtype, is predictive of the risk of remaining on treatment in patients with juvenile DM and may be useful for discussing probable treatment length with parents and patients. Understanding these associations may identify patients at greater risk of severe disease.

Calcinosis in juvenile dermatomyositis is influenced by both anti-NXP2 autoantibody status and age at disease onset.

OBJECTIVE: Calcinosis is a major cause of morbidity in JDM and has previously been linked to anti-NXP2 autoantibodies, younger age at disease onset and more persistent disease activity. This study aimed to investigate the clinical associations of anti-NXP2 autoantibodies in patients with JDM stratified by age at disease onset. METHODS: A total of 285 patients with samples and clinical data were recruited via the UK Juvenile Dermatomyositis Cohort and Biomarker Study. The presence of anti-NXP2 was determined by both immunoprecipitation and ELISA. Logistic regression analysis was performed to assess the age-dependent relationship between anti-NXP2 and the development of calcinosis and disease activity measures. RESULTS: We identified anti-NXP2 autoantibodies in 56 patients (20%). While in all patients younger age at disease onset was associated with an increased risk of calcinosis and this relationship was nearly linear, anti-NXP2 autoantibodies substantially increased the risk of calcinosis across all ages (P = 0.025) and were detectable prior to calcinosis development. Children with anti-NXP2 autoantibodies had a greater degree of weakness (median lowest ever Childhood Myositis Assessment Score 29.6 vs 42) and were less likely to be in remission at 2 years post-diagnosis. No difference in disease activity was seen 4 years post-diagnosis. CONCLUSION: Children diagnosed at a young age have a high risk of calcinosis regardless of autoantibody status. However, the presence of anti-NXP2 autoantibodies substantially increases the risk of calcinosis across all ages and is associated with disease severity.

Anti-MDA5 autoantibodies in juvenile dermatomyositis identify a distinct clinical phenotype: a prospective cohort study.

INTRODUCTION: The aim of this study was to define the frequency and associated clinical phenotype of anti-MDA5 autoantibodies in a large UK based, predominantly Caucasian, cohort of patients with juvenile dermatomyositis (JDM). METHODS: Serum samples and clinical data were obtained from 285 patients with JDM recruited to the UK Juvenile Dermatomyositis Cohort and Biomarker Study. The presence of anti-MDA5 antibodies was determined by immunoprecipitation and confirmed by ELISA using recombinant MDA5 protein. Results were compared with matched clinical data, muscle biopsies (scored by an experienced paediatric neuropathologist) and chest imaging (reviewed by an experienced paediatric radiologist). RESULTS: Anti-MDA5 antibodies were identified in 7.4% of JDM patients and were associated with a distinct clinical phenotype including skin ulceration (P = 0.03) oral ulceration (P = 0.01), arthritis (P <0.01) and milder muscle disease both clinically (as determined by Childhood Myositis Assessment Score (P = 0.03)) and histologically (as determined by a lower JDM muscle biopsy score (P <0.01)) than patients who did not have anti-MDA5 antibodies. A greater proportion of children with anti-MDA5 autoantibodies achieved disease inactivity at two years post-diagnosis according to PRINTO criteria (P = 0.02). A total of 4 out of 21 children with anti-MDA5 had interstitial lung disease; none had rapidly progressive interstitial lung disease. CONCLUSIONS: Anti-MDA5 antibodies can be identified in a small but significant proportion of patients with JDM and identify a distinctive clinical sub-group. Screening for anti-MDA5 autoantibodies at diagnosis would be useful to guide further investigation for lung disease, inform on prognosis and potentially confirm the diagnosis, as subtle biopsy changes could otherwise be missed.

The diagnostic utility of autoantibodies in adult and juvenile myositis.

PURPOSE OF REVIEW: The purpose of this study is to review recent advances in the diagnostic utility of autoantibodies in dermatomyositis. RECENT FINDINGS: Alternative nonspecialist testing methods have been developed for anti-transcription intermediary factor 1 gamma, anti-MDA5 and anti-nuclear matrix protein 2, which are potentially exploitable by any hospital laboratory. Although these have yet to be validated for diagnostic use, it is likely that testing for myositis-specific antibodies will soon become readily available. SUMMARY: The identification of myositis-specific autoantibodies provides both diagnostic and prognostic information and offers a unique opportunity to adopt a stratified approach to treatment. Their identification, in many cases, should prevent the need for invasive diagnostic tests such as muscle biopsy.

Novel autoantibodies and clinical phenotypes in adult and juvenile myositis.

Autoantibodies targeting intracellular proteins involved in key processes are detected in patients with idiopathic inflammatory myopathies. These myositis-specific autoantibodies have been increasingly demonstrated to correlate with distinct clinical phenotypes within the myositis spectrum. This review highlights the clinical associations of the myositis-specific autoantibodies, with particular attention to the recently identified and characterized novel myositis autoantibodies: p155/140, p140 (MJ), CADM-140 (MDA5), SAE, and 200/100.

Pathogenic mechanisms of disease in myositis: autoantigens as clues.

PURPOSE OF REVIEW: There is increasing evidence of autoimmunity in dermatomyositis and polymyositis, with strong correlations between particular myositis-specific autoantibodies (MSAs) and clinical subsets. It is now clear that corresponding autoantigens are selectively targeted, have distinct adjuvant properties and are upregulated in target tissues, suggesting a role in disease pathogenesis. This review highlights recent findings including the identification of novel MSAs and studies investigating autoantigen properties and expression in both target tissues and tumours. RECENT FINDINGS: During the review period, the clinical associations of anti-SAE and anti-p140 have been further described. Studies of autoantigen expression have demonstrated upregulation of Mi-2 in response to ultraviolet (UV) damage and expression of myositis-specific autoantigens in rat newborn skeletal muscle. The role of type I interferon and adjuvant activity has also been highlighted through the identification of the CADM140 autoantigen as MDA5, a protein involved in innate immunity. SUMMARY: There are now a number of models indicating roles of autoantigens in disease pathogenesis. Our increased understanding of the autoantigenic properties of these targeted proteins will help to determine the mechanisms involved in the initiation and propagation of myositis. In turn, these findings may lead to therapeutic advances including the development of more targeted treatments.

Myositis-specific autoantibodies: their clinical and pathogenic significance in disease expression.

The idiopathic inflammatory myopathies (IIMs)--DM and PM--have been historically defined by broad clinical and pathological criteria. These conditions affect both adults and children with clinical features including muscle weakness, skin disease, internal organ involvement and an association with cancer in adults. Using a clinico-serological approach, DM and PM can be defined into more homogeneous subsets. Over the last few years, myositis-specific autoantibodies (MSAs) have been better characterized including autoantibodies directed against the aminoacyl tRNA-synthetase enzymes, the signal-recognition particle and the Mi-2 protein. In addition, clinically significant novel autoantibodies--anti-CADM-140, anti-SAE (small ubiquitin-like modifier activating enzyme), anti-p155/140 and anti-p140--have been described in the adult and juvenile disease spectrum. MSAs are directed against cytoplasmic or nuclear components involved in key regulatory intracellular processes including protein synthesis, translocation and gene transcription. The striking association between unique serological profiles and distinct clinical phenotypes suggests that target autoantigens may play a role in disease induction and propagation. In this review, we discuss the clinical utility and pathogenic significance of MSAs in disease expression.

Newly identified autoantibodies: relationship to idiopathic inflammatory myopathy subsets and pathogenesis.

PURPOSE OF REVIEW: There is increasing evidence that patients with polymyositis and dermatomyositis have specific clinico-serological profiles. Myositis-specific autoantibodies target intracellular proteins involved in key processes such as translocation and nuclear transcription, and are closely linked to patterns of disease expression. This review highlights the recent work on novel myositis-specific autoantibodies, their autoantigen targets, the relationship to clinical subsets and potential role in pathogenesis. RECENT FINDINGS: During the annual review period novel autoantibodies have been described in adult-onset dermatomyositis (anti-SAE autoantibodies) and juvenile dermatomyositis (anti-p155/140 autoantibodies) (anti-MJ or anti-p140 autoantibodies). These findings are important because the function of the autoantigen targets may point to shared pathogenic pathways. Studies highlighting the potential role of autoantigen-driven responses and autoantibody production in disease initiation and propagation are discussed, as well as further evidence on the relationship between autoantigens and corresponding target tissues. SUMMARY: Considerable progress has been made emphasizing the striking association between genotype, serotype and clinical phenotype in the myositis disease spectrum. Further characterization of the identity and function of autoantigen systems in target tissues will greatly facilitate investigation of models of autoimmunity in this disease.

Antigen binding to GM1 ganglioside results in delayed presentation: minimal effects of GM1 on presentation of antigens internalized via other pathways.

Plasma membrane rafts are sphingolipid- and cholesterol-rich patches that function as membrane trafficking and surface signalling regions. Ganglioside GM1 is an integral component of these microdomains, and Escherichia coli enterotoxin B subunit (EtxB) is a pentamer that binds with high affinity to GM1 resulting in GM1 cross-linking. We previously demonstrated that antigen coupled directly to EtxB resulted in enhanced presentation relative to antigen taken up by fluid-phase endocytosis. Here we demonstrate a new role for GM1 in antigen presentation by examining the effects of cross-linking GM1 on the kinetics of presentation and processing of antigen by the B-cell receptor (BCR), fluid-phase endocytosis and GM1-targeted antigen. EtxB bound to B cells does not augment the subsequent kinetics or magnitude of presentation of either BCR-internalized antigen or soluble antigen. Moreover, presentation of GM1-bound antigen is significantly slower than antigen presentation following BCR-mediated uptake. In contrast to the rapid internalization of BCR-bound antigen (which has a half life of 60 min), the majority of EtxB-bound antigen forms a plasma membrane depot detectable for many hours after initial incubation (and with a half life of 12 hr). We conclude that cross-linking of GM1 by EtxB minimally affects the processing and presentation of antigens internalized via other pathways. Nevertheless, binding of antigens to GM1 results in delayed presentation that has important implications for in vivo immunization using GM1-targeted adjuvants.