Concanavalin A inhibits pathophysiological effects of anti-ganglioside GQ1b antibodies at the mouse neuromuscular synapse

SARS-CoV-2 and Guillain-Barré Syndrome: Lessons from Viral Infections

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the COVID-19 pandemic. COVID-19 has a broad clinical spectrum from asymptomatic patients to multiorgan dysfunction and septic shock. Most of the common symptoms of COVID-19 are classified as respiratory disorders, but some reports show neurological involvements. During the COVID-19 pandemic, a case series of neurological complications, such as Guillain-Barré syndrome (GBS), were reported. GBS is a neuroimmune disorder with acute inflammatory radicular polyneuropathy in different parts of the peripheral nerve. Some studies have reported GBS as an inflammatory neuropathy related to various viral infections, such as cytomegalovirus (CMV), Epstein-Barr Virus (EBV), herpes simplex virus (HSV), human immunodeficiency virus (HIV), influenza, and Zika virus. There are some immunomodulation approaches for the management of GBS. Studies have evaluated the effects of the various therapeutic approaches, including intravenous immunoglobulin (IVIG), plasma exchange (PE), complement inhibitors, and corticosteroids to regulate overactivation of immune responses during GBS in experimental and clinical studies. In this regard, the possible association between GBS and SARS-CoV-2 infection during the outbreak of the current pandemic and also the mentioned therapeutic approaches were reviewed.

The Guillain-Barré syndrome

The latest estimation for the frequency of Guillain-Barré syndrome (GBS) is 1.1 to 1.8 per 100000 persons per year. Guillain-Barré syndrome is today divided into two major subtypes: acute inflammatory demyelinating polyneuropathy (AIDP) and the axonal subtypes, acute motor axonal neuropathy (AMAN) and acute motor and sensory axonal neuropathy (AMSAN). The axonal forms of GBS are caused by certain autoimmune mechanisms, due to a molecular mimicry between antecedent bacterial infection (particularly Campylobacter jejuni) and human peripheral nerve gangliosides. Improvements in patient management in intensive care units has permitted a dramatic drop in mortality rates. Immunotherapy, including plasma exchange (PE) or intravenous immunoglobulin (IVIg), seems to shorten the time to recovery, but their effect remains limited. Further clinical investigations are needed to assess the effect of PE or IVIg on the GBS patients with mild affection, no response, or relapse.

Pathogenesis and treatment of immune-mediated neuropathies

Immune-mediated neuropathies represent a heterogeneous spectrum of peripheral nerve disorders that can be classified according to time course, predominant involvement of motor/sensory fibers, distribution of deficits and paraclinical parameters such as electrophysiology and serum antibodies. In the last few years, significant advances have been achieved in elucidating underlying pathomechanisms, which made it possible to identify potential therapeutic targets. In this review, we discuss the latest development in pathogenesis and treatment of immune-mediated neuropathies.

Antiganglioside antibodies and their pathophysiological effects on Guillain-Barré syndrome and related disorders--a review

Guillain-Barré syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy which can cause acute quadriplegia. Infection with micro-organisms, including Campylobacter jejuni (C. jejuni), Haemophilus influenzae, and Cytomegalovirus (CMV), is recognized as a main triggering event for the disease. Lipooligosaccharide (LOS) genes are responsible for the formation of human ganglioside-like LOS structures in infectious micro-organisms that can induce GBS. Molecular mimicry of LOSs on the surface of infectious agents and of ganglioside antigens on neural cells is thought to induce cross-reactive humoral and cellular immune responses. Patients with GBS develop antibodies against those gangliosides, resulting in autoimmune targeting of peripheral nerve sites, leading to neural damage. Heterogeneity of ganglioside expression in the peripheral nervous system (PNS) may underlie the differential clinical manifestation of the GBS variants. Recent studies demonstrate that some GBS sera react with ganglioside complexes consisting of two different gangliosides, such as GD1a and GD1b, or GM1 and GD1a, but not with each constituent ganglioside alone. The discovery of antiganglioside complex antibodies not only improves the detection rate of autoantibodies in GBS, but also provides a new concept in the antibody-antigen interaction through clustered carbohydrate epitopes. Although ganglioside mimicry is one of the possible etiological causes of GBS, unidentified factors may also contribute to the pathogenesis of GBS. While GBS is not considered a genetic disease, host factors, particularly human lymphocyte antigen type, appear to have a role in the pathogenesis of GBS following C. jejuni infection.

Anti-GQ1b antibody does not affect neuromuscular transmission in human limb muscle

Anti-ganglioside GQ1b antibody induces neuromuscular blocking on mouse phrenic nerve-diaphragm preparations. Several reports suggest that patients with this antibody show abnormal neuromuscular transmission in the facial or limb muscles, but limb muscle weakness is unusual in Miller Fisher syndrome that is often associated with anti-GQ1b antibody. To determine whether anti-GQ1b sera affect neuromuscular transmission in human limb muscles, axonal-stimulating single fiber electromyography was performed in the forearm muscle of seven patients with anti-GQ1b antibody. All showed normal jitter and no blocking. Anti-GQ1b antibody does not affect neuromuscular transmission in human limb muscles. The different findings in mouse and human may be explained by the extent of expression of GQ1b on the motor nerve terminals in the muscle examined.