Comparative B cell epitope profiling in Japanese and North American cohorts of MDA5+ dermatomyositis reveals a direct association between immune repertoire and pulmonary mortality.

OBJECTIVES: Anti-melanoma differentiation-associated gene 5 antibody-positive (MDA5+) dermatomyositis patients exhibit clinical features that vary by geographical and ethnic/genetic distribution. We therefore investigated whether B cell epitope profiles and corresponding clinical features distinguished two independent cohorts of MDA5+ dermatomyositis. METHODS: We used ELISA-based methods to determine the relationship between antibody recognition of overlapping 155 amino acid MDA5 subfragments and clinical features of 17 MDA5+ dermatomyositis patients from Japan. Associations between clinical features and standardized anti-MDA5 subfragment antibody titers were assessed via Brunner Munzel testing and compared with clinical/serological profiles of an independent North American cohort. ROC analyses and Kaplan-Meier curves were used to further assess the relationship between anti-MDA5 fragment antibody levels and specific clinical features/outcomes. RESULTS: Clinical characterization of a Japanese cohort of 17 MDA5+ dermatomyositis patients revealed a high prevalence of arthritis (47%) and interstitial lung disease (ILD) (100%). Serological profiling demonstrated predominant antibody recognition of MDA5 fragments A (aa 1-155), B (aa 130-284), and E (aa 517-671) in a pattern that was distinct from North American MDA5+ patients (n = 24) whose sera preferentially recognized fragment H (aa 905-1026). Statistical analysis revealed a striking association between anti-fragment A antibody levels and rapidly progressive ILD (RP-ILD) among Japanese patients (p< 0.01). ROC and Kaplan Meier curves also demonstrated a strong relationship between anti-fragment A antibody levels, RP-ILD, and pulmonary death in combined cohort analyses. CONCLUSIONS: Japanese and North American MDA5+ dermatomyositis patients manifest markedly different B cell epitope profiles that are associated with higher prevalence of RP-ILD and worse clinical outcome among Japanese patients.

Development and Internal Validation of a Clinical and Genetic Risk Score for Rheumatoid Arthritis-Associated Interstitial Lung Disease.

OBJECTIVE: Although clinical and genetic risk factors have been identified for rheumatoid arthritis-associated interstitial lung disease (RA-ILD), there are no current tools allowing for risk stratification. We sought to develop and validate an ILD risk model in a large, multicentre, prospective RA cohort. METHODS: Participants in the Veterans Affairs RA (VARA) registry were genotyped for 12 single nucleotide polymorphisms (SNPs) associated with idiopathic pulmonary fibrosis. ILD was validated through systematic record review. A genetic risk score (GRS) was computed from minor alleles weighted by effect size with ILD, using backward selection. The GRS was combined with clinical risk factors within a logistic regression model. Internal validation was completed using bootstrapping, and model performance was assessed by the area under the receiver operating curve (AUC). RESULTS: Of 2,386 participants (89% male, mean age 69.5 years), 9.4% had ILD. Following backward selection, five SNPs contributed to the GRS. The GRS and clinical factors outperformed clinical factors alone in discriminating ILD (AUC 0.675 vs 0.635, p< 0.001). The shrinkage-corrected performance for combined and clinical-only models was 0.667 (95% CI 0.628, 0.712) and 0.623 (95% CI 0.584, 0.651), respectively. Twenty percent of the cohort had a combined risk score below a cut-point with >90% sensitivity. CONCLUSION: A clinical and genetic risk model discriminated ILD in a large, multicentre RA cohort better than a clinical-only model, excluding 20% of the cohort from low-yield testing. These results demonstrate the potential utility of a GRS in RA-ILD and support further investigation into individualized risk stratification and screening.

Serum cytokine profiles of adults with idiopathic inflammatory myopathies.

OBJECTIVES: There is a paucity of available biomarkers of disease activity in idiopathic inflammatory myopathies (IIM), and serum cytokines/chemokines hold potential as candidate biomarkers. We aimed to determine serum cytokine profiles of IIM patients with active disease as compared to patients in remission and healthy controls. METHODS: The IIM patients with active disease (included patients enrolled in repository corticotropin injection trial), in remission, and healthy controls were enrolled in this cross-sectional observational study. Serum concentrations of 51 cytokines/chemokines were obtained by utilising a bead-based multiplex cytokine assay (Luminex®). The myositis core set measures were obtained for all the patients. Cytokines with the best predictive ability to differentiate these clinical groups were assessed with three methods: 1) Least Absolute Shrinkage and Selection Operator modelling, 2) stepwise approach, and 3) logistic regression model. RESULTS: Twenty-one IIM patients with active disease, 11 IIM patients in remission and 10 healthy controls were enrolled. Myositis patients had elevated levels of chemokines that attract eosinophils (eotaxin) and dendritic cells, NK cells, cytotoxic T-cells and monocytes/macrophages (CXCL-9, IP-10), cytokines that drive T-helper 1 responses (TNF-a, lymphotoxin-a), matrix degrading enzymes (MMP-3 and -9), and IGFBP-2 compared to healthy controls. Myositis patients with active disease had higher levels of lymphotoxin-a, CXCL-9, MIP-1a, MIP-1b and MMP-3 than patients in remission. CONCLUSIONS: This study demonstrated differences in cytokine profiles of IIM patients (active and inactive disease) compared to healthy controls and identified some cytokines that could potentially be used as biomarkers. Larger longitudinal studies are needed to validate our findings.

Rheumatoid Arthritis-Associated Interstitial Lung Disease (RA-ILD): Update on Prevalence, Risk Factors, Pathogenesis, and Therapy.

PURPOSE OF REVIEW: Rheumatoid arthritis is frequently complicated by interstitial lung disease (RA-ILD), an underappreciated contributor to excess morbidity and mortality. The true prevalence of RA-ILD is difficult to define given the variability in diagnostic criteria used. The lack of standardized screening methods, an incomplete understanding of disease pathogenesis, and dearth of validated biomarkers have limited the development of controlled clinical trials for this disease. RECENT FINDINGS: Numerous studies have focused on clinical, radiographic, genetic, molecular, and/or serologic markers of disease severity as well as risk of disease progression. In addition to defining valuable clinical biomarkers, these studies have provided insights regarding the pathogenesis of RA-ILD and potential therapeutic targets. Additional studies involving immunomodulatory and/or anti-fibrotic agents have assessed new therapeutic options for different stages of RA-ILD. RA-ILD continues to be a major contributor to the increased morbidity and mortality associated with RA. Advancements in our understanding of disease pathogenesis at a molecular level are necessary to drive the development of more targeted therapy.

Correlation between B cell epitope profile and clinical features of anti-MDA5 antibody-positive dermatomyositis.

OBJECTIVES: Anti-melanoma differentiation-associated gene 5 (MDA5) antibody-positive (MDA5+) dermatomyositis patients exhibit a variety of clinical features. We therefore investigated whether patterns of B cell epitope recognition are linked to the clinical course of MDA5+ dermatomyositis. METHODS: Our cross-sectional study used ELISA-based methods to determine the relationship between antibody recognition of overlapping 155 amino acid MDA5 subfragments and clinical features of 24 MDA5+ myositis patients. Correlations between clinical features and standardized anti-MDA5 subfragment antibody titers were assessed via Spearman's rank correlation coefficients. RESULTS: Twenty-four MDA5+ patients submitted serum samples within a median of 0 (interquartile range, 0-74) days from the initial clinic visit. In addition to typical dermatomyositis rashes, these patients exhibited muscle symptoms (n = 11), vascular dysfunction (n = 9), and interstitial lung disease (ILD) (n = 16). Female patients exhibited higher titers of antibodies recognizing fragment H (aa 905-1026) compared to male patients. Muscle involvement was associated with higher levels of anti-fragment F (aa 646-801) antibody. Conversely, patients with vascular abnormalities had higher anti-fragment B (aa 130-284) and E (aa 517-671) antibody titers than those without vascular dysfunction. Four patients died due to ILD progression and showed higher anti-fragment A (aa 1-155) antibody titers than the other 20 patients. Differences in the ratio of anti-fragment to anti-full length MDA5 antibody titers were found for sex (H: anti-MDA5) and vascular dysfunction (anti-fragment B, E: anti-MDA5). CONCLUSIONS: Various clinical features of MDA5+ dermatomyositis correlated with levels of antibodies targeting selected subfragments of this autoantigen, providing a link between fragment-specific immune responses and disease course.

The impact of disease severity measures on survival in U.S. veterans with rheumatoid arthritis-associated interstitial lung disease.

OBJECTIVES: To determine whether RA and interstitial lung disease (ILD) severity measures are associated with survival in patients with RA-ILD. METHODS: We studied US veterans with RA-ILD participating in a multicentre, prospective RA cohort study. RA disease activity (28-joint DAS [DAS28-ESR]) and functional status (multidimensional HAQ [MDHAQ]) were collected longitudinally while pulmonary function tests (forced vital capacity [FVC], diffusing capacity for carbon monoxide) were obtained from medical records. Vital status and cause of death were determined from the National Death Index and administrative data. Predictors of death were assessed using multivariable Cox regression models adjusting for age, sex, smoking status, ILD duration, comorbidity burden and medications. RESULTS: We followed 227 RA-ILD participants (93% male and mean age of 69 years) over 1073 person-years. Median survival after RA-ILD diagnosis was 8.5 years. Respiratory diseases (28%) were the leading cause of death, with ILD accounting for 58% of respiratory deaths. Time-varying DAS28-ESR (adjusted hazard ratio [aHR] 1.21; 95% CI: 1.03, 1.41) and MDHAQ (aHR 1.85; 95% CI: 1.29, 2.65) were separately associated with mortality independent of FVC and other confounders. Modelled together, the presence of either uncontrolled disease activity (moderate/high DAS28-ESR) or FVC impairment (<80% predicted) was significantly associated with mortality risk. Those with a combination of moderate/high disease activity and FVC <80% predicted had the highest risk of death (aHR 4.43; 95% CI: 1.70, 11.55). CONCLUSION: Both RA and ILD disease severity measures are independent predictors of survival in RA-ILD. These findings demonstrate the prognostic value of monitoring the systemic features of RA-ILD.

Increased susceptibility to organic dust exposure-induced inflammatory lung disease with enhanced rheumatoid arthritis-associated autoantigen expression in HLA-DR4 transgenic mice.

Immunogenetic as well as environmental and occupational exposures have been linked to the development of rheumatoid arthritis (RA), RA-associated lung disease, and other primary lung disorders. Importantly, various inhalants can trigger post-translational protein modifications, resulting in lung autoantigen expression capable of stimulating pro-inflammatory and/or pro-fibrotic immune responses. To further elucidate gene-environment interactions contributing to pathologic lung inflammation, we exploited an established model of organic dust extract (ODE) exposure with and without collagen-induced arthritis (CIA) in C57BL/6 wild type (WT) versus HLA-DR4 transgenic mice. ODE-induced airway infiltration driven by neutrophils was significantly increased in DR4 versus WT mice, with corresponding increases in bronchoalveolar lavage fluid (BALF) levels of TNF-⍺, IL-6, and IL-33. Lung histopathology demonstrated increased number of ectopic lymphoid aggregates comprised of T and B cells following ODE exposure in DR4 mice. ODE also induced citrullination, malondialdehyde acetaldehyde (MAA) modification, and vimentin expression that co-localized with MAA and was enhanced in DR4 mice. Serum and BALF anti-MAA antibodies were strikingly increased in ODE-treated DR4 mice. Coupling ODE exposure with Type II collagen immunization (CIA) resulted in similarly augmented pro-inflammatory lung profiles in DR4 mice (relative to WT mice) that was accompanied by a profound increase in infiltrating lung CD4+ and CD8+ T cells as well as CD19+CD11b+ autoimmune B cells. Neither modeling strategy induced significant arthritis. These findings support a model in which environmental insults trigger enhanced post-translational protein modification and lung inflammation sharing immunopathological features with RA-associated lung disease in the selected immunogenetic background of HLA-DR4 mice.

Role of Intravenous Immunoglobulin in Necrotizing Autoimmune Myopathy.

BACKGROUND/OBJECTIVE: Immune-mediated necrotizing myopathy (IMNM) is a subtype of myositis that is associated with a refractory phenotype and poorer prognosis. The aim of the study was to provide single large center experience of outcomes of intravenous immunoglobulin (IVIg) for patients with IMNM using longitudinally collected data. METHODS: This case series longitudinally evaluated 4 of the 6 myositis core set measures at baseline and at 3 and 6 months after IVIg on 20 adult IMNM patients from 2014 to 2019 at the University of Pittsburgh. We assessed patients for improvement in core set measures, prednisone dose, adverse effects, and by the "limited" ACR/EULAR 2016 myositis response criteria. The mean differences in CK and manual muscle testing (MMT-8) were compared using a paired t test. A clinically significant response was defined as a >10% absolute improvement in the MMT-8 and a >50% absolute reduction in serum CK at 6 months of IVIg. RESULTS: Intravenous immunoglobulin treatment was associated with marked improvement in IMNM patients, with 85% of patient meeting clinically significant response. The median (interquartile range) relative percent improvement in CK level was 96% (85%-98%) and in MMT was 29% (14%-36%) at 6 months.There was a significant reduction in the mean (SD) dose of prednisone at 6 months and had minimal adverse effects. In addition, with IVIg, most (13/14) patients had at least minimal improvement as per ACR/EULAR 2016 myositis response criteria. CONCLUSIONS: Based on objective, meaningful improvement in MMT-8 and CK as well as marked reduction in prednisone doses with acceptable tolerability, early implementation of IVIg should be considered in adult IMNM.

Extensive Citrullination Promotes Immunogenicity of HSP90 through Protein Unfolding and Exposure of Cryptic Epitopes.

Post-translational protein modifications such as citrullination have been linked to the breach of immune tolerance and clinical autoimmunity. Previous studies from our laboratory support this concept, demonstrating that autoantibodies targeting citrullinated isoforms of heat shock protein 90 (HSP90) are associated with rheumatoid arthritis complicated by interstitial lung disease. To further explore the relationship between citrullination and structural determinants of HSP90 immunogenicity, we employed a combination of ELISA-based epitope profiling, computational modeling, and mass-spectrometric sequencing of peptidylarginine deiminase (PAD)-modified protein. Remarkably, ELISAs involving selected citrullinated HSP90ß/α peptides identified a key epitope corresponding to an internal Arg residue (R502 [HSP90ß]/R510 [HSP90α]) that is normally buried within the crystal structure of native/unmodified HSP90. In vitro time/dose-response experiments reveal an ordered pattern of PAD-mediated deimination events culminating in citrullination of R502/R510. Conventional as well as scaled molecular dynamics simulations further demonstrate that citrullination of selected Arg residues leads to progressive disruption of HSP90 tertiary structure, promoting exposure of R502/R510 to PAD modification and subsequent autoantibody binding. Consistent with this process, ELISAs incorporating variably deiminated HSP90 as substrate Ag indicate a direct relationship between the degree of citrullination and the level of ex vivo Ab recognition. Overall, these data support a novel structural paradigm whereby citrullination-induced shifts in protein structure generate cryptic epitopes capable of bypassing B cell tolerance in the appropriate genetic context.

Rheumatoid Arthritis-Associated Interstitial Lung Disease: Current Concepts.

PURPOSE OF REVIEW: Among the many extra-articular complications of rheumatoid arthritis (RA), interstitial lung disease (ILD) contributes significantly to morbidity and mortality. Prevalence estimates for RA-ILD vary widely depending on the specific clinical, radiographic, and functional criteria used to establish the diagnosis. A key unresolved issue is whether early, subclinical forms of RA-ILD represent a precursor to end stage, fibrotic lung disease. Based on uncertainties surrounding the natural history of RA-ILD, incomplete understanding of underlying disease pathogenesis, and lack of controlled clinical trials, evidence-based therapeutic strategies remain largely undefined. RECENT FINDINGS: Correlative clinico-epidemiological studies have identified key risk factors for disease progression. Complementing these findings, the identification of specific molecular and serological markers of RA-ILD has improved our understanding of disease pathogenesis and established the foundation for predictive biomarker profiling. Experience from case series and cohort studies suggests that newer biological agents such as rituximab may be viable treatment options. RA-ILD continues to have a major impact on "disease intrinsic" morbidity and mortality. Increased understanding of disease pathogenesis and the natural history of subclinical RA-ILD will promote the development of more refined therapeutic strategies.