Anti-acetylcholine Receptor Antibody-positive Myasthenia Gravis Research Articles

Gut microbiota-derived butyrate restores impaired regulatory T cells in patients with AChR myasthenia gravis via mTOR-mediated autophagy

More than 80% of patients with myasthenia gravis (MG) are positive for anti-acetylcholine receptor (AChR) antibodies. Regulatory T cells (Tregs) suppress overproduction of these antibodies, and patients with AChR antibody-positive MG (AChR MG) exhibit impaired Treg function and reduced Treg numbers. The gut microbiota and their metabolites play a crucial role in maintaining Treg differentiation and function. However, whether impaired Tregs correlate with gut microbiota activity in patients with AChR MG remains unknown. Here, we demonstrate that butyric acid-producing gut bacteria and serum butyric acid level are reduced in patients with AChR MG. Butyrate supplementation effectively enhanced Treg differentiation and their suppressive function of AChR MG. Mechanistically, butyrate activates autophagy of Treg cells by inhibiting the mammalian target of rapamycin. Activation of autophagy increased oxidative phosphorylation and surface expression of cytotoxic T-lymphocyte-associated protein 4 on Treg cells, thereby promoting Treg differentiation and their suppressive function in AChR MG. This observed effect of butyrate was blocked using chloroquine, an autophagy inhibitor, suggesting the vital role of butyrate-activated autophagy in Tregs of patients with AChR MG. We propose that gut bacteria derived butyrate has potential therapeutic efficacy against AChR MG by restoring impaired Tregs.

Evidence for genetic causal relationships between gut microbiome, metabolites, and myasthenia gravis: a bidirectional Mendelian randomization study.

Myasthenia gravis (MG) is an autoimmune disease observed to have connections with gut microbiome. We aimed to systematically assess the causal relationships between gut microbiome, gut microbiome-derived metabolites, and MG using Mendelian randomization (MR) approach. Summary-level genetic datasets from large-scale genome-wide association studies regarding 196 gut microbial taxa from the MiBioGen consortium (n=18,340), 72 derived metabolites from the TwinsUK and KORA studies (n=7,824), and antiacetylcholine receptor (AChR) antibody-positive MG (case=1,873, control=36,370) were employed for MR causal estimates. The inverse-variance weighted (IVW) method was utilized as the main analysis with MR-Egger, maximum likelihood, simple mode, and weighted median as complements. The tests of Cochran's Q, MR-Egger intercept, Steiger, MR-PRESSO and leave-one-out were implemented for sensitivity analyses. The forward MR estimates of IVW revealed significant causal associations of the abundance of phylum Actinobacteria, class Gammaproteobacteria, family Defluviitaleac, family Family XIII, and family Peptococcaceae with a reduced risk of MG. Conversely, the abundance of phylum Lentisphaerae, order Mollicutes RF9, order Victivallales, and genus Faecalibacterium was causally associated with an increased risk of MG. The reversed MR analysis proved negative causal correlations between the MG and the abundance of family Peptostreptococcaceae, genus Romboutsia, and genus Subdoligranulum. Regarding the derived metabolites, the IVW estimates revealed that elevated levels of beta-hydroxyisovalerate and methionine were causally associated with a decreased risk of MG, while increased levels of choline and kynurenine were linked to an increased risk of MG. Furthermore, genetically predicted MG was associated with a decreased level of cholesterol. The results obtained from complementary MR methods were similar. These findings remained robust in all sensitivity analyses. Our MR findings support the causal effects of specific gut microbiome taxa and derived metabolites on AChR antibody-positive MG, and vice versa, yielding novel insights into prevention and therapy targets of MG. Future studies may be warranted for validation and pursuing the precise mechanisms.

Smoking and younger age at onset in anti-acetylcholine receptor antibody-positive myasthenia gravis

Smoking is a known risk factor for the development and progression of several autoimmune diseases. Previous studies have pointed out the association of smoking with the development and worsening of symptoms in myasthenia gravis (MG), but further investigation is necessary to confirm this association. Smoking history was investigated in a cross-sectional study of 139 patients with anti-acetylcholine receptor antibody-positive MG, and the association of smoking history with the age at the onset of MG was analyzed. Patients who had been smoking at the onset of MG were significantly younger compared with those who had never smoked or had quit before the onset of MG. A linear regression analysis adjusting for sex and the presence/absence of thymoma showed a significant association between smoking at onset and younger age at onset (regression coefficient −9.05; 95% confidence interval, −17.6, −0.51; p = 0.039). Among patients with smoking exposure within 10 years prior to or at the onset of MG, women were significantly younger at the onset of MG compared with men. Our results suggest that smoking is an independent risk factor for the earlier development of anti-acetylcholine receptor antibody-positive MG and further support the putative link between smoking and MG.

Clinical characteristics and outcomes of myasthenia gravis patients with double positive antibodies against acetylcholine receptor and muscle-specific tyrosine kinase

Objective: To investigate the clinical manifestations, treatment characteristics and outcomes of myasthenia gravis (MG) dually positive for anti-acetylcholine receptor antibody (AChR-Ab) and anti-muscle-specific tyrosine kinase antibody (MuSK-Ab). Method: MG patients hospitalized in the First Affiliated Hospital of Sun Yat-sen University from August 2017 to November 2020 were retrospectively collected. Thirty-four MuSK-Ab positive MG (MuSK-MG) patients, 11 double-antibodies positive MG (DP-MG) patients, and 80 AChR-Ab positive MG (AChR-MG) patients were included and allocated to three different groups. The clinical data of patients in the three groups were collected, and the differences of demographic characteristics, clinical manifestations and treatment outcomes between DP-MG patients and AChR-MG and MuSK-MG patients were analyzed. Result: The proportion of female and male patients in DP-MG group was 7/11 and 4/11 respectively, and the onset age of DP-MG was (41±27) years.The difference in gender distribution between DP-MG and AChR-MG groups was statistically significant (P<0.05). The proportion of extraocular muscle involvement in the DP-MG and MuSK-MG groups (8/11 and 52.9%) was lower than that in the AChR-MG group (83.8%), and the difference was statistically significant (P<0.05). The incidence of myasthenia crisis in DP-MG and MuSK-MG groups (54.5% and 61.8%) were higher than that in AChR-MG group (20.0%), with astatistically significant difference(P<0.05). The positive rate of neostigmine test in DP-MG and MuSK-MG groups(8/11 and 74.2%) were lower than that of AChR-MG group (96.8%), and the positive rate of low frequency repetitive nerve stimulation (RNS) in DP-MG group (5/10) was lower than that in AChR-MG group (85.1%), with statistically significant differences (all P<0.05). MuSK-Ab titer was positively correlated with the course of disease (r=0.466, P<0.05), and antibody titer decreased after symptom improvement (P<0.05). The response of patients in DP-MG and MuSK-MG groups to cholinesterase inhibitors (2/11 and 9.1%) was worse than that in the AChR-MG group (66.3%), and the incidence of side effects in the two groups (5/11 and 39.4%) was higher than that in the AChR-MG group (15.0%), with statistically significant differences (all P<0.05). There were 4 DP-MG patients underwent thymectomy, and the pathological results detected two cases of thymoma and two cases of thymic hyperplasia. Subsequent follow-up showed that 5 (5/11) DP-MG patients achieved minimal manifestation status or better status. Conclusion: The gender distribution, age of onset, pharmacological characteristics and electrophysiological examination of DP-MG patients were similar to those of MuSK-MG patients, but the severity of DP-MG patients was between that of AChR-MG and MuSK-MG patients.

Roles of IL-35-producing T and B cells in anti-acetylcholine receptor antibody-positive myasthenia gravis

BackgroundInterleukin 35 (IL-35) plays an anti-inflammatory in numerous autoimmune diseases. However, the potential roles of IL-35-producing T and B cells and serum IL-35 levels in the pathogenesis of myasthenia gravis (MG) and its association with disease activity in patients with MG remain unclear. MethodsThe percentages of IL-35-producing CD4 + CD25 + T cells and CD19 + B cells among peripheral blood mononuclear cells were determined in 37 patients with anti-acetylcholine receptor (AChR) antibody-positive MG and 35 healthy controls (HCs) by performing a flow cytometry analysis. Serum IL-35 levels in participants were determined using an enzyme-linked immunosorbent assay. Further, the correlations between IL35 levels and disease activity were analysed. ResultsThe percentages of IL-35-producing CD4 + CD25 + T cells and CD19 + B cells were significantly lower in patients with anti-AChR antibody-positive MG than in HCs (p = 0.001 and p = 0.002, respectively). Furthermore, patients with thymoma and patients with generalized MG had lower percentages of IL-35-producing CD4 + CD25 + T cells and CD19 + B cells than those without thymoma and those with ocular MG (p = 0.001 and p = 0.003; p = 0.008 and p = 0.001, respectively). Interestingly, the suppression of IL-35 secretion correlated negatively with the activities of daily living scores of patients with MG (r = -0.4774, p = 0.0028) and the quantitative MG scores (r = -0.4656, p = 0.0037). The proportions of IL-35-producing T cells and B cells and serum levels of IL-35 increased after treatment. ConclusionsIL-35 may represent a potential biomarker for the clinical evaluation of MG.

Serum level of soluble urokinase plasminogen activator receptor (suPAR) as a disease severity marker of myasthenia gravis: a pilot study.

Myasthenia gravis (MG) is an autoantibody-mediated inflammatory disease of the neuromuscular junction. Biomarkers indicating disease activity in MG are warranted. Recently, the soluble urokinase plasminogen activator receptor (suPAR) has been reported to be associated with inflammation, tissue damage, disease activity and prognosis in various diseases, including autoimmune diseases. In this study, serum suPAR levels were measured in 40patients with anti-acetylcholine receptor antibody-positive MG and 30controls, and their correlations with clinical variables and severity scale scores were investigated. We identified that serum suPAR levels significantly correlated with MG activities of daily living scale (Spearman's ρ=0·45; P=0·004) and MG Foundation of America classification (Spearman's ρ=0·37; P=0·02) at serum sampling, but not with anti-acetylcholine receptor antibody titers. In conclusion, serum suPAR levels can be a candidate for a novel biomarker of disease activity in anti-acetylcholine receptor antibody-positive MG.

Increased serum acetylcholine receptor α1 subunit protein in anti-acetylcholine receptor antibody-positive myasthenia gravis

Complement-dependent disruption of motor endplate is detected in anti-acetylcholine receptor (AChR) antibody-positive myasthenia gravis (MG). We measured serum AChR α1 subunit protein levels, which may be associated with neuromuscular damage, in 55 patients with MG (47 were seropositive and 8 were negative) and in 20 controls. Serum AChR α1 subunit protein concentrations were higher in patients with anti-AChR antibody-positive MG than those in controls (P = .04), were negatively correlated with MG activities of daily living score (P = .01), and tended to be higher in ocular MG than in generalized MG. AChR α1 subunit protein elevation may be related to seropositive MG pathogenesis, especially in the ocular type.

Safety of tapering tacrolimus dose in patients with well‐controlled anti‐acetylcholine receptor antibody‐positive myasthenia gravis

Tapering immunosuppressants is desirable in patients with well-controlled myasthenia gravis (MG). However, the association between tapering of calcineurin inhibitor dosage and reduction-associated exacerbation is not known. The aim of this study was to clarify the frequency of reduction-associated exacerbation when tacrolimus is tapered in stable patients with anti-acetylcholine receptor antibody-positive MG, and to determine the factors that predict exacerbations. We retrospectively analyzed 115 patients in whom tacrolimus dosage was tapered. The reduction-associated exacerbation was defined as the appearance or worsening of one or more MG symptoms <3months after the reduction. Tacrolimus dosage was successfully tapered in 110 patients (96%) without any exacerbation. Five patients (4%) experienced an exacerbation, but symptoms were reversed in all patients when the tacrolimus dose was increased to the previous maintenance level. No patient developed an MG crisis. The age at onset was significantly earlier (30 vs. 56years, P=0.025) and the reduction in dosage was significantly larger (2.0 vs. 1.0mg/day, P=0.002) in patients with reduction-associated exacerbation than in those without exacerbation. The cut-off values determined in a receiver-operating characteristic curve analysis were 52years (sensitivity, 57%; specificity, 100%) for the age at onset and 1.5mg (sensitivity, 80%; specificity, 100%) for the dose reduction. Tapering of tacrolimus was possible in most patients with well-controlled anti-acetylcholine receptor antibody-positive MG. Early age at onset and a large reduction from maintenance dosage were associated with exacerbation. Reductions ≤1.5mg/day from the maintenance dosage should be considered for patients with late-onset disease.

3,4-Diaminopyridine for the treatment of myasthenia gravis with electrophysiological patterns of Lambert-Eaton myasthenic syndrome

3,4-Diaminopyridine (34DAP) is a presynaptic transmission enhancer. Its efficacy for Lambert-Eaton myasthenic syndrome (LEMS) and myasthenia gravis (MG) was demonstrated. However, there are cases sharing the characteristics of both disease and the effect of 34DAP in “gray zone” patients is sparse. Recently, we prescribed 34DAP to five anti-acetylcholine receptor antibody-positive MG patients with electrophysiological LEMS patterns and three LEMS patients, and carefully monitored the responses. Sero-positive MG patients exhibited more favorable responses than LEMS patients. The combination of 34DAP and pyridostigmine resulted in the best outcomes. No significant side effects were recorded during the follow-up period. In conclusion, this study results provide evidence that 34DAP could be effective in sero-positive MG patients with pre-synaptic dysfunction.

The effect of interleukin (IL)-21 and CD4+ CD25++ T cells on cytokine production of CD4+ responder T cells in patients with myasthenia gravis.

Impairment of the suppressive function of regulatory T (Treg ) cells has been reported in myasthenia gravis (MG). In this study, cytokine-related mechanisms that may lead to the defect of Treg were investigated in patients with anti-acetylcholine receptor antibody-positive MG (AChR + MG). Proliferation and cytokine production of responder T (Tresp ) cells in response to polyclonal activation were measured in a suppression assay. The effect of interleukin (IL)-21 on suppression was evaluated in vitro in co-culture. IL-21 increased the proliferation of Tresp cells in Tresp /Treg co-cultures. Tresp cells from patients with MG secreted significantly lower levels of IL-2. In patients with MG, IL-2 levels did not change with the addition of Treg to cultures, whereas it decreased significantly in controls. In Tresp /Treg co-cultures, IL-4, IL-6 and IL-10 production increased in the presence of Treg in patients. Interferon (IFN)-γ was decreased, whereas IL-17A was increased in both patient and control groups. IL-21 inhibited the secretion of IL-4 in MG and healthy controls (HC), and IL-17A in HC only. The results demonstrated that IL-21 enhances the proliferation of Tresp cells in the presence of Treg . An effect of IL-21 mainly on Tresp cells through IL-2 is implicated.

Evaluation of immunoglobulin G and immunoglobulin G subclass levels in serum of antimuscle specific kinase and anti-acetylcholine receptor antibody positive myasthenia gravis patients

Due to policy boundaries, the results and conclusions of my thesis cannot be disclosed in this paper. Instead this paper will provide background information about myasthenia gravis (MG) and the role of immunoglobulin G (IgG) antibodies in autoimmune MG. Additionally, previous literature will be discussed to elucidate the aim and relevance of my internship project. During the internship, total IgG and IgG subclass (IgG1, IgG2, IgG3, and IgG4) concentrations were evaluated in serum of anti-muscle specific kinase antibody positive MG (MuSK-MG), anti-acetylcholine receptor antibody positive MG (AChR-MG) patients and compared with the total IgG and IgG subclass levels in healthy control serum.

Remarkably increased resistin levels in anti-AChR antibody-positive myasthenia gravis.

Resistin is a pro-inflammatory cytokine involved in the pathogenesis of autoimmune diseases. To investigate serum resistin levels in patients with myasthenia gravis (MG) and determine if there are associations between resistin levels and disease severity, we measured serum resistin levels in 102 patients with anti-acetylcholine receptor antibody-positive MG (AChR-MG). We further analyzed associations between serum resistin levels and clinical variables in patients with MG. Our findings demonstrate that serum resistin levels are elevated in patients with AChR-generalized MG and AChR-MG with thymoma and are correlated with disease severity. Resistin has potential as a useful serum biomarker for inflammation in AChR-MG.

Association of anti-aquaporin-4 antibody-positive neuromyelitis optica with myasthenia gravis

We describe 2 patients who developed anti-aquaporin-4 antibody-positive neuromyelitis optica (NMO) following the development of anti-acetylcholine receptor antibody-positive myasthenia gravis (MG). A literature review of 13 similar cases in addition to the present 2 cases of NMO with MG showed predominance among Asian women and frequent development of NMO following thymectomy for MG. Moreover, in one of our patients, serial assays of anti-aquaporin-4 antibody and anti-acetylcholine receptor antibody were performed. Accumulating evidence for the coexistence of NMO and MG suggests that a common immunopathogenesis of NMO and MG may exist, and the association of NMO with MG may be more frequent than hitherto believed.