A new era in the treatment of multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system with a multifactorial aetiology and highly variable natural history. A growing understanding of the immunopathogenesis of the condition has led to an expanding array of therapies for this previously untreatable disease. While a cure for MS remains elusive, the potential to reduce inflammatory disease activity by preventing relapses and minimising disease progression is achievable. The importance of early treatment in minimising long-term disability is increasingly recognised. Most of the newer, more effective therapies are associated with risks and practical problems that necessitate an active management strategy and continuous vigilance. While the initiation of these therapies is likely to remain the responsibility of neurologists, other specialist physicians and general practitioners will be involved in the identification and management of adverse effects

Clinical and scientific aspects of muscle-specific tyrosine kinase-related myasthenia gravis

Purpose of review: Antibodies to muscle-specific tyrosine kinase (MuSK) characterize up to 5% of myasthenia gravis patients. This review focuses on the differences to clinical antiacetylcholine receptor-myasthenia gravis, and on the physiology and animal studies that elucidate the role of MuSK and help explain the clinical disease. Recent findings: MuSK forms the core of a protein complex in the postsynaptic membrane at the neuromuscular junction. During development, MuSK tyrosine kinase signaling is vital for the formation and stabilization of the postsynaptic endplate; it is now clear that long-term homeostasis of mature neuromuscular junctions requires MuSK function. Patient MuSK-antibodies are largely of the IgG4 type and in cell culture block the assembly and activation of MuSK kinase. Active immunization and passive transfer mouse models show reduced postsynaptic acetylcholine receptors and disturbed synaptic alignment, diminished synaptic potentials and impaired muscle activation. MuSK myasthenia gravis patients display particular bulbar and respiratory muscle involvement, with a high rate of myasthenic crises. Plasma exchange and immunosuppression with corticosteroids and rituximab appear to be most effective in treating MuSK myasthenia gravis. In contrast, the cholinesterase inhibitors, such as pyridostigmine, appear less suitable for this form of myasthenia gravis. Summary: MuSK myasthenia gravis has distinct clinical and pathophysiological features.8 page(s

Neurological immunotherapy in the era of COVID-19 - looking for consensus in the literature

The coronavirus disease 2019 (COVID-19) pandemic is concerning for patients with neuroimmunological diseases who are receiving immunotherapy. Uncertainty remains about whether immunotherapies increase the risk of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or increase the risk of severe disease and death upon infection. National and international societies have developed guidelines and statements, but consensus does not exist in several areas. In this Review, we attempt to clarify where consensus exists and where uncertainty remains to inform management approaches based on the first principles of neuroimmunology. We identified key questions that have been addressed in the literature and collated the recommendations to generate a consensus calculation in a Delphi-like approach to summarize the information. We summarize the international recommendations, discuss them in light of the first available data from patients with COVID-19 receiving immunotherapy and provide an overview of management approaches in the COVID-19 era. We stress the principles of medicine in general and neuroimmunology in particular because, although the risk of viral infection has become more relevant, most of the considerations apply to the general management of neurological immunotherapy. We also give special consideration to immunosuppressive treatment and cell-depleting therapies that might increase susceptibility to SARS-CoV-2 infection but reduce the risk of severe COVID-19

Author Correction: Neurological immunotherapy in the era of COVID-19 - looking for consensus in the literature

n the originally published version of this article, the description of the study by Sormani et al. (ref. 14) in the third paragraph of the section entitled ‘B cell-depleting therapies’ was incorrect. The description should read: In 232 patients with multiple sclerosis and suspected or proven COVID-19, the severity of COVID-19 was classified as mild (no or mild pneumonia) in 222 (96%), severe (shortness of breath, respiratory rate ≥30 breaths/min, blood oxygen saturation ≤93%, PaO2:FiO2 50% within 24–48 h) in 4 (2%) and critical (respiratory failure, septic shock and multiple organ dysfunction or failure) in 6 (3%). Of the 6 patients with critical illness, 1 recovered and 5 died. Of 28 patients receiving a B cell-depleting therapy, 3 (10%) developed a severe or critical disease course

Guillain-Barré Syndrome: Modern theories of etiology

Guillain-Barr, syndrome (GBS) is a classic failure of the immune system with a life-threatening attack upon a critical self-component. The active phase of the disease is short, concordant with the latency of a primary adaptive immune response. Triggers for GBS include infection and (rarely) vaccination; cross-reactivity between infectious and neural epitopes has been well demonstrated, particularly for Campylobacter jejuni and motor axonal forms of GBS in which non-protein gangliosides are antigenic. Most people are probably exposed to a GBS trigger, but only rarely does the disease develop. We propose that GBS illustrates competing determinants of the immune system's decision about whether to mount a response, and that in unlucky affected individuals, co-presentation of cross-reactive antigens with danger signals activating pattern-recognition receptors overcomes normal self-recognition such that a primary response is initiated that attacks the nerve. Then, in most cases of GBS, the response rapidly turns off, and second attacks rarely occur. This suggests active restoration of tolerance, and specific privileged site attributes of nerve and declining danger signals as the trigger wanes may contribute to this restoration. Standard immunosuppression has not been effective in GBS. We suggest this is because immune tolerance is already being restored by the time such therapies are initiated. This in turn suggests that improvements in GBS outcomes are likely to come from better protection of the nerve cells under attack while normal resumption of tolerance is permitted to proceed rather than exploring more aggressive immunosuppressive approaches

Effects of the β2-adrenoceptor agonist, albuterol, in a mouse model of anti-MuSK myasthenia gravis

The β2-adrenergic receptor agonist, albuterol, has been reported beneficial in treating several forms of congenital myasthenia. Here, for the first time, we examined the potential benefit of albuterol in a mouse model of anti-Muscle Specific Kinase (MuSK) myasthenia gravis. Mice received 15 daily injections of IgG from anti-MuSK positive patients, which resulted in whole-body weakness. At neuromuscular junctions in the tibialis anterior and diaphragm muscles the autoantibodies caused loss of postsynaptic acetylcholine receptors, and reduced the amplitudes of the endplate potential and spontaneous miniature endplate potential in the diaphragm muscle. Treatment with albuterol (8 mg/kg/day) during the two-week anti-MuSK injection series reduced the degree of weakness and weight loss, compared to vehicle-treated mice. However, the compound muscle action potential recorded from the gastrocnemius muscle displayed a decremental response in anti-MuSK-injected mice whether treated with albuterol or vehicle. Ongoing albuterol treatment did not increase endplate potential amplitudes compared to vehicle-treated mice nor did it prevent the loss of acetylcholine receptors from motor endplates. On the other hand, albuterol treatment significantly reduced the degree of fragmentation of endplate acetylcholine receptor clusters and increased the extent to which the remaining receptor clusters were covered by synaptophysin-stained nerve terminals. The results provide the first evidence that short-term albuterol treatment can ameliorate weakness in a robust mouse model of anti-MuSK myasthenia gravis. The results also demonstrate that it is possible for albuterol treatment to reduce whole-body weakness without necessarily reversing myasthenic impairment to the structure and function of the neuromuscular junction.11 page(s

Muscle-specific kinase (MuSK) autoantibodies suppress the MuSK pathway and ACh receptor retention at the mouse neuromuscular junction

Muscle-specific kinase (MuSK) autoantibodies from myasthenia gravis patients can block the activation of MuSK in vitro and/or reduce the postsynaptic localization of MuSK. Here we use a mouse model to examine the effects of MuSK autoantibodies upon some key components of the postsynaptic MuSK pathway and upon the regulation of junctional ACh receptor (AChR) numbers. Mice became weak after 14 daily injections of anti-MuSK-positive patient IgG. The intensity and area of AChR staining at the motor endplate was markedly reduced. Pulse-labelling of AChRs revealed an accelerated loss of pre-existing AChRs from postsynaptic AChR clusters without a compensatory increase in incorporation of (newly synthesized) replacement AChRs. Large, postsynaptic AChR clusters were replaced by a constellation of tiny AChR microaggregates. Puncta of AChR staining also appeared in the cytoplasm beneath the endplate. Endplate staining for MuSK, activated Src, rapsyn and AChR were all reduced in intensity. In the tibialis anterior muscle there was also evidence that phosphorylation of the AChR β-subunit-Y390 was reduced at endplates. In contrast, endplate staining for β-dystroglycan (through which rapsyn couples AChR to the synaptic basement membrane) remained intense. The results suggest that anti-MuSK IgG suppresses the endplate density of MuSK, thereby down-regulating MuSK signalling activity and the retention of junctional AChRs locally within the postsynaptic membrane scaffold.17 page(s