Evidence of Clostridium perfringens epsilon toxin associated with multiple sclerosis

The epsilon toxin from Clostridium perfringens stimulates calcium-activated chloride channels, generating extracellular vesicles in Xenopus oocytes

The epsilon toxin (Etx) from Clostridium perfringens has been identified as a potential trigger of multiple sclerosis, functioning as a pore-forming toxin that selectively targets cells expressing the plasma membrane (PM) myelin and lymphocyte protein (MAL). Previously, we observed that Etx induces the release of intracellular ATP in sensitive cell lines. Here, we aimed to re-examine the mechanism of action of the toxin and investigate the connection between pore formation and ATP release. We examined the impact of Etx on Xenopus laevis oocytes expressing human MAL. Extracellular ATP was assessed using the luciferin-luciferase reaction. Activation of calcium-activated chloride channels (CaCCs) and a decrease in the PM surface were recorded using the two-electrode voltage-clamp technique. To evaluate intracellular Ca2+ levels and scramblase activity, fluorescent dyes were employed. Extracellular vesicles were imaged using light and electron microscopy, while toxin oligomers were identified through western blots. Etx triggered intracellular Ca2+ mobilization in the Xenopus oocytes expressing hMAL, leading to the activation of CaCCs, ATP release, and a reduction in PM capacitance. The toxin induced the activation of scramblase and, thus, translocated phospholipids from the inner to the outer leaflet of the PM, exposing phosphatidylserine outside in Xenopus oocytes and in an Etx-sensitive cell line. Moreover, Etx caused the formation of extracellular vesicles, not derived from apoptotic bodies, through PM fission. These vesicles carried toxin heptamers and doughnut-like structures in the nanometer size range. In conclusion, ATP release was not directly attributed to the formation of pores in the PM, but to scramblase activity and the formation of extracellular vesicles.

The communication mechanism of the gut-brain axis and its effect on central nervous system diseases: A systematic review

Gut microbiota is involved in intricate and active metabolic processes the host's brain function, especially its role in immune responses, secondary metabolism, and symbiotic connections with the host. Gut microbiota can promote the production of essential metabolites, neurotransmitters, and other neuroactive chemicals that affect the development and treatment of central nervous system diseases. This article introduces the relevant pathways and manners of the communication between the brain and gut, summarizes a comprehensive overview of the current research status of key gut microbiota metabolites that affect the functions of the nervous system, revealing those adverse factors that affect typical communication between the brain-gut axis, and outlining the efforts made by researchers to alleviate these neurological diseases through targeted microbial interventions. The relevant pathways and manners of communication between the brain and gut contribute to the experimental design of new treatment plans and drug development. The factors that may cause changes in gut microbiota and affect metabolites, as well as current intervention methods are summarized, which helps improve gut microbiota brain dialogue, prevent adverse triggering factors from interfering with the gut microbiota system, and minimize neuropathological changes.

Multiple Sclerosis and Clostridium perfringens Epsilon Toxin: Is There a Relationship?

Recent research has suggested a link between multiple sclerosis and the gut microbiota. This prospective pilot study aimed to investigate the composition of the gut microbiota in MS patients, the presence of Clostridium perfringens epsilon toxin in the serum of MS patients, and the influence of disease-modifying drugs (DMDs) on epsilon toxin levels and on the microbiota. Epsilon toxin levels in blood were investigated by two methods, a qualitative ELISA and a highly sensitive quantitative ELISA. Neither epsilon toxin nor antibodies against it were detected in the analyzed serum samples. 16S ribosomal RNA sequencing was applied to obtain insights into the composition of the gut microbiota of MS patients. No significant differences in the quantity, diversity, and the relative abundance of fecal microbiota were observed in the gut microbiota of MS patients receiving various DMDs, including teriflunomide, natalizumab, ocrelizumab, and fingolimod, or no therapy. The present study did not provide evidence supporting the hypothesis of a causal relationship between Clostridium perfringens epsilon toxin and multiple sclerosis.

The Molecular Architecture and Mode of Action of Clostridium perfringens ε-Toxin

Clostridium perfringens ε-toxin has long been associated with a severe enterotoxaemia of livestock animals, and more recently, was proposed to play a role in the etiology of multiple sclerosis in humans. The remarkable potency of the toxin has intrigued researchers for many decades, who suggested that this indicated an enzymatic mode of action. Recently, there have been major breakthroughs by finding that it is a pore-forming toxin which shows exquisite specificity for cells bearing the myelin and lymphocyte protein (MAL) receptor. This review details the molecular structures of the toxin, the evidence which identifies MAL as the receptor and the possible roles of other cell membrane components in toxin binding. The information on structure and mode of action has allowed the functions of individual amino acids to be investigated and has led to the creation of mutants with reduced toxicity that could serve as vaccines. In spite of this progress, there are still a number of key questions around the mode of action of the toxin which need to be further investigated.

Gastrointestinal Dysfunction in Multiple Sclerosis and Related Conditions

Nervous system disorders may be accompanied by gastrointestinal (GI) dysfunction. Brain lesions may be responsible for GI problems such as decreased peristalsis (e.g., lesions in the basal ganglia, pontine defecation center/Barrington's nucleus), decreased abdominal strain (e.g., lesions in the parabrachial nucleus), hiccupping and vomiting (e.g., lesions in the area postrema), and appetite loss (e.g., lesions in the hypothalamus). Decreased peristalsis also may be caused by lesions of the spinal long tracts or the intermediolateral nucleus projecting to the myenteric plexus. This review addresses GI dysfunction caused by multiple sclerosis, neuromyelitis optica spectrum disorder, and myelin oligodendrocyte glycoprotein-associated disorder. Neuro-associated GI dysfunction may develop concurrently with brain or spinal cord dysfunction or may predate it. Collaboration between gastroenterologists and neurologists is highly desirable when caring for patients with GI dysfunction related to nervous system disorders, particularly since patients with these symptoms may visit a gastroenterologist prior to the establishment of a neurological diagnosis.

Is Clostridium perfringens epsilon toxin associated with multiple sclerosis?

Clostridium perfringens epsilon toxin is associated with enterotoxaemia in livestock. More recently, it is proposed to play a role in multiple sclerosis (MS) in humans. Compared to matched controls, strains of C. perfringens which produce epsilon toxin are significantly more likely to be isolated from the gut of MS patients and at significantly higher levels; similarly, sera from MS patients are significantly more likely to contain antibodies to epsilon toxin. Epsilon toxin recognises the myelin and lymphocyte (MAL) protein receptor, damaging the blood-brain barrier and brain cells expressing MAL. In the experimental autoimmune encephalomyelitis model of MS, the toxin enables infiltration of immune cells into the central nervous system, inducing an MS-like disease. These studies provide evidence that epsilon toxin plays a role in MS, but do not yet fulfil Koch's postulates in proving a causal role.

Clostridium perfringens epsilon-toxin requires acid sphingomyelinase for cellular entry

OBJECTIVES

Clostridium perfringens epsilon-toxin is considered to be a crucial agent in enterotoxemia in domestic animals. Epsilon-toxin enters host cells via endocytosis and results in the formation of late endosome/lysosome-derived vacuoles. In the present study, we found that acid sphingomyelinase promotes the internalization of epsilon-toxin in MDCK cells.

METHODS

We measured the extracellular release of acid sphingomyelinase (ASMase) by epsilon-toxin. We examined the role of ASMase in epsilon-toxin-induced cytotoxicity using selective inhibitors and knockdown of ASMase. Production of ceramide after toxin treatment was determined by immunofluorescence technique.

RESULTS

Blocking agents of ASMase and exocytosis of lysosomes inhibited this epsilon-toxin-induced vacuole formation. Lysosomal ASMase was liberated to extracellular space during treatment of the cells with epsilon-toxin in the presence of Ca2+. RNAi-mediated attenuation of ASMase blocked epsilon-toxin-induced vacuolation. Moreover, incubation of MDCK cells with epsilon-toxin led to production of ceramide. The ceramide colocalized with lipid raft-binding cholera toxin subunit B (CTB) in the cell membrane, indicating that conversion of lipid raft associated sphingomyelin to ceramide by ASMase facilitates lesion of MDCK cells and internalization of epsilon-toxin.

CONCLUSIONS

Based on the present results, ASMase is required for efficient internalization of epsilon-toxin.

Clostridium perfringens Epsilon Toxin Binds to and Kills Primary Human Lymphocytes

Clostridium perfringens epsilon toxin (ETX) is the third most lethal bacterial toxin and has been suggested to be an environmental trigger of multiple sclerosis, an immune-mediated disease of the human central nervous system. However, ETX cytotoxicity on primary human cells has not been investigated. In this article, we demonstrate that ETX preferentially binds to and kills human lymphocytes expressing increased levels of the myelin and lymphocyte protein MAL. Using flow cytometry, ETX binding was determined to be time and dose dependent and was highest for CD4+ cells, followed by CD8+ and then CD19+ cells. Similar results were seen with ETX-induced cytotoxicity. To determine if ETX preference for CD4+ cells was related to MAL expression, MAL gene expression was determined by RT-qPCR. CD4+ cells had the highest amount of Mal gene expression followed by CD8+ and CD19+ cells. These data indicate that primary human cells are susceptible to ETX and support the hypothesis that MAL is a main receptor for ETX. Interestingly, ETX bindings to human lymphocytes suggest that ETX may influence immune response in multiple sclerosis.

Development and evaluation of cell membrane-based biomimetic nanoparticles loaded by Clostridium perfringens epsilon toxin: a novel vaccine delivery platform for Clostridial-associated diseases

As Clostridium perfringens (C. perfringens) epsilon toxin (ETX) ranks as the third most potent clostridial toxin after botulinum and tetanus toxins, vaccination is necessary for creatures that can be affected by it to be safe from the effects of this toxin. Nowadays, nanostructures are good choices for carriers for biological environments. We aimed to synthesize biomimetic biodegradable nanodevices to enhance the efficiency of the ETX vaccine. For this purpose, poly(lactic-co-glycolic acid) (PLGA) copolymer loaded with purified epsilon protoxin (proETX) to create nanoparticles called nanotoxins (NTs) and then coated by RBC membrane-derived vesicles (RVs) to form epsilon nanotoxoids (RV-NTs). The resulting RV-NTs shaped smooth spherical surfaces with double-layer core/shell structure with an average particle size of 105.9 ± 35.1 nm and encapsulation efficiency of 97.5% ± 0.13%. Compared with NTs, the RV-NTs were more stable for 15 consecutive days. In addition, although both structures showed a long-term cumulative release, the release rates from RV-NTs were slower than NTs during 144 hours. According to the results of cell viability, ETX loading in PLGA and entrapment in the RBC membrane decreased the toxicity of the toxin. The presence of PLGA enhances the uptake of proETX, and the synthesized structures showed no significant lesion after injection. These results demonstrate that NTs and RV-NTs could serve as an effective vaccine platform to deliver ETX for future in vivo assays.

Clostridium perfringens-Opportunistic Foodborne Pathogen, Its Diversity and Epidemiological Significance

The C. perfringens species is associated with various environments, such as soils, sewage, and food. However, it is also a component of the gastrointestinal (GI) microflora (i.e., microbiota) of sick and healthy humans and animals. C. perfringens is linked with different systemic and enteric diseases in livestock and humans, such as gas gangrene, food poisoning, non-foodborne diarrhoea, and enterocolitis. The strains of this opportunistic pathogen are known to secrete over 20 identified toxins that are considered its principal virulence factors. C. perfringens belongs to the anaerobic bacteria community but can also survive in the presence of oxygen. The short time between generations, the multi-production capability of toxins and heat-resistant spores, the location of many virulence genes on mobile genetic elements, and the inhabitance of this opportunistic pathogen in different ecological niches make C. perfringens a very important microorganism for public health protection. The epidemiological evidence for the association of these strains with C. perfringens-meditated food poisoning and some cases of non-foodborne diseases is very clear and well-documented. However, the genetic diversity and physiology of C. perfringens should still be studied in order to confirm the importance of suspected novel virulence traits. A very significant problem is the growing antibiotic resistance of C. perfringens strains. The aim of this review is to show the current basic information about the toxins, epidemiology, and genetic and molecular diversity of this opportunistic pathogen.

Epsilon toxin-producing Clostridium perfringens colonize the multiple sclerosis gut microbiome overcoming CNS immune privilege

Multiple sclerosis (MS) is a complex disease of the CNS thought to require an environmental trigger. Gut dysbiosis is common in MS, but specific causative species are unknown. To address this knowledge gap, we used sensitive and quantitative PCR detection to show that people with MS were more likely to harbor and show a greater abundance of epsilon toxin-producing (ETX-producing) strains of C. perfringens within their gut microbiomes compared with individuals who are healthy controls (HCs). Isolates derived from patients with MS produced functional ETX and had a genetic architecture typical of highly conjugative plasmids. In the active immunization model of experimental autoimmune encephalomyelitis (EAE), where pertussis toxin (PTX) is used to overcome CNS immune privilege, ETX can substitute for PTX. In contrast to PTX-induced EAE, where inflammatory demyelination is largely restricted to the spinal cord, ETX-induced EAE caused demyelination in the corpus callosum, thalamus, cerebellum, brainstem, and spinal cord, more akin to the neuroanatomical lesion distribution seen in MS. CNS endothelial cell transcriptional profiles revealed ETX-induced genes that are known to play a role in overcoming CNS immune privilege. Together, these findings suggest that ETX-producing C. perfringens strains are biologically plausible pathogens in MS that trigger inflammatory demyelination in the context of circulating myelin autoreactive lymphocytes.

Gut Microbiota Changes during Dimethyl Fumarate Treatment in Patients with Multiple Sclerosis

The gut microbiota is involved in the development of the immune system and can modulate the risk for immune-mediated disorders such as multiple sclerosis (MS). Dysbiosis has been demonstrated in MS patients and its restoration by disease-modifying treatments (DMTs) is hypothesized. We aimed to study the changes in gut microbiota composition during the first 6 months of treatment with dimethyl fumarate (DMF), an oral DMT, and to identify the microorganisms associated with DMF side effects. We collected and analyzed the gut microbiota of 19 MS patients at baseline and after 1, 3, and 6 months of DMF treatment. We then cross-sectionally compared gut microbiota composition according to the presence of gastrointestinal (GI) symptoms and flushing. Overall, the gut microbiota biodiversity showed no changes over the 6-month follow-up. At the genus level, DMF was associated with decreased Clostridium abundance after 6 months. In subjects reporting side effects, a higher abundance of Streptococcus, Haemophilus, Clostridium, Lachnospira, Blautia, Subdoligranulum, and Tenericutes and lower of Bacteroidetes, Barnesiella, Odoribacter, Akkermansia, and some Proteobacteria families were detected. Our results suggest that gut microbiota may be involved in therapeutic action and side effects of DMF, representing a potential target for improving disease course and DMT tolerability.

Interaction of Clostridium perfringens Epsilon Toxin with the Plasma Membrane: The Role of Amino Acids Y42, Y43 and H162

Clostridium perfringens epsilon toxin (Etx) is a pore forming toxin that causes enterotoxaemia in ruminants and may be a cause of multiple sclerosis in humans. To date, most in vitro studies of Etx have used the Madin-Darby canine kidney (MDCK) cell line. However, studies using Chinese hamster ovary (CHO) cells engineered to express the putative Etx receptor, myelin and lymphocyte protein (MAL), suggest that amino acids important for Etx activity differ between species. In this study, we investigated the role of amino acids Y42, Y43 and H162, previously identified as important in Etx activity towards MDCK cells, in Etx activity towards CHO-human MAL (CHO-hMAL) cells, human red blood cells (hRBCs) and synthetic bilayers using site-directed mutants of Etx. We show that in CHO-hMAL cells Y42 is critical for Etx binding and not Y43 as in MDCK cells, indicating that surface exposed tyrosine residues in the receptor binding domain of Etx impact efficiency of cell binding to MAL-expressing cells in a species-specific manner. We also show that Etx mutant H162A was unable to lyse CHO-hMAL cells, lysed hRBCs, whilst it was able to form pores in synthetic bilayers, providing evidence of the complexity of Etx pore formation in different lipid environments.

Pathology and Pathogenesis of Brain Lesions Produced by Clostridium perfringens Type D Epsilon Toxin

Clostridium perfringens type D epsilon toxin (ETX) produces severe, and frequently fatal, neurologic disease in ruminant livestock. The disorder is of worldwide distribution and, although vaccination has reduced its prevalence, ETX still causes substantial economic loss in livestock enterprises. The toxin is produced in the intestine as a relatively inactive prototoxin, which is subsequently fully enzymatically activated to ETX. When changed conditions in the intestinal milieu, particularly starch overload, favor rapid proliferation of this clostridial bacterium, large amounts of ETX can be elaborated. When sufficient toxin is absorbed from the intestine into the systemic circulation and reaches the brain, two neurologic syndromes can develop from this enterotoxemia. If the brain is exposed to large amounts of ETX, the lesions are fundamentally vasculocentric. The neurotoxin binds to microvascular endothelial receptors and other brain cells, the resulting damage causing increased vascular permeability and extravasation of plasma protein and abundant fluid into the brain parenchyma. While plasma protein, particularly albumin, pools largely perivascularly, the vasogenic edema becomes widely distributed in the brain, leading to a marked rise in intracranial pressure, coma, sometimes cerebellar herniation, and, eventually, often death. When smaller quantities of ETX are absorbed into the bloodstream, or livestock are partially immune, a more protracted clinical course ensues. The resulting brain injury is characterized by bilaterally symmetrical necrotic foci in certain selectively vulnerable neuroanatomic sites, termed focal symmetrical encephalomalacia. ETX has also been internationally listed as a potential bioterrorism agent. Although there are no confirmed human cases of ETX intoxication, the relatively wide species susceptibility to this toxin and its high toxicity mean it is likely that human populations would also be vulnerable to its neurotoxic actions. While the pathogenesis of ETX toxicity in the brain is incompletely understood, the putative mechanisms involved in neural lesion development are discussed.

Intestinal inflammation and the microbiota: Beyond diversity

The recent manuscript entitled “Relationship between clinical features and intestinal microbiota in Chinese patients with ulcerative colitis” reported a difference in the intestinal microbiota of patients with ulcerative colitis according to the severity of the colitis. The influence of the intestinal microbiota on the development and progress of gastrointestinal disorders is well established. Besides the diversity in the microbiome, the presence of virulence factors and toxins by commensal bacteria may affect an extensive variety of cellular processes, contributing to the induction of a proinflammatory environment.

Involvement of the Intestinal Microbiota in the Appearance of Multiple Sclerosis: Aloe vera and Citrus bergamia as Potential Candidates for Intestinal Health

Multiple sclerosis (MS) is a neurological and inflammatory autoimmune disease of the Central Nervous System in which selective activation of T and B lymphocytes prompts a reaction against myelin, inducing demyelination and axonal loss. Although MS is recognized to be an autoimmune pathology, the specific causes are many; thus, to date, it has been considered a disorder resulting from environmental factors in genetically susceptible individuals. Among the environmental factors hypothetically involved in MS, nutrition seems to be well related, although the role of nutritional factors is still unclear. The gut of mammals is home to a bacterial community of about 2000 species known as the “microbiota”, whose composition changes throughout the life of each individual. There are five bacterial phylas that make up the microbiota in healthy adults: Firmicutes (79.4%), Bacteroidetes (16.9%), Actinobacteria (2.5%), Proteobacteria (1%) and Verrucomicrobia (0.1%). The diversity and abundance of microbial populations justifies a condition known as eubiosis. On the contrary, the state of dysbiosis refers to altered diversity and abundance of the microbiota. Many studies carried out in the last few years have demonstrated that there is a relationship between the intestinal microflora and the progression of multiple sclerosis. This correlation was also demonstrated by the discovery that patients with MS, treated with specific prebiotics and probiotics, have greatly increased bacterial diversity in the intestinal microbiota, which might be otherwise reduced or absent. In particular, natural extracts of Aloe vera and bergamot fruits, rich in polyphenols and with a high percentage of polysaccharides (mostly found in indigestible and fermentable fibers), appear to be potential candidates to re-equilibrate the gut microbiota in MS patients. The present review article aims to assess the pathophysiological mechanisms that reveal the role of the microbiota in the development of MS. In addition, the potential for supplementing patients undergoing early stages of MS with Aloe vera as well as bergamot fibers, on top of conventional drug treatments, is discussed.

Morais L. Convergent pathways of the gut microbiota-brain axis and neurodegenerative disorders

Recent research has been uncovering the role of the gut microbiota for brain health and disease. These studies highlight the role of gut microbiota on regulating brain function and behavior through immune, metabolic, and neuronal pathways. In this review we provide an overview of the gut microbiota axis pathways to lay the groundwork for upcoming sessions on the links between the gut microbiota and neurogenerative disorders. We also discuss how the gut microbiota may act as an intermediate factor between the host and the environment to mediate disease onset and neuropathology. Based on the current literature, we further examine the potential for different microbiota-based therapeutic strategies to prevent, to modify, or to halt the progress of neurodegeneration.

Plant Polysaccharides Modulate Immune Function via the Gut Microbiome and May Have Potential in COVID-19 Therapy

Plant polysaccharides can increase the number and variety of beneficial bacteria in the gut and produce a variety of active substances, including short-chain fatty acids (SCFAs). Gut microbes and their specific metabolites have the effects of promoting anti-inflammatory activity, enhancing the intestinal barrier, and activating and regulating immune cells, which are beneficial for improving immunity. A strong immune system reduces inflammation caused by external viruses and other pathogens. Coronavirus disease 2019 (COVID-19) is still spreading globally, and patients with COVID-19 often have intestinal disease and weakened immune systems. This article mainly evaluates how polysaccharides in plants can improve the immune system barrier by improving the intestinal microecological balance, which may have potential in the prevention and treatment of COVID-19.

Bacterial neurotoxic metabolites in multiple sclerosis cerebrospinal fluid and plasma

The identification of intestinal dysbiosis in patients with neurological and psychiatric disorders has highlighted the importance of gut-brain communication, and yet the question regarding the identity of the components responsible for this cross-talk remains open. We previously reported that relapsing remitting multiple sclerosis patients treated with dimethyl fumarate have a prominent depletion of the gut microbiota, thereby suggesting that studying the composition of plasma and CSF samples from these patients may help to identify microbially derived metabolites. We used a functional xenogeneic assay consisting of cultured rat neurons exposed to CSF samples collected from multiple sclerosis patients before and after dimethyl fumarate treatment to assess neurotoxicity and then conducted a metabolomic analysis of plasma and CSF samples to identify metabolites with differential abundance. A weighted correlation network analysis allowed us to identify groups of metabolites, present in plasma and CSF samples, whose abundance correlated with the neurotoxic potential of the CSF. This analysis identified the presence of phenol and indole group metabolites of bacterial origin (e.g. p-cresol sulphate, indoxyl sulphate and N-phenylacetylglutamine) as potentially neurotoxic and decreased by treatment. Chronic exposure of cultured neurons to these metabolites impaired their firing rate and induced axonal damage, independent from mitochondrial dysfunction and oxidative stress, thereby identifying a novel pathway of neurotoxicity. Clinical, radiological and cognitive test metrics were also collected in treated patients at follow-up visits. Improved MRI metrics, disability and cognition were only detected in dimethyl fumarate-treated relapsing remitting multiple sclerosis patients. The levels of the identified metabolites of bacterial origin (p-cresol sulphate, indoxyl sulphate and N-phenylacetylglutamine) were inversely correlated to MRI measurements of cortical volume and directly correlated to the levels of neurofilament light chain, an established biomarker of neurodegeneration. Our data suggest that phenol and indole derivatives from the catabolism of tryptophan and phenylalanine are microbially derived metabolites, which may mediate gut-brain communication and induce neurotoxicity in multiple sclerosis.

Navarro M, Li J, Shrestha A, Uzal F, A. McClane B. Pathogenicity and virulence of Clostridium perfringens

Clostridium perfringens is an extremely versatile pathogen of humans and livestock, causing wound infections like gas gangrene (clostridial myonecrosis), enteritis/enterocolitis (including one of the most common human food-borne illnesses), and enterotoxemia (where toxins produced in the intestine are absorbed and damage distant organs such as the brain). The virulence of this Gram-positive, spore-forming, anaerobe is largely attributable to its copious toxin production; the diverse actions and roles in infection of these toxins are now becoming established. Most C. perfringens toxin genes are encoded on conjugative plasmids, including the pCW3-like and the recently discovered pCP13-like plasmid families. Production of C. perfringens toxins is highly regulated via processes involving two-component regulatory systems, quorum sensing and/or sporulation-related alternative sigma factors. Non-toxin factors, such as degradative enzymes like sialidases, are also now being implicated in the pathogenicity of this bacterium. These factors can promote toxin action in vitro and, perhaps in vivo, and also enhance C. perfringens intestinal colonization, e.g. NanI sialidase increases C. perfringens adherence to intestinal tissue and generates nutrients for its growth, at least in vitro. The possible virulence contributions of many other factors, such as adhesins, the capsule and biofilms, largely await future study.

Densitometric analysis of rep-PCR data: Insight into genetic variability and transmission of Clostridium perfringens typed with an improved multiplex PCR

An epidemiological study was conducted in North-East India (part of Indo-Burma biodiversity hotspot) to better understand the distribution, diversity, and transmission of Clostridium perfringens among livestock, pets, wild animals (captive), and humans. A total of 160 C. perfringens isolates were recovered from 642 diarrhoeic faecal samples with an isolation rate of 24.92%. Isolation rate was the highest among captive wild animals (37.5%) followed by dog (34.6%), human (33.8%), pig (32.7%), cattle (20.8%), goat (18.3%) and poultry (9.3%). Isolates were toxin typed using a seven gene multiplex PCR designed for simultaneous detection of cpa, cpb, cpb2, etx, iap, cpe and netB. The majority of isolates, 128 (80%) were of type A, followed by 17 (10.62%), 5 (3.12%), 4 (2.5%), 3 (1.87%), 2 (1.25%) and 1 (0.63%) isolates of type C, D, E, G, F and B, respectively. Beta 2 toxin gene was present in 65 (50%) of type A isolates, followed by 7 (41.2%), 4 (80%), 1(25%), and 1 (100%) of type C, D, G and B isolates, respectively. Beta 2 toxin has a high prevalence among dogs (28.6%), cattle (27.3%), and pig (20.8%) compared to humans, goat, wild animals, and poultry (1.2-14.3%). The prevalence of CPE and NetB toxin-positive strains was low, with only 3 (1.8%) and 5 (3.1%) isolates, respectively. Association of C. perfringens with diarrhoea in Civet Cat, Golden Langur, and Gray Langur has been reported for the first time. The genetic diversity and transmission of isolates were investigated using automated rep-PCR (Diversilab®, bioMérieux) using two densitometry-based matrices: modified Kullback-Leibler (KL) and Pearson's correlation (PC). The PC and modified KL matrices formed three distinct clusters with 59% and 27.2% similarity, respectively. C. perfringens diversity and transmission were best studied using modified KL matrix that placed more emphasis on the presence of bands rather than intensity. However, the PC method was found to be more suitable for differentiating strains within a toxin type, with slightly higher D-values.

Unravelling the potential of gut microbiota in sustaining brain health and their current prospective towards development of neurotherapeutics

Increasing incidences of neurological disorders, such as Parkinson's disease (PD), multiple sclerosis (MS), Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS) are being reported, but an insight into their pathology remains elusive. Findings have suggested that gut microbiota play a major role in regulating brain functions through the gut-brain axis. A unique bidirectional communication between gut microbiota and maintenance of brain health could play a pivotal role in regulating incidences of neurodegenerative diseases. Contrarily, the present life style with changing food habits and disturbed circadian rhythm may contribute to gut homeostatic imbalance and dysbiosis leading to progression of several neurological disorders. Therefore, dysbiosis, as a primary factor behind intestinal disorders, may also augment inflammation, intestinal and blood-brain barrier permeability through microbiota-gut-brain axis. This review primarily focuses on the gut-brain axis functions, specific gut microbial population, metabolites produced by gut microbiota, their role in regulating various metabolic processes and role of gut microbiota towards development of neurodegenerative diseases. However, several studies have reported a decrease in abundance of a specific gut microbial population and a corresponding increase in other microbial family, with few findings revealing some contradictions. Reports also showed that colonization of gut microbiota isolated from patients suffering from neurodegenerative disease leads to the development of enhance pathological outcomes in animal models. Hence, a systematic understanding of the dominant role of specific gut microbiome towards development of different neurodegenerative diseases could possibly provide novel insight into the use of probiotics and microbial transplantation as a substitute approach for treating/preventing such health maladies.

The Contribution of Gut Microbiota-Brain Axis in the Development of Brain Disorders

Different bacterial families colonize most mucosal tissues in the human organism such as the skin, mouth, vagina, respiratory, and gastrointestinal districts. In particular, the mammalian intestine hosts a microbial community of between 1,000 and 1,500 bacterial species, collectively called "microbiota." Co-metabolism between the microbiota and the host system is generated and the symbiotic relationship is mutually beneficial. The balance that is achieved between the microbiota and the host organism is fundamental to the organization of the immune system. Scientific studies have highlighted a direct correlation between the intestinal microbiota and the brain, establishing the existence of the gut microbiota-brain axis. Based on this theory, the microbiota acts on the development, physiology, and cognitive functions of the brain, although the mechanisms involved have not yet been fully interpreted. Similarly, a close relationship between alteration of the intestinal microbiota and the onset of several neurological pathologies has been highlighted. This review aims to point out current knowledge as can be found in literature regarding the connection between intestinal dysbiosis and the onset of particular neurological pathologies such as anxiety and depression, autism spectrum disorder, and multiple sclerosis. These disorders have always been considered to be a consequence of neuronal alteration, but in this review, we hypothesize that these alterations may be non-neuronal in origin, and consider the idea that the composition of the microbiota could be directly involved. In this direction, the following two key points will be highlighted: (1) the direct cross-talk that comes about between neurons and gut microbiota, and (2) the degree of impact of the microbiota on the brain. Could we consider the microbiota a valuable target for reducing or modulating the incidence of certain neurological diseases?

Gastrointestinal dysfunction in neuroinflammatory diseases: Multiple sclerosis, neuromyelitis optica, acute autonomic ganglionopathy and related conditions

Disorders of the nervous system can produce a variety of gastrointestinal (GI) dysfunctions. Among these, lesions in various brain structures can cause appetite loss (hypothalamus), decreased peristalsis (presumably the basal ganglia, pontine defecation center/Barrington's nucleus), decreased abdominal strain (presumably parabrachial nucleus/Kolliker-Fuse nucleus) and hiccupping and vomiting (area postrema/dorsal vagal complex). In addition, decreased peristalsis with/without loss of bowel sensation can be caused by lesions of the spinal long tracts and the intermediolateral nucleus or of the peripheral nerves and myenteric plexus. Recently, neural diseases of inflammatory etiology, particularly those affecting the PNS, are being recognized to contribute to GI dysfunction. Here, we review neuroinflammatory diseases that potentially cause GI dysfunction. Among such CNS diseases are multiple sclerosis, neuromyelitis optica spectrum disorder, myelin oligodendrocyte glycoprotein associated disorder, and autoimmune encephalitis. Peripheral nervous system diseases impacting the gut include Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy, acute sensory-autonomic neuropathy/acute motor-sensory-autonomic neuropathy, acute autonomic ganglionopathy, myasthenia gravis and acute autonomic neuropathy with paraneoplastic syndrome. Finally, collagen diseases, such as Sjogren syndrome and systemic sclerosis, and celiac disease affect both CNS and PNS. These neuro-associated GI dysfunctions may predate or present concurrently with brain, spinal cord or peripheral nerve dysfunction. Such patients may visit gastroenterologists or physicians first, before the neurological diagnosis is made. Therefore, awareness of these phenomena among general practitioners and collaboration between gastroenterologists and neurologists are highly recommended in order for their early diagnosis and optimal management, as well as for systematic documentation of their presentations and treatment.

Production and purification of Clostridium perfringens type D epsilon toxin and IgY antitoxin

The aim of this study was to purify Clostridium perfringens type D epsilon toxin and produce and purify anti-epsilon chicken immunoglobulin Y (IgY). A single-step ion exchange chromatography resulted in a high-yield and high-purity toxin, while ion exchange chromatography followed by gel filtration resulted in the highest purity of the toxin, but at a lower yield. Purified and inactivated epsilon toxin were then administered in chickens via four inoculations and IgY was obtained at a high purity and yield, with an antibody titer of 50 IU/mL and high levels of avidity (73.2%). In summary, C. perfringens type D epsilon toxin and chicken anti-epsilon IgY were successfully produced and purified, and may be used for the diagnosis of enterotoxemia caused by the epsilon toxin, as well as in potency tests of existing and future vaccines against enterotoxemia.

Clinical Features and Gut Microbial Alterations in Anti-leucine-rich Glioma-Inactivated 1 Encephalitis-A Pilot Study

Anti-leucine-rich glioma-inactivated 1 (anti-LGI1) encephalitis is a rare autoimmune encephalitis (AE). We investigated the clinical features and gut microbial alterations of anti-LGI1 encephalitis. Fifteen patients newly diagnosed with anti-LGI1 encephalitis were recruited in the study prior to the administration of immunotherapy. The control group contains 25 well-matched healthy controls (HCs). All participants were Han Chinese from South China. Their clinical data and fecal samples were collected. The diversity and composition of gut microbiota were analyzed by 16S ribosomal RNA (16S rRNA) gene sequencing. The results showed that anti-LGI1 encephalitis was characterized by cognitive impairment, faciobrachial dystonic seizures, hyponatremia, and psychiatric symptoms. Abnormal EEG and brain MRI were presented in 9 and 10 patients, respectively. Compared to HCs, the anti-LGI1 encephalitis patients exhibited a decreased microbial diversity and an altered overall composition of gut microbiome. At the phylum level, anti-LGI1 encephalitis patients exhibited a higher abundance of Proteobacteria and a lower abundance of Firmicutes. The alterations in the phylum level were associated with autoimmune and inflammatory disorders. At the genus level, there was an increase in Sphingomonas, Anaerofustis, Succinvibrio, Clostridium, and SMB53 (genera related to movement disorders, psychiatric diseases, and with proinflammatory effects). However, the Faecalibacterium, Roseburia, Lachnospira, Ruminococcus, and Blautia [genera with ability to produce short-chain fatty acids (SCFAs)] were obviously reduced in the patient group. Our results suggest that anti-LGI1 encephalitis is characterized by special clinical features and is accompanied by alterations in specific gut microbiota. For the limited sample size and non-applicability to other populations, further studies are warranted to explore the relationships between gut microbiota and anti-LGI1 encephalitis.

Pre-clinical and Clinical Implications of "Inside-Out" vs. "Outside-In" Paradigms in Multiple Sclerosis Etiopathogenesis

Multiple Sclerosis (MS) is an immune-mediated neurological disorder, characterized by central nervous system (CNS) inflammation, oligodendrocyte loss, demyelination, and axonal degeneration. Although autoimmunity, inflammatory demyelination and neurodegeneration underlie MS, the initiating event has yet to be clarified. Effective disease modifying therapies need to both regulate the immune system and promote restoration of neuronal function, including remyelination. The challenge in developing an effective long-lived therapy for MS requires that three disease-associated targets be addressed: (1) self-tolerance must be re-established to specifically inhibit the underlying myelin-directed autoimmune pathogenic mechanisms; (2) neurons must be protected from inflammatory injury and degeneration; (3) myelin repair must be engendered by stimulating oligodendrocyte progenitors to remyelinate CNS neuronal axons. The combined use of chronic and relapsing remitting experimental autoimmune encephalomyelitis (C-EAE, R-EAE) (“outside-in”) as well as progressive diphtheria toxin A chain (DTA) and cuprizone autoimmune encephalitis (CAE) (“inside-out”) mouse models allow for the investigation and specific targeting of all three of these MS-associated disease parameters. The “outside-in” EAE models initiated by myelin-specific autoreactive CD4⁺ T cells allow for the evaluation of both myelin-specific tolerance in the absence or presence of neuroprotective and/or remyelinating agents. The “inside-out” mouse models of secondary inflammatory demyelination are triggered by toxin-induced oligodendrocyte loss or subtle myelin damage, which allows evaluation of novel therapeutics that could promote remyelination and neuroprotection in the CNS. Overall, utilizing these complementary pre-clinical MS models will open new avenues for developing therapeutic interventions, tackling MS from the “outside-in” and/or “inside-out”.

Cardiopulmonary Lesions in Sheep Produced by Experimental Acute Clostridium Perfringens Type D Enterotoxemia

Enterotoxemia caused by Clostridium perfringens type D is one of the most prevalent clostridial diseases of sheep. The lesions of the acute form of this disease, particularly the cerebral lesions, are well characterized; however, detailed descriptions of the cardiac and pulmonary lesions are lacking. Here we describe cardiopulmonary lesions in experimental acute type D enterotoxemia in sheep and determine the role of epsilon toxin (ETX) in the development of these lesions. Four groups of 6 sheep were intraduodenally inoculated with either a wild-type C. perfringens type D strain; its etx knockout mutant, which is unable to produce ETX; the etx mutant complemented with the wild-type etx gene, which regains the ETX toxigenic ability; or sterile culture medium as a control. All sheep were subjected to postmortem examination within 24 hours of inoculation. Lesion scores were compared between groups for pulmonary edema; hydrothorax; ascites; hydropericardium; endocardial, myocardial and epicardial hemorrhages; microscopic lesions of acute myocardial degeneration and necrosis; and myocardial, endocardial, and epicardial edema, hemorrhage, and inflammation. Only sheep inoculated with the wild-type and complemented ETX-toxigenic bacterial strains developed cardiopulmonary lesions, which were present in varying degrees of severity and proportions. These lesions were not present in sheep inoculated with the etx mutant or in the negative control. We conclude that severe acute cardiopulmonary lesions in sheep with experimental enterotoxemia are associated with the capacity of the strains to produce ETX. These changes are likely contributors to the clinical signs and even death of affected animals.

Central residues of the amphipathic β-hairpin loop control the properties of Clostridium perfringens epsilon-toxin channel

Clostridium perfringens epsilon toxin (ETX) is a heptameric pore-forming toxin of the aerolysin toxin family. ETX is the most potent toxin of this toxin family and the third most potent bacterial toxin with high cytotoxic and lethal activities in animals. In addition, ETX shows a demyelinating activity in nervous tissue leading to devastating multifocal central nervous system white matter disease in ruminant animals. Pore formation in target cell membrane is most likely the initial critical step in ETX biological activity. Eight single to quadruple ETX mutants were generated by replacement of polar residues (serine, threonine, glutamine) in middle positions of the β-strands forming the β-barrel and facing the channel lumen with charged glutamic residues. Channel activity and ion selectivity were monitored in artificial lipid monolayer membranes and cytotoxicity was investigated in MDCK cells by the viability MTT test and propidium iodide entry. All the mutants formed channels with similar conductance in artificial lipid membranes and increasing cation selectivity for increasing number of mutations. Here, we show that residues in the central position of each β-strand of the amphipathic β-hairpin loop that forms the transmembrane pore, control the size and ion selectivity of the channel. While the highest cationic ETX mutants were not cytotoxic, no strict correlation was observed between ion selectivity and cytotoxicity.

The Microbiome as a Therapeutic Target for Multiple Sclerosis: Can Genetically Engineered Probiotics Treat the Disease?

There is an increasing interest in the intestinal microbiota as a critical regulator of the development and function of the immune, nervous, and endocrine systems. Experimental work in animal models has provided the foundation for clinical studies to investigate associations between microbiota composition and function and human disease, including multiple sclerosis (MS). Initial work done using an animal model of brain inflammation, experimental autoimmune encephalomyelitis (EAE), suggests the existence of a microbiota-gut-brain axis connection in the context of MS, and microbiome sequence analyses reveal increases and decreases of microbial taxa in MS intestines. In this review, we discuss the impact of the intestinal microbiota on the immune system and the role of the microbiome-gut-brain axis in the neuroinflammatory disease MS. We also discuss experimental evidence supporting the hypothesis that modulating the intestinal microbiota through genetically modified probiotics may provide immunomodulatory and protective effects as a novel therapeutic approach to treat this devastating disease.

The important role of polysaccharides from a traditional Chinese medicine-Lung Cleansing and Detoxifying Decoction against the COVID-19 pandemic

The new coronavirus pneumonia, named COVID-19 by the World Health Organization, has become a pandemic. It is highly pathogenic and reproduces quickly. There are currently no specific drugs to prevent the reproduction and spread of COVID-19. Some traditional Chinese medicines, especially the Lung Cleansing and Detoxifying Decoction (Qing Fei Pai Du Tang), have shown therapeutic effects on mild and ordinary COVID-19 patients. Polysaccharides are important ingredients in this decoction. This review summarizes the potential pharmacological activities of polysaccharides isolated by hot water extraction from Lung Cleansing and Detoxifying Decoction, which is consistent with its production method, to provide the theoretical basis for ongoing research on its application.

Clostridium perfringens Epsilon-Toxin Impairs the Barrier Function in MDCK Cell Monolayers in a Ca2+-Dependent Manner

Epsilon-toxin produced by Clostridium perfringens significantly contributes to the pathogeneses of enterotoxemia in ruminants and multiple sclerosis in humans. Epsilon-toxin forms a heptameric oligomer in the host cell membrane, promoting cell disruption. Here, we investigate the effect of epsilon-toxin on epithelial barrier functions. Epsilon-toxin impairs the barrier integrity of Madin-Darby Canine Kidney (MDCK) cells, as demonstrated by decreased transepithelial electrical resistance (TEER), increased paracellular flux marker permeability, and the decreased cellular localization of junctional proteins, such as occludin, ZO-1, and claudin-1. U73122, an endogenous phospholipase C (PLC) inhibitor, inhibited the decrease in TEER and the increase in the permeability of flux marker induced by epsilon-toxin. The application of epsilon-toxin to MDCK cells resulted in the biphasic formation of 1,2-diacylglycerol (DAG) and inositol-1,4,5-triphosphate (IP₃). U73122 blocked the formation of DAG and IP₃ induced by the toxin. Epsilon-toxin also specifically activated endogenous PLC-γ1. Epsilon-toxin dose-dependently increased the cytosolic calcium ion concentration ([Ca²⁺]i). The toxin-induced elevation of [Ca²⁺]i was inhibited by U73122. Cofilin is a key regulator of actin cytoskeleton turnover and tight-junction (TJ) permeability regulation. Epsilon-toxin caused cofilin dephosphorylation. These results demonstrate that epsilon-toxin induces Ca²⁺ influx through activating the phosphorylation of PLC-γ1 and then causes TJ opening accompanied by cofilin dephosphorylation.

[Norepinephrine and intestinal microbiome in the early stages of demyelination: clinical-immunological parallels]

Biogenic amines are key mediators of neuroimmune interaction and may influence on multiple sclerosis (MS) pathogenesis and MS course. At the same time, the role of biogenic amines in immunoregulation of early stages of demyelination, in particular clinically isolated syndrome (CIS) and radiologically isolated syndrome (RIS) is still unclear. This literature review addresses a role of norepinephrine in the regulation of neuroimmune interactions in the early stages of the demyelination. Neuropsychological disorders, immunological characteristics, gut-brain axis as well as the role of norepinephrine in these interactions in patients with CIS, RIS and early MS are discussed.

Gut-brain communication in demyelinating disorders

Multiple Sclerosis (MS) is an autoimmune demyelinating disorder resulting from the interplay of genetic predisposition and environmental variables, including gut microbiota, diet and life style factors. Here, we first discuss the evidence supporting the effect of early life events, diet and body mass index on the composition of the microbiota, and then review studies on gut dysbiosis conducted in MS patients and in animal models. We address the effect of disease, immunomodulatory therapies, diet and probiotics on enrichment or depletion of gut microbial species. Finally, we discuss the ability of gut bacteria to produce toxins and metabolites which serve as signals for the cross-talk between the gut and the brain.

Pathogenesis and diagnostic features of brain and ophthalmic damage produced by Clostridium perfringens type D epsilon toxin

Clostridium perfringens type D epsilon toxin (EXT) causes an important neurologic disorder of sheep, goats and, rarely, cattle. The disease can occur in peracute, acute, subacute, and chronic forms. High circulating levels of ETX produce vasculocentric brain lesions, in which microvascular endothelial injury results in diagnostically useful perivascular and intramural extravasations of plasma protein, especially in sheep, and less frequently in goats. With lower toxin doses, a more protracted clinical course tends to occur, particularly in sheep, leading to focal, bilaterally symmetrical, necrotic foci in certain brain regions. Although these morphologic features usually permit the diagnostic pathologist to make a definitive etiologic diagnosis, there are many aspects of the pathogenesis of these cerebral lesions that are not completely understood. ETX has also been shown to produce microvascular damage in the retina of rats, resulting in severe, diffuse vasogenic edema, similar to that found in brains exposed to this neurotoxin. The pathoclisis and vascular theories offer alternative explanations of the differential susceptibility of different brain regions to the same neurotoxic insult.

Epsilon Toxin from Clostridium perfringens Causes Inhibition of Potassium inward Rectifier (Kir) Channels in Oligodendrocytes

Epsilon toxin (ETX), produced by Clostridium perfringens types B and D, causes serious neurological disorders in animals. ETX can bind to the white matter of the brain and the oligodendrocytes, which are the cells forming the myelin sheath around neuron axons in the white matter of the central nervous system. After binding to oligodendrocytes, ETX causes demyelination in rat cerebellar slices. We further investigated the effects of ETX on cerebellar oligodendrocytes and found that ETX induced small transmembrane depolarization (by ~ +6.4 mV) in rat oligodendrocytes primary cultures. This was due to partial inhibition of the transmembrane inward rectifier potassium current (Kir). Of the two distinct types of Kir channel conductances (~25 pS and ~8.5 pS) recorded in rat oligodendrocytes, we found that ETX inhibited the large-conductance one. This inhibition did not require direct binding of ETX to a Kir channel. Most likely, the binding of ETX to its membrane receptor activates intracellular pathways that block the large conductance Kir channel activity in oligodendrocyte. Altogether, these findings and previous observations pinpoint oligodendrocytes as a major target for ETX. This supports the proposal that ETX might be a cause for Multiple Sclerosis, a disease characterized by myelin damage.

Clostridium perfringens epsilon toxin induces blood brain barrier permeability via caveolae-dependent transcytosis and requires expression of MAL

Clostridium perfringens epsilon toxin (ETX) is responsible for causing the economically devastating disease, enterotoxaemia, in livestock. It is well accepted that ETX causes blood brain barrier (BBB) permeability, however the mechanisms involved in this process are not well understood. Using in vivo and in vitro methods, we determined that ETX causes BBB permeability in mice by increasing caveolae-dependent transcytosis in brain endothelial cells. When mice are intravenously injected with ETX, robust ETX binding is observed in the microvasculature of the central nervous system (CNS) with limited to no binding observed in the vasculature of peripheral organs, indicating that ETX specifically targets CNS endothelial cells. ETX binding to CNS microvasculature is dependent on MAL expression, as ETX binding to CNS microvasculature of MAL-deficient mice was not detected. ETX treatment also induces extravasation of molecular tracers including 376Da fluorescein salt, 60kDA serum albumin, 70kDa dextran, and 155kDA IgG. Importantly, ETX-induced BBB permeability requires expression of both MAL and caveolin-1, as mice deficient in MAL or caveolin-1 did not exhibit ETX-induced BBB permeability. Examination of primary murine brain endothelial cells revealed an increase in caveolae in ETX-treated cells, resulting in dynamin and lipid raft-dependent vacuolation without cell death. ETX-treatment also results in a rapid loss of EEA1 positive early endosomes and accumulation of large, RAB7-positive late endosomes and multivesicular bodies. Based on these results, we hypothesize that ETX binds to MAL on the apical surface of brain endothelial cells, causing recruitment of caveolin-1, triggering caveolae formation and internalization. Internalized caveolae fuse with early endosomes which traffic to late endosomes and multivesicular bodies. We believe that these multivesicular bodies fuse basally, releasing their contents into the brain parenchyma.

Clostridium perfringens epsilon toxin (ETX) is an extremely lethal bacterial toxin known to cause a devastating disease in livestock animals and may be a possible cause of multiple sclerosis in humans. ETX is well known to cause disruption of the blood-brain barrier (BBB), a critical structure necessary for proper brain function. Deterioration of this barrier allows entry of toxic blood-borne material to enter the brain. Although ETX-induced BBB dysfunction is well accepted, how this happens is unknown. Here, we demonstrate that ETX causes BBB permeability by inducing formation of cell-surface invaginations called caveolae in endothelial cells, the cells that line blood vessels. Importantly, only endothelial cells from the brain and other central nervous system organs appear to be a target of ETX, as the toxin only binds to blood vessels in these organs and not blood vessels from other organs. These ETX-induced caveolae fuse with other caveolae and specialized intracellular vesicles called endosomes. We predict that these endosomes engulf blood-borne material during their internalization, allowing material to travel from the blood, through the cell, and into brain tissue. We also show that expression of the protein MAL and caveolin-1 is necessary for ETX-induced BBB permeability.

Clostridium perfringens type D epsilon toxin produces a rapid and dose-dependent cytotoxic effect on cerebral microvascular endothelial cells in vitro

Clostridium perfringens type D epsilon toxin (ETX) is responsible for a severe and frequently fatal neurologic disorder in ruminant livestock. Light microscopic, immunohistochemical, and ultrastructural studies have suggested that ETX injury to the cerebral microvasculature, with subsequent severe, generalized vasogenic edema and increased intracranial pressure, is critically important in producing neurologic dysfunction. However, the effect of ETX on brain capillary endothelial cells in vitro has not been examined previously, to our knowledge. We exposed a well-characterized human blood-brain barrier cell line to increasing concentrations of ETX, and demonstrated a direct and dose-dependent endotheliotoxic effect. Our findings are concordant with the primacy of vasculocentric brain lesions in the diagnosis of acute epsilon toxin enterotoxemia in ruminant livestock.

Clostridium perfringens epsilon toxin vaccine candidate lacking toxicity to cells expressing myelin and lymphocyte protein

A variant form of Clostridium perfringens epsilon toxin (Y30A-Y196A) with mutations, which shows reduced binding to Madin–Darby canine kidney (MDCK) cells and reduced toxicity in mice, has been proposed as the next-generation enterotoxaemia vaccine. Here we show that, unexpectedly, the Y30A-Y196A variant does not show a reduction in toxicity towards Chinese hamster ovary (CHO) cells engineered to express the putative receptor for the toxin (myelin and lymphocyte protein; MAL). The further addition of mutations to residues in a second putative receptor binding site of the Y30A-Y196A variant further reduces toxicity, and we selected Y30A-Y196A-A168F for further study. Compared to Y30A-Y196A, Y30A-Y196A-A168F showed more than a 3-fold reduction in toxicity towards MDCK cells, more than a 4-fold reduction in toxicity towards mice and at least 200-fold reduction in toxicity towards CHO cells expressing sheep MAL. The immunisation of rabbits or sheep with Y30A-Y196A-A168F induced high levels of neutralising antibodies against epsilon toxin, which persisted for at least 1 year. Y30A-Y196A-A168F is a candidate for development as a next-generation enterotoxaemia vaccine.

Cells expressing myelin and lymphocyte protein (MAL), the putative receptor for Clostridium perfringens’ epsilon toxin, can be sensitive to otherwise attenuated mutants of the toxin. Here, the team led by Richard Titball at United Kingdom’s University of Exeter found that a previous variant exhibits differential toxic effects when cells express sheep or human MAL. To circumvent this, Titball’s team applied site-directed mutagenesis of the receptor binding site to develop a new variant with enhanced reduction in toxicity towards MAL-expressing cells and able to induce high levels of neutralising antibodies upon immunisation of sheep. These findings suggests that testing genetic toxoids in cells expressing MAL from the target species might be relevant for enterotoxaemia vaccine development and warrant further studies into the role of MAL in epsilon toxin-mediated pathogenesis.

The pore structure of Clostridium perfringens epsilon toxin

Epsilon toxin (Etx), a potent pore forming toxin (PFT) produced by Clostridium perfringens, is responsible for the pathogenesis of enterotoxaemia of ruminants and has been suggested to play a role in multiple sclerosis in humans. Etx is a member of the aerolysin family of β-PFTs (aβ-PFTs). While the Etx soluble monomer structure was solved in 2004, Etx pore structure has remained elusive due to the difficulty of isolating the pore complex. Here we show the cryo-electron microscopy structure of Etx pore assembled on the membrane of susceptible cells. The pore structure explains important mutant phenotypes and suggests that the double β-barrel, a common feature of the aβ-PFTs, may be an important structural element in driving efficient pore formation. These insights provide the framework for the development of novel therapeutics to prevent human and animal infections, and are relevant for nano-biotechnology applications.

Epsilon toxin (Etx) is a potent pore forming toxin (PFT) produced by Clostridium perfringens. Here authors show the cryo-EM structure of the Etx pore assembled on the membrane of susceptible cells and shed light on pore formation and mutant phenotypes.

Clostridium perfringens Epsilon Toxin Compromises the Blood-Brain Barrier in a Humanized Zebrafish Model

Clostridium perfringens epsilon toxin (ETX) is hypothesized to mediate blood-brain barrier (BBB) permeability by binding to the myelin and lymphocyte protein (MAL) on the luminal surface of endothelial cells (ECs). However, the kinetics of this interaction and a general understanding of ETX's behavior in a live organism have yet to be appreciated. Here we investigate ETX binding and BBB breakdown in living Danio rerio (zebrafish). Wild-type zebrafish ECs do not bind ETX. When zebrafish ECs are engineered to express human MAL (hMAL), proETX binding occurs in a time-dependent manner. Injection of activated toxin in hMAL zebrafish initiates BBB leakage, hMAL downregulation, blood vessel stenosis, perivascular edema, and blood stasis. We propose a kinetic model of MAL-dependent ETX binding and neurovascular pathology. By generating a humanized zebrafish BBB model, this study contributes to our understanding of ETX-induced BBB permeability and strengthens the proposal that MAL is the ETX receptor.

The Beneficial and Debilitating Effects of Environmental and Microbial Toxins, Drugs, Organic Solvents and Heavy Metals on the Onset and Progression of Multiple Sclerosis

Multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system is common amongst young adults, leading to major personal and socioeconomic burdens. However, it is still considered complex and challenging to understand and treat, in spite of the efforts made to explain its etiopathology. Despite the discovery of many genetic and environmental factors that might be related to its etiology, no clear answer was found about the causes of the illness and neither about the detailed mechanism of these environmental triggers that make individuals susceptible to MS. In this review, we will attempt to explore the major contributors to MS autoimmunity including genetic, epigenetic and ecological factors with a particular focus on toxins, chemicals or drugs that may trigger, modify or prevent MS disease.

A Novel Panel of Rabbit Monoclonal Antibodies and Their Diverse Applications Including Inhibition of Clostridium perfringens Epsilon Toxin Oligomerization

The pore-forming epsilon toxin (ETX) produced by Clostridium perfringens is among the most lethal bacterial toxins known. Sensitive antibody-based reagents are needed to detect toxin, distinguish mechanisms of cell death, and prevent ETX toxicity. Using B-cell immuno-panning and cloning techniques, seven ETX-specific monoclonal antibodies were generated from immunized rabbits. ETX specificity and sensitivity were evaluated via western blot, ELISA, immunocytochemistry (ICC), and flow cytometry. ETX-neutralizing function was evaluated both in vitro and in vivo. All antibodies recognized both purified ETX and epsilon protoxin via western blot with two capable of detecting the ETX-oligomer complex. Four antibodies detected ETX via ELISA and three detected ETX bound to cells via ICC or flow cytometry. Several antibodies prevented ETX-induced cell death by either preventing ETX binding or by blocking ETX oligomerization. Antibodies that blocked ETX oligomerization inhibited ETX endocytosis and cellular vacuolation. Importantly, one of the oligomerization-blocking antibodies was able to protect against ETX-induced death post-ETX exposure in vitro and in vivo. Here we describe the production of a panel of rabbit monoclonal anti-ETX antibodies and their use in various biological assays. Antibodies possessing differential specificity to ETX in particular conformations will aid in the mechanistic studies of ETX cytotoxicity, while those with ETX-neutralizing function may be useful in preventing ETX-mediated mortality.

Identification of epsilon toxin-producing Clostridium perfringens strains in American retail food

Food samples (n = 216) from New York city were tested for the presence of C. perfringens via PCR for specific toxin genes. Thirty-four (16%) samples were positive for C. perfringens. Of these 34, 31 (91.2%) were type A or E, one (2.9%) was type B, and two (5.9%) were type D.

Comparative pathogenesis of enteric clostridial infections in humans and animals

Several enteric clostridial diseases can affect humans and animals. Of these, the enteric infections caused by Clostridium perfringens and Clostridium difficile are amongst the most prevalent and they are reviewed here. C. perfringens type A strains encoding alpha toxin (CPA) are frequently associated with enteric disease of many animal mammalian species, but their role in these diseased mammals remains to be clarified. C. perfringens type B encoding CPA, beta (CPB) and epsilon (ETX) toxins causes necro-hemorrhagic enteritis, mostly in sheep, and these strains have been recently suggested to be involved in multiple sclerosis in humans, although evidence of this involvement is lacking. C. perfringens type C strains encode CPA and CPB and cause necrotizing enteritis in humans and animals, while CPA and ETX producing type D strains of C. perfringens produce enterotoxemia in sheep, goats and cattle, but are not known to cause spontaneous disease in humans. The role of C. perfringens type E in animal or human disease remains poorly defined. The newly revised toxinotype F encodes CPA and enterotoxin (CPE), the latter being responsible for food poisoning in humans, and the less prevalent antibiotic associated and sporadic diarrhea. The role of these strains in animal disease has not been fully described and remains controversial. Another newly created toxinotype, G, encodes CPA and necrotic enteritis toxin B-like (NetB), and is responsible for avian necrotic enteritis, but has not been associated with human disease. C. difficile produces colitis and/or enterocolitis in humans and multiple animal species. The main virulence factors of this microorganism are toxins A, B and an ADP-ribosyltransferase (CDT). Other clostridia causing enteric diseases in humans and/or animals are Clostridium spiroforme, Clostridium piliforme, Clostridium colinum, Clostridium sordellii, Clostridium chauvoei, Clostridium septicum, Clostridium botulinum, Clostridium butyricum and Clostridium neonatale. The zoonotic transmission of some, but not all these clostridsial species, has been demonstrated.