Proinflammatory Histidyl–Transfer RNA Synthetase–Specific CD 4+ T Cells in the Blood and Lungs of Patients With Idiopathic Inflammatory Myopathies

Pathogenic mechanisms of disease in idiopathic inflammatory myopathies: autoantibodies as clues

Idiopathic inflammatory myopathies (IIMs) encompass a spectrum of autoimmune diseases characterized by muscle inflammation and systemic involvement. This review aimed to synthesize current evidence on the clinical significance and pathogenic mechanisms underlying autoantibodies associated with IIMs. Autoantibodies targeting aminoacyl-tRNA synthetases (ARS) play a pivotal role in antisynthetase syndrome (ASS), highlighting associations with interstitial lung disease (ILD) and distinctive clinical features. Anti-Mi-2 antibodies in dermatomyositis (DM) are hallmarked by characteristic cutaneous manifestations and favorable prognostic outcomes. Conversely, anti-TIF1 antibodies are correlated with DM and a higher risk of malignancies, implicating CD8+ T cells in its pathogenesis. Anti-MDA5 antibodies signify clinically amyopathic DM (CADM) with severe ILD, linked to dysregulated neutrophil extracellular trap (NET) formation. In immune-mediated necrotizing myopathies (IMNMs), anti-SRP and anti-HMGCR antibodies induce complement-mediated myopathy, typically following statin exposure. Additionally, anti-TRIM72 antibodies emerge as potential diagnostic markers in IIMs. Anti-cN1A autoantibodies are linked to inclusion body myositis (IBM) and play a decisive role in muscle protein degradation. Meanwhile, anti-FHL1 autoantibodies are associated with severe disease manifestations and muscle damage, as established in experimental models. Anti-eIF3 autoantibodies, recently identified in polymyositis (PM) patients, are rarely detected (<1%) and associated with a favorable prognosis. Elucidating these autoantibodies is anticipated to not only assist in early diagnosis and disease stratification but also inform targeted therapeutic interventions, emphasizing the intricate interplay between autoimmunity, cellular dysfunction, and clinical outcomes in IIMs.

Relationship between Jo-1 B Cell Epitope Profile and Clinical Features of Anti-Synthetase Syndrome

OBJECTIVE

Anti-histidyl-transfer RNA synthetase (Jo-1) antibodies are associated with myositis as well as different extramuscular organ complications comprising the anti-synthetase syndrome. This study aimed to clarify the relationship between anti-Jo-1 epitope recognition patterns and specific clinical features of this syndrome.

METHODS

B cell epitope mapping was performed via enzyme-linked immunosorbent assay in 180 patients who were anti-Jo-1 antibody-positive using overlapping peptides/protein fragments spanning the amino-terminal 151 amino acids of Jo-1 as substrate antigens. Statistical associations with clinical features were assessed through rank-sum, correlation, and cluster analyses.

RESULTS

The level of reactivity against subfragments spanning amino acids 1-151 of Jo-1 paralleled that of full-length Jo-1, confirming the immunodominance of this amino-terminal region. The corresponding frequencies of reactivity to peptides 1 (amino acids [aa] 1-21), 3 (aa 27-47), 4 (aa 40-60), 10 (aa 118-138), and 11 (aa 131-151) were 6.1%, 42.5%, 6.8%, 6.7%, and 20.3%. While anti-full-length Jo-1 antibodies were significantly associated with Raynaud phenomenon, anti-fragment A2 (aa 1-60) and A3 (aa 1-90) antibodies were associated with proximal muscle weakness, Raynaud phenomenon, arthritis, and sicca syndrome. Anti-fragment A4 (aa 1-120) and A5 (aa 1-151) antibodies were also associated with sicca syndrome. Peptide 1 (aa 1-21) antibodies were associated with Raynaud phenomenon and dysphagia. Whereas anti-peptide 3 (aa 27-47) antibodies were also linked to Raynaud phenomenon, anti-peptide 9 (aa 105-125) antibodies were associated with mechanic's hands.

CONCLUSION

Autoantibodies targeting different amino-terminal subfragments and/or peptides of Jo-1 were associated with specific clinical features of the anti-synthetase syndrome, demonstrating the biomarker potential of B cell epitope profiling in this disorder.

Disease-specific autoantibody production in the lungs and salivary glands of anti-synthetase syndrome

Interstitial lung disease is a common complication of anti-synthetase syndrome (ASS), and lymphocytic infiltration is often observed in the lesion. We have recently reported that disease-specific autoantibodies are produced by infiltrating lymphocytes in some autoimmune diseases. Here, we investigate the antigen specificity of B cells in the lung lesions of ASS patients. A total of 177 antibodies were produced from antibody-secreting cells in bronchoalveolar fluid (BALF) of three each of serum anti-Jo-1 and serum anti-EJ antibody-positive patients. Twelve to 30% and 50 to 62% of these antibodies were disease-specific autoantibodies, respectively. These autoantibodies recognized conformational epitopes of the whole self-antigen and had affinity maturations, indicating that self-antigens themselves are the target of humoral immunity. In addition, 100 antibodies were produced from two salivary gland tissues, obtained by chance, of ASS patients. Salivary glands are not generally recognized as lesions of ASS, but unexpectedly, ASS-related autoantibody production was also observed similar to that of BALF. Immunostaining confirmed the presence of ASS-related autoantibody-producing cells in salivary glands. Our results suggest that disease-specific autoantibody production at lesion sites is a common pathogenesis of autoimmune diseases, and that tissue-specific production of autoantibodies can provide insights regarding the distribution of organ manifestations in autoimmune diseases.

Clinical and prognostic associations of anti-Jo-1 antibody levels in patients with antisynthetase syndrome

OBJECTIVE

To investigate the association of serum anti-Jo-1 antibody levels with the disease activity and prognosis in anti-Jo-1-positive patients with antisynthetase syndrome (ASS).

METHODS

This study included 115 anti-Jo-1-positive patients with ASS who were admitted to China-Japan Friendship Hospital between 2009 and 2019. Anti-Jo-1 antibody serum levels at initial admission and follow-up were determined by enzyme-linked immunosorbent assay (ELISA). Global and organ disease activity was assessed at baseline and follow-up according to the International Myositis Assessment and Clinical Studies guidelines.

RESULTS

Among enrolled patients, 70 (60.9%) patients initially presented with interstitial lung disease (ILD), and 46 (40%) patients presented with with muscle weakness at initial admission. At baseline, patients with ILD had lower levels of anti-Jo-1 antibodies than those without ILD (p = 0.012). Baseline anti-Jo-1 antibody levels were higher in patients with muscle weakness, skin involvement, and arthritis (all p < 0.05) compared to those without these manifestations. Baseline anti-Jo-1 antibody levels were positively correlated with skin visual analogue scale (VAS) scores (r = 0.25, p = 0.006), but not with disease activity in other organs. However, changes in anti-Jo-1 antibody levels were significantly positively correlated with the changes in PGA (β = 0.002, p = 0.001), muscle (β = 0.003, p < 0.0001), and pulmonary (β = 0.002, p = 0.013) VAS scores, but not with skin and joint VAS scores. Older age of onset (hazard ratio [HR] 1.069, 95% confidence interval [CI]:1.010-1.133, p = 0.022) and higher C-reactive protein (CRP) levels (HR 1.333, 95% CI: 1.035-1.717, p = 0.026) were risk factors for death.

CONCLUSION

Anti-Jo-1 titers appear to correlate more with disease activity changes over time rather than with organ involvement at baseline, which provides better clinical guidance for assessing the disease course using anti-Jo-1 levels.

A Review of Antisynthetase Syndrome-Associated Interstitial Lung Disease

Our objective in this review article is to present a clinical case of a patient with antisynthetase syndrome (ASyS) and provide an overview of the pathogenesis, classification criteria, antibody profiles, clinical features, and current knowledge of treatment options, focusing on interstitial lung disease (ILD). ASyS is an uncommon autoimmune disease with a heterogenous clinical presentation characterized by the presence of autoantibodies against an aminoacyl-tRNA synthetase and manifested by myositis, fever, inflammatory arthritis, Raynaud's phenomenon, mechanics hands, and ILD. ASyS-associated ILD (ASyS-ILD) is the most serious complication of ASyS, which may evolve to rapidly progressive ILD; therefore, it often requires thorough clinical and radiologic evaluation including recognition of a specific clinical phenotype associated with the antisynthetase antibodies (ASAbs) to guide therapeutic interventions.

Anti-synthetase syndrome in a child with pneumomediastinum: a case report and literature review

BACKGROUND

Anti-synthetase syndrome (ASS) is a group of rare clinical subtypes within inflammatory myopathies, predominantly affecting adult females. Instances of critical illness associated with ASS in children are even rarer.

CASE PRESENTATION

We report the case of a 7-year-old boy finally diagnosed with ASS, combined with pneumomediastinum. He presented with intermittent fever persisting for 12 days, paroxysmal cough for 11 days, chest pain, and shortness of breath for 4 days, prompting admission to our hospital. Pre-admission chest CT revealed diffuse pneumomediastinum, subcutaneous pneumatosis in the neck and bilateral chest wall, consolidation, atelectasis, and reticular nodular shadowing in both lungs, as well as pericardial effusion and bilateral pleural effusions. Laboratory tests revealed a positive result for serum MP immunoglobulin M (MP-IgM) and MP immunoglobulin G (MP-IgG). The patient was initially diagnosed with mycoplasma pneumoniae (MP) infection, and following 3 days of antibiotic treatment, the patient's tachypnea worsened. Positive results in muscle enzyme antibody tests included anti-PL-12 antibody IgG, anti-Jo-1 antibody IgG, and anti-RO-52 antibody IgG. Ultrasonography detected moderate effusions in the right shoulder, bilateral elbow, and knee joints. Corticosteroids pulse therapy was initiated on the 27th day following disease onset, and continued for 3 days, followed by sequential therapy for an additional 12 days. The child was discharged on the 43rd day, and subsequent follow-up revealed a significant improvement in consolidation and interstitial lesions in both lungs.

CONCLUSIONS

ASS in children may combine with rapidly progressive interstitial lung disease (RPILD) and pneumomediastinum. It is crucial to promptly identify concurrent immunologic abnormalities during the outbreak of MP, particularly when the disease exhibits rapid progression with ineffective conventional antibiotic therapy.

Idiopathic inflammatory myopathies: current insights and future frontiers

Idiopathic inflammatory myopathies are a group of autoimmune diseases with a broad spectrum of clinical presentations, primarily characterised by immune-mediated muscle injury. Until recently, there was little insight into the pathogenesis of idiopathic inflammatory myopathies, which challenged the recognition of the breadth of heterogeneity of this group of diseases as well as the development of new therapeutics. However, the landscape of idiopathic inflammatory myopathies is evolving. In the past decade, advances in diagnostic tools have facilitated an enhanced understanding of the underlying disease mechanisms in idiopathic inflammatory myopathies, enabling the expansion of therapeutic trials. The fields of transcriptomics, prot§eomics, and machine learning offer the potential to gain greater insights into the underlying pathophysiology of idiopathic inflammatory myopathies. Harnessing insights gained from these sophisticated tools could contribute to the identification of differences at a molecular level among patients, accelerating the development of targeted, tailored therapies. Bolstered by the validation and standardisation of robust outcome measures, many promising therapies are in clinical trial development. Although challenges remain, there is great optimism in the field due to the progress in innovative diagnostics, outcome measures, and therapeutic approaches. In this Review, we discuss the expanding landscape of idiopathic inflammatory myopathies as the frontier of precision medicine becomes imminent.

The Role of Environmental Factors in the Development of Idiopathic Inflammatory Myopathies: a Narrative Review

PURPOSE OF REVIEW

This review aims to evaluate recent findings on the role of environmental factors in the development and clinical presentation of idiopathic inflammatory myopathies (IIMs).

RECENT FINDINGS

A targeted literature review was conducted to identify reports relevant to the association between environmental factors and IIMs published over the past three years. There has been an increasing number of publications dealing with the association of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or vaccination with the development of IIMs, highlighting the significant role of the antiviral immune response in the pathogenesis of the disease. Traditional environmental factors associated with the pathogenic process of IIM subclassifications included drugs such as statins and immune checkpoint inhibitors, ultraviolet radiation, smoking, air pollutants, and vitamin D deficiency. Correlations of seasonality and residence with the onset of certain IIM subtypes suggest a potential role of environmental triggers in the pathogenic process. An interplay between genetic predisposition and various environmental factors might contribute to the development of IIMs as well as the heterogeneous clinical and serological presentation of IIMs. The growing evidence on the role of environmental factors in the development of IIMs provides important clues to elucidate the pathophysiology of these disease entities. The mechanisms underlying the interactions between genetic predisposition and environmental factors should be investigated in the future.

Clinical characteristics and prognostic analysis of idiopathic inflammatory myopathy with positive anti-aminoacyl-tRNA synthetase antibodies: A single center experience

OBJECTIVES

To identify the differences of clinical characteristics, laboratory findings, and the long-term outcomes in patients with anti-synthetase syndrome (ASS) of different anti-aminoacyl-transfer RNA synthetase antibodies.

METHODS

We retrospectively enrolled 119 patients with ASS, and the clinical characteristics and laboratory findings were collected. Additionally, multivariate COX regression analysis was performed to estimate the risk factors of prognosis in patients with ASS.

RESULTS

The frequency of interstitial lung disease (ILD) reached 93.3% in our cohort, of 28 (23.5%) was classified as rapidly progressive (RP)-ILD. The highest incidence of RP-ILD was 36.4% in the PL12 group of ASS patients. The ILD group was characterized by an older age, a lower prevalence of V sign, and a higher prevalence of pulmonary symptoms when contrasted with the non-ILD group. There were statistical differences of clinical significance in arthritis, myositis, mechanic's hands, triad, shawl sign, V sign, and Raynaud's phenomenon among the four subgroups (all p < .05). Additionally, the prevalence rates of arthritis, myositis, mechanic's hands, triad, and V sign in the anti-Jo1 antibody-positive group were significantly higher than anti-Jo1 antibody-negative patients with ASS (all p < .05). Multivariate Cox regression analysis showed mechanic's hands (odds ratio [OR] = 6.47, p < .001), anti-nuclear antibodies (ANA) (OR = 2.13, p = .026), ILD (OR = 10.50, p < .001), and V sign (OR = 0.30, p = .007) were independent factors affecting the prognosis of patients with ASS. The incidences of RP-ILD, arthritis, myositis, triad, mechanic's hands, and shawl sign were more frequent in the anti-Ro52 antibody-positive group than the anti-Ro52 antibody-negative patients with ASS (all p < .05).

CONCLUSIONS

Patients with ASS accompanied with ILD are highly prevalent. Mechanic's hands, ANA, and ILD may be a potential biomarker for predicting a poor prognosis in patients with ASS. Additionally, the detection of the anti-Ro52 antibody provides valuable insights for managing and predicting disease progression and long-term outcomes.

Characteristics and prognostic implications of peripheral blood lymphocyte subsets in patients with anti-MDA5 antibody positive dermatomyositis-interstitial lung disease

OBJECTIVES

To examine the characteristics of blood lymphocyte subsets in dermatomyositis-interstitial lung disease (DM-ILD) inflicted patients with positive anti-melanoma differentiation-associated gene 5 (anti-MDA5), as well as its prognosis value in this set of patients.

METHODS

Data were retrospectively collected from 253 DM-ILD patients from three hospitals in China between January 2016 to January 2021. Patients were grouped into anti-MDA5 antibody positive group (MDA5+ DM-ILD) and anti-MDA5 antibody negative group (MDA5- DM-ILD) based on myositis-specific autoantibody test results. Demographic characteristics, lymphocyte subsets patterns and other clinical features were compared between the two groups. The association of lymphocyte subsets with 180-day mortality was investigated using survival analysis in MDA5+ DM-ILD.

RESULTS

Out of 253 eligible patients with DM-ILD, 59 patients were anti-MDA5+ and 194 were anti-MDA5-. Peripheral blood lymphocyte count, CD3+ count, percentage of CD3+, CD3+CD4+ count, and CD3+CD8+ count was lower in MDA5+ DM-ILD than in MDA5- DM-ILD- (all P < 0.001) as well as CD3-CD19+ count (P = 0.04). In MDA5+ DM-ILD, CD3+CD8+ count ≤ 49.22 cell/μL (HR = 3.81, 95%CI [1.20,12.14]) and CD3-CD19+ count ≤ 137.64 cell/μL (HR = 3.43, 95%CI [1.15,10.24]) were independent predictors of mortality. CD3+CD8+ count ≤ 31.38 cell/μL was associated with a higher mortality risk in all DM-ILD patients (HR = 8.6, 95%CI [2.12,31.44]) after adjusting for anti-MDA5 and other clinical characteristics.

CONCLUSION

Significant lymphocytes decrease was observed in MDA5+ DM-ILD patients. CD3+CD8+ cell count was associated with worse prognosis in both MDA5+ DM-ILD and all DM-ILD patients.

Antigen-driven T cell-macrophage interactions mediate the interface between innate and adaptive immunity in histidyl-tRNA synthetase-induced myositis

Introduction

Previous work in humans has demonstrated that both innate and adaptive immune signaling pathways contribute to the pathogenesis of idiopathic inflammatory myopathy (IIM), a systemic autoimmune disease targeting muscle as well as extra-muscular organs. To better define interactive signaling networks in IIM, we characterized the cellular phenotype and transcriptomic profiles of muscle-infiltrating cells in our established murine model of histidyl-tRNA synthetase (HRS)-induced myositis.

Methods

Myositis was induced in wild type (WT) and various congenic/mutant strains of C57BL/6 mice through intramuscular immunization with recombinant HRS. Histopathological, immunohistochemical, flow cytometric, and transcriptomic assessments were used to characterize the functional relationship between muscle-infiltrating cell populations in these strains lacking different components of innate and/or adaptive immune signaling.

Results

RAG1 KO mice developed markedly reduced muscle inflammation relative to WT mice, demonstrating a key requirement for T cells in driving HRS-induced myositis. While the reduction of mononuclear cell infiltrates in CD4-Cre.MyD88fl/fl conditional knockout mice and OT-II TCR transgenic mice highlighted roles for both innate and TCR-mediated/adaptive immune signaling in T cells, diminished inflammation in Lyz2-Cre.MyD88fl/fl conditional knockout mice underscored the importance of macrophage/myeloid cell populations in supporting T cell infiltration. Single cell RNA sequencing-based clustering of muscle-infiltrating subpopulations and associated pathway analyses showed that perturbations of T cell signaling/function alter the distribution and phenotype of macrophages, fibroblasts, and other non-lymphoid cell populations contributing to HRS-induced myositis.

Discussion

Overall, HRS-induced myositis reflects the complex interplay between multiple cell types that collectively drive a TH1-predominant, pro-inflammatory tissue phenotype requiring antigen-mediated activation of both MyD88- and TCR-dependent T cell signaling pathways.

Plasma proteomic profiling reveals KRT19 could be a potential biomarker in patients with anti-MDA5+ dermatomyositis

OBJECTIVE

To investigate the immune response-related protein profiling in plasma of patients with idiopathic inflammatory myopathies (IIMs), especially in anti-MDA5+ dermatomyositis (DM).

METHODS

A total of 166 IIM patients and 107 healthy controls (HCs) were enrolled in our study. Ninety-two plasma immune response-related proteins were detected by Olink proteomics in 36 IIM patients and 25 HCs. The expression of plasma KRT19 was validated in another 130 IIM patients, 82 HCs, and 55 other rheumatic diseases.

RESULTS

A total of 46 differentially expressed proteins were detected, including 12 upregulated proteins and 34 downregulated proteins in IIM patients compared with HCs. Pathway analysis revealed lactoferrin danger signal response pathway, TLR4 signaling and tolerance, infection, and IL-10 signaling pathway were activated. The immune response-related protein profiling significantly altered in anti-MDA5+ DM patients, with LAMP3, HSD11B1, and KRT19 significantly increased, while SH2D1A, ITGA11, TRIM21, CD28, ITGB6, and HEXIM1 tremendously decreased. In addition, KRT19 was significantly increased in IIM patients, especially in anti-MDA5+ DM patients with the diagnostic value of a significant area under the ROC curve of 0.881.

CONCLUSION

Immune response-related proteins are significantly altered in patients with anti-MDA5+ DM patients. KRT19 could be a potential biomarker for anti-MDA5+ DM patients. Key Points • What is already known on this topic? Anti-MDA5+ DM is a distinctive subtype of IIM. Plasma immune response-related proteins panel needs to be investigated. • What this study adds? Plasma protein profiling of immune response-related proteins significantly altered in patients with idiopathic inflammatory myopathies (IIM), especially in anti-MDA5+ DM patients. • How this study might affect research, practice, or policy? KRT19 could be a potential biomarker in patients with anti-MDA5+ dermatomyositis.

Murine models of idiopathic inflammatory myopathy

Idiopathic inflammatory myopathies (IIMs) are characterized by inflammation of muscles and other organs. Several myositis-specific autoantibodies (MSAs) have been identified in IIMs and were found to be associated with distinct clinical features. Although MSAs are valuable for the diagnosis of IIMs, the pathogenic roles of these antibodies remain unknown. To investigate the pathogenesis of IIMs, several animal models of experimental myositis have been established. Classical murine models of autoimmune myositis, experimental autoimmune myositis, and C protein-induced myositis are established by immunization with muscle-specific antigens, myosin, and skeletal C protein, respectively. Furthermore, a murine model of experimental myositis was generated by immunization with a murine recombinant histidyl-tRNA synthetase, Jo-1, in which muscle and lung inflammation reflecting anti-synthetase syndrome are induced depending on acquired immunity. Recently, the transfer of human IgGs from patients with immune-mediated necrotizing myopathy, comprising anti-signal recognition particles and anti-3-hydroxy-3-methylglutaryl coenzyme A reductase antibodies, was found to induce complement-mediated myositis in recipient mice. CD8⁺ T cell-mediated myositis can be established depending on autoimmunity against transcriptional intermediary factor 1γ (TIF1γ), an autoantigen for MSAs induced by recombinant human TIF1γ immunization. These new murine models reflecting MSA-related IIMs are useful tools for accurately understanding the pathological mechanisms underlying IIMs.

Mechanistic perspectives on anti-aminoacyl-tRNA synthetase syndrome

Antisynthetase syndrome (ASSD) is an autoimmune disease characterized by circulating autoantibodies against one of eight aminoacyl-tRNA synthetases (aaRSs). Although these autoantibodies are believed to play critical roles in ASSD pathogenesis, the nature of their roles remains unclear. Here we describe ASSD pathogenesis and discuss ASSD-linked aaRSs - from the WHEP domain that may impart immunogenicity to the role of tRNA in eliciting the innate immune response and the secretion of aaRSs from cells. Through these explorations, we propose that ASSD pathogenesis involves the tissue-specific secretion of aaRSs and that extracellular tRNAs or tRNA fragments and their ability to engage Toll-like receptor signaling may be important disease factors.

Predictors of progression in idiopathic inflammatory myopathies with interstitial lung disease

The idiopathic inflammatory myopathies (IIMs) are a group of connective tissue diseases that afect multiple organ systems, including the lungs. Interstitial lung disease (ILD) is the most common and heterogeneous complication of IIMs, with its degree ranging from mild to fatal. Thus, it is critical to identify clinical features and validated biomarkers for predicting disease progression and prognosis, which could be beneficial for therapy adjustment. In this review, we discuss predictors for rapid progression of IIM-ILD and propose guidance for disease monitoring and implications of therapy. Systematic screening of myositis-specific antibodies, measuring serum biomarker levels, pulmonary function tests, and chest high-resolution computer tomography will be beneficial for the evaluation of disease progression and prognosis.

Environmental Risks for Inflammatory Myopathies

This is an up-to-date review on external environmental factors for adult-onset idiopathic inflammatory myopathies (IIMs). Environmental factors with suggestive evidence including ultraviolet radiation, smoking, infectious agents (viruses in particular), pollutants, medications (ie, statin) and vitamin D deficiency are discussed. We also discuss the potential implications of environmental factors in IIM development, identify current challenges, and provide insight into future investigations.

Autoantibodies: Pathogenic or epiphenomenon

Idiopathic inflammatory myopathies (IIM) are heterogeneous autoimmune diseases. There are distinct subgroups, including antisynthetase syndrome, dermatomyositis, polymyositis, immune-mediated necrotizing myopathy, and sporadic inclusion body myositis. In patients with IIM, autoantibodies are present in up to 80% of the patients. These autoantibodies are often characterized as myositis-specific autoantibodies (MSA) or myositis-associated autoantibodies (MAA). The recognition of the importance of autoantibodies, especially MSA, is increasing in recent years. In this chapter, we provide an overview of the MSAs, including some new autoantibodies of interest as they target mainly muscle-specific autoantigen, in clinical classification, the measurement of the disease activity, and a possible role in the pathogenesis in the patients with IIM.

Possible future avenues for myositis therapeutics: DM, IMNM and IBM

Idiopathic inflammatory myopathies (IIMs) represent a heterogeneous group of systemic autoimmune diseases characterized by immune-mediated muscle injury. As insights into pathogenesis of IIM evolve, novel therapeutic strategies have become available to optimize outcomes. Herein, we summarize novel and emerging strategies in the management of dermatomyositis (DM), immunemediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM).

Expression of Inflammatory Markers in the Muscles of Patients with Idiopathic Inflammatory Myopathy According to the Presence of Interstitial Lung Disease

BACKGROUND

Several studies have identified factors associated with the development of interstitial lung disease (ILD) in patients with idiopathic inflammatory myopathies (IIMs). However, few have assessed the association between ILD and muscle biopsy findings, including inflammatory marker expressions analyzed using immunohistochemistry (IHC).

METHODS

Muscle biopsies from patients who were newly diagnosed with IIMs between 2000 and 2017 were reviewed. ILD was diagnosed based on chest computed tomography findings at the time of diagnosis of IIMs. IHC staining was performed for CD3, CD4, CD8, CD20, CD68, CD163, MX1, MHC class I, and HLA-DR. The factors associated with the presence of ILD were evaluated by logistic regression analysis.

RESULTS

Of the 129 patients with IIM, 49 (38%) had ILD. In the muscle biopsy findings, CD4 expression, MX1 expression on immune cells, and expression of MHC class I and HLA-DR on myofibers were more common in patients with ILD than those without. In the logistic regression analysis, the HLA-DR expression on myofibers was significantly associated with the risk of ILD (OR, 2.39; 95% CI, 1.24-4.90, p = 0.012) after adjusting for pathologic findings, clinical features, and autoantibodies.

CONCLUSION

The expression of HLA-DR on myofibers was associated with the presence of ILD in patients with IIM.

Aminoacyl-tRNA Synthetases: On Anti-Synthetase Syndrome and Beyond

Anti-synthetase syndrome (ASSD) is an autoimmune disease characterized by the presence of autoantibodies targeting one of several aminoacyl t-RNA synthetases (aaRSs) along with clinical features including interstitial lung disease, myositis, Raynaud’s phenomenon, arthritis, mechanic’s hands, and fever. The family of aaRSs consists of highly conserved cytoplasmic and mitochondrial enzymes, one for each amino acid, which are essential for the RNA translation machinery and protein synthesis. Along with their main functions, aaRSs are involved in the development of immune responses, regulation of transcription, and gene-specific silencing of translation. During the last decade, these proteins have been associated with cancer, neurological disorders, infectious responses, and autoimmune diseases including ASSD. To date, several aaRSs have been described to be possible autoantigens in different diseases. The most commonly described are histidyl (HisRS), threonyl (ThrRS), alanyl (AlaRS), glycyl (GlyRS), isoleucyl (IleRS), asparaginyl (AsnRS), phenylalanyl (PheRS), tyrosyl (TyrRS), lysyl (LysRS), glutaminyl (GlnRS), tryptophanyl (TrpRS), and seryl (SerRS) tRNA synthetases. Autoantibodies against the first eight autoantigens listed above have been associated with ASSD while the rest have been associated with other diseases. This review will address what is known about the function of the aaRSs with a focus on their autoantigenic properties. We will also describe the anti-aaRSs autoantibodies and their association to specific clinical manifestations, and discuss their potential contribution to the pathogenesis of ASSD.

Single-Cell Transcriptomics Reveals Peripheral Immune Responses in Anti-Synthetase Syndrome-Associated Interstitial Lung Disease

OBJECTIVE

Interstitial lung diseases (ILDs) secondary to anti-synthetase syndrome (ASS) greatly influence the prognoses of patients with ASS. Here we aimed to investigate the peripheral immune responses to understand the pathogenesis of this condition.

METHODS

We performed single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) from 5 patients with ASS-ILD and 3 healthy donors (HDs). Flow cytometry of PBMCs was performed to replenish the results of scRNA-seq.

RESULTS

We used scRNA-seq to depict a high-resolution visualization of cellular landscape in PBMCs from patients with ASS-ILD. Patients showed upregulated interferon responses among NK cells, monocytes, T cells, and B cells. And the ratio of effector memory CD8 T cells to naïve CD8 T cells was significantly higher in patients than that in HDs. Additionally, Th1, Th2, and Th17 cell differentiation signaling pathways were enriched in T cells. Flow cytometry analyses showed increased proportions of Th17 cells and Th2 cells, and decreased proportion of Th1 cells in patients with ASS-ILD when compared with HDs, evaluated by the expression patterns of chemokine receptors.

CONCLUSIONS

The scRNA-seq data analyses reveal that ASS-ILD is characterized by upregulated interferon responses, altered CD8 T cell homeostasis, and involvement of differentiation signaling pathways of CD4 T cells. The flow cytometry analyses show that the proportions of Th17 cells and Th2 cells are increased and the proportion of Th1 cells is decreased in patients with ASS-ILD. These findings may provide foundations of novel therapeutic targets for patients with this condition.

Longitudinal assessment of reactivity and affinity profile of anti-Jo1 autoantibodies to distinct HisRS domains and a splice variant in a cohort of patients with myositis and anti-synthetase syndrome

Background

To address the reactivity and affinity against histidyl-transfer RNA synthetase (HisRS) autoantigen of anti-Jo1 autoantibodies from serum and bronchoalveolar lavage fluid (BALF) in patients with idiopathic inflammatory myopathies/anti-synthetase syndrome (IIM/ASSD). To investigate the associations between the reactivity profile and clinical data over time.

Methods

Samples and clinical data were obtained from (i) 25 anti-Jo1⁺ patients (19 sera with 16 longitudinal samples and 6 BALF/matching sera at diagnosis), (ii) 29 anti-Jo1⁻ patients (25 sera and 4 BALF/matching sera at diagnosis), and (iii) 27 age/gender-matched healthy controls (24 sera and 3 BALF/matching sera). Reactivity towards HisRS full-length (HisRS-FL), three HisRS domains (WHEP, antigen binding domain (ABD), and catalytic domain (CD)), and the HisRS splice variant (SV) was tested. Anti-Jo1 IgG reactivity was evaluated by ELISA and western blot using IgG purified from serum by affinity chromatography. In paired serum-BALF, anti-Jo1 IgG and IgA reactivity was analyzed by ELISA. Autoantibody affinity was measured by surface plasmon resonance using IgG purified from sera. Correlations between autoantibody reactivity and clinical data were evaluated at diagnosis and longitudinally.

Results

Anti-Jo1 IgG from serum and BALF bound HisRS-FL, WHEP, and SV with high reactivity at the time of diagnosis and recognized both conformation-dependent and conformation-independent HisRS epitopes. Anti-HisRS-FL IgG displayed high affinity early in the disease. At the time of IIM/ASSD diagnosis, the highest autoantibody levels against HisRS-FL were found in patients ever developing interstitial lung disease (ILD) and arthritis, but with less skin involvement. Moreover, the reactivity of anti-WHEP IgG in BALF correlated with poor pulmonary function.

Levels of autoantibodies against HisRS-FL, HisRS domains, and HisRS splice variant generally decreased over time. With some exceptions, longitudinal anti-HisRS-FL antibody levels changed in line with ILD activity.

Conclusion

High levels and high-affinity anti-Jo1 autoantibodies towards HisRS-FL were found early in disease in sera and BALF. In combination with the correlation of anti-HisRS-FL antibody levels with ILD and ILD activity in longitudinal samples as well as of anti-WHEP IgG in BALF with poor pulmonary function, this supports the previously raised hypothesis that the lung might have a role in the immune reaction in anti-Jo1-positive patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02745-6.

Clinical Value of 18F-FDG PET/CT Scan and Cytokine Profiles in Secondary Hemophagocytic Lymphohistiocytosis in Idiopathic Inflammatory Myopathy Patients: A Pilot Study

Background

Secondary hemophagocytic lymphohistiocytosis (sHLH) is a rare but fatal complication in idiopathic inflammatory myopathy (IIM) patients. The clinical value of radiological manifestations and serum cytokines remain unknown in this systemic crisis. This study aims to investigate the clinical value of PET/CT scan and cytokine profiles in predicting and understanding sHLH in IIM patients.

Methods

Adult IIM patients who were admitted to the four divisions of the First Affiliated Hospital, Zhejiang University School of Medicine (FAHZJU) from January 1, 2017 to December 31, 2020 were reviewed. PET/CT scan, cytokine profiles, and other factors of patients who met the inclusion and exclusion criteria were collected and analyzed.

Results

Sixty-nine out of 352 IIM patients were finally enrolled into the study. Ten patients developed sHLH and 70.0% of them died within 6 months. After false discovery rate (FDR) correction and multivariate logistic regression analysis, increased serum interferon (IFN)-γ level (p = 0.017), higher spleen mean standard uptake value (SUVmean, p = 0.035), and positivity of anti-MDA5 antibody (p = 0.049) were found to be significantly correlated with development of sHLH in IIM patients. The combination of serum IFN-γ, spleen SUVmean, and anti-MDA5 antibody found a balanced and satisfying predictor with a cutoff value of 0.047 and AUC of 0.946. A moderate correlation was identified between ferritin and spleen SUVmean (p = 0.001, r = 0.380) as well as serum IFN-γ(p = 0.001, r = 0.398). Before FDR correction, higher bilateral lung SUVmean (p = 0.034) and higher colon/rectum SUVmean (p = 0.013) were also observed in IIM patients who developed sHLH. By narrowing down to IIM patients with sHLH, anti-MDA5-antibody-positive DM patients tended to suffer from unfavorable outcome (p = 0.004) in Kaplan–Meier survival analysis.

Conclusion

Increased serum level of IFN-γ, elevated splenic FDG uptake, and positivity of anti-MDA5 antibody were significantly correlated with development of sHLH in IIM patients. Lung and lower digestive tract might also be affected due to systemic immune activation in IIM patients with sHLH. In addition, splenic FDG uptake, in combination with serum IFN-γand anti-MDA5 antibody, was found valuable in predicting development of sHLH in IIM patients. Among IIM patients with sHLH, anti-MDA5-antibody-positive DM patients showed higher tendency for unfavorable outcome.

Idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIM), also known as myositis, are a heterogeneous group of autoimmune disorders with varying clinical manifestations, treatment responses and prognoses. Muscle weakness is usually the classical clinical manifestation but other organs can be affected, including the skin, joints, lungs, heart and gastrointestinal tract, and they can even result in the predominant manifestations, supporting that IIM are systemic inflammatory disorders. Different myositis-specific auto-antibodies have been identified and, on the basis of clinical, histopathological and serological features, IIM can be classified into several subgroups - dermatomyositis (including amyopathic dermatomyositis), antisynthetase syndrome, immune-mediated necrotizing myopathy, inclusion body myositis, polymyositis and overlap myositis. The prognoses, treatment responses and organ manifestations vary among these groups, implicating different pathophysiological mechanisms in each subtype. A deeper understanding of the molecular pathways underlying the pathogenesis and identifying the auto-antigens of the immune reactions in these subgroups is crucial to improving outcomes. New, more homogeneous subgroups defined by auto-antibodies may help define disease mechanisms and will also be important in future clinical trials for the development of targeted therapies and in identifying biomarkers to guide treatment decisions for the individual patient.

Serum Amphiregulin and Heparin-Binding Epidermal Growth Factor as Biomarkers in Patients with Idiopathic Inflammatory Myopathy

Background. The epidermal growth factors amphiregulin (AREG) and heparin-binding epidermal growth factor (HB-EGF) are implicated in the pathogenesis of several autoimmune diseases, but their clinical and pathological roles in idiopathic inflammatory myopathy (IIM) are unclear. Methods. Serum AREG and HB-EGF levels were measured by ELISA in patients with IIM (n = 37), systemic sclerosis (n = 17), and rheumatoid arthritis (n = 10), and for seven age- and sex-matched healthy controls (HCs). Associations between serum AREG or HB-EGF levels and the clinical parameters were analyzed. Results. Serum AREG levels in IIM patients were significantly elevated compared to those in HCs (median, 20.7 and 10.7 pg/mL, respectively; p = 0.025). In particular, serum AREG levels in IIM patients with interstitial lung disease (ILD) were higher than those of HCs (22.4 pg/mL, p = 0.027). The disease duration in patients with elevated serum AREG levels was significantly shorter compared to those who had normal serum AREG levels (7 and 21 months, respectively; p = 0.0012). Serum HB-EGF levels were significantly increased in IIM patients with elevated CK levels (136.2 pg/mL; p = 0.020) and patients with anti-Mi-2 antibody (183.7 pg/mL; p = 0.045) compared to those in HCs (74.9 pg/mL). Conclusion. These results suggested that AREG could be a promising biomarker associated with early-phase IIM-related ILD, and that HB-EGF expression was associated with muscle injury and regeneration in IIM.

Antigen-driven autoantibody production in lungs of interstitial lung disease with autoimmune disease

Interstitial lung disease (ILD) sometimes becomes a life-threatening complication of systemic autoimmune diseases; however, little is known about the immune response in lung lesions. We aimed to investigate humoural immunity in ILD associated with rheumatoid arthritis (RA), sjögren's syndrome (SjS), and mixed connective tissue disease (MCTD), using bronchoalveolar fluid (BALF) and serum samples from 15 patients with autoimmune disease associated-ILD. We first showed that BALF contained higher titers of disease-related autoantibodies than serum, suggesting the possibility of autoantibody production in lungs. Next, we produced 326 monoclonal antibodies from antibody-secreting cells in BALF, and the reactivity and their revertants, in which somatic hypermutations were reverted to germline, were analyzed. Among 123 antibodies from RA-ILD, 16 disease-related antibodies (anti-modified protein antibodies and rheumatoid factors) were identified, of which one antibody had both properties. The revertant antibodies changed their target modification in a complicated manner, suggesting that the antibodies were selected against various modifications in lungs. Among 146 antibodies from SjS-ILD and/or MCTD-ILD, seven anti-SSA/Ro60 antibodies and 15 anti-RNP antibodies were identified. Some of the anti-RNP antibodies recognized multiple RNP constituent proteins simultaneously, indicating that epitope spreading may progress in lungs. Our results revealed the existence of an active autoimmunity in the lungs of autoimmune disease associated-ILD.

The role of interferons type I, II and III in myositis: A review

The classification of idiopathic inflammatory myopathies (IIM) is based on clinical, serological and histological criteria. The identification of myositis-specific antibodies has helped to define more homogeneous groups of myositis into four dominant subsets: dermatomyositis (DM), antisynthetase syndrome (ASyS), sporadic inclusion body myositis (sIBM) and immune-mediated necrotising myopathy (IMNM). sIBM and IMNM patients present predominantly with muscle involvement, whereas DM and ASyS patients present additionally with other extramuscular features, such as skin, lung and joints manifestations. Moreover, the pathophysiological mechanisms are distinct between each myositis subsets. Recently, interferon (IFN) pathways have been identified as key players implicated in the pathophysiology of myositis. In DM, the key role of IFN, especially type I IFN, has been supported by the identification of an IFN signature in muscle, blood and skin of DM patients. In addition, DM-specific antibodies are targeting antigens involved in the IFN signalling pathways. The pathogenicity of type I IFN has been demonstrated by the identification of mutations in the IFN pathways leading to genetic diseases, the monogenic interferonopathies. This constitutive activation of IFN signalling pathways induces systemic manifestations such as interstitial lung disease, myositis and skin rashes. Since DM patients share similar features in the context of an acquired activation of the IFN signalling pathways, we may extend underlying concepts of monogenic diseases to acquired interferonopathy such as DM. Conversely, in ASyS, available data suggest a role of type II IFN in blood, muscle and lung. Indeed, transcriptomic analyses highlighted a type II IFN gene expression in ASyS muscle tissue. In sIBM, type II IFN appears to be an important cytokine involved in muscle inflammation mechanisms and potentially linked to myodegenerative features. For IMNM, currently published data are scarce, suggesting a minor implication of type II IFN. This review highlights the involvement of different IFN subtypes and their specific molecular mechanisms in each myositis subset.

In vitro and ex vitro functional characterization of human HLA-DRB1∗04 restricted T cell receptors

Recent advances in single-cell sequencing technologies enable the generation of large-scale data sets of paired TCR sequences from patients with autoimmune disease. Methods to validate and characterize patient-derived TCR data are needed, as well as relevant model systems that can support the development of antigen-specific tolerance inducing drugs. We have generated a pipeline to allow streamlined generation of 'artificial' T cells in a robust and reasonably high throughput manner for in vitro and in vivo studies of antigen-specific and patient-derived immune responses. Hereby chimeric (mouse-human) TCR alpha and beta constructs are re-expressed in three different formats for further studies: (i) transiently in HEK cells for peptide-HLA tetramer validation experiments, (ii) stably in the TCR-negative 58 ​T cell line for functional readouts such as IL-2 production and NFAT-signaling, and lastly (iii) in human HLA-transgenic mice for studies of autoimmune disease and therapeutic interventions. As a proof of concept, we have used human HLA-DRB1∗04:01 restricted TCR sequences specific for a type I diabetes-associated GAD peptide, and an influenza-derived HA peptide. We show that the same chimeric TCR constructs can be used in each of the described assays facilitating sequential validation and prioritization steps leading to humanized animal models.

Antisynthetase syndrome - much more than just a myopathy

The aim of the study was to summarize current knowledge on antisynthetase syndrome (ASS), including its epidemiology, pathogenesis, proposed so far diagnostic criteria, heterogeneity of clinical manifestations, prognostic factors and therapeutic possibilities. PubMed database was screened for "antisynthetase syndrome" OR "antisynthetase antibodies" between February and April 2020. Aminoacyl-tRNA synthetases participate in the immune system activation as antigens, but also serve chemoattractive and cytokine-resembling roles, initiating innate and adaptive pathways. Exposure to various inhaled antigens may induce the autoimmune cascade leading to ASS. NK cells with its impaired INF-y production as well as formation of NETs by neutrophils contribute to pathogenesis. The prevalence of symptoms vary significantly depending on the study with muscular, articular and pulmonary involvement being the most frequently observed. Although classified as subtype of idiopathic inflammatory myopathies, myositis may not necessarily be the prominent manifestation. Since clinical presentation is heterogeneous and symptoms can emerge gradually, ASS could be considered as a heterogeneous spectrum rather than a homogenous disease entity. The currently available classification criteria do not fully correspond with the clinical patterns of the disease. Therapy is based on glucocorticosteroids and other immunosuppressive agents. Randomized controlled trials, dedicated for patients with ASS, are needed to form treatment algorithms.

Monitoring disease activity and damage in adult and juvenile idiopathic inflammatory myopathy

PURPOSE OF REVIEW

We have reviewed the literature to identify significant advances related to disease activity and damage in the idiopathic inflammatory myopathies (IIMs) from January 2019 to July 2020.

RECENT FINDINGS

New observations in the field from 2019 to 2020 have resulted in a better understanding of the clinical association and pathogenic origins of IIM. The use of patient-reported outcome measures and perspectives, identifying biomarkers and making better use of autoantibody testing are summarized. Basic sciences have led to an improved understanding of the role of NETosis in calcinosis, and of interferon type 1, in IIM. Preliminary insights are offered into Covid-19 in the setting of IIM, and the use of potential tools for monitoring disease remotely, which may assume larger importance for optimal disease management during a global pandemic. The wider exploration of newer imaging modalities and the use of nailfold capillaroscopy is a further step in better management of the condition.

SUMMARY

The summarized research in IIM is a step forward in being able to further define, and to distinguish disease activity from damage, in order to potentially aid future clinical diagnosis and management in this challenging disease.

Myositis autoantibodies: recent perspectives

PURPOSE OF REVIEW

To provide an overview of recent discoveries related to myositis-specific autoantibodies (MSAs) and assays used for their measurement.

RECENT FINDINGS

New autoantibody specificities have been reported including a MSA directed against eukaryotic initiation factor 3 and a myositis-associated autoantibody directed against heat shock factor 1. The association of anti-TIF1γ with cancer-associated dermatomyositis dependent on age has been confirmed in several large cohorts. Despite MSAs being almost entirely mutually exclusive, several myositis autoantigens are overexpressed in regenerating muscle and do not correlate with the corresponding MSA in any one patient. Further mechanisms may determine the final MSA specificity and are likely to include the need for autoantigen processing and presentation with adaptive T-cell help. The presence of CD4-positive T cells specific for histidyl tRNA synthetase protein in bronchial lavage fluid from antisynthetase patients lends support to this view. Finally, it is widely held that MSA do play an important role in clinical practice among some evidence and concern about commercial assay reliability.

SUMMARY

MSAs continue to provide important tools for clinical diagnosis and management as well as insights into disease mechanisms. Further improvement in the standardization and reliability of routine detection of MSAs is a high priority.

Clinical manifestations and treatment of antisynthetase syndrome

Antisynthetase syndrome (ASyS) is an autoimmune disease clinically manifested most often by interstitial lung disease, myositis, and arthritis. Raynaud's syndrome, fever, and rashes are also commonly seen. This syndrome is characterized by the highly specific presence of antibodies against various aminoacyl transfer RNA synthetases, including Jo-1 and others. In this chapter, we provide an overview of ASyS, including pathogenesis, common clinical manifestations, and treatment strategies. We discuss the spectrum of disease seen with specific antisynthetase antibodies and examine the differences in phenotype between patients with different antisynthetase antibodies. We outline common treatment strategies, which should generally target the most severe and life- or organ-threatening disease manifestations. Finally, we discuss short- and long-term prognosis in ASyS.

Roles of aminoacyl-tRNA synthetases in immune regulation and immune diseases

Aminoacyl-tRNA synthetases (ARSs) play a vital role in protein synthesis by linking amino acids to their cognate transfer RNAs (tRNAs). This typical function has been well recognized over the past few decades. However, accumulating evidence reveals that ARSs are involved in a wide range of physiological and pathological processes apart from translation. Strikingly, certain ARSs are closely related to different types of immune responses. In this review, we address the infection and immune responses induced by pathogen ARSs, as well as the potential anti-infective compounds that target pathogen ARSs. Meanwhile, we describe the functional mechanisms of ARSs in the development of immune cells. In addition, we focus on the roles of ARSs in certain immune diseases, such as autoimmune diseases, infectious diseases, and tumor immunity. Although our knowledge of ARSs in the immunological context is still in its infancy, research in this field may provide new ideas for the treatment of immune-related diseases.