Mouse Model Of Myasthenia Gravis Research Articles

A Bead-Based Nonradioactive Immunoassay for Autoantibody Testing in a Mouse Model of Myasthenia Gravis.

Serological testing for anti-acetylcholine receptor (AChR) autoantibodies is not only crucial for the diagnosing, disease monitoring, and treatment management of patients with myasthenia gravis (MG) but also for preclinical studies utilizing MG disease models. However, there are no specific guidelines on which methods to use in clinical diagnostic or research laboratories to detect or quantify any MG-specific autoantibodies. Conventional autoantibody assays, particularly those for anti-AChR antibodies, are varied and mostly laboratory-specific. Here, we report our new nonradioactive immunoprecipitation-immunoblotting method for assessing autoantibodies (anti-AChR antibodies) in a mouse model of MG. This simple, efficient, reproducible, and cost-effective assay appears superior to the enzyme-linked immunosorbent assay but comparable to the radioimmunoprecipitation or cell-based assay in specificity and sensitivity. Thus, the newly developed assay can serve as a valuable alternative to classical assays and is suitable for routine testing of AChR-specific autoantibodies in preclinical studies. The further optimization of our assay may facilitate its application in the diagnosis and therapeutic management of patients with MG.

B Cell Targeting mAb–siRNA Conjugates Reduced Autoantibody in Experimental Myasthenia

Abstract Conjugates of monoclonal antibodies (mAbs) and siRNA have been used for target cell-specific gene repression. B cells are integrally involved in the anti-Acetylcholine receptor autoantibody-mediated pathogenic development of autoimmune myasthenia gravis (MG). Here we show that simultaneous targeting of the critical receptors expressed on pathogenic B-cell subsets with the optimized dose of mAb-siRNA conjugates markedly depleted target B cells and substantially reduced pathogenic autoantibody in a mouse model of MG. The results show the potential of mAb-conjugates in the treatment of myasthenia gravis. Supported by grants from AFM-Telethon, France

B cell-specific mAb–siRNA conjugates improve experimental myasthenia

Myasthenia gravis (MG) is a debilitating autoimmune disease characterized by muscle fatigue and weakness caused by autoantibody- and complement-mediated damage to the neuromuscular junction. This study sought to compare the efficacy of unique sets of monoclonal antibody–siRNA conjugates, individually (mono) or in combination (duo), against the crucial receptors predominantly or solely expressed on two subsets of B cells—plasma B cells and their precursor (transitional mature B) cells in a mouse model of MG. At the optimized doses, the conjugates, likely due to the combined activities of mAb and siRNA, substantially decreased the expression levels of CD268 (B cell-activating factor receptor) in mature B cells and CD269 (B-cell maturation antigen) in plasma cells concomitantly with reducing the levels of acetylcholine receptor (AChR)-specific autoantibodies. PEGylation, but not pretreatment with an antibody against type 1 interferon receptor, further improved duoconjugate-induced reduction in the autoantibody levels. Our results show that the duoconjugate treatment significantly improved the clinical symptoms of MG, consistent with the preservation of bungarotoxin-bound functional AChRs. In the future, developing similar target-specific combination molecules can potentially turn into a new and effective therapeutic approach for MG.

Histone Deacetylase Isoforms Differentially Modulate Inflammatory and Autoantibody Responses in a Mouse Model of Myasthenia Gravis.

Myasthenia gravis (MG) is an autoimmune disease characterized by chronic muscle fatigue and weakness caused by autoantibodies and complement-mediated damage at neuromuscular junctions. Histone deacetylases (HDACs) are crucial epigenetic regulators of proinflammatory gene expression; however, it is unclear whether HDACs modulate chronic inflammation or autoantibody production associated with MG pathogenesis. We examined expression profiles and serum levels of key inflammatory cytokines (IL-6 and IL-21) and acetylcholine receptor (AChR)-specific autoantibodies following pharmacological inhibition of key HDAC isoforms in a mouse model of MG. We found that HDAC inhibition significantly reduced the production of IL-6, but not IL-21, in AChR-stimulated PBMCs and splenocytes (n = 5 per group). Trichostatin (pan-HDAC inhibitor) treatment of MG-PBMCs (n = 2) also exhibited reduced production of induced IL-6. Although HDAC1 inhibition lowered IL-6 levels the most, HDAC2 inhibition depleted intracellular IL-6 and markedly reduced serum anti-AChR IgG2b in EAMG mice. The transcriptomic profiling and pathway mapping also revealed that autoimmunity-linked, major cell signaling pathways were differentially altered by HDAC1/2 inhibition. HDAC inhibition-mediated reduction in IL-6 and autoantibody levels also correlated with milder disease and preservation of muscle AChR in the treated mice. Overall, our findings revealed isoform-specific functional variance of HDACs in reducing inflammation and identified HDAC-regulated many genes underlying specific inflammatory and autoantibody pathways in EAMG. Thus, the study provides a rationale for further research to evaluate the HDACs or their gene targets as a potential adjunct treatment for MG.

Perturbed Microbial Ecology in Myasthenia Gravis: Evidence from the Gut Microbiome and Fecal Metabolome.

Myasthenia gravis (MG) is a devastating acquired autoimmune disease. Emerging evidence indicates that the gut microbiome plays a key role in maintaining immune system homeostasis. This work reports that MG is characterized by decreased α‐phylogenetic diversity, and significantly disturbed gut microbiome and fecal metabolome. The altered gut microbial composition is associated with fecal metabolome changes, with 38.75% of altered bacterial operational taxonomic units showing significant correlations with a range of metabolite biomarkers. Some microbes are particularly linked with MG severity. Moreover, a combination of microbial makers and their correlated metabolites enable discriminating MG from healthy controls (HCs) with 100% accuracy. To investigate whether disturbed gut mcirobiome might contribute to the onset of MG, germ‐free (GF) mice are initially colonized with MG microbiota (MMb) or healthy microbiota (HMb), and then immunized in a classic mouse model of MG. The MMb mice demonstrate substantially impaired locomotion ability compared with the HMb mice. This effect could be reversed by cocolonizing GF mice with both MMb and HMb. The MMb mice also exhibit similar disturbances of fecal metabolic pathways as found in MG. Together these data demonstrate disturbances in microbiome composition and activity that are likely to be relevant to the pathogenesis of MG.

Dose dependent effect of BAFF receptor specific mAb-siRNA conjugate in experimental myasthenia

Abstract We investigated potential therapeutic effect of a conjugate of BAFF receptor specific- monoclonal antibody and short interference RNA in a mouse model of myasthenia gravis (EAMG). We found that at high dose, conjugate treatment caused significant accumulation of Fas expressing CD19+/ B220+ cells and increased type 1 interferon in lymph nodes. Low dose did not induce FAS expression but caused marked BAFF receptor deficiency in lymph nodes that was further associated with improved MG symptoms. Conjugate treatment, however, did not reduce the levels of autoantibody. Our findings, thus, reveal a previously undocumented, dose dependent, immunomodulatory distant effect resulting from BAFF receptor specific mAb-siRNA conjugate treatment in an in vivo model of autoimmune disease.

High-dose BAFF receptor specific mAb-siRNA conjugate generates Fas-expressing B cells in lymph nodes and high-affinity serum autoantibody in a myasthenia mouse model

We investigated potential therapeutic effects of a conjugate of BAFF receptor specific-monoclonal antibody and short interference RNA in a mouse model of myasthenia gravis (EAMG). Whereas high-dose siRNA conjugate resulted in significant accumulation of Fas expressing CD19+/B220+ cells and concurrent expression of type 1 interferon in lymph nodes, low-dose conjugate did not induce FAS expression but caused marked BAFF receptor deficiency in lymph nodes that was further associated with improved MG symptoms. Unexpectedly, despite inhibiting BAFF receptor significantly in PBMCs and secondary lymphoid organs, conjugate treatment did not reduce the levels of autoantibody. Rather, at high dose, it caused robust increase in high affinity anti-AChR antibody and increased levels of serum IL10 and IL-4 cytokines. Our findings reveal a previously undocumented, dose dependent, immunomodulatory distant effect resulting from BAFF receptor specific mAb-siRNA conjugate treatment in an in vivo model of autoimmune disease.

Guidelines for standard preclinical experiments in the mouse model of myasthenia gravis induced by acetylcholine receptor immunization

Myasthenia gravis (MG) is an autoimmune disorder characterized by generalized muscle weakness due to neuromuscular junction (NMJ) dysfunction brought by acetylcholine receptor (AChR) antibodies in most cases. Although steroids and other immunosuppressants are effectively used for treatment of MG, these medications often cause severe side effects and a complete remission cannot be obtained in many cases. For pre-clinical evaluation of more effective and less toxic treatment methods for MG, the experimental autoimmune myasthenia gravis (EAMG) induced by Torpedo AChR immunization has become one of the standard animal models. Although numerous compounds have been recently proposed for MG mostly by using the active immunization EAMG model, only a few have been proven to be effective in MG patients. The variability in the experimental design, immunization methods and outcome measurements of pre-clinical EAMG studies make it difficult to interpret the published reports and assess the potential for application to MG patients. In an effort to standardize the active immunization EAMG model, we propose standard procedures for animal care conditions, sampling and randomization of mice, experimental design and outcome measures. Utilization of these standard procedures might improve the power of pre-clinical EAMG experiments and increase the chances for identifying promising novel treatment methods that can be effectively translated into clinical trials for MG.

3,4-Diaminopyridine improves neuromuscular transmission in a MuSK antibody-induced mouse model of myasthenia gravis

This study investigated the effect of 3,4-diaminopyridine (3,4-DAP), a potent potentiator of transmitter release, on neuromuscular transmission in vivo in a mouse model of myasthenia gravis (MG) caused by antibodies against muscle-specific kinase (MuSK; MuSK-MG) and ex vivo in diaphragm muscle from these mice. 3,4-DAP significantly improved neuromuscular transmission, predominantly by increasing acetylcholine (ACh) release, supporting presynaptic potentiation as an effective treatment strategy for MuSK-MG patients who have defective transmitter release. In MuSK-MG, we suggest that only low-dose acetylcholinesterase (AChE) inhibitors be used to avoid side effects, and we propose that 3,4-DAP may be effective as a symptomatic therapy.

The membrane attack pathway of complement drives pathology in passively induced experimental autoimmune myasthenia gravis in mice.

The human neuromuscular disease myasthenia gravis (MG) is characterized by the generation of autoantibodies reactive with nicotinic acetylcholine receptors (AChR) that cause loss of AChR from the neuromuscular end-plate with resultant failure of neuromuscular transmission. A role for complement (C) in AChR loss has been suggested based upon morphological identification of C at the end-plate in MG and from the effects of C inhibition in murine models. Here we provide further evidence implicating C, and specifically the membrane attack complex (MAC), in a mouse model of MG. Mice deficient in the C regulators Daf1 and/or Cd59a were tested in the model. Wild-type mice were resistant to disease while mice deficient in Daf1 had mild disease symptoms with evidence of C activation and AChR loss at end-plates. Cd59a-deficient mice had very mild disease with some muscle inflammation and essentially undamaged end-plates. In contrast, mice deficient in both C regulators developed a severe paralytic disease with marked muscle inflammation and loss of end-plates. Inhibition of MAC assembly abrogated clinical disease in these double-deficient mice, demonstrating conclusively that MAC formation was driving pathology in the model. These findings provoke us to suggest that current anti-C therapeutics targeting MAC assembly will be beneficial in MG patients resistant to conventional therapies.

Recall immune memory: a new tool for generating late onset autoimmune myasthenia gravis

Most patients with autoimmune myasthenia gravis (MG) produce autoantibodies against their muscle acetylcholine receptors (AChR), causing debilitating muscle weakness. Approximately 60% of MG patients first exhibit myasthenic symptoms after the age of 40. Yet, in the C57BL/6 mouse model of MG, older mice are resistant to induction of myasthenia gravis. To understand the immunological basis for this resistance, the effects of age on the B-cell responses to AChR from Torpedo californica, the inducing antigen, were addressed. As expected, the primary B-cell response was lower in 20-month-old mice than in 2-month-old mice; the isotype profile was not altered by age. When mice were re-immunized, the anti-T-AChR titers increased in both young and old animals, suggesting that a memory response was elicited. Importantly, memory B-cells activated in young animals were largely resistant to the age-associated loss of immune function and the recall memory response was vigorous. Furthermore, the antibodies produced in re-stimulated older mice were functional, as evidenced by the appearance of MG symptoms in some of these animals. Thus, by eliciting a recall memory response, the first examples of late onset MG in mice have been generated. By analogy, late onset MG in humans may be due to re-activation of B-cell responses initiated at a younger age.

Prevention of autoimmune attack by targeting specific T-cell receptors in a severe combined immunodeficiency mouse model of myasthenia gravis.

Myasthenia gravis (MG) is an autoimmune disease targeting the skeletal muscle acetylcholine receptor. We have previously demonstrated a selection bias of CD4+ T cells expressing the Vbeta5.1 T-cell receptor gene in the thymus of HLA-DR3 patients with MG. To evaluate the pathogenicity of these cells, severe combined immunodeficiency mice engrafted with MG thymic lymphocytes were treated with anti-Vbeta5.1 antibody. Signs of pathogenicity (eg, acetylcholine receptor loss and complement deposits at the muscle end plates of chimeric mice) were prevented in anti-Vbeta5.1-treated severe combined immunodeficiency chimeras. Pathogenicity was mediated by autoantibodies against acetylcholine receptor. Thymic cells depleted of Vbeta5.1-positive cells in vitro before cell transfer were nonpathogenic, indicating that Vbeta5.1-positive cells are involved in the production of pathogenic autoantibodies. Acetylcholine receptor loss was prevented by Vbeta5.1 targeting in HLA-DR3 patients only, demonstrating specificity for HLA-DR3-peptide complexes. The action of the anti-Vbeta5.1 antibody involved both the in vivo depletion of Vbeta5.1-expressing cells and an increase in the interferon-gamma/interleukin-4 ratio, pointing to an immune deviation-based mechanism. This demonstration that a selective and specific T-helper cell population is involved in controlling pathogenic autoantibodies in MG holds promise for the treatment of MG.

Comparison of T cell sites recognized by thymic and blood lymphocytes in Myasthenia Gravis patients

We investigated potential therapeutic effects of a conjugate of BAFF receptor specific-monoclonal antibody and short interference RNA in a mouse model of myasthenia gravis (EAMG). Whereas high-dose siRNA conjugate resulted in significant accumulation of Fas expressing CD19+/B220+ cells and concurrent expression of type 1 interferon in lymph nodes, low-dose conjugate did not induce FAS expression but caused marked BAFF receptor deficiency in lymph nodes that was further associated with improved MG symptoms. Unexpectedly, despite inhibiting BAFF receptor significantly in PBMCs and secondary lymphoid organs, conjugate treatment did not reduce the levels of autoantibody. Rather, at high dose, it caused robust increase in high affinity anti-AChR antibody and increased levels of serum IL10 and IL-4 cytokines. Our findings reveal a previously undocumented, dose dependent, immunomodulatory distant effect resulting from BAFF receptor specific mAb-siRNA conjugate treatment in an in vivo model of autoimmune disease.

Nerve stimulation test in murine experimental autoimmune myasthenia gravis.

Use of the mouse model of myasthenia gravis (murine EAMG), ideally suited for immunological study, has been hampered by the relatively mild character of the disease and by the extended time and effort required for inducing severe disease. Electromyographic measurement of the compound action potential after repetitive stimuli, the nerve stimulation test, was evaluated for its ability to diagnose neuromuscular transmission defects in mice immunized with Torpedo acetylcholine receptor. With the combination of provocative maneuvers and raising of the body temperature, EAMG could be diagnosed in nearly all immunized animals a few weeks after immunization, whereas clinical evaluation of muscle weakness was positive in less than half of immunized mice months after the first immunization. Thus, EMG provides a means of objective evaluation of the disease and attempts at its experimental modification.

Experimental myasthenia gravis. A murine system.

Mice from eight inbred strains were immunized with acetylcholine receptor (AChR) purified from Torpedo californica. All mice developed high concentrations of serum antibodies (10(-6) M) against the immunogen and approximately 80% possessed antibodies reactive with mouse nicotinic AChR. 33% of the mice immunized (n = 236) developed muscular weakness and flaccid paralysis. Behavioral, electrophysiological, and pharmacological similarities were found between the experimentally induced muscular weakness and the disease myasthenia gravis. Susceptibility to experimental myasthenia was found to be strain dependent in that the frequency of paralysis was much greater in some strains than others. The occurrence of muscular weakness and flaccid paralysis did not correlate with the concentration of antibodies reactive with T. californica or mouse AChR. Anti-receptor antibodies which increased the rate of AChR degradation on the mouse muscle cell line, BC3H-1, were found in the serum of both myasthenic and nonmyasthenic mice. 40% of the mice tested possessed antibodies reactive with antigenic determinants present on mouse receptor but not T. californica receptor. The occurrence of antibodies unique to mouse receptor did not correlate with myasthenia. Thus, myasthenia in the mouse does not occur simply as a consequence of the presence of antibodies directed against cell surface antigenic determinants of AChR. If anti-AChR antibodies are both necessary and sufficient for the induction of myasthenia, then these studies suggest that populations of a particular structure and/or specificity are required. It is anticipated that the mouse model of myasthenia gravis will permit the regulation of the anti-receptor immune response to be studied in detail.