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Special Issue "Enterotoxins"

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A special issue of Toxins (ISSN 2072-6651). This special issue belongs to the section "Bacterial Toxins".

Deadline for manuscript submissions: closed (30 April 2010)

Special Issue Editor

Guest Editor
Dr. C. Chris Yun (Website)

Emory University, School of Medicine, Division of Digestive Diseases, Whitehead Bldg., Suite 201, 615 Michael St. Atlanta, GA 30322, USA
Phone: +1 404 712 2865
Fax: +1 404 727 5767
Interests: effects of lysophosphoipids in colon cancer and colitis; sodium and fluid absorption in the intestine and kidney; protein-protein interaction; chemokine sin colon cancer; cancer therapeutics; GPCR signaling

Special Issue Information

Dear Colleagues,

Enterotoxins elicit their primary effects in the intestinal tract, initiating a metabolic cascade that results in excessive fluid and electrolyte secretion. Enterotoxins are frequently cytotoxic and kill cells by altering the apical membrane permeability of the mucosal epithelial cells of the intestinal wall. The uniform host response is the development of diarrhea. However, at a cellular level and subcellular level, certain enterotoxins induce sophisticated and fascinating metabolic alterations, which can affect the local immune system in a characteristic fashion. In some cases, enterotoxins induce disease outside the gastrointestinal tract, affecting other organ systems. Enterotoxins can exert diverse effects at the same time, either inducing or suppressing the immune cascade. This special issue of Toxins deals with major achievement and recent advances in enterotoxin secretion, toxin trafficking, toxin recognition, host interaction, and disease progression.

C. Chris Yun, Ph. D.
Guest Editor

Keywords

  • enterotoxin
  • immune response
  • diarrhea
  • ion channel
  • epithelial cells
  • membrane permeability

Published Papers (25 papers)

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Research

Jump to: Review

Open AccessArticle Staphylococcal Superantigen (TSST-1) Mutant Analysis Reveals that T Cell Activation Is Required for Biological Effects in the Rabbit Including the Cytokine Storm
Toxins 2010, 2(9), 2272-2288; doi:10.3390/toxins2092272
Received: 2 August 2010 / Revised: 1 September 2010 / Accepted: 7 September 2010 / Published: 9 September 2010
Cited by 5 | PDF Full-text (281 KB) | XML Full-text
Abstract
Staphylococcal superantigens (sAgs), such as toxic shock syndrome toxin 1 (TSST-1), induce massive cytokine production, which may result in toxic shock syndrome (TSS) and sepsis. Recently, we reported that in vitro studies in human peripheral blood mononuclear cells (PBMC) do not reflect [...] Read more.
Staphylococcal superantigens (sAgs), such as toxic shock syndrome toxin 1 (TSST-1), induce massive cytokine production, which may result in toxic shock syndrome (TSS) and sepsis. Recently, we reported that in vitro studies in human peripheral blood mononuclear cells (PBMC) do not reflect the immunological situation of the host, because after exposure to superantigens (sAgs) in vivo, mononuclear cells (MNC) leave the circulation and migrate to organs, e.g., the spleen, liver and lung. Our experimental model of choice is the rabbit because it is comparable to humans in its sensitivity to sAg. T cell activation has been assessed by lymphocyte proliferation and IL-2 gene expression after in vivo challenge with TSST-1 and the mutant antigens; expression of the genes of proinflammatory cytokines were taken as indicators for the inflammatory reaction after the combined treatment with TSST-1 and LPS. The question as to whether the biological activities of TSST-1, e.g., lymphocyte extravasation, toxicity and increased sensitivity to LPS, are mediated by T cell activation or activation by MHC II-only, are unresolved and results are contradictory. We have addressed this question by studying these reactions in vivo, with two TSST-1 mutants: one mutated at the MHC binding site (G31R) with reduced MHC binding with residual activity still present, and the other at the T cell binding site (H135A) with no residual function detectable. Here, we report that the mutant G31R induced all the biological effects of the wild type sAg, while the mutant with non-functional TCR binding did not retain any of the toxic effects, proving the pivotal role of T cells in this system. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessArticle How Should Staphylococcal Food Poisoning Outbreaks Be Characterized?
Toxins 2010, 2(8), 2106-2116; doi:10.3390/toxins2082106
Received: 21 June 2010 / Accepted: 5 August 2010 / Published: 10 August 2010
Cited by 31 | PDF Full-text (170 KB) | HTML Full-text | XML Full-text
Abstract
Staphylococcal food poisoning is one of the most common food-borne diseases and results from the ingestion of staphylococcal enterotoxins (SEs) preformed in food by enterotoxigenic strains of Staphylococcus aureus. To date, more than 20 SEs have been described: SEA to SElV. All [...] Read more.
Staphylococcal food poisoning is one of the most common food-borne diseases and results from the ingestion of staphylococcal enterotoxins (SEs) preformed in food by enterotoxigenic strains of Staphylococcus aureus. To date, more than 20 SEs have been described: SEA to SElV. All SEs have superantigenic activity whereas only a few have been proved to be emetic, representing a potential hazard for consumers. Characterization of staphylococcal food poisoning outbreaks (SFPOs) has considerably progressed compared to 80 years ago, when staphylococci were simply enumerated and only five enterotoxins were known for qualitative detection. Today, SFPOs can be characterized by a number of approaches, such as the identification of S. aureus biovars, PCR and RT-PCR methods to identify the se genes involved, immunodetection of specific SEs, and absolute quantification by mass spectrometry. An integrated gene-to-protein approach for characterizing staphylococcal food poisoning is advocated. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessArticle Unexpected Modulation of Recall B and T Cell Responses after Immunization with Rotavirus-like Particles in the Presence of LT-R192G
Toxins 2010, 2(8), 2007-2027; doi:10.3390/toxins2082007
Received: 13 July 2010 / Accepted: 3 August 2010 / Published: 5 August 2010
Cited by 3 | PDF Full-text (609 KB) | HTML Full-text | XML Full-text
Abstract
LT-R192G, a mutant of the thermolabile enterotoxin of E. coli, is a potent adjuvant of immunization. Immune responses are generally analyzed at the end of protocols including at least 2 administrations, but rarely after a prime. To investigate this point, we [...] Read more.
LT-R192G, a mutant of the thermolabile enterotoxin of E. coli, is a potent adjuvant of immunization. Immune responses are generally analyzed at the end of protocols including at least 2 administrations, but rarely after a prime. To investigate this point, we compared B and T cell responses in mice after one and two intrarectal immunizations with 2/6 rotavirus-like particles (2/6-VLP) and LT-R192G. After a boost, we found, an unexpected lower B cell expansion measured by flow cytometry, despite a secondary antibody response. We then analyzed CD4+CD25+Foxp3+ regulatory T cells (Tregs) and CD4+CD25+Foxp3 helper T cells after in vitro (re)stimulation of mesenteric lymph node cells with the antigen (2/6-VLP), the adjuvant (LT-R192G) or both. 2/6-VLP did not activate CD4+CD25+Foxp3 nor Foxp3+ T cells from non-immunized and 2/6-VLP immunized mice, whereas they did activate both subsets from mice immunized with 2/6-VLP in the presence of adjuvant. LT-R192G dramatically decreased CD4+CD25+Foxp3+ T cells from non-immunized and 2/6-VLP immunized mice but not from mice immunized with 2/6-VLP and adjuvant. Moreover, in this case, LT-R192G increased Foxp3 expression on CD4+CD25+Foxp3+ cells, suggesting specific Treg activation during the recall. Finally, when both 2/6-VLP and LT-R192G were used for restimulation, LT-R192G clearly suppressed both 2/6-VLP-specific CD4+CD25+Foxp3 and Foxp3+ T cells. All together, these results suggest that LT-R192G exerts different effects on CD4+CD25+Foxp3+ T cells, depending on a first or a second contact. The unexpected immunomodulation observed during the recall should be considered in designing vaccination protocols. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessArticle Uncoupling of T Cell Receptor Zeta Chain Function during the Induction of Anergy by the Superantigen, Staphylococcal Enterotoxin A
Toxins 2010, 2(7), 1704-1717; doi:10.3390/toxins2071704
Received: 5 May 2010 / Revised: 17 June 2010 / Accepted: 28 June 2010 / Published: 30 June 2010
PDF Full-text (267 KB) | HTML Full-text | XML Full-text
Abstract
Staphylococcus aureus enterotoxins have immunomodulatory properties. In this study, we show that Staphylococcal enterotoxin A (SEA) induces a strong proliferative response in a murine T cell clone independent of MHC class II bearing cells. SEA stimulation also induces a state of hypo-responsiveness [...] Read more.
Staphylococcus aureus enterotoxins have immunomodulatory properties. In this study, we show that Staphylococcal enterotoxin A (SEA) induces a strong proliferative response in a murine T cell clone independent of MHC class II bearing cells. SEA stimulation also induces a state of hypo-responsiveness (anergy). We characterized the components of the T cell receptor (TCR) during induction of anergy by SEA. Most interestingly, TCR zeta chain phosphorylation was absent under SEA anergizing conditions, which suggests an uncoupling of zeta chain function. We characterize here a model system for studying anergy in the absence of confounding costimulatory signals. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessArticle Shiga Toxin Is Transported into the Nucleoli of Intestinal Epithelial Cells via a Carrier-Dependent Process
Toxins 2010, 2(6), 1318-1335; doi:10.3390/toxins2061318
Received: 22 April 2010 / Revised: 19 May 2010 / Accepted: 3 June 2010 / Published: 7 June 2010
Cited by 3 | PDF Full-text (457 KB) | HTML Full-text | XML Full-text
Abstract
Shiga toxin (Stx) produced by the invasive Shigella dysenteriae serotype 1 (S. dysenteriae1) causes gastrointestinal and kidney complications. It has been assumed that Stx is released intracellularly after enterocyte invasion by S. dysenteriae1. However, there is little information about [...] Read more.
Shiga toxin (Stx) produced by the invasive Shigella dysenteriae serotype 1 (S. dysenteriae1) causes gastrointestinal and kidney complications. It has been assumed that Stx is released intracellularly after enterocyte invasion by S. dysenteriae1. However, there is little information about Stx distribution inside S. dysenteriae1-infected enterocytes. Here, we use intestinal epithelial T84 cells to characterize the trafficking of Stx delivered into the cytosol, in ways that mimic aspects of S. dysenteriae1 infection. We find that cytoplasmic Stx is transported into nucleoli. Stx nucleolar movement is carrier- and energy-dependent. Stx binding to the nucleoli of normal human enterocytes in vitro supports possible roles for nucleolar trafficking in toxin-induced intestinal pathology. Full article
(This article belongs to the Special Issue Enterotoxins)

Review

Jump to: Research

Open AccessReview Cure and Curse: E. coli Heat-Stable Enterotoxin and Its Receptor Guanylyl Cyclase C
Toxins 2010, 2(9), 2213-2229; doi:10.3390/toxins2092213
Received: 15 July 2010 / Revised: 12 August 2010 / Accepted: 24 August 2010 / Published: 26 August 2010
Cited by 10 | PDF Full-text (461 KB) | HTML Full-text | XML Full-text
Abstract
Enterotoxigenic Escherichia coli (ETEC) associated diarrhea is responsible for roughly half a million deaths per year, the majority taking place in developing countries. The main agent responsible for these diseases is the bacterial heat-stable enterotoxin STa. STa is secreted by ETEC and [...] Read more.
Enterotoxigenic Escherichia coli (ETEC) associated diarrhea is responsible for roughly half a million deaths per year, the majority taking place in developing countries. The main agent responsible for these diseases is the bacterial heat-stable enterotoxin STa. STa is secreted by ETEC and after secretion binds to the intestinal receptor guanylyl cyclase C (GC-C), thus triggering a signaling cascade that eventually leads to the release of electrolytes and water in the intestine. Additionally, GC-C is a specific marker for colorectal carcinoma and STa is suggested to have an inhibitory effect on intestinal carcinogenesis. To understand the conformational events involved in ligand binding to GC-C and to devise therapeutic strategies to treat both diarrheal diseases and colorectal cancer, it is paramount to obtain structural information on the receptor ligand system. Here we summarize the currently available structural data and report on physiological consequences of STa binding to GC-C in intestinal epithelia and colorectal carcinoma cells. Full article
(This article belongs to the Special Issue Enterotoxins)
Figures

Open AccessReview Staphylococcal Enterotoxins
Toxins 2010, 2(8), 2177-2197; doi:10.3390/toxins2082177
Received: 29 June 2010 / Revised: 9 August 2010 / Accepted: 12 August 2010 / Published: 18 August 2010
Cited by 93 | PDF Full-text (577 KB) | HTML Full-text | XML Full-text
Abstract
Staphylococcus aureus (S. aureus) is a Gram positive bacterium that is carried by about one third of the general population and is responsible for common and serious diseases. These diseases include food poisoning and toxic shock syndrome, which are caused [...] Read more.
Staphylococcus aureus (S. aureus) is a Gram positive bacterium that is carried by about one third of the general population and is responsible for common and serious diseases. These diseases include food poisoning and toxic shock syndrome, which are caused by exotoxins produced by S. aureus. Of the more than 20 Staphylococcal enterotoxins, SEA and SEB are the best characterized and are also regarded as superantigens because of their ability to bind to class II MHC molecules on antigen presenting cells and stimulate large populations of T cells that share variable regions on the b chain of the T cell receptor. The result of this massive T cell activation is a cytokine bolus leading to an acute toxic shock. These proteins are highly resistant to denaturation, which allows them to remain intact in contaminated food and trigger disease outbreaks. A recognized problem is the emergence of multi-drug resistant strains of S. aureus and these are a concern in the clinical setting as they are a common cause of antibiotic-associated diarrhea in hospitalized patients. In this review, we provide an overview of the current understanding of these proteins. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview Different Types of Cell Death Induced by Enterotoxins
Toxins 2010, 2(8), 2158-2176; doi:10.3390/toxins2082158
Received: 13 July 2010 / Accepted: 3 August 2010 / Published: 11 August 2010
Cited by 6 | PDF Full-text (296 KB) | HTML Full-text | XML Full-text
Abstract
The infection of bacterial organisms generally causes cell death to facilitate microbial invasion and immune escape, both of which are involved in the pathogenesis of infectious diseases. In addition to the intercellular infectious processes, pathogen-produced/secreted enterotoxins (mostly exotoxins) are the major weapons [...] Read more.
The infection of bacterial organisms generally causes cell death to facilitate microbial invasion and immune escape, both of which are involved in the pathogenesis of infectious diseases. In addition to the intercellular infectious processes, pathogen-produced/secreted enterotoxins (mostly exotoxins) are the major weapons that kill host cells and cause diseases by inducing different types of cell death, particularly apoptosis and necrosis. Blocking these enterotoxins with synthetic drugs and vaccines is important for treating patients with infectious diseases. Studies of enterotoxin-induced apoptotic and necrotic mechanisms have helped us to create efficient strategies to use against these well-characterized cytopathic toxins. In this article, we review the induction of the different types of cell death from various bacterial enterotoxins, such as staphylococcal enterotoxin B, staphylococcal alpha-toxin, Panton-Valentine leukocidin, alpha-hemolysin of Escherichia coli, Shiga toxins, cytotoxic necrotizing factor 1, heat-labile enterotoxins, and the cholera toxin, Vibrio cholerae. In addition, necrosis caused by pore-forming toxins, apoptotic signaling through cross-talk pathways involving mitochondrial damage, endoplasmic reticulum stress, and lysosomal injury is discussed. Full article
(This article belongs to the Special Issue Enterotoxins)
Figures

Open AccessReview Multiple Roles of Staphylococcus aureus Enterotoxins: Pathogenicity, Superantigenic Activity, and Correlation to Antibiotic Resistance
Toxins 2010, 2(8), 2117-2131; doi:10.3390/toxins2082117
Received: 3 July 2010 / Accepted: 9 August 2010 / Published: 10 August 2010
Cited by 41 | PDF Full-text (214 KB) | HTML Full-text | XML Full-text
Abstract
Heat-stable enterotoxins are the most notable virulence factors associated with Staphylococcus aureus, a common pathogen associated with serious community and hospital acquired diseases. Staphylococcal enterotoxins (SEs) cause toxic shock-like syndromes and have been implicated in food poisoning. But SEs also act [...] Read more.
Heat-stable enterotoxins are the most notable virulence factors associated with Staphylococcus aureus, a common pathogen associated with serious community and hospital acquired diseases. Staphylococcal enterotoxins (SEs) cause toxic shock-like syndromes and have been implicated in food poisoning. But SEs also act as superantigens that stimulate T-cell proliferation, and a high correlation between these activities has been detected. Most of the nosocomial S. aureus infections are caused by methicillin-resistant S. aureus (MRSA) strains, and those resistant to quinolones or multiresistant to other antibiotics are emerging, leaving a limited choice for their control. This review focuses on these diverse roles of SE, their possible correlations and the influence in disease progression and therapy. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview Toxin Mediated Diarrhea in the 21st Century: The Pathophysiology of Intestinal Ion Transport in the Course of ETEC, V. cholerae and Rotavirus Infection
Toxins 2010, 2(8), 2132-2157; doi:10.3390/toxins2082132
Received: 23 June 2010 / Accepted: 9 August 2010 / Published: 10 August 2010
Cited by 11 | PDF Full-text (391 KB) | HTML Full-text | XML Full-text
Abstract
An estimated 4 billion episodes of diarrhea occur each year. As a result, 2–3 million children and 0.5–1 million adults succumb to the consequences of this major healthcare concern. The majority of these deaths can be attributed to toxin mediated diarrhea by [...] Read more.
An estimated 4 billion episodes of diarrhea occur each year. As a result, 2–3 million children and 0.5–1 million adults succumb to the consequences of this major healthcare concern. The majority of these deaths can be attributed to toxin mediated diarrhea by infectious agents, such as E. coli, V. cholerae or Rotavirus. Our understanding of the pathophysiological processes underlying these infectious diseases has notably improved over the last years. This review will focus on the cellular mechanism of action of the most common enterotoxins and the latest specific therapeutic approaches that have been developed to contain their lethal effects. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview Bacterial Heat-Stable Enterotoxins: Translation of Pathogenic Peptides into Novel Targeted Diagnostics and Therapeutics
Toxins 2010, 2(8), 2028-2054; doi:10.3390/toxins2082028
Received: 18 July 2010 / Accepted: 3 August 2010 / Published: 5 August 2010
Cited by 15 | PDF Full-text (427 KB) | HTML Full-text | XML Full-text
Abstract
Heat-stable toxins (STs) produced by enterotoxigenic bacteria cause endemic and traveler’s diarrhea by binding to and activating the intestinal receptor guanylyl cyclase C (GC-C). Advances in understanding the biology of GC-C have extended ST from a diarrheagenic peptide to a novel therapeutic agent. [...] Read more.
Heat-stable toxins (STs) produced by enterotoxigenic bacteria cause endemic and traveler’s diarrhea by binding to and activating the intestinal receptor guanylyl cyclase C (GC-C). Advances in understanding the biology of GC-C have extended ST from a diarrheagenic peptide to a novel therapeutic agent. Here, we summarize the physiological and pathophysiological role of GC-C in fluid-electrolyte regulation and intestinal crypt-villus homeostasis, as well as describe translational opportunities offered by STs, reflecting the unique characteristics of GC-C, in treating irritable bowel syndrome and chronic constipation, and in preventing and treating colorectal cancer. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview Therapeutic Down-Modulators of Staphylococcal Superantigen-Induced Inflammation and Toxic Shock
Toxins 2010, 2(8), 1963-1983; doi:10.3390/toxins2081963
Received: 30 June 2010 / Revised: 16 July 2010 / Accepted: 28 July 2010 / Published: 29 July 2010
Cited by 12 | PDF Full-text (356 KB) | HTML Full-text | XML Full-text
Abstract
Staphylococcal enterotoxin B (SEB) and related superantigenic toxins are potent stimulators of the immune system and cause a variety of diseases in humans, ranging from food poisoning to toxic shock. These toxins bind directly to major histocompatibility complex (MHC) class II molecules [...] Read more.
Staphylococcal enterotoxin B (SEB) and related superantigenic toxins are potent stimulators of the immune system and cause a variety of diseases in humans, ranging from food poisoning to toxic shock. These toxins bind directly to major histocompatibility complex (MHC) class II molecules on antigen-presenting cells and specific Vb regions of T-cell receptors (TCR), resulting in hyperactivation of both monocytes/macrophages and T lymphocytes. Activated host cells produce massive amounts of proinflammatory cytokines and chemokines, activating inflammation and coagulation, causing clinical symptoms that include fever, hypotension, and shock. This review summarizes the in vitro and in vivo effects of staphylococcal superantigens, the role of pivotal mediators induced by these toxins in the pathogenic mechanisms of tissue injury, and the therapeutic agents to mitigate the toxic effects of superantigens. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview NetB, a Pore-Forming Toxin from Necrotic Enteritis Strains of Clostridium perfringens
Toxins 2010, 2(7), 1913-1927; doi:10.3390/toxins2071913
Received: 22 June 2010 / Revised: 9 July 2010 / Accepted: 22 July 2010 / Published: 23 July 2010
Cited by 30 | PDF Full-text (333 KB) | HTML Full-text | XML Full-text
Abstract
The Clostridium perfringens necrotic enteritis B-like toxin (NetB) is a recently discovered member of the β-barrel pore-forming toxin family and is produced by a subset of avian C. perfringens type A strains. NetB is cytotoxic for avian cells and is associated with [...] Read more.
The Clostridium perfringens necrotic enteritis B-like toxin (NetB) is a recently discovered member of the β-barrel pore-forming toxin family and is produced by a subset of avian C. perfringens type A strains. NetB is cytotoxic for avian cells and is associated with avian necrotic enteritis. This review examines the current state of knowledge of NetB: its role in pathogenesis, its distribution and expression in C. perfringens and its vaccine potential. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview The Systemic and Pulmonary Immune Response to Staphylococcal Enterotoxins
Toxins 2010, 2(7), 1898-1912; doi:10.3390/toxins2071898
Received: 21 June 2010 / Accepted: 12 July 2010 / Published: 21 July 2010
Cited by 1 | PDF Full-text (133 KB) | HTML Full-text | XML Full-text
Abstract
In response to environmental cues the human pathogen Staphylococcus aureus synthesizes and releases proteinaceous enterotoxins. These enterotoxins are natural etiologic entities of severe food poisoning, toxic shock syndrome, and acute diseases. Staphylococcal enterotoxins are currently listed as Category B Bioterrorism Agents by [...] Read more.
In response to environmental cues the human pathogen Staphylococcus aureus synthesizes and releases proteinaceous enterotoxins. These enterotoxins are natural etiologic entities of severe food poisoning, toxic shock syndrome, and acute diseases. Staphylococcal enterotoxins are currently listed as Category B Bioterrorism Agents by the Center for Disease Control and Prevention. They are associated with respiratory illnesses, and may contribute to exacerbation of pulmonary disease. This likely stems from the ability of Staphylococcal enterotoxins to elicit powerful episodes of T cell stimulation resulting in release of pro-inflammatory cytokines. Here, we discuss the role of the immune system and potential mechanisms of disease initiation and progression. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview The Enterotoxicity of Clostridium difficile Toxins
Toxins 2010, 2(7), 1848-1880; doi:10.3390/toxins2071848
Received: 18 June 2010 / Revised: 23 June 2010 / Accepted: 9 July 2010 / Published: 14 July 2010
Cited by 28 | PDF Full-text (247 KB) | HTML Full-text | XML Full-text
Abstract
The major virulence factors of Clostridium difficile infection (CDI) are two large exotoxins A (TcdA) and B (TcdB). However, our understanding of the specific roles of these toxins in CDI is still evolving. It is now accepted that both toxins are enterotoxic [...] Read more.
The major virulence factors of Clostridium difficile infection (CDI) are two large exotoxins A (TcdA) and B (TcdB). However, our understanding of the specific roles of these toxins in CDI is still evolving. It is now accepted that both toxins are enterotoxic and proinflammatory in the human intestine. Both purified TcdA and TcdB are capable of inducing the pathophysiology of CDI, although most studies have focused on TcdA. C. difficile toxins exert a wide array of biological activities by acting directly on intestinal epithelial cells. Alternatively, the toxins may target immune cells and neurons once the intestinal epithelial barrier is disrupted. The toxins may also act indirectly by stimulating cells to produce chemokines, proinflammatory cytokines, neuropeptides and other neuroimmune signals. This review considers the mechanisms of TcdA- and TcdB-induced enterotoxicity, and recent developments in this field. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview Cholera-Like Enterotoxins and Regulatory T cells
Toxins 2010, 2(7), 1774-1795; doi:10.3390/toxins2071774
Received: 4 May 2010 / Revised: 23 June 2010 / Accepted: 28 June 2010 / Published: 6 July 2010
Cited by 7 | PDF Full-text (375 KB) | HTML Full-text | XML Full-text
Abstract
Cholera toxin (CT) and the heat-labile enterotoxin of E. coli (LT), as well as their non toxic mutants, are potent mucosal adjuvants of immunization eliciting mucosal and systemic responses against unrelated co-administered antigens in experimental models and in humans (non toxic mutants). [...] Read more.
Cholera toxin (CT) and the heat-labile enterotoxin of E. coli (LT), as well as their non toxic mutants, are potent mucosal adjuvants of immunization eliciting mucosal and systemic responses against unrelated co-administered antigens in experimental models and in humans (non toxic mutants). These enterotoxins are composed of two subunits, the A subunit, responsible for an ADP-ribosyl transferase activity and the B subunit, responsible for cell binding. Paradoxically, whereas the whole toxins have adjuvant properties, the B subunits of CT (CTB) and of LT (LTB) have been shown to induce antigen specific tolerance when administered mucosally with antigens in experimental models as well as, recently, in humans, making them an attractive strategy to prevent or treat autoimmune or allergic disorders. Immunomodulation is a complex process involving many cell types notably antigen presenting cells and regulatory T cells (Tregs). In this review, we focus on Treg cells and cholera-like enterotoxins and their non toxic derivates, with regard to subtype, in vivo/in vitro effects and possible role in the modulation of immune responses to coadministered antigens. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview Food Poisoning and Staphylococcus aureus Enterotoxins
Toxins 2010, 2(7), 1751-1773; doi:10.3390/toxins2071751
Received: 3 May 2010 / Revised: 24 June 2010 / Accepted: 30 June 2010 / Published: 5 July 2010
Cited by 148 | PDF Full-text (476 KB) | HTML Full-text | XML Full-text
Abstract
Staphylococcus aureus produces a wide variety of toxins including staphylococcal enterotoxins (SEs; SEA to SEE, SEG to SEI, SER to SET) with demonstrated emetic activity, and staphylococcal-like (SEl) proteins, which are not emetic in a primate model (SElL [...] Read more.
Staphylococcus aureus produces a wide variety of toxins including staphylococcal enterotoxins (SEs; SEA to SEE, SEG to SEI, SER to SET) with demonstrated emetic activity, and staphylococcal-like (SEl) proteins, which are not emetic in a primate model (SElL and SElQ) or have yet to be tested (SElJ, SElK, SElM to SElP, SElU, SElU2 and SElV). SEs and SEl s have been traditionally subdivided into classical (SEA to SEE) and new (SEG to SElU2) types. All possess superantigenic activity and are encoded by accessory genetic elements, including plasmids, prophages, pathogenicity islands, νSa genomic islands, or by genes located next to the staphylococcal cassette chromosome (SCC) implicated in methicillin resistance. SEs are a major cause of food poisoning, which typically occurs after ingestion of different foods, particularly processed meat and dairy products, contaminated with S. aureus by improper handling and subsequent storage at elevated temperatures. Symptoms are of rapid onset and include nausea and violent vomiting, with or without diarrhea. The illness is usually self-limiting and only occasionally it is severe enough to warrant hospitalization. SEA is the most common cause of staphylococcal food poisoning worldwide, but the involvement of other classical SEs has been also demonstrated. Of the new SE/SEls, only SEH have clearly been associated with food poisoning. However, genes encoding novel SEs as well as SEls with untested emetic activity are widely represented in S. aureus, and their role in pathogenesis may be underestimated. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview Production, Secretion and Biological Activity of Bacillus cereus Enterotoxins
Toxins 2010, 2(7), 1690-1703; doi:10.3390/toxins2071690
Received: 4 May 2010 / Revised: 14 June 2010 / Accepted: 28 June 2010 / Published: 29 June 2010
Cited by 22 | PDF Full-text (131 KB) | HTML Full-text | XML Full-text
Abstract
Bacillus cereus behaves as an opportunistic pathogen frequently causing gastrointestinal diseases, and it is increasingly recognized to be responsible for severe local or systemic infections. Pathogenicity of B. cereus mainly relies on the secretion of a wide array of toxins and enzymes [...] Read more.
Bacillus cereus behaves as an opportunistic pathogen frequently causing gastrointestinal diseases, and it is increasingly recognized to be responsible for severe local or systemic infections. Pathogenicity of B. cereus mainly relies on the secretion of a wide array of toxins and enzymes and also on the ability to undergo swarming differentiation in response to surface-sensing. In this report, the pathogenicity exerted by B. cereus toxins is described with particular attention to the regulatory mechanisms of production and secretion of HBL, Nhe and CytK enterotoxins. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview AB Toxins: A Paradigm Switch from Deadly to Desirable
Toxins 2010, 2(7), 1612-1645; doi:10.3390/toxins2071612
Received: 26 May 2010 / Revised: 8 June 2010 / Accepted: 23 June 2010 / Published: 25 June 2010
Cited by 18 | PDF Full-text (894 KB) | HTML Full-text | XML Full-text
Abstract
To ensure their survival, a number of bacterial and plant species have evolved a common strategy to capture energy from other biological systems. Being imperfect pathogens, organisms synthesizing multi-subunit AB toxins are responsible for the mortality of millions of people and animals [...] Read more.
To ensure their survival, a number of bacterial and plant species have evolved a common strategy to capture energy from other biological systems. Being imperfect pathogens, organisms synthesizing multi-subunit AB toxins are responsible for the mortality of millions of people and animals annually. Vaccination against these organisms and their toxins has proved rather ineffective in providing long-term protection from disease. In response to the debilitating effects of AB toxins on epithelial cells of the digestive mucosa, mechanisms underlying toxin immunomodulation of immune responses have become the focus of increasing experimentation. The results of these studies reveal that AB toxins may have a beneficial application as adjuvants for the enhancement of immune protection against infection and autoimmunity. Here, we examine similarities and differences in the structure and function of bacterial and plant AB toxins that underlie their toxicity and their exceptional properties as immunomodulators for stimulating immune responses against infectious disease and for immune suppression of organ-specific autoimmunity. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview Specificity of Interaction between Clostridium perfringens Enterotoxin and Claudin-Family Tight Junction Proteins
Toxins 2010, 2(7), 1595-1611; doi:10.3390/toxins2071595
Received: 18 May 2010 / Revised: 7 June 2010 / Accepted: 23 June 2010 / Published: 24 June 2010
Cited by 14 | PDF Full-text (568 KB) | HTML Full-text | XML Full-text
Abstract
Clostridium perfringens enterotoxin (CPE), a major cause of food poisoning, forms physical pores in the plasma membrane of intestinal epithelial cells. The ability of CPE to recognize the epithelium is due to the C-terminal binding domain, which binds to a specific [...] Read more.
Clostridium perfringens enterotoxin (CPE), a major cause of food poisoning, forms physical pores in the plasma membrane of intestinal epithelial cells. The ability of CPE to recognize the epithelium is due to the C-terminal binding domain, which binds to a specific motif on the second extracellular loop of tight junction proteins known as claudins. The interaction between claudins and CPE plays a key role in mediating CPE toxicity by facilitating pore formation and by promoting tight junction disassembly. Recently, the ability of CPE to distinguish between specific claudins has been used to develop tools for studying roles for claudins in epithelial barrier function. Moreover, the high affinity of CPE to selected claudins makes CPE a useful platform for targeted drug delivery to tumors expressing these claudins. Full article
(This article belongs to the Special Issue Enterotoxins)
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Open AccessReview Heat-Labile Enterotoxin: Beyond G M1 Binding
Toxins 2010, 2(6), 1445-1470; doi:10.3390/toxins2061445
Received: 29 April 2010 / Revised: 22 May 2010 / Accepted: 7 June 2010 / Published: 14 June 2010
Cited by 16 | PDF Full-text (2404 KB) | HTML Full-text | XML Full-text
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a significant source of morbidity and mortality worldwide. One major virulence factor released by ETEC is the heat-labile enterotoxin LT, which is structurally and functionally similar to cholera toxin. LT consists of five B subunits carrying a [...] Read more.
Enterotoxigenic Escherichia coli (ETEC) is a significant source of morbidity and mortality worldwide. One major virulence factor released by ETEC is the heat-labile enterotoxin LT, which is structurally and functionally similar to cholera toxin. LT consists of five B subunits carrying a single catalytically active A subunit. LTB binds the monosialoganglioside GM1, the toxin’s host receptor, but interactions with A-type blood sugars and E. coli lipopolysaccharide have also been identified within the past decade. Here, we review the regulation, assembly, and binding properties of the LT B-subunit pentamer and discuss the possible roles of its numerous molecular interactions. Full article
(This article belongs to the Special Issue Enterotoxins)
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Open AccessReview On the Interaction of Clostridium perfringens Enterotoxin with Claudins
Toxins 2010, 2(6), 1336-1356; doi:10.3390/toxins2061336
Received: 5 May 2010 / Revised: 21 May 2010 / Accepted: 4 June 2010 / Published: 8 June 2010
Cited by 19 | PDF Full-text (270 KB) | HTML Full-text | XML Full-text
Abstract
Clostridium perfringens causes one of the most common foodborne illnesses, which is largely mediated by the Clostridium perfringens enterotoxin (CPE). The toxin consists of two functional domains. The N-terminal region mediates the cytotoxic effect through pore formation in the plasma membrane of [...] Read more.
Clostridium perfringens causes one of the most common foodborne illnesses, which is largely mediated by the Clostridium perfringens enterotoxin (CPE). The toxin consists of two functional domains. The N-terminal region mediates the cytotoxic effect through pore formation in the plasma membrane of the mammalian host cell. The C-terminal region (cCPE) binds to the second extracellular loop of a subset of claudins. Claudin-3 and claudin-4 have been shown to be receptors for CPE with very high affinity. The toxin binds with weak affinity to claudin-1 and -2 but contribution of these weak binding claudins to CPE-mediated disease is questionable. cCPE is not cytotoxic, however, it is a potent modulator of tight junctions. This review describes recent progress in the molecular characterization of the cCPE-claudin interaction using mutagenesis, in vitro binding assays and permeation studies. The results promote the development of recombinant cCPE-proteins and CPE-based peptidomimetics to modulate tight junctions for improved drug delivery or to treat tumors overexpressing claudins. Full article
(This article belongs to the Special Issue Enterotoxins)
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Open AccessReview Toxin-Specific Antibodies for the Treatment of Clostridium difficile: Current Status and Future Perspectives
Toxins 2010, 2(5), 998-1018; doi:10.3390/toxins2050998
Received: 26 March 2010 / Revised: 29 April 2010 / Accepted: 5 May 2010 / Published: 7 May 2010
Cited by 14 | PDF Full-text (279 KB) | HTML Full-text | XML Full-text
Abstract
Therapeutic agents targeting bacterial virulence factors are gaining interest as non-antibiotic alternatives for the treatment of infectious diseases. Clostridium difficile is a Gram-positive pathogen that produces two primary virulence factors, enterotoxins A and B (TcdA and TcdB), which are responsible for Clostridium [...] Read more.
Therapeutic agents targeting bacterial virulence factors are gaining interest as non-antibiotic alternatives for the treatment of infectious diseases. Clostridium difficile is a Gram-positive pathogen that produces two primary virulence factors, enterotoxins A and B (TcdA and TcdB), which are responsible for Clostridium difficile-associated disease (CDAD) and are targets for CDAD therapy. Antibodies specific for TcdA and TcdB have been shown to effectively treat CDAD and prevent disease relapse in animal models and in humans. This review summarizes the various toxin-specific antibody formats and strategies under development, and discusses future directions for CDAD immunotherapy, including the use of engineered antibody fragments with robust biophysical properties for systemic and oral delivery. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview The Role of Lymphostatin/EHEC Factor for Adherence-1 in the Pathogenesis of Gram Negative Infection
Toxins 2010, 2(5), 954-962; doi:10.3390/toxins2050954
Received: 21 March 2010 / Revised: 22 April 2010 / Accepted: 27 April 2010 / Published: 5 May 2010
Cited by 2 | PDF Full-text (145 KB) | HTML Full-text | XML Full-text
Abstract
Lymphostatin/EHEC factor for adherence-1 is a novel large toxin represented in various Gram negative bacteria, highly associated with the development of infectious diarrhea and hemolytic uremic syndrome. In vitro and in vivo experiments identified lymphostatin/EFA-1 as a toxin with a central role [...] Read more.
Lymphostatin/EHEC factor for adherence-1 is a novel large toxin represented in various Gram negative bacteria, highly associated with the development of infectious diarrhea and hemolytic uremic syndrome. In vitro and in vivo experiments identified lymphostatin/EFA-1 as a toxin with a central role in the pathogenesis of Gram negative bacteria, responsible for bacterial adhesion, intestinal colonization, immunosuppression, and disruption of gut epithelial barrier function. Full article
(This article belongs to the Special Issue Enterotoxins)
Open AccessReview Cholera Toxin: An Intracellular Journey into the Cytosol by Way of the Endoplasmic Reticulum
Toxins 2010, 2(3), 310-325; doi:10.3390/toxins2030310
Received: 27 January 2010 / Revised: 27 February 2010 / Accepted: 2 March 2010 / Published: 5 March 2010
Cited by 54 | PDF Full-text (333 KB) | HTML Full-text | XML Full-text
Abstract
Cholera toxin (CT), an AB5-subunit toxin, enters host cells by binding the ganglioside GM1 at the plasma membrane (PM) and travels retrograde through the trans-Golgi Network into the endoplasmic reticulum (ER). In the ER, a portion of CT, the [...] Read more.
Cholera toxin (CT), an AB5-subunit toxin, enters host cells by binding the ganglioside GM1 at the plasma membrane (PM) and travels retrograde through the trans-Golgi Network into the endoplasmic reticulum (ER). In the ER, a portion of CT, the enzymatic A1-chain, is unfolded by protein disulfide isomerase and retro-translocated to the cytosol by hijacking components of the ER associated degradation pathway for misfolded proteins. After crossing the ER membrane, the A1-chain refolds in the cytosol and escapes rapid degradation by the proteasome to induce disease by ADP-ribosylating the large G-protein Gs and activating adenylyl cyclase. Here, we review the mechanisms of toxin trafficking by GM1 and retro-translocation of the A1-chain to the cytosol. Full article
(This article belongs to the Special Issue Enterotoxins)

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