Myasthenia Gravis: paradox versus paradigm in autoimmunity

FOSL1-mediated LINC01566 negatively regulates CD4+ T-cell activation in myasthenia gravis

BACKGROUND

Myasthenia gravis (MG) is an autoimmune disease characterized by pathogenic antibodies that target structures of the neuromuscular junction. The evidence suggests that the regulation of long noncoding RNAs (lncRNAs) that is mediated by transcription factors (TFs) plays a key role in the pathophysiology of MG. Nevertheless, the detailed molecular mechanisms of lncRNAs in MG remain largely undetermined.

METHODS

Using microarray analysis, we analyzed the lncRNA levels in MG. By bioinformatics analysis, LINC01566 was found to potentially play an important role in MG. First, qRT‒PCR was performed to verify the LINC1566 expressions in MG patients. Then, fluorescence in situ hybridization was conducted to determine the localization of LINC01566 in CD4 + T cells. Finally, the impact of LINC01566 knockdown or overexpression on CD4 + T-cell function was also analyzed using flow cytometry and CCK-8 assay. A dual-luciferase reporter assay was used to validate the binding of the TF FOSL1 to the LINC01566 promoter.

RESULTS

Based on the lncRNA microarray and differential expression analyses, we identified 563 differentially expressed (DE) lncRNAs, 450 DE mRNAs and 19 DE TFs in MG. We then constructed a lncRNA-TF-mRNA network. Through network analysis, we found that LINC01566 may play a crucial role in MG by regulating T-cell-related pathways. Further experiments indicated that LINC01566 is expressed at low levels in MG patients. Functionally, LINC01566 is primarily distributed in the nucleus and can facilitate CD4 + T-cell apoptosis and inhibit cell proliferation. Mechanistically, we hypothesized that LINC01566 may negatively regulate the expressions of DUSP3, CCR2, FADD, SIRPB1, LGALS3 and SIRPB1, which are involved in the T-cell activation pathway, to further influence the cellular proliferation and apoptosis in MG. Moreover, we found that the effect of LINC01566 on CD4 + T cells in MG was mediated by the TF FOSL1, and in vitro experiments indicated that FOSL1 can bind to the promoter region of LINC01566.

CONCLUSIONS

In summary, our research revealed the protective roles of LINC01566 in clinical samples and cellular experiments, illustrating the potential roles and mechanism by which FOSL1/LINC01566 negatively regulates CD4 + T-cell activation in MG.

Dihydroartemisinin ameliorates experimental autoimmune myasthenia gravis by regulating CD4+ T cells and modulating gut microbiota

BACKGROUND

Dihydroartemisinin (DHA), a derivative and active metabolite of artemisinin, possesses various immunomodulatory properties. However, its role in myasthenia gravis (MG) has not been clearly explored. Here, we investigated the role of DHA in experimental autoimmune myasthenia gravis (EAMG) and its potential mechanisms.

METHODS

The AChR97-116 peptide-induced EAMG model was established in Lewis rats and treated with DHA. Flow cytometry was used to assess the release of Th cell subsets and Treg cells, and 16S rRNA gene amplicon sequence analysis was applied to explore the relationship between the changes in the intestinal flora after DHA treatment. In addition, network pharmacology and molecular docking were utilized to explore the potential mechanism of DHA against EAMG, which was further validated in the rat model by immunohistochemical and RT-qPCR for further validation.

RESULTS

In this study, we demonstrate that oral administration of DHA ameliorated clinical symptoms in rat models of EAMG, decreased the expression level of Th1 and Th17 cells, and increased the expression level of Treg cells. In addition, 16S rRNA gene amplicon sequence analysis showed that DHA restored gut microbiota dysbiosis in EAMG rats by decreasing Ruminococcus abundance and increasing the abundance of Clostridium, Bifidobacterium, and Allobaculum. Using network pharmacology, 103 potential targets of DHA related to MG were identified, and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that PI3K-AKT signaling pathway was related to the treatment of DHA on EAMG. Meanwhile, molecular docking verified that DHA has good binding affinity to AKT1, CASP3, EGFR, and IGF1. Immunohistochemical staining showed that DHA treatment significantly inhibited the phosphorylated expression of AKT and PI3K in the spleen tissues of EAMG rats. In EAMG rats, RT-qPCR results also showed that DHA reduced the mRNA expression levels of PI3K and AKT1.

CONCLUSIONS

DHA ameliorated EAMG by inhibiting the PI3K-AKT signaling pathway, regulating CD4+ T cells and modulating gut microbiota, providing a novel therapeutic approach for the treatment of MG.

Myasthenia gravis and five autoimmune diseases: a bidirectional Mendelian randomization study

BACKGROUND

The association between myasthenia gravis (MG) and other autoimmune diseases is well established. In this study, we aimed to investigate the causal effects between MG and five other autoimmune diseases, including autoimmune thyroid disease (AITD), multiple sclerosis (MS), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and type 1 diabetes (T1DM).

METHODS

We conducted a bidirectional Mendelian randomization (MR) study by using seven published genome-wide association studies (GWAS), including MG (1873 patients versus 36,370 controls), AITD (autoimmune hypothyroidism) (22,997 patients versus 175,475 controls), AITD (autoimmune hyperthyroidism) (962 patients versus 172,976 controls), MS (47,429 patients versus 68,374 controls), RA (14,361 patients versus 43,923 controls), SLE (4222 patients versus 8431 controls), and T1DM (9266 patients versus 15,574 controls). We used the inverse-variance-weighted (IVW) method, weighted-median (WM) estimator, MR-Egger regression, and MR PRESSO in our analyses. We also carried out detailed sensitivity analyses for each direction using the aforementioned methods.

RESULTS

When MG was treated as the exposure, MR evidence suggested a causal relationship between MG and T1DM, SLE, AITD (both hypothyroidism and hyperthyroidism), and MS (excluding RA). Using the IVW method, we found that MG was associated with increased risk of T1DM (OR = 1.94; 95% CI, 1.16-3.26; p = 0.012), SLE (OR = 1.47; 95% CI, 1.02-2.13; p = 0.04), AITD (hypothyroidism) (OR = 1.31; 95% CI, 1.02-1.68; p = 0.039), AITD (hyperthyroidism) (OR = 1.55; 95% CI, 1.15-2.09; p = 0.004), and MS (OR = 1.46; 95% CI, 1.01-2.09; p = 0.041). When MG was treated as the outcome, MR evidence suggested that RA, T1DM, and SLE were causal factors in MG. Using the IVW method, we found that the risk of MG increased with exposure to RA (OR = 1.21; 95% CI, 1.08-1.37; p = 0.002), T1DM (OR = 1.09; 95% CI, 1.02-1.16; p = 0.006), and SLE (OR = 1.12; 95% CI, 1.02-1.23; p = 0.018).

CONCLUSIONS

This study demonstrated a causal relationship between MG and several other autoimmune diseases. Our results supported a bidirectional causal association between MG and SLE/T1DM. Our findings also provided reliable evidence that MG is associated with increased risk of AITD. Meanwhile, we also showed that RA is a possible causal driver of MG risk.

Curcumin protects mice with myasthenia gravis by regulating the gut microbiota, short-chain fatty acids, and the Th17/Treg balance

Curcumin is widely used as a traditional drug in Asia. Interestingly, curcumin and its metabolites have been demonstrated to influence the microbiota. However, the effect of curcumin on the gut microbiota in patients with myasthenia gravis (MG) remains unclear. This study aimed to investigate the effects of curcumin on the gut microbiota community, short-chain fatty acids (SCFAs) levels, intestinal permeability, and Th17/Treg balance in a Torpedo acetylcholine receptor (T-AChR)-induced MG mouse model. The results showed that curcumin significantly alleviated the clinical symptoms of MG mice induced by T-AChR. Curcumin modified the gut microbiota composition, increased microbial diversity, and, in particular, reduced endotoxin-producing Proteobacteria and Desulfovibrio levels in T-AChR-induced gut dysbiosis. Moreover, we found that curcumin significantly increased fecal butyrate levels in mice with T-AChR-induced gut dysbiosis. Butyrate levels increased in conjunction with the increase in butyrate-producing species such as Oscillospira, Akkermansia, and Allobaculum in the curcumin-treated group. In addition, curcumin repressed the increased levels of lipopolysaccharide (LPS), zonulin, and FD4 in plasma. It enhanced Occludin expression in the colons of MG mice induced with T-AChR, indicating dramatically alleviated gut permeability. Furthermore, curcumin treatment corrected T-AChR-induced imbalances in Th17/Treg cells. In summary, curcumin may protect mice against myasthenia gravis by modulating both the gut microbiota and SCFAs, improving gut permeability, and regulating the Th17/Treg balance. This study provides novel insights into curcumin's clinical value in MG therapy.

Rs1800629 polymorphism in TNF-alpha is associated with the susceptibility and initial short-term glucocorticoids efficacy in myasthenia gravis patients

Tumor necrosis factor-alpha (TNF-α) is a potent pro-inflammatory agent involved in various autoimmune and inflammatory diseases including myasthenia gravis (MG). In this study, we enrolled 409 adult MG patients and 487 healthy individuals to investigate the association between TNF-α polymorphism and MG. We found the rs1800629 A allele frequency was significantly higher in the MG group than in the control group. Subgroup analysis revealed that the A allele frequencies were significantly higher in the early-onset subgroup, non-thymoma subgroup, ocular-onset subgroup, and mild severity subgroup than in the control group. To minimize the interactions between clinical features, we used a comprehensive classification and found that the rs1800629 A allele frequency was significantly higher in the non-thymoma AChR-Ab negative subgroup than in the control group. In the analysis of initial short-term glucocorticoids (GC) efficacy in the treatment-naive patients, the rs1800629 A allele frequency was significantly higher in the unresponsive subgroup than in the responsive group and the control group. Logistic regression demonstrated the rs1800629 genotypes in the dominant model and disease duration prior to GC treatment independently contributed to initial short-term GC efficacy. In conclusion, our study revealed that in Chinese adult MG patients, rs1800629 polymorphism in TNF-α was associated with the susceptibility of MG and might indicate the initial short-term GC efficacy.

Autoimmune thyroid disease and myasthenia gravis: a study bidirectional Mendelian randomization

Background

Previous studies have suggested a potential association between AITD and MG, but the evidence is limited and controversial, and the exact causal relationship remains uncertain.

Objective

Therefore, we employed a Mendelian randomization (MR) analysis to investigate the causal relationship between AITD and MG.

Methods

To explore the interplay between AITD and MG, We conducted MR studies utilizing GWAS-based summary statistics in the European ancestry. Several techniques were used to ensure the stability of the causal effect, such as random-effect inverse variance weighted, weighted median, MR-Egger regression, and MR-PRESSO. Heterogeneity was evaluated by calculating Cochran's Q value. Moreover, the presence of horizontal pleiotropy was investigated through MR-Egger regression and MR-PRESSO.

Results

The IVW method indicates a causal relationship between both GD(OR 1.31,95%CI 1.08 to 1.60,P=0.005) and autoimmune hypothyroidism (OR: 1.26, 95% CI: 1.08 to 1.47, P =0.002) with MG. However, there is no association found between FT4(OR 0.88,95%CI 0.65 to 1.18,P=0.406), TPOAb(OR: 1.34, 95% CI: 0.86 to 2.07, P =0.186), TSH(OR: 0.97, 95% CI: 0.77 to 1.23, P =0.846), and MG. The reverse MR analysis reveals a causal relationship between MG and GD(OR: 1.50, 95% CI: 1.14 to 1.98, P =3.57e-3), with stable results. On the other hand, there is a significant association with autoimmune hypothyroidism(OR: 1.29, 95% CI: 1.04 to 1.59, P =0.019), but it is considered unstable due to the influence of horizontal pleiotropy (MR PRESSO Distortion Test P < 0.001). MG has a higher prevalence of TPOAb(OR: 1.84, 95% CI: 1.39 to 2.42, P =1.47e-5) positivity and may be linked to elevated TSH levels(Beta:0.08,95% CI:0.01 to 0.14,P =0.011), while there is no correlation between MG and FT4(Beta:-9.03e-3,95% CI:-0.07 to 0.05,P =0.796).

Conclusion

AITD patients are more susceptible to developing MG, and MG patients also have a higher incidence of GD.

Causal relationship between gut microbiota and myasthenia gravis: a bidirectional mendelian randomization study

BACKGROUND

Observational studies have demonstrated an association between gut microbiota and myasthenia gravis; however, the causal relationship between the two still lacks clarity. Our goals are to ascertain the existence of a bidirectional causal relationship between gut microbiota composition and myasthenia gravis, and to investigate how gut microbiota plays a role in reducing the risk of myasthenia gravis.

METHODS

We acquired gut microbiota data at the phylum, class, order, family, and genus levels from the MiBioGen consortium (N = 18,340) and myasthenia gravis data from the FinnGen Research Project (426 cases and 373,848 controls). In the two-sample Mendelian randomization analysis, we assessed the causal relationship between the gut microbiota and myasthenia gravis. We also conducted bidirectional MR analysis to determine the direction of causality. The inverse variance weighted, mendelian randomization-Egger, weighted median, simple mode, and weighted mode were used to test the causal relationship between the gut microbiota and severe myasthenia gravis. We used MR-Egger intercept and Cochran's Q test to assess for pleiotropy and heterogeneity, respectively. Furthermore, we utilized the MR-PRESSO method to evaluate horizontal pleiotropy and detect outliers.

RESULTS

In the forward analysis, the inverse-variance weighted method revealed that there is a positive correlation between the genus Lachnoclostridium (OR = 2.431,95%CI 1.047-5.647, p = 0.039) and the risk of myasthenia gravis. Additionally, the family Clostridiaceae1 (OR = 0.424,95%CI 0.202-0.889, p = 0.023), family Defluviitaleaceae (OR = 0.537,95%CI  0.290-0.995, p = 0.048), family Enterobacteriaceae (OR = 0.341,95%CI  0.135-0.865, p = 0.023), and an unknown genus (OR = 0.407,95%CI  0.209-0.793, p = 0.008) all demonstrated negative correlation with the risk of developing myasthenia gravis. Futhermore, reversed Mendelian randomization analysis proved a negative correlation between the risk of myasthenia gravis and genus Barnesiella (OR = 0.945,95%CI  0.906-0.985, p = 0.008).

CONCLUSION

Our research yielded evidence of a causality connection in both directions between gut microbiota and myasthenia gravis. We identified specific types of microbes associated with myasthenia gravis, which offers a fresh window into the pathogenesis of this disease and the possibility of developing treatment strategies. Nonetheless, more studies, both basic and clinical, are necessary to elucidate the precise role and therapeutic potential of the gut microbiota in the pathogenesis of myasthenia gravis.

Clinical features of myasthenia gravis with neurological and systemic autoimmune diseases

Multiple reports on the co-existence of autoimmune diseases and myasthenia gravis (MG) have raised considerable concern. Therefore, we reviewed autoimmune diseases in MG to explore their clinical presentations and determine whether the presence of autoimmune diseases affects the disease severity and treatment strategies for MG. We reviewed all the major immune-mediated coexisting autoimmune conditions associated with MG. PubMed, Embase and Web of Science were searched for relevant studies from their inception to January 2023. There is a higher frequency of concomitant autoimmune diseases in patients with MG than in the general population with a marked risk in women. Most autoimmune comorbidities are linked to AChR-MG; however, there are few reports of MuSK-MG. Thyroid disorders, systemic lupus erythematosus, and vitiligo are the most common system autoimmune diseases associated with MG. In addition, MG can coexist with neurological autoimmune diseases, such as neuromyelitis optica (NMO), inflammatory myopathy (IM), multiple sclerosis (MS), and autoimmune encephalitis (AE), with NMO being the most common. Autoimmune diseases appear to develop more often in early-onset MG (EOMG). MS coexists more commonly with EOMG, while IM coexists with LOMG. In addition, MG complicated by autoimmune diseases tends to have mild clinical manifestations, and the coexistence of autoimmune diseases does not influence the clinical course of MG. The clinical course of neurological autoimmune diseases is typically severe. Autoimmune diseases occur most often after MG or as a combined abnormality; therefore, timely thymectomy followed by immunotherapy could be effective. In addition, thymoma-associated AChR MG is associated with an increased risk of AE and IM, whereas NMO and MS are associated with thymic hyperplasia. The co-occurrence of MG and autoimmune diseases could be attributed to similar immunological mechanisms with different targets and common genetic factor predisposition. This review provides evidence of the association between MG and several comorbid autoimmune diseases.

Anti-dsDNA Is Associated with Favorable Prognosis in Myasthenia Gravis: A Retrospective Study

Objectives. To investigate the presence of serum antinuclear antibody (ANA) and anti-double-stranded DNA antibody (anti-dsDNA) in patients with myasthenia gravis (MG) and analyze the clinical characteristics and prognostic factors associated with MG. Methods. We retrospectively enrolled 363 patients with MG and analyzed the clinical characteristics and follow-up data between patients positive and negative for ANA and anti-dsDNA. We defined a Myasthenia Gravis Activities of Daily Living (MG-ADL) reduction as a main prognosis predictor and used logistic regression to determine independent factors associated with prognosis. We built a nomogram to predict prognosis and evaluate the internal validity of the model. Results. Ninety-eight (27.0%) patients were positive for ANA, and 51 (14.0%) were positive for anti-dsDNA. Patients positive for ANA and anti-dsDNA antibodies tended to be female and positive for acetylcholine receptor antibody (AChR-Ab). The rate of thymoma was higher in anti-dsDNA-positive patients with MG (p-dsDNA-MG) than in patients negative for anti-dsDNA (49.0% vs. 26.0%, $p=0.001$ ), and p-dsDNA-MG was associated with reduced MG-ADL score. Regression analysis showed that except for age of onset ( $\text{OR}=0.986$ , $95\%\text{CI}=0.973–0.999$ , $p=0.037$ ), anti-dsDNA ( $\text{OR}=2.800$ , $95\%\text{CI}=1.381–5.679$ , $p=0.004$ ), ptosis ( $\text{OR}=2.930$ , $95\%\text{CI}=1.827–4.699$ , $p<0.001$ ), and eye movement disorder ( $\text{OR}=2.815$ , $95\%\text{CI}=1.672–4.741$ , $p<0.001$ ) were independent predictive factors of a favorable prognosis of MG. These predictors were used to generate a nomogram with an excellent predictive value. Conclusions. Being female and the presence of AChR-Ab were features of ANA- or anti-dsDNA-positive MG. The presence of anti-dsDNA was associated with a favorable prognosis of MG.

Association of early-onset myasthenia gravis and primary Sjögren's syndrome: a case-based narrative review

Coexistent myasthenia gravis (MG) and primary Sjögren's syndrome (pSS) is an absolute rarity. That is kind of a surprise as both entities seem to share the same corresponding immunologic mechanisms. We hereby report the case of a 41-year-old woman with coincident early-onset MG (EOMG) and pSS. Because EOMG was the leading clinical feature, she was primarily treated by innovative non-intubated uniportal subxiphoid video-assisted thoracoscopic surgery (VATS) thymectomy. As the association of EOMG and pSS is so unusual, we contextualize our findings with the relevant literature. Particular relevance is an anti-nuclear antibody screening throughout the clinical course of MG and-in reverse-a screening for MG variables when pSS patients complain either muscle fatigability or fatigable ptosis. As pSS patients do not develop any serious morbidity, supervising MG progress in patients with both diseases is of utmost importance. Apart from conscientious pSS diagnosis, prompt adjusting of EOMG progress is the essential aspect of targeted treatment. In this context, it is relevant that therapeutic decisions are made in a multidisciplinary approach. Due to its rarity, multicenter prospective studies of larger sample sizes are indispensably needed to obtain a better understanding of this unusual link.

Cross-syndrome: myasthenia gravis and the demyelinating diseases of the central nervous system combination. Systematic literature review and case reports

Nowadays the problem of comorbidity is still relevant. In this review, we describe clinical cases of the disease of the neuromuscular junction (myasthenia gravis (MG) generalized form) and the demyelinating disease of the central nervous system (DD CNS) (multiple sclerosis, neuromyelitis optica spectrum disorder (NMOSD), etc.) combinations registered in our practice with precise pathogenetic analysis. Although the number of the described associations is growing every year, the exact development mechanisms of this cross syndrome as well as the nature of the association between the discussed autoimmune diseases remain unknown. At the beginning of both disorders there is a considerable loss of auto tolerance of the immune system and, as a result, an increased response from autoreactive T-lymphocytes to the structures of the nervous system: brain cells and neuromuscular synapses. There are three main theories for comorbidity: initial predisposition, direct case relationship with disease-modifying therapy (DMT) application, and coincidence. It is known that early diagnostics of MG and timely administration of necessary adequate treatment reduce the risk of process generalization and lead to a decline in mortality. Therefore, the offer to examine MS patients with atypical symptoms for possible MG identification seems very rational. Similarly, MG patients having uncharacteristic symptoms that can be indicative of other autoimmune nervous system diseases also demand special diagnostics. Considering the presence of similar pathogenetic links, several authors propose a possibility of a new nosological unit establishment, including described comorbidity.

Multiple Sclerosis and Autoimmunity: A Veiled Relationship

Multiple sclerosis (MS) is an autoimmune inflammatory illness that affects the central nervous system (CNS) when the body's immune system attacks its tissue. It is characterized by demyelination and varying degrees of axonal loss. This article has compiled various studies elaborating MS and other autoimmune diseases (ADs) co-occurrence. Several conditions that fall into this category, including type 1 diabetes (T1D), rheumatoid arthritis (RA), Guillain-Barre syndrome (GBS), myasthenia gravis (MG), and many others, are found in MS patients and their relatives, suggesting one or more common etiologic mechanisms, including genetic, environmental, and immunological factors, supporting the concept of a possible influence of poly-autoimmunity on MS and the rest of ADs, as well as providing a significant feature for early detection of the disease and also a potential treatment option by clinical neurologists.

Hearing disorders in lupus patients: correlation with duration and severity of the disease

Background

Hearing loss can greatly affect the overall quality of life. Several studies have reported that patients with SLE may suffer from audio-vestibular manifestations. The aim of this study is to evaluate the influence of systemic lupus erythematosus (SLE) on hearing and association of hearing impairment with severity and duration of SLE.

Results

Pure-tone audiometry (PTA) (air conduction and bone conduction) thresholds showed significant elevation in SLE group than controls (P ≤ 0.05). It was observed also that there is a significant association between SLE severity and duration with sensorineural hearing loss (SNHL) and its degree.

Conclusion

SLE can lead to hearing loss, and there is a positive association of SLE severity and duration with degree of hearing loss.

The LINC00452/miR-204/CHST4 Axis Regulating Thymic Tregs Might Be Involved in the Progression of Thymoma-Associated Myasthenia Gravis

Background

Myasthenia gravis (MG) is an autoimmune disease that mainly affects neuromuscular junctions and is usually associated with immune disorders in the thymoma. The competitive endogenous RNA (ceRNA) hypothesis has been demonstrated to be an intrinsic mechanism regulating the development of several autoimmune diseases; however, the mechanism where the ceRNA network regulates immune cells in patients with thymoma-associated MG (TAMG) has rarely been explored.

Methods

RNA-seq data and clinical information of 124 patients with thymoma were obtained from The Cancer Genome Atlas (TCGA) database. The patients were divided into two groups according to whether they were diagnosed with MG. We applied the propensity score matching method to reduce the incidence of baseline confounders. We then constructed a ceRNA network with differentially expressed RNAs between the groups based on four public databases. The expression of genes of interest was validated by qPCR. Moreover, we predicted the immune cells that infiltrated the thymoma and then analyzed the association between immune cells and RNA in the ceRNA network. To further determine the function of the mRNAs associated with immune cells in patients with TAMG, we performed gene set enrichment analysis in thymoma patients with MG.

Results

After matching, 94 patients were included in the following analysis. A total of 847 mRNAs, 409 lncRNAs, and 45 miRNAs were differentially expressed between the groups. The ceRNA network, including 18 lncRNAs, four miRNAs, and 13 mRNAs, was then constructed. We then confirmed that CHST4 and LINC00452, miR-204-3p and miR-204-5p were differentially expressed between patients with TAMG and thymoma patients without MG (NMG) by qPCR. Moreover, we found that the percentage of predicted regulatory T (Treg) cells was significantly decreased in patients with TAMG. Further analysis indicated that the LINC00452/miR-204/CHST4 axis might regulate thymic regulatory T cells (Tregs) in the progression of MG.

Conclusions

In this research, we constructed a ceRNA network involved in the progression of TAMG, discovered that thymic Tregs were significantly decreased in patients with TAMG, and assumed that the LINC00452/miR-204/CHST4 axis may regulate thymic Tregs in the development of TAMG. These findings may deepen our understanding of the roles of the ceRNA network in regulating TAMG and highlight the function of CHST4 in recruiting peripheral T cells in the progression of TAMG.

CAR-T Regulatory (CAR-Treg) Cells: Engineering and Applications

Regulatory T cells are critical for maintaining immune tolerance. Recent studies have confirmed their therapeutic suppressive potential to modulate immune responses in organ transplant and autoimmune diseases. However, the unknown and nonspecific antigen recognition of polyclonal Tregs has impaired their therapeutic potency in initial clinical findings. To address this limitation, antigen specificity can be conferred to Tregs by engineering the expression of transgenic T-cell receptor (TCR) or chimeric antigen receptor (CAR). In contrast to TCR Tregs, CAR Tregs are major histocompatibility complex (MHC) independent and less dependent on interleukin-2 (IL-2). Furthermore, CAR Tregs maintain Treg phenotype and function, home to the target tissue and show enhanced suppressive efficacy compared to polyclonal Tregs. Additional development of engineered CAR Tregs is needed to increase Tregs' suppressive function and stability, prevent CAR Treg exhaustion, and assess their safety profile. Further understanding of Tregs therapeutic potential will be necessary before moving to broader clinical applications. Here, we summarize recent studies utilizing CAR Tregs in modulating immune responses in autoimmune diseases, transplantation, and gene therapy and future clinical applications.

Rheumatoid arthritis and myasthenia gravis: a case-based review of the therapeutic options

Introduction

Myasthenia gravis is an autoimmune disease affecting the neuromuscular junction, often associated with other autoimmune diseases, including rheumatoid arthritis. Patients with rheumatoid arthritis present an increased prevalence of myasthenia gravis compared to the general population. While these two diseases share some therapeutic options, such as glucocorticoids, methotrexate, and rituximab, there are no guidelines for treating concomitant disease. We aim to review the available evidence and to discuss the efficacy and safety of the therapeutic options in patients with rheumatoid arthritis associated with myasthenia gravis.

Method

We described three patients with rheumatoid arthritis associated with myasthenia gravis and we performed a systematic review of the associated literature.

Results

A 48-year-old man and two women (48 and 55 years old) with concomitant diagnoses of active rheumatoid arthritis and well-controlled myasthenia gravis are described. They were treated with methotrexate, leflunomide, upadacitinib, and adalimumab. None of them experienced changes in their myasthenic symptoms. We found 9 additional cases from our literature review. Methotrexate, rituximab, upadacitinib, diphenyl sulfone, auranofin, and loxoprofen sodium did not show an impact on the seven patients with previously well-controlled myasthenia. Glucocorticoids, methotrexate, and rituximab proved effective in active myasthenia gravis and arthritis. Conflicting data emerged for Tumor-necrosis factor inhibitors.

Conclusions

Although the available evidence remains scarce, we consider glucocorticoids, methotrexate, and rituximab as safe and effective options. The role of tumor-necrosis factor inhibitors remains uncertain. Eventually, Janus Kinase inhibitors are a novel interesting option for these patients.

Key Points • To date, the only evidence on the treatment of patients with rheumatoid arthritis and concomitant myasthenia gravis derives from case reports. • Based on the review of the available case reports and on the cases we described, we consider glucocorticoids, methotrexate, and rituximab as safe and effective options, while the role of Tumor-necrosis factor inhibitors remains uncertain. • Based on the cases we described, Janus Kinase inhibitors are a novel interesting option for patients with concomitant rheumatoid arthritis and myasthenia gravis.

Juvenile Generalized Myasthenia Gravis With AChR and MuSK Antibody Double Positivity: A Case Report With a Review of the Literature

Myasthenia gravis is an autoimmune disease mediated by B cells and is associated with acetylcholine receptor (AChR) and muscle-specific receptor tyrosine kinase (MuSK) antibodies in the postsynaptic membrane at the neuromuscular junction. The presence of both antibodies in the serum of patients with myasthenia gravis has been rarely reported. Case description: A 9-year-old girl was admitted to our hospital with the chief complaints of reduced facial expression for 3 months and unclear speech and choking from drinking water for 2 months. The diagnosis of generalized myasthenia gravis was made based on clinical manifestations, repetitive electrical nerve stimulation, neostigmine tests, specific antibody tests and other auxiliary examinations. We found the rare coexistence of two key antibodies (anti-AChR and anti-MuSK antibodies) in the patient's serum. The patient experienced myasthenic crisis and received respiratory support even though she was taking prednisone therapy. Due to the poor response to treatment with pyridostigmine bromide, glucocorticoids and IVIG, we administered rituximab therapy, and she responded well and achieved clinical remission. This suggests that clinicians should pay more attention to atypical cases and antibody detection. Rituximab should be considered when conventional treatment fails.

Epstein-Barr Virus in Myasthenia Gravis: Key Contributing Factor Linking Innate Immunity with B-Cell-Mediated Autoimmunity

Epstein-Barr virus (EBV), a common human herpes virus latently infecting most of the world’s population with periodic reactivations, is the main environmental factor suspected to trigger and/or sustain autoimmunity by its ability to disrupt B-cell tolerance checkpoints. Myasthenia gravis (MG) is a prototypic autoimmune disorder, mostly caused by autoantibodies to acetylcholine receptor (AChR) of the neuromuscular junction, which cause muscle weakness and fatigability. Most patients display hyperplastic thymus, characterized by ectopic germinal center formation, chronic inflammation, exacerbated Toll-like receptor activation, and abnormal B-cell activation. After an overview on MG clinical features and intra-thymic pathogenesis, in the present chapter, we describe our main findings on EBV presence in MG thymuses, including hyperplastic and thymoma thymuses, in relationship with innate immunity activation and data from other autoimmune conditions. Our overall data strongly indicate a critical contribution of EBV to innate immune dysregulation and sustained B-cell-mediated autoimmune response in the pathological thymus of MG patients.

SARS-CoV-2 Proteome Harbors Peptides Which Are Able to Trigger Autoimmunity Responses: Implications for Infection, Vaccination, and Population Coverage

Autoimmune diseases (ADs) could occur due to infectious diseases and vaccination programs. Since millions of people are expected to be infected with SARS-CoV-2 and vaccinated against it, autoimmune consequences seem inevitable. Therefore, we have investigated the whole proteome of the SARS-CoV-2 for its ability to trigger ADs. In this regard, the entire proteome of the SARS-CoV-2 was chopped into more than 48000 peptides. The produced peptides were searched against the entire human proteome to find shared peptides with similar experimentally confirmed T-cell and B-cell epitopes. The obtained peptides were checked for their ability to bind to HLA molecules. The possible population coverage was calculated for the most potent peptides. The obtained results indicated that the SARS-CoV-2 and human proteomes share 23 peptides originated from ORF1ab polyprotein, nonstructural protein NS7a, Surface glycoprotein, and Envelope protein of SARS-CoV-2. Among these peptides, 21 peptides had experimentally confirmed equivalent epitopes. Amongst, only nine peptides were predicted to bind to HLAs with known global allele frequency data, and three peptides were able to bind to experimentally confirmed HLAs of equivalent epitopes. Given the HLAs which have already been reported to be associated with ADs, the ESGLKTIL, RYPANSIV, NVAITRAK, and RRARSVAS were determined to be the most harmful peptides of the SARS-CoV-2 proteome. It would be expected that the COVID-19 pandemic and the vaccination against this pathogen could significantly increase the ADs incidences, especially in populations harboring HLA-B*08:01, HLA-A*024:02, HLA-A*11:01 and HLA-B*27:05. The Southeast Asia, East Asia, and Oceania are at higher risk of AD development.

Association Between Myasthenia Gravis and Systemic Lupus Erythematosus as a Comorbid State

Systemic lupus erythematosus (SLE) and myasthenia gravis (MG) are autoimmune states which have presentational similitude. Both conditions test serologically positive for anti-nuclear antibodies and require exceptional differential diagnostic acumen to segregate one from the other. The hypothesized factors provoking these diseases may be immunological, genetic, hormonal, or environmental and can be better understood by large-scale controlled epidemiological studies. Biochemical factors such as variation in CXC (an α chemokine subfamily), CXCL13, and granulocyte-macrophage colony-stimulating factor levels are assumed to play a pivotal role in the pathogenesis of SLE and MG; however, further studies are required to understand their exact mechanism and effect on the underlying autoimmune diseases. Following this, another precipitating factor for this overlap is believed to be thymectomy which is performed to eliminate MG symptoms. Although thymectomy is the effective treatment modality in MG patients, other findings and data support the view that this procedure may lead to the development of other autoimmune states such as SLE. It is evident from previously published data and case reports that patients with one autoimmune disease who underwent thymectomy contracted SLE and became more susceptible to other autoimmune diseases compared to the general population. Post-thymectomy follow-up of patients provides us with mechanistic clues for understanding the development of SLE-MG overlap; hence, in MG patients who have undergone thymectomy, any clinical and immune serological SLE suspicion should be carefully evaluated.

Detection of IgM and IgG Antibodies to Human Parvovirus B19 in Sera of Patients with Thymoma-Associated Myasthenia Gravis

Much uncertainty still exists about the viral etiology of myasthenia gravis (MG). To address this, we explored the relationship between human parvovirus B19 (PVB19) infection and MG by investigating the presence of PVB19-specific antibodies in serum. A total of 131 patients with MG (including 47 with thymoma-associated MG, 14 with hyperplasia-associated MG, and 70 with unknown thymic lesions) and 172 healthy volunteers were enrolled in this study. Enzyme linked immunosorbent assay was conducted to detect virus-specific antibodies in cell-free serum. The data were analyzed using Pearson chi-square (χ²) and Fisher's exact tests. In the 131 patients with MG, there was no significant difference between male (53.41 ± 14.65 years) and female (50.19 ± 15.28 years) groups regarding mean age (p > 0.05). Among all MG subgroups, the largest age group comprised participants aged 30-60 years. We found that the frequency of detecting immunoglobulin G (IgG) antibodies against PVB19 VP1 and VP2 was significantly higher among patients with MG (68.70%) than in healthy controls (41.86%) (p < 0.001). In particular, the positive rate for anti-PVB19 IgG in patients with thymoma-associated MG (35/47, 74.47%) was significantly higher than that in healthy participants (72/172, 41.86%; p < 0.001). The findings of this study indicate that PVB19 infection may play a role in the etiopathogenesis of MG, particularly in patients with thymoma-associated MG. The study protocol was registered at ClinicalTrials.gov with the identifier ChiCTR-1900023338.

Myasthenia Gravis Coexisting With Primary Sjögren's Syndrome: Report of Three Cases and Literature Review

Objective: The coexistence of myasthenia gravis (MG) and primary Sjögren's syndrome (pSS) is rarely reported. This study aims to describe the clinical features, treatment and outcome of MG coexisting with pSS.

Materials and Methods: Herein we reported three cases with the two coexisting diseases, and also searched the PubMed, Medline databases, and China Wanfang databases for the relevant case reports written in English, Chinese, or Japanese with detailed data.

Results: We reviewed a total of 17 patients with both diseases. Fifteen patients were female. The median age at onset was 48 years (range 28–78 years). MG was the initial disease in nine of 17 cases. The median interval between the onsets of the two diseases was 30 months (range 7 months to 20 years). The symptoms of MG included fatigable ptosis (64.7%), bulbar symptoms (58.8%), muscle fatigability (64.7%), diplopia (64.7%), dyspnea (23.5%), and facial paralysis (5.9%). Anti-acetylcholine receptor antibody was positive in 70.6% patients. All the patients had sicca symptoms. Manifestations of pSS also included swollen exocrine glands (23.5%), joint pain (23.5%), hair loss (11.8%), leukopenia (11.8%), recurrent oral ulcers (5.9%), Raynaud phenomenon (5.9%), and fever (5.9%). ANA positivity was present in 70.6% patients, anti-SSA positivity in 47.1%, and double positivity of anti-SSA and anti-SSB in 17.6%. There were 12 patients (70.6%) with two autoimmune diseases (pSS and MG), and five patients with more than two autoimmune diseases. Cholinesterase inhibitors were the most commonly prescribed drugs (82.4%). Seven patients received thymectomy and one patient improved after the operation. Two patients were given intravenous methylprednisolone pulse therapy, and four patients oral steroids combined with immunosuppressants initially. Intravenous immunoglobulin and plasma exchange were used in two patients, respectively, for the respiratory failure. All the patients improved following treatment except one patient who died of MG crisis due to medication withdrawal.

Conclusion: The coexistence of SS with MG is quite rare. The onset of MG may occur before or after the diagnosis of SS. Co-morbidity with MG does not seem to adversely affect the course of SS. Thus, controlling the progress of MG is the critical aspect of treatment.

Association Between Systemic Lupus Erythematosus and Myasthenia Gravis: Coincidence or Sequelae?

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease and myasthenia gravis (MG) is an organ-specific autoimmune disease, both may exhibit positive anti-nuclear antibodies and a female preponderance. They may have similar features and can coexist in a patient or precede one another.

This review article is based on electronic searches using PubMed as the primary database. Most of the articles used for this review were published in the last ten years with the exception of seven articles which were from 1995-2009. No guidelines have been followed. A total of 55 research articles were found related to the topic of this review article, and further scanning was done to eliminate some articles that did not meet the criteria.

The coexistence of autoimmune diseases has been reported in many cases. The prevalence of a second autoimmune disease is higher among patients with a primary diagnosis of autoimmune disease than the general population. The prevalence of SLE in MG patients or vice-versa is greater than the general population. The association has been hypothesized to many mechanisms: thymectomy resulting in loss of central tolerance and generation of autoantibodies, regulatory T cell dysfunction, the dysregulated function of Fas receptor (CD95), anti-malarial drugs directly affecting the neuromuscular junction, the role of chemokine CXCL13 and GM-CSF in the pathogenesis. The association is rare, and the presence of one should be closely followed for further progression into other diseases. More research work needs to be done for a clear conclusion.

Comparative Analysis of Thymic and Blood Treg in Myasthenia Gravis: Thymic Epithelial Cells Contribute to Thymic Immunoregulatory Defects

The thymus is involved in autoimmune Myasthenia gravis (MG) associated with anti-acetylcholine (AChR) antibodies. In MG, thymic regulatory T cells (Treg) are not efficiently suppressive, and conventional T cells (Tconv) are resistant to suppression. To better understand the specific role of the thymus in MG, we compared the phenotype and function of peripheral and thymic Treg and Tconv from controls and MG patients. Suppression assays with thymic or peripheral CD4 + T cells showed that the functional impairment in MG was more pronounced in the thymus than in the periphery. Phenotypic analysis of Treg showed a significant reduction of resting and effector Treg in the thymus but not in the periphery of MG patients. CD31, a marker lost with excessive immunoreactivity, was significantly reduced in thymic but not blood resting Treg. These results suggest that an altered thymic environment may explain Treg differences between MG patients and controls. Since thymic epithelial cells (TECs) play a major role in the generation of Treg, we co-cultured healthy thymic CD4 + T cells with control or MG TECs and tested their suppressive function. Co-culture with MG TECs consistently hampers regulatory activity, as compared with control TECs, suggesting that MG TECs contribute to the immune regulation defects of MG CD4 + T cells. MG TECs produced significantly higher thymic stromal lymphopoietin (TSLP) than control TECs, and a neutralizing anti-TSLP antibody partially restored the suppressive capacity of Treg derived from co-cultures with MG TECs, suggesting that TSLP contributed to the defect of thymic Treg in MG patients. Finally, a co-culture of MG CD4 + T cells with control TECs restored numbers and function of MG Treg, demonstrating that a favorable environment could correct the immune regulation defects of T cells in MG. Altogether, our data suggest that the severe defect of thymic Treg is at least partially due to MG TECs that overproduce TSLP. The Treg defects could be corrected by replacing dysfunctional TECs by healthy TECs. These findings highlight the role of the tissue environment on the immune regulation.

Effects of Mitophagy on Regulatory T Cell Function in Patients With Myasthenia Gravis

Objective: This study was conducted to determine whether regulatory T cells (CD4⁺CD25⁺T, Tregs) show abnormal mitophagy as well as the function of Tregs in patients with myasthenia gravis (MG).

Methods: CD4⁺T cells and CD4⁺CD25⁺Treg cells were obtained from 15 patients with MG (MG group) and 15 controls (N group). Tregs from the MG group were subjected to rapamycin-induced culture for 48 h (Rapa group) and 3-methyladenine-induced culture for 48 h (3-MA group). The levels of mitophagy in Tregs were then observed through electron and confocal microscopy. Expression of the autophagy-related protein LC3-II was detected by western blotting, and mitochondrial function in each group was evaluated by flow cytometry. Inhibition of Treg cell proliferation was detected by flow cytometry.

Results: Mitophagy in the MG group was lower than that in the N group; it was higher in the Rapa group compared to that in the MG group and lowered in the 3-MA group than in the MG group. Expression of the autophagy-related protein LC3-II was lower in the MG group than in the N group, higher in the Rapa group than in the MG group, and lower in the 3-MA group than in the MG group. The mitochondrial membrane potential was lower in the MG group compared to that in the N group; it was higher in the Rapa group than in the MG group and lowered in the 3-MA group than in the MG group. Inhibition of Treg proliferation was lower in the MG group than in the N group; it was higher in the Rapa group than in the MG group and lowered in the 3-MA group than in the MG group.

Conclusion: The decreased mitochondrial membrane potential and mitophagy in Tregs in the MG group may be related to a decreased inhibition of Treg proliferation. The mitochondrial membrane potential was increased after adding the autophagy agent Rapa to enhance mitophagy, and the proliferation inhibition function of Tregs was also enhanced. The autophagy agent 3-MA down-regulated mitophagy, which decreased the mitochondrial membrane potential and inhibitory effect of Tregs. These results reveal the possible cellular immune mechanism of Treg dysfunction in MG.

miR-146a in Myasthenia Gravis Thymus Bridges Innate Immunity With Autoimmunity and Is Linked to Therapeutic Effects of Corticosteroids

Toll-like receptor (TLR)-mediated innate immune responses are critically involved in the pathogenesis of myasthenia gravis (MG), an autoimmune disorder affecting neuromuscular junction mainly mediated by antiacetylcholine receptor antibodies. Considerable evidence indicate that uncontrolled TLR activation and chronic inflammation significantly contribute to hyperplastic changes and germinal center (GC) formation in the MG thymus, ultimately leading to autoantibody production and autoimmunity. miR-146a is a key modulator of innate immunity, whose dysregulation has been associated with autoimmune diseases. It acts as inhibitor of TLR pathways, mainly by targeting the nuclear factor kappa B (NF-κB) signaling transducers, interleukin 1 receptor associated kinase 1 (IRAK1) and tumor necrosis factor (TNF) receptor associated factor 6 (TRAF6); miR-146a is also able to target c-REL, inducible T-cell costimulator (ICOS), and Fas cell surface death receptor (FAS), known to regulate B-cell function and GC response. Herein, we investigated the miR-146a contribution to the intrathymic MG pathogenesis. By real-time PCR, we found that miR-146a expression was significantly downregulated in hyperplastic MG compared to control thymuses; contrariwise, IRAK1, TRAF6, c-REL, and ICOS messenger RNA (mRNA) levels were upregulated and negatively correlated with miR-146a levels. Microdissection experiments revealed that miR-146a deficiency in hyperplastic MG thymuses was not due to GCs, but restricted to the GC-surrounding medulla, characterized by IRAK1 overexpression. We also showed higher c-REL and ICOS mRNA levels, and lower FAS mRNA levels, in GCs than in the remaining medulla, according to the contribution of these molecules in GC formation. By double immunofluorescence, an increased proportion of IRAK1-expressing dendritic cells and macrophages was found in hyperplastic MG compared to control thymuses, along with GC immunoreactivity for c-REL. Interestingly, in corticosteroid-treated MG patients intrathymic miR-146a and mRNA target levels were comparable to those of controls, suggesting that immunosuppressive therapy may restore the microRNA (miRNA) levels. Indeed, an effect of prednisone on miR-146a expression was demonstrated in vitro on peripheral blood cells. Serum miR-146a levels were lower in MG patients compared to controls, indicating dysregulation of the circulating miRNA. Our overall findings strongly suggest that defective miR-146a expression could contribute to persistent TLR activation, lack of inflammation resolution, and hyperplastic changes in MG thymuses, thus linking TLR-mediated innate immunity to B-cell-mediated autoimmunity. Furthermore, they unraveled a new mechanism of action of corticosteroids in inducing control of autoimmunity in MG via miR-146a.

The Muscle Is Not a Passive Target in Myasthenia Gravis

Myasthenia gravis (MG) is a rare autoimmune disease mediated by pathogenic antibodies (Ab) directed against components of the neuromuscular junction (NMJ), mainly the acetylcholine receptor (AChR). The etiological mechanisms are not totally elucidated, but they include a combination of genetic predisposition, triggering event(s), and hormonal components. MG disease is associated with defective immune regulation, chronic cell activation, inflammation, and the thymus is frequently abnormal. MG is characterized by muscle fatigability that is very invalidating and can be life-threatening when respiratory muscles are affected. MG is not cured, and symptomatic treatments with acetylcholinesterase inhibitors and immunosuppressors are life-long medications associated with severe side effects (especially glucocorticoids). While the muscle is the ultimate target of the autoimmune attack, its place and role are not thoroughly described, and this mini-review will focus on the cascade of pathophysiologic mechanisms taking place at the NMJ and its consequences on the muscle biology, function, and regeneration in myasthenic patients, at the histological, cellular, and molecular levels. The fine structure of the synaptic cleft is damaged by the Ab binding that is coupled to focal complement-dependent lysis in the case of MG with anti-AChR antibodies. Cellular and molecular reactions taking place in the muscle involve several cell types as well as soluble factors. Finally, the regenerative capacities of the MG muscle tissue may be altered. Altogether, the studies reported in this review demonstrate that the muscle is not a passive target in MG, but interacts dynamically with its environment in several ways, activating mechanisms of compensation that limit the pathogenic mechanisms of the autoantibodies.

Hospital and healthcare insurance system record-based epidemiological study of myasthenia gravis in southern and northern China

OBJECTIVE

This is the first cross-region epidemiological study of myasthenia gravis (MG) in China. We estimated the incidence, prevalence, and medical costs of MG in southern China and explored the differences between the southern and northern Chinese populations.

METHODS

We collected and analyzed records from 20 hospitals in the southern city, Guangzhou, 13 hospitals in the northern city, Harbin, and two healthcare insurance systems: job based and residence based in Guangzhou during 2000-2017.

RESULTS

(1) The estimated annual incidence of MG was 1.55-3.66 per 100,000, and the estimated prevalence of MG was 2.19-11.07 per 100,000 in southern China based on insurance records. (2) The proportion of hospitalized MG patients in the south-based hospital records was three times as high as that in the north-based hospital records. (3) Female MG prevalence was significantly higher than male MG prevalence in Guangzhou, while the similar gender difference in Harbin was not statistically significant due to higher variation in earlier years. (4) The average expense was $35-42 for each outpatient service and $2526-2673 for each hospitalization expense in the south. (5) Contrary to the increase of insurance-based estimate of MG prevalence, the proportion of hospitalized MG patients did not increase over the years, suggesting rising awareness and utilization of health insurance.

CONCLUSIONS

The southern MG population had a significantly higher prevalence and a lower response threshold to medication than the northern MG population. These results are calling for further investigations on the genetic, cultural, and environmental variations of the Chinese MG populations between north and south.

Ligandomes obtained from different HLA-class II-molecules are homologous for N- and C-terminal residues outside the peptide-binding cleft

Human CD4+ T lymphocytes play an important role in inducing potent immune responses. T cells are activated and stimulated by peptides presented in human leucocyte antigen (HLA)-class II molecules. These HLA-class II molecules typically present peptides of between 12 and 20 amino acids in length. The region that interacts with the HLA molecule, designated as the peptide-binding core, is highly conserved in the residues which anchor the peptide to the molecule. In addition, as these peptides are the product of proteolytic cleavages, certain conserved residues may be expected at the N- and C-termini outside the binding core. To study whether similar conserved residues are present in different cell types, potentially harbouring different proteolytic enzymes, the ligandomes of HLA-DRB1*03:01/HLA-DRB > 1 derived from two different cell types (dendritic cells and EBV-transformed B cells) were identified with mass spectrometry and the binding core and N- and C-terminal residues of a total of 16,568 peptides were analysed using the frequencies of the amino acids in the human proteome. Similar binding motifs were found as well as comparable conservations in the N- and C-terminal residues. Furthermore, the terminal conservations of these ligandomes were compared to the N- and C-terminal conservations of the ligandome acquired from dendritic cells homozygous for HLA-DRB1*04:01. Again, comparable conservations were evident with only minor differences. Taken together, these data show that there are conservations in the terminal residues of peptides, presumably the result of the activity of proteases involved in antigen processing.

Autoimmune vertigo: an update on vestibular disorders associated with autoimmune mechanisms

The role of the immune system in mediating cochleovestibular pathologies has received increasing attention in recent years. Autoimmune vertigo may be an invalidating condition and may worsen the quality of life of affected patients, especially in the cases of delayed diagnosis. Since the etiopathogenesis is still not clear, also the treatment is not yet completely delineated. According to the clinical presentation, autoimmune vertigo can present as an isolated disorder or in association with systemic autoimmune diseases. The main feature in autoimmune vertigo is the presence of an abnormal immune response, in either absence or presence of systemic autoimmune disease, directed against delicate components of the inner ear. This may determine a functional or anatomical alteration, with an inflammatory reaction often devastating for hearing and balance. Being the exact pathogenesis unknown, the diagnosis of autoimmune vertigo is based either on clinical criteria or on a positive response to steroids. The earlier the diagnosis is made, the sooner the therapy can be installed, giving a chance to the recovery of inner ear damages. Corticosteroids represent the most effective and universally accepted treatment, even if other immunomodulatory drugs are now having a more extensive use. HIGHLIGHTS: Vertigo is relatively frequent in autoimmune diseases; however, it is often misdiagnosed or attributed to central nervous system alterations rather to specific inner ear involvement. Vertigo and other audiovestibular symptoms may be the first manifestation of an autoimmune disease and if correctly addressed could significantly contribute to early diagnosis of the underlying autoimmune disease. Early diagnosis of immune-related vertigo can lead to prompt initiation of targeted therapy with elevate chances of preventing irreversible damages to the inner ear. The presence of alternating phases of well-being and disabling symptoms in patients with vertigo should always been considered, as they could suggest an underlying autoimmune condition.

Autoimmune Attack of the Neuromuscular Junction in Myasthenia Gravis: Nicotinic Acetylcholine Receptors and Other Targets

The nicotinic acetylcholine receptor (nAChR) family, the archetype member of the pentameric ligand-gated ion channels, is ubiquitously distributed in the central and peripheral nervous systems, and its members are the targets for both genetic and acquired forms of neurological disorders. In the central nervous system, nAChRs contribute to the pathological mechanisms of neurodegenerative disorders, such as Alzheimer and Parkinson diseases. In the peripheral nerve-muscle synapse, the vertebrate neuromuscular junction, "classical" myasthenia gravis (MG) and other forms of neuromuscular transmission disorders are antibody-mediated autoimmune diseases. In MG, antibodies to the nAChR bind to the postsynaptic receptors and activate the classical complement pathway culminating in the formation of the membrane attack complex, with the subsequent destruction of the postsynaptic apparatus. Divalent nAChR-antibodies also cause internalization and loss of the nAChRs. Loss of receptors by either mechanism results in the muscle weakness and fatigability that typify the clinical manifestations of the disease. Other targets for antibodies, in a minority of patients, include muscle specific kinase (MuSK) and low-density lipoprotein related protein 4 (LRP4). This brief Review analyzes the current status of muscle-type nAChR in relation to the pathogenesis of autoimmune diseases affecting the peripheral cholinergic synapse.

Myasthenia gravis: from autoantibodies to therapy

PURPOSE OF REVIEW

The current article reviews the recent advances in the field of myasthenia gravis, which span from autoantibody profiling and pathogenic mechanisms to therapy innovation. The overview is highlighting specifically the data and the needs of targeted treatments in the light of precision medicine in myasthenia gravis.

RECENT FINDINGS

Novel data published recently further increased our knowledge on myasthenia gravis. The use of cell-based assays has greatly improved autoantibody detection in myasthenia gravis patients, and the mechanisms of action of these antibodies have been described. The role of Toll-like receptor activation in the generation of thymic alterations and anti-acetylcholine receptor autosensitization has been further investigated implementing our understanding on the relationships between innate immunity and autoimmunity. Additional studies have been focused on the alterations of T-cell/B-cell regulatory mechanisms in thymus and peripheral blood of myasthenia gravis patients. microRNAs and genetic factors are also emerging as key biomarkers in myasthenia gravis pathogenesis and prediction of drug efficacy in individual patients.

SUMMARY

The recent immunological and pathological findings in myasthenia gravis promise to improve myasthenia gravis treatment, via the development of more precise and personalized therapies.

Cytometric cell-based assays for anti-striational antibodies in myasthenia gravis with myositis and/or myocarditis

The purposes of the present study were to identify anti-striational antibodies in myasthenia gravis (MG) patients with myositis and/or myocarditis using a combination of cell-based assays and flow cytometry (cytometric cell-based assays) and to describe the main clinical implications. Among 2,609 stored samples collected from all over Japan between 2003 and 2016, we had serum samples from 30 MG patients with myositis and/or myocarditis. Cytometric cell-based assays with titin, ryanodine receptor, and voltage-gated Kv1.4 were performed. Autoantibodies were determined by differences in phycoerythin fluorescence between the 293F cells and titin-transfected cells. MG patients with myositis and/or myocarditis as well as late-onset and thymoma-associated MG had anti-titin, anti-ryanodine receptor, and anti-Kv1.4 antibodies. In contrast, patients with early-onset MG, those with other myopathies and healthy controls did not have anti-titin or anti-Kv1.4 antibodies with some exceptions, but they possessed anti-ryanodine receptor antibodies. Thirty MG patients with myositis and/or myocarditis showed a severe generalized form, and 21 of them had thymoma. Anti-titin and anti-Kv1.4 antibodies were found in 28 (93%) and 15 (50%) patients, respectively, and all patients had at least one of these antibodies. Cytometric cell-based assays thus demonstrated that anti-striational antibodies are biomarkers of MG with myositis and/or myocarditis.

Il-23/Th17 cell pathway: A promising target to alleviate thymic inflammation maintenance in myasthenia gravis

IL-23/Th17 pathway has been identified to sustain inflammatory condition in several autoimmune diseases and therefore being targeted in various therapeutic and effective approaches. Patients affected with autoimmune myasthenia gravis exhibit a disease effector tissue, the thymus, that harbors ectopic germinal centers that sustain production of auto-antibodies, targeting proteins located in the neuromuscular junction, cause of the organ-specific chronic autoimmune disease. The present study aims to investigate the IL-23/Th17 cell pathway in the thymic inflammatory and pathogenic events. We found that thymuses of MG patients displayed overexpression of Interleukin-17, signature cytokine of activated Th17 cells. This activation was sustained by a higher secretion of Interleukin-23 by TEC, in addition to the increased expression of cytokines involved in Th17 cell development. The overexpression of Interleukin-23 was due to a dysregulation of interferon type I pathway. Besides, Interleukin-17 secreted, and Th17 cells were localized around thymic ectopic germinal centers. These cells expressed podoplanin, a protein involved in B-cell maturation and antibody secretion. Finally, production of Interleukin-23 was also promoted by Interleukin-17 secreted itself by Th17 cells, highlighting a chronic loop of inflammation sustained by thymic cell interaction. Activation of the IL-23/Th17 pathway in the thymus of autoimmune myasthenia gravis patients creates an unstoppable loop of inflammation that may participate in ectopic germinal center maintenance. To alleviate the physio-pathological events in myasthenia gravis patients, this pathway may be considered as a new therapeutic target.

NAT2 Gene Polymorphisms in Turkish Patients with Psoriasis Vulgaris

Psoriasis is a common, chronic, and autoimmune skin disease. Factors that play a role in etiopathogenesis of psoriasis include internal factors such as genetic susceptibility and immunological factors and external factors such as stress, infection, trauma, drug, and environmental compounds. N-acetyltransferase 2 (NAT2) is a xenobiotic enzyme that is involved in the metabolism of drugs, environmental toxins, and carcinogens. In this study, we aimed to demonstrate whether the variations in the NAT2 gene lead to a predisposition to psoriasis by affecting the enzyme's ability to metabolize drugs and environmental components or not. Three polymorphisms (rs1799929, rs1799930, and rs1799931) in NAT2 gene were genotyped and compared by real-time PCR method in 260 psoriasis vulgaris patients and 200 healthy controls. There was no difference in the genotype distributions and allele frequencies of polymorphisms between psoriasis vulgaris patients and controls. When the effects of polymorphisms on the clinical features of the disease, such as onset age and severity, are assessed, it has been found that rs1799930 and rs1799929 are, respectively, associated with early onset age and severity of the disease. In conclusion, rs1799929, rs1799930, and rs1799931 polymorphisms of the NAT-2 gene do not appear to be a risk factor for the development of psoriasis. Conversely, they may have an effect on either more severe or early onset cases of the disease.

Thyroid Hormones Play Role in Sarcopenia and Myopathies

Skeletal muscle maintains posture and enables movement by converting chemical energy into mechanical energy, further contributing to basal energy metabolism. Thyroid hormones (thyroxine, or T4, and triiodothyronine, or T3) participate in contractile function, metabolic processes, myogenesis and regeneration of skeletal muscle. T3 classically modulates gene expression after binding to thyroid hormone nuclear receptors. Thyroid hormone effects depend on nuclear receptor occupancy, which is directly related to intracellular T3 levels. Sarcolemmal thyroid hormone levels are regulated by their transport across the plasma membrane by specific transporters, as well as by the action of deiodinases types 2 and 3, which can activate or inactivate T4 and T3. Thyroid hormone level oscillations have been associated with the worsening of many myopathies such as myasthenia gravis, Duchenne muscular dystrophy (DMD) and rhabdomyolysis. During aging skeletal muscle show a decrease in mass and quality, known as sarcopenia. There is increasing evidence that thyroid hormones could have a role in the sarcopenic process. Therefore, in this review, we aim to discuss the main effects of thyroid hormones in skeletal muscular aging processes and myopathy-related pathologies.

NMO-IgG and AQP4 Peptide Can Induce Aggravation of EAMG and Immune-Mediated Muscle Weakness

Neuromyelitis optica (NMO) and myasthenia gravis (MG) are autoimmune diseases mediated by autoantibodies against either aquaporin 4 (AQP4) or acetylcholine receptor (AChR), respectively. Recently, we and others have reported an increased prevalence of NMO in patients with MG. To verify whether coexisting autoimmune disease may exacerbate experimental autoimmune MG, we tested whether active immunization with AQP4 peptides or passive transfer of NMO-Ig can affect the severity of EAMG. Injection of either AQP4 peptide or NMO-Ig to EAMG or to naive mice caused increased fatigability and aggravation of EAMG symptoms as expressed by augmented muscle weakness (but not paralysis), decremental response to repetitive nerve stimulation, increased neuromuscular jitter, and aberration of immune responses. Thus, our study shows increased disease severity in EAMG mice following immunization with the NMO autoantigen AQP4 or by NMO-Ig, mediated by augmented inflammatory response. This can explain exacerbation or increased susceptibility of patients with one autoimmune disease to develop additional autoimmune syndrome.

Myasthenia gravis as a prognostic marker in patients with thymoma

Background

Thymoma is the most common mediastinal tumor, representing <1% of all cancers. It is usually associated with paraneoplastic disorders, mainly myasthenia gravis (MG). The aim of the present study was to describe patients with thymoma and the differences between those with MG and those without it.

Methods

A retrospective 10-year database of the patients with thymoma treated at a single cancer referral hospital (National Institute of Cancer, Mexico City), was analyzed.

Results

Sixty-four files from patients with thymoma were analyzed, 18 of them had MG. The symptoms that occurred most frequently in patients with MG were ptosis, diplopia, appendicular weakness, dysphonia and dysphagia. The most frequent Myasthenia Gravis Foundation of America (MGFA) stage was IIIb followed by stage I. Almost all the patients with MG had positive Acetylcholine Receptor antibodies (P<0.001), with not specified antibodies in four patients. The median overall survival showed a trend to be higher among the patients with MG, but there were no significant differences.

Conclusions

In patients with thymoma MG manifests with different clinical and autoimmune traits, but not survival differences. A larger multi-centric study should be encouraged to evaluate the prognostic implications of having MG in patients with thymoma.

Myasthenia Gravis and Associated Diseases

BACKGROUND:

Myasthenia gravis (MG) is an autoimmune disease caused by the action of specific antibodies to the postsynaptic membrane of the neuromuscular junction, leading to impaired neuromuscular transmission. Patients with MG have an increased incidence of other autoimmune diseases.

AIM:

to determine the presence of other associated diseases in patients with MG.

METHOD:

A group of 127 patients with MG followed in 10 years period, in which the presence of other associated diseases has been analysed.

RESULTS:

The sex ratio is in favour of the female sex, the average age of the initial manifestation of the disease is less than 50 years, 65.4% of the patients with MG have another disease. 15.0% patients have associated another autoimmune disease. Thyroid disease is the most common associated with MG, rarely rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and other autoimmune diseases. Other diseases include hypertension, heart disease, diabetes, respiratory diseases, dyslipidemia. 10.2% of the patients are diagnosed with extrathymic tumours of various origins.

CONCLUSION:

Associated diseases are common in patients with MG, drawing attention to the possible common basis for their coexistence, as well as their impact on the intensity and treatment of the disease.

Pathophysiological mechanisms of autoimmunity

Autoimmune diseases (AIDs) are chronic disorders characterized by inflammatory reactions against self-antigens that can be either systemic or organ specific. AIDs can differ in their epidemiologic features and clinical presentations, yet all share a remarkable complexity. AIDs result from an interplay of genetic and epigenetic factors with environmental components that are associated with imbalances in the immune system. Many of the pathogenic mechanisms of AIDs are also implicated in myasthenia gravis (MG), an AID in which inflammation of the thymus leads to a neuromuscular disorder. Our goal here is to highlight the similarities and differences between MG and other AIDs by reviewing the common transcriptome signatures and the development of germinal centers and by discussing some unresolved questions about autoimmune mechanisms. This review will propose hypotheses to explain the origin of regulatory T (T_reg ) cell defects and the causes of chronicity and specificity of AIDs.

Toll-like receptors 7 and 9 in myasthenia gravis thymus: amplifiers of autoimmunity?

Pathogen infections and dysregulated Toll-like receptor (TLR)-mediated innate immune responses are suspected to play key roles in autoimmunity. Among TLRs, TLR7 and TLR9 have been implicated in several autoimmune conditions, mainly because of their ability to promote abnormal B cell activation and survival. Recently, we provided evidence of Epstein-Barr virus (EBV) persistence and reactivation in the thymus of myasthenia gravis (MG) patients, suggesting an involvement of EBV in the intrathymic pathogenesis of the disease. Considerable data highlight the existence of pathogenic crosstalk among EBV, TLR7, and TLR9: EBV elicits TLR7/9 signaling, which in turn can enhance B cell dysfunction and autoimmunity. In this article, after a brief summary of data demonstrating TLR activation in MG thymus, we provide an overview on the contribution of TLR7 and TLR9 to autoimmune diseases and discuss our recent findings indicating a pivotal role for these two receptors, along with EBV, in driving, perpetuating, and/or amplifying intrathymic B cell dysregulation and autoimmune responses in MG. Development of therapeutic approaches targeting TLR7 and TLR9 signaling could be a novel strategy for treating the chronic inflammatory autoimmune process in myasthenia gravis.

Gut microbiota and probiotics: novel immune system modulators in myasthenia gravis?

Gut microorganisms (microbiota) live in symbiosis with the host and influence human nutrition, metabolism, physiology, and immune development and function. The microbiota prevents pathogen infection to the host, and in turn the host provides a niche for survival. The alteration of gut bacteria composition (dysbiosis) could contribute to the development of immune-mediated diseases by influencing the immune system activation and driving the pro- and anti-inflammatory responses in order to promote or counteract immune reactions. Probiotics are nonpathogenic microorganisms able to interact with the gut microbiota and provide health benefits; their use has recently been exploited to dampen immunological response in several experimental models of autoimmune diseases. Here, we focus on the relationships among commensal bacteria, probiotics, and the gut, describing the main interactions occurring with the immune system and recent data supporting the clinical efficacy of probiotic administration in rheumatoid arthritis, multiple sclerosis, and myasthenia gravis (MG) animal models. The encouraging results suggest that selected strains of probiotics should be evaluated in clinical trials as adjuvant therapy to restore the disrupted tolerance in myasthenia gravis.

Immunopathogenesis in Myasthenia Gravis and Neuromyelitis Optica

Myasthenia gravis (MG) and neuromyelitis optica (NMO) are autoimmune channelopathies of the peripheral neuromuscular junction (NMJ) and central nervous system (CNS) that are mainly mediated by humoral immunity against the acetylcholine receptor (AChR) and aquaporin-4 (AQP4), respectively. The diseases share some common features, including genetic predispositions, environmental factors, the breakdown of tolerance, the collaboration of T cells and B cells, imbalances in T helper 1 (Th1)/Th2/Th17/regulatory T cells, aberrant cytokine and antibody secretion, and complement system activation. However, some aspects of the immune mechanisms are unique. Both targets (AChR and AQP4) are expressed in the periphery and CNS, but MG mainly affects the NMJ in the periphery outside of CNS, whereas NMO preferentially involves the CNS. Inflammatory cells, including B cells and macrophages, often infiltrate the thymus but not the target—muscle in MG, whereas the infiltration of inflammatory cells, mainly polymorphonuclear leukocytes and macrophages, in NMO, is always observed in the target organ—the spinal cord. A review of the common and discrepant characteristics of these two autoimmune channelopathies may expand our understanding of the pathogenic mechanism of both disorders and assist in the development of proper treatments in the future.