Pathogenic autoantibody internalization in myositis

Objectives

Myositis is a heterogeneous family of autoimmune muscle diseases. As myositis autoantibodies recognize intracellular proteins, their role in disease pathogenesis has been unclear. This study aimed to determine whether myositis autoantibodies reach their autoantigen targets within muscle cells and disrupt the normal function of these proteins.

Methods

Confocal immunofluorescence microscopy was used to localize antibodies and other proteins of interest in myositis muscle biopsies. Bulk RNA sequencing was used to study the transcriptomic profiles of 668 samples from patients with myositis, disease controls, and healthy controls. Antibodies from myositis patients were introduced into cultured myoblasts by electroporation and the transcriptomic profiles of the treated myoblasts were studied by bulk RNA sequencing.

Results

In patients with myositis autoantibodies, antibodies accumulated inside myofibers in the same subcellular compartment as the autoantigen. Each autoantibody was associated with effects consistent with dysfunction of its autoantigen, such as the derepression of genes normally repressed by Mi2/NuRD in patients with anti-Mi2 autoantibodies, the accumulation of RNAs degraded by the nuclear RNA exosome complex in patients with anti-PM/Scl autoantibodies targeting this complex, and the accumulation of lipids within myofibers of anti-HMGCR-positive patients. Internalization of patient immunoglobulin into cultured myoblasts recapitulated the transcriptomic phenotypes observed in human disease, including the derepression of Mi2/NuRD-regulated genes in anti-Mi2-positive dermatomyositis and the increased expression of genes normally degraded by the nuclear RNA exosome complex in anti-PM/Scl-positive myositis.

Conclusions

In myositis, autoantibodies are internalized into muscle fibers, disrupt the biological function of their autoantigen, and mediate the pathophysiology of the disease.

Neurological adverse events related to immune-checkpoint inhibitors in Spain: a retrospective cohort study

BACKGROUND

Neurological immune-related adverse events associated with immune checkpoint inhibitors can have several clinical manifestations, but the syndromes and prognostic factors are still not well known. We aimed to characterise and group the clinical features, with a special focus in patients presenting with encephalopathy, and to identify predictors of response to therapy and survival.

METHODS

This retrospective observational study included patients with neurological immune-related adverse events from 20 hospitals in Spain whose clinical information, serum samples, and CSF samples were studied at Hospital Clinic de Barcelona, Barcelona, Spain. Patients with pre-existing paraneoplastic syndromes or evidence of alternative causes for their neurological symptoms were excluded. We reviewed the clinical information, classified their clinical features, and determined the presence of neural antibodies. Neurological status was assessed by the treating physician one month after adverse event onset (as improvement vs no improvement) and at the last evaluation (complete recovery or modified Rankin Scale score decrease of at least 2 points, indicating good outcome, vs all other modified Rankin Scale scores, indicating poor outcome); if the participant had died, the date and cause of death were recorded. We used Fisher's exact tests and Mann-Whitney U tests to analyse clinical features, and multivariable logistic regression to analyse prognostic factors.

FINDINGS

From Jan 1, 2018, until Feb 1, 2023, 83 patients with suspected neurological immune-related adverse events after use of immune checkpoint inhibitors were identified, of whom 64 patients were included. These patients had a median age of 67 years (IQR 59-74); 42 (66%) were male and 22 (34%) were female. The predominant tumours were lung cancer (30 [47%] patients), melanoma (13 [21%] patients), and renal cell carcinoma (seven [11%] patients). Neural antibodies were detected in 14 (22%) patients; 52 (81%) patients had CNS involvement and 12 (19%) had peripheral nervous system involvement. Encephalopathy occurred in 45 (70%) patients, 12 (27%) of whom had antibodies or well defined syndromes consistent with definite paraneoplastic or autoimmune encephalitis, 24 (53%) of whom had encephalitis without antibodies or clinical features characteristic of a defined syndrome, and nine (20%) of whom had encephalopathy without antibodies or inflammatory changes in CSF or brain MRI. Nine (14%) of 64 patients had combined myasthenia and myositis, five of them with myocarditis. Even though 58 (91%) of 64 patients received steroids and 31 (48%) of 64 received additional therapies, 18 (28%) did not improve during the first month after adverse event onset, and 11 of these 18 people died. At the last follow-up for the 53 remaining patients (median 6 months, IQR 3-13), 20 (38%) had a poor outcome (16 deaths, one related to a neurological immune-related adverse event). Mortality risk was increased in patients with lung cancer (vs those with other cancers: HR 2·5, 95% CI 1·1-6·0) and in patients with encephalopathy without evidence of CNS inflammation or combined myocarditis, myasthenia, and myositis (vs those with the remaining syndromes: HR 5·0, 1·4-17·8 and HR 6·6, 1·4-31·0, respectively).

INTERPRETATION

Most neurological immune-related adverse events involved the CNS and were antibody negative. The presence of myocarditis, myasthenia, and myositis, of encephalopathy without inflammatory changes, or of lung cancer were independent predictors of death. Most deaths occurred during the first month of symptom onset. If our findings are replicated in additional cohorts, they could confirm that these patients need early and intensive treatment.

FUNDING

The Instituto de Salud Carlos III and the European Union.

Variants in DTNA cause a mild, dominantly inherited muscular dystrophy

DTNA encodes α-dystrobrevin, a component of the macromolecular dystrophin-glycoprotein complex (DGC) that binds to dystrophin/utrophin and α-syntrophin. Mice lacking α-dystrobrevin have a muscular dystrophy phenotype, but variants in DTNA have not previously been associated with human skeletal muscle disease. We present 12 individuals from four unrelated families with two different monoallelic DTNA variants affecting the coiled-coil domain of α-dystrobrevin. The five affected individuals from family A harbor a c.1585G > A; p.Glu529Lys variant, while the recurrent c.1567_1587del; p.Gln523_Glu529del DTNA variant was identified in the other three families (family B: four affected individuals, family C: one affected individual, and family D: two affected individuals). Myalgia and exercise intolerance, with variable ages of onset, were reported in 10 of 12 affected individuals. Proximal lower limb weakness with onset in the first decade of life was noted in three individuals. Persistent elevations of serum creatine kinase (CK) levels were detected in 11 of 12 affected individuals, 1 of whom had an episode of rhabdomyolysis at 20 years of age. Autism spectrum disorder or learning disabilities were reported in four individuals with the c.1567_1587 deletion. Muscle biopsies in eight affected individuals showed mixed myopathic and dystrophic findings, characterized by fiber size variability, internalized nuclei, and slightly increased extracellular connective tissue and inflammation. Immunofluorescence analysis of biopsies from five affected individuals showed reduced α-dystrobrevin immunoreactivity and variably reduced immunoreactivity of other DGC proteins: dystrophin, α, β, δ and γ-sarcoglycans, and α and β-dystroglycans. The DTNA deletion disrupted an interaction between α-dystrobrevin and syntrophin. Specific variants in the coiled-coil domain of DTNA cause skeletal muscle disease with variable penetrance. Affected individuals show a spectrum of clinical manifestations, with severity ranging from hyperCKemia, myalgias, and exercise intolerance to childhood-onset proximal muscle weakness. Our findings expand the molecular etiologies of both muscular dystrophy and paucisymptomatic hyperCKemia, to now include monoallelic DTNA variants as a novel cause of skeletal muscle disease in humans.

Coordinated local RNA overexpression of complement induced by interferon gamma in myositis

Complement proteins are deposited in the muscles of patients with myositis. However, the local expression and regulation of complement genes within myositis muscle have not been well characterized. In this study, bulk RNA sequencing (RNAseq) analyses of muscle biopsy specimens revealed that complement genes are locally overexpressed and correlate with markers of myositis disease activity, including the expression of interferon-gamma (IFNγ)-induced genes. Single cell and single nuclei RNAseq analyses showed that most local expression of complement genes occurs in macrophages, fibroblasts, and satellite cells, with each cell type expressing different sets of complement genes. Biopsies from immune-mediated necrotizing myopathy patients, who have the lowest levels of IFNγ-induced genes, also had the lowest complement gene expression levels. Furthermore, data from cultured human cells showed that IFNγ upregulates complement expression in macrophages, fibroblasts, and muscle cells. Taken together, our results suggest that in myositis muscle, IFNγ coordinates the local overexpression of complement genes that occurs in several cell types.

Rituximab for Inflammatory Myopathies in a Colombian Cohort

INTRODUCTION/OBJECTIVES

Rituximab (RTX) is a treatment for refractory inflammatory myopathies, such as dermatomyositis (DM) and polymyositis (PM). This study describes the characteristics of patients receiving RTX for myositis in our institution to evaluate its efficacy.

METHOD

We collected demographic data from all patients diagnosed with DM or PM who received RTX between 2011 and 2018. Clinical and serological variables (including creatine phosphokinase [CPK] levels) were analyzed. Remission of disease was defined as no evidence of disease activity (active myositis) for longer than a 6-month continuous period while undergoing myositis therapy or no medication.

RESULTS

Eighteen patients who had received first-line immunosuppressants were included. Fifteen (83%) had DM, 2 (11%) had PM, 1 had juvenile dermatomyositis, and 14 (77%) were women. All patients received glucocorticoids. Three patients (16.6%) were treated with RTX as monotherapy, and 15 (83.3%) were treated with RTX combined with other immunosuppressants. On average, there were 2 RTX treatment cycles. Improved muscular weakness was found in 13 cases (72%), and improved serum CPK levels were found in 15 cases (83%). Twelve patients (66%) achieved remission.

CONCLUSIONS

Most patients experienced an objective improvement, as reflected in their serum CPK values and degree of muscular weakness. This suggests that RTX could be helpful in treating refractory myositis.

A multidisciplinary registry of patients with autoimmune and immune-mediated diseases with symptomatic COVID-19 from a single center

Background and aim

There is increasing interest regarding SARS-CoV-2 infection in patients with autoimmune and immune-mediated inflammatory diseases (AI/IMID) with some discrepancies in different cohorts about their risk and outcomes. The aim was to describe a multidisciplinary cohort of patients with AI/IMID and symptomatic SARS-CoV-2 infection in a single tertiary center and analyze sociodemographic, clinical, and therapeutic factors associated with poor outcomes.

Methods

A retrospective observational study was conducted from the 1st of March until May 29th, 2020 in a University tertiary hospital in Barcelona, Spain. Patients with an underlying AI/IMID and symptomatic SARS-CoV-2 infection were identified in our local SARS-CoV-2 infection database. Controls (2:1) were selected from the same database and matched by age and gender. The primary outcome was severe SARS-CoV-2 infection, which was a composite endpoint including admission to the intensive care unit (ICU), need for mechanical ventilation (MV), and/or death. Several covariates including age, sex, and comorbidities among others were combined into a multivariate model having severe SARS-CoV-2 as the dependent variable. Also, a sensitivity analysis was performed evaluating AID and IMID separately.

Results

The prevalence of symptomatic SARS-CoV-2 infection in a cohort of AI/IMID patients was 1.3%. Eighty-five patients with AI/IMID and symptomatic SARS-CoV-2 were identified, requiring hospitalization in 58 (68%) cases. A total of 175 patients admitted for SARS-CoV-2 (58 with AI/IMID and 117 matched-controls) were analyzed. In logistic regression analysis, a significant inverse association between AI/IMID group and severe SARS-CoV-2 (OR 0.28; 95% CI 0.12–0.61; p = 0.001), need of MV (OR 0.20; IC 95% 0.05–0.71; p = 0.014), and ICU admission (OR 0.25; IC 95% 0.10–0.62; p = 0.003) was found.

Conclusions

Patients with AI/IMID who require admission for SARS-CoV-2 infection have a lower risk of developing severe disease, including the need to stay in the ICU and MV.

•

Patients with AI/IMID fwho required admission for SARS CoV2 infection have a lower risk of developing severe disease.

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Among patients with AID and IMID, there were no differences in terms of severity.

•

According to the 7-category ordinal scale, maximum oxygen requirement was lower among AI/IMID group.

Identification of distinctive interferon gene signatures in different types of myositis

OBJECTIVE

Activation of the type 1 interferon (IFN1) pathway is a prominent feature of dermatomyositis (DM) muscle and may play a role in the pathogenesis of this disease. However, the relevance of the IFN1 pathway in patients with other types of myositis such as the antisynthetase syndrome (AS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM) is largely unknown. Moreover, the activation of the type 2 interferon (IFN2) pathway has not been comprehensively explored in myositis. In this cross-sectional study, our objective was to determine whether IFN1 and IFN2 pathways are differentially activated in different types of myositis by performing RNA sequencing on muscle biopsy samples from 119 patients with DM, IMNM, AS, or IBM and on 20 normal muscle biopsies.

METHODS

The expression of IFN1- and IFN2-inducible genes was compared between the different groups.

RESULTS

The expression of IFN1-inducible genes was high in DM, moderate in AS, and low in IMNM and IBM. In contrast, the expression of IFN2-inducible genes was high in DM, IBM, and AS but low in IMNM. The expression of IFN-inducible genes correlated with the expression of genes associated with inflammation and muscle regeneration. Of note, ISG15 expression levels alone performed as well as composite scores relying on multiple genes to monitor activation of the IFN1 pathway in myositis muscle biopsies.

CONCLUSIONS

IFN1 and IFN2 pathways are differentially activated in different forms of myositis. This observation may have therapeutic implications because immunosuppressive medications may preferentially target each of these pathways.

Myositis Autoantigen Expression Correlates With Muscle Regeneration but Not Autoantibody Specificity

OBJECTIVE

Although more than a dozen myositis-specific autoantibodies (MSAs) have been identified, most patients with myositis are positive for a single MSA. The specific overexpression of a given myositis autoantigen in myositis muscle has been proposed as initiating and/or propagating autoimmunity against that particular autoantigen. The present study was undertaken to test this hypothesis.

METHODS

In order to quantify autoantigen RNA expression, RNA sequencing was performed on muscle biopsy samples from control subjects, MSA-positive patients with myositis, regenerating mouse muscles, and cultured human muscle cells.

RESULTS

Muscle biopsy samples were available from 20 control subjects and 106 patients with autoantibodies recognizing hydroxymethylglutaryl-coenzyme A reductase (n = 40), signal recognition particles (n = 9), Jo-1 (n = 18), nuclear matrix protein 2 (n = 12), Mi-2 (n = 11), transcription intermediary factor 1γ (n = 11), or melanoma differentiation-associated protein 5 (n = 5). The increased expression of a given autoantigen in myositis muscle was not associated with autoantibodies recognizing that autoantigen (all q > 0.05). In biopsy specimens from both myositis muscle and regenerating mouse muscles, autoantigen expression correlated directly with the expression of muscle regeneration markers and correlated inversely with the expression of genes encoding mature muscle proteins. Myositis autoantigens were also expressed at high levels in cultured human muscle cells.

CONCLUSION

Most myositis autoantigens are highly expressed during muscle regeneration, which may relate to the propagation of autoimmunity. However, factors other than overexpression of specific autoantigens are likely to govern the development of unique autoantibodies in individual patients with myositis.

Muscular and extramuscular clinical features of patients with anti-PM/Scl autoantibodies

OBJECTIVE

To define the clinical features of myositis patients with anti-PM/Scl-75 and/or anti-PM/Scl-100 autoantibodies at disease onset and during the course of disease and compare them to patients with other forms of myositis.

METHODS

In this longitudinal cohort study, the prevalence and severity of clinical features at disease onset and during follow-up were compared between anti-PM/Scl-positive patients and those with the antisynthetase syndrome (AS), dermatomyositis (DM), and immune-mediated necrotizing myopathy (IMNM).

RESULTS

Forty-one anti-PM/Scl-positive, 132 AS, 178 DM, and 135 IMNM patients were included. Although muscle weakness was a presenting feature in just 37% of anti-PM/Scl-positive patients, 93% eventually developed weakness. Unlike the other groups, anti-PM-Scl-positive patients had more severe weakness in arm abductors than hip flexors. Interstitial lung disease was a presenting feature in just 10% of anti-PM/Scl-positive patients, but occurred in 61% during follow-up; fewer patients with DM (13%, p < 0.001) and IMNM (6%, p < 0.001) and more patients with AS (80%, p < 0.05) developed interstitial lung disease during the course of disease. Mechanic's hands (80%), Raynaud syndrome (78%), sclerodactyly (66%), telangiectasias (66%), esophageal reflux disease (61%), subcutaneous edema (46%), puffy hands (39%), and calcinosis (39%) occurred more frequently in anti-PM/Scl-positive patients than in the other groups. Although 30% of anti-PM/Scl-positive patients met criteria for systemic sclerosis, less than 5% had renal crisis or finger ulcerations. No differences were found between patients with only anti-PM/Scl-100 or only anti-PM/Scl-75 autoantibodies.

CONCLUSIONS

Unlike patients with DM, AS, or IMNM, anti-PM/Scl-positive patients have weaker arm abductors than hip flexors. Anti-PM/Scl-positive patients also have the most extensive extramuscular features.

Imbalance in mitochondrial dynamics and apoptosis in pregnancies among HIV-infected women on HAART with obstetric complications

Background

HIV infection and HAART trigger genetic and functional mitochondrial alterations leading to cell death and adverse clinical manifestations. Mitochondrial dynamics enable mitochondrial turnover and degradation of damaged mitochondria, which may lead to apoptosis.

Objectives

To evaluate markers of mitochondrial dynamics and apoptosis in pregnancies among HIV-infected women on HAART and determine their potential association with obstetric complications.

Methods

This controlled, single-site, observational study without intervention included 26 HIV-infected pregnant women on HAART and 18 control pregnancies and their newborns. Maternal PBMCs and neonatal cord blood mononuclear cells (CBMCs) were isolated at the first trimester of gestation and at delivery. The placenta was homogenized at 5% w/v. Mitochondrial dynamics, fusion events [mitofusin 2 (Mfn2)/β-actin] and fission events [dynamin-related protein 1 (Drp1/β-actin)] and apoptosis (caspase 3/β-actin) were assessed by western blot analysis.

Results

Obstetric complications were significantly more frequent in pregnancies among HIV-infected women [OR 5.00 (95% CI 1.21-20.70)]. Mfn2/β-actin levels in PBMCs from controls significantly decreased during pregnancy (202.13 ± 57.45%), whereas cases maintained reduced levels from the first trimester of pregnancy and no differences were observed in CBMCs. Mfn2/β-actin and Drp1/β-actin contents significantly decreased in the placenta of cases. Caspase 3/β-actin levels significantly increased during pregnancy in PBMCs of cases (50.00 ± 7.89%), remaining significantly higher than in controls. No significant differences in caspase 3/β-actin content of neonatal CBMCs were observed, but there was a slight increased trend in placenta from cases.

Conclusions

HIV- and HAART-mediated mitochondrial damage may be enhanced by decreased mitochondrial dynamics and increased apoptosis in maternal and placental compartments but not in the uninfected fetus. However, direct effects on mitochondrial dynamics and implication of apoptosis were not demonstrated in adverse obstetric outcomes.

Cardiac and placental mitochondrial characterization in a rabbit model of intrauterine growth restriction

BACKGROUND

Intrauterine growth restriction (IUGR) is associated with cardiovascular remodeling persisting into adulthood. Mitochondrial bioenergetics, essential for embryonic development and cardiovascular function, are regulated by nuclear effectors as sirtuins. A rabbit model of IUGR and cardiovascular remodeling was generated, in which heart mitochondrial alterations were observed by microscopic and transcriptomic analysis. We aimed to evaluate if such alterations are translated at a functional mitochondrial level to establish the etiopathology and potential therapeutic targets for this obstetric complication.

METHODS

Hearts and placentas from 16 IUGR-offspring and 14 controls were included to characterize mitochondrial function.

RESULTS

Enzymatic activities of complexes II, IV and II + III in IUGR-hearts (-11.96 ± 3.16%; -15.58 ± 5.32%; -14.73 ± 4.37%; p < 0.05) and II and II + III in IUGR-placentas (-17.22 ± 3.46%; p < 0.005 and -29.64 ± 4.43%; p < 0.001) significantly decreased. This was accompanied by a not significant reduction in CI-stimulated oxygen consumption and significantly decreased complex II SDHB subunit expression in placenta (-44.12 ± 5.88%; p < 0.001). Levels of mitochondrial content, Coenzyme Q and cellular ATP were conserved. Lipid peroxidation significantly decreased in IUGR-hearts (-39.02 ± 4.35%; p < 0.001), but not significantly increased in IUGR-placentas. Sirtuin3 protein expression significantly increased in IUGR-hearts (84.21 ± 31.58%; p < 0.05) despite conserved anti-oxidant SOD2 protein expression and activity in both tissues.

CONCLUSIONS

IUGR is associated with cardiac and placental mitochondrial CII dysfunction. Up-regulated expression of Sirtuin3 may explain attenuation of cardiac oxidative damage and preserved ATP levels under CII deficiency.

GENERAL SIGNIFICANCE

These findings may allow the design of dietary interventions to modulate Sirtuin3 expression and consequent regulation of mitochondrial imbalance associated with IUGR and derived cardiovascular remodeling.

Clinical characteristics of adult patients with inborn errors of metabolism in Spain: A review of 500 cases from university hospitals

Patients with inborn errors of metabolism (IEMs) have become an emerging and challenging group in the adult healthcare system whose needs should be known in order to implement appropriate policies and to adapt adult clinical departments. We aimed to analyze the clinical characteristics of adult patients with IEMs who attend the most important Spanish hospitals caring for these conditions. A cohort study was conducted in 500 patients, categorized by metabolic subtype according to pathophysiological classification. The most prevalent group of IEMs was amino acid disorders, with 108 (21.6%) patients diagnosed with phenylketonuria. Lysosomal storage disorders were the second group, in which 32 (6.4%) and 25 (5%) patients had Fabry disease and Gaucher disease respectively. The great clinical heterogeneity, the significant delay in diagnosis after symptom onset, the existence of some degree of physical dependence in a great number of patients, the need for a multidisciplinary and coordinated approach, and the lack of specific drug treatment are common features in this group of conditions.

The diagnosis and classification of polymyositis

Polymyositis is classified as a separate entity among idiopathic inflammatory myopathies but it is considered as the least common since it is an exclusion diagnosis. This myopathy usually presents with subacute-chronic symmetric proximal limb weakness, although some extramuscular manifestations are common. Creatine kinase values may be increased up to 50-fold in active disease. Muscle biopsy is characterized by endomysial inflammatory infiltrate consisting predominantly of CD8+ T cells that invade healthy muscle fibres expressing the MHC-I antigen. Although serum autoantibodies, EMG and imaging techniques can help in diagnosis, muscle histopathology is a pivotal value. The clinical picture together with the pathological findings confers the also called PM pattern. A broad differential diagnosis is needed before concluding a diagnosis of pure PM. Sporadic inclusion-body myositis, toxic, endocrine and metabolic myopathies as well as muscular dystrophies are the major categories to be ruled out. Finally, a diagnostic algorithm for suspected cases of PM is also proposed.