Clostridium difficile toxin B is an inflammatory enterotoxin in human intestine.
ABSTRACT Clostridium difficile causes antibiotic-associated diarrhea and pseudomembranous colitis, diseases afflicting millions of people each year. Although C. difficile releases 2 structurally similar exotoxins, toxin A and toxin B, animal experiments suggest that only toxin A mediates diarrhea and enterocolitis. However, toxin A-negative/toxin B-positive strains of C. difficile recently were isolated from patients with antibiotic-associated diarrhea and colitis, indicating that toxin B also may be pathogenic in humans.
Here we used subcutaneously transplanted human intestinal xenografts in immunodeficient mice to generate a chimeric animal model for C. difficile toxin-induced pathology of human intestine.
We found that intraluminal toxin B, like equivalent concentrations of toxin A, induced intestinal epithelial cell damage, increased mucosal permeability, stimulated interleukin (IL)-8 synthesis, and caused an acute inflammatory response characterized by neutrophil recruitment and tissue damage. Laser capture microdissection and real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) showed that intestinal epithelial cell-specific IL-8 gene expression also was increased significantly after luminal exposure to C. difficile toxins in vivo.
We conclude that C. difficile toxin B, like toxin A, is a potent inflammatory enterotoxin for human intestine. Future therapeutic or vaccine strategies for C. difficile infection therefore need to target both toxins.
Article: Yersinia enterocolitica YopT and Clostridium difficile toxin B induce expression of GILZ in epithelial cells.[show abstract] [hide abstract]
ABSTRACT: Glucocorticoid induced-leucine zipper (GILZ) has been shown to be induced in cells by different stimuli such as glucocorticoids, IL-10 or deprivation of IL-2. GILZ has anti-inflammatory properties and may be involved in signalling modulating apoptosis. Herein we demonstrate that wildtype Yersinia enterocolitica which carry the pYV plasmid upregulated GILZ mRNA levels and protein expression in epithelial cells. Infection of HeLa cells with different Yersinia mutant strains revealed that the protease activity of YopT, which cleaves the membrane-bound form of Rho GTPases was sufficient to induce GILZ expression. Similarly, Clostridium difficile toxin B, another bacterial inhibitor of Rho GTPases induced GILZ expression. YopT and toxin B both increased transcriptional activity of the GILZ promoter in HeLa cells. GILZ expression could not be linked to the inactivation of an individual Rho GTPase by these toxins. However, forced expression of RhoA and RhoB decreased basal GILZ promoter activity. Furthermore, MAPK activation proved necessary for profound GILZ induction by toxin B. Promoter studies and gel shift analyses defined binding of upstream stimulatory factor (USF) 1 and 2 to a canonical c-Myc binding site (E-box) in the GILZ promoter as a crucial step of its trans-activation. In addition we could show that USF-1 and USF-2 are essential for basal as well as toxin B induced GILZ expression. These findings define a novel way of GILZ promoter trans-activation mediated by bacterial toxins and differentiate it from those mediated by dexamethasone or deprivation of IL-2.PLoS ONE 01/2012; 7(7):e40730. · 4.09 Impact Factor
Article: The role of toxin A and toxin B in Clostridium difficile-associated disease: Past and present perspectives.[show abstract] [hide abstract]
ABSTRACT: Recently, we constructed and characterized isogenic tcdA and tcdB mutants of a virulent Clostridium difficile strain and used a hamster model of disease to demonstrate that toxin B, not toxin A, is essential for virulence of this emerging pathogen. Earlier studies had shown that purified toxin A alone was able to induce C. difficile disease pathology and that purified toxin B was not effective unless it was co-administered with toxin A, suggesting that the toxins act synergistically. In this addendum we discuss this paradigm-shifting conclusion in the context of current strain epidemiology, particularly with respect to naturally occurring toxin A-negative, toxin B-positive isolates and the NAP1/027 epidemic isolates. The role of toxin receptors and how variant toxins might exert their effects is also discussed in relation to the published data. We conclude that it is critical to use the natural infection process to dissect the role of toxins in disease, and that future studies are contingent on such work. The impact and importance of animal models of C. difficile virulence are therefore considered within this frame of reference.Gut Microbes 01/2010; 1(1):58-64.
Article: Adenovirus-based vaccination against Clostridium difficile toxin A allows for rapid humoral immunity and complete protection from toxin A lethal challenge in mice.[show abstract] [hide abstract]
ABSTRACT: Clostridium difficile associated diarrhea (CDAD) is a critical public health problem worldwide with over 300,000 cases every year in the United States alone. Clearly, a potent vaccine preventing the morbidity and mortality caused by this detrimental pathogen is urgently required. However, vaccine efforts to combat C. difficile infections have been limited both in scope as well as to efficacy, as such there is not a vaccine approved for use against C. difficile to date. In this study, we have used a highly potent Adenovirus (Ad) based platform to create a vaccine against C. difficile. The Ad-based vaccine was able to generate rapid and robust humoral as well as cellular (T-cell) immune responses in mice that correlated with provision of 100% protection from lethal challenge with C. difficile toxin A. Most relevant to the clinical utility of this vaccine formulation was our result that toxin A specific IgGs were readily detected in plasma of Ad immunized mice as early as 3 days post vaccination. In addition, we found that several major immuno-dominant T cell epitopes were identified in toxin A, suggesting that the role of the cellular arm in protection from C. difficile infections may be more significant than previously appreciated. Therefore, our studies confirm that an Adenovirus based-C. difficile vaccine could be a promising candidate for prophylactic vaccination both for use in high risk patients and in high-risk environments.Vaccine 12/2011; 30(8):1492-501. · 3.77 Impact Factor