1
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Matylitsky J, Krieg A, Schumacher J, Borho J, Barth H, Papatheodorou P. Inhibition of Clostridioides difficile toxins TcdA and TcdB by the amiodarone derivative dronedarone. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2024:10.1007/s00210-024-03248-8. [PMID: 38935126 DOI: 10.1007/s00210-024-03248-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Accepted: 06/18/2024] [Indexed: 06/28/2024]
Abstract
The dreaded nosocomial pathogen Clostridioides difficile causes diarrhea and severe inflammation of the colon, especially after the use of certain antibiotics. The bacterium releases two deleterious toxins, TcdA and TcdB, into the gut, which are mainly responsible for the symptoms of C. difficile-associated diseases (CDADs). Both toxins are capable of entering independently into various host cells, e.g., intestinal epithelial cells, where they mono-O-glucosylate and inactivate Rho and/or Ras GTPases, important molecular switches for various cellular functions. We have shown recently that the cellular uptake of the Clostridioides difficile toxins TcdA and TcdB (TcdA/B) is inhibited by the licensed class III antiarrhythmic drug amiodarone (Schumacher et al. in Gut Microbes 15(2):2256695, 2023). Mechanistically, amiodarone delays the cellular uptake of both toxins into target cells most likely by lowering membrane cholesterol levels and by interfering with membrane insertion and/or pore formation of TcdA/B. However, serious side effects, such as thyroid dysfunction and severe pulmonary fibrosis, limit the clinical use of amiodarone in patients with C. difficile infection (CDI). For that reason, we aimed to test whether dronedarone, an amiodarone derivative with a more favorable side effect profile, is also capable of inhibiting TcdA/B. To this end, we tested in vitro with various methods the impact of dronedarone on the intoxication of Vero and CaCo-2 cells with TcdA/B. Importantly, preincubation of both cell lines with dronedarone for 1 h at concentrations in the low micromolar range rendered the cells less sensitive toward TcdA/B-induced Rac1 glucosylation, collapse of the actin cytoskeleton, cell rounding, and cytopathic effects, respectively. Our study points toward the possibility of repurposing the already approved drug dronedarone as the preferable safer-to-use alternative to amiodarone for inhibiting TcdA/B in the (supportive) therapy of CDADs.
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Affiliation(s)
- Jauheni Matylitsky
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Anica Krieg
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Judith Schumacher
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Joscha Borho
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Holger Barth
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Panagiotis Papatheodorou
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
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2
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Pourliotopoulou E, Karampatakis T, Kachrimanidou M. Exploring the Toxin-Mediated Mechanisms in Clostridioides difficile Infection. Microorganisms 2024; 12:1004. [PMID: 38792835 PMCID: PMC11124097 DOI: 10.3390/microorganisms12051004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2024] [Revised: 05/14/2024] [Accepted: 05/15/2024] [Indexed: 05/26/2024] Open
Abstract
Clostridioides difficile infection (CDI) is the leading cause of nosocomial antibiotic-associated diarrhea, and colitis, with increasing incidence and healthcare costs. Its pathogenesis is primarily driven by toxins produced by the bacterium C. difficile, Toxin A (TcdA) and Toxin B (TcdB). Certain strains produce an additional toxin, the C. difficile transferase (CDT), which further enhances the virulence and pathogenicity of C. difficile. These toxins disrupt colonic epithelial barrier integrity, and induce inflammation and cellular damage, leading to CDI symptoms. Significant progress has been made in the past decade in elucidating the molecular mechanisms of TcdA, TcdB, and CDT, which provide insights into the management of CDI and the future development of novel treatment strategies based on anti-toxin therapies. While antibiotics are common treatments, high recurrence rates necessitate alternative therapies. Bezlotoxumab, targeting TcdB, is the only available anti-toxin, yet limitations persist, prompting ongoing research. This review highlights the current knowledge of the structure and mechanism of action of C. difficile toxins and their role in disease. By comprehensively describing the toxin-mediated mechanisms, this review provides insights for the future development of novel treatment strategies and the management of CDI.
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Affiliation(s)
- Evdokia Pourliotopoulou
- Department of Microbiology, Medical School, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece;
| | | | - Melania Kachrimanidou
- Department of Microbiology, Medical School, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece;
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3
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Zhou R, He L, Zhang J, Zhang X, Li Y, Zhan X, Tao L. Molecular basis of TMPRSS2 recognition by Paeniclostridium sordellii hemorrhagic toxin. Nat Commun 2024; 15:1976. [PMID: 38438396 PMCID: PMC10912200 DOI: 10.1038/s41467-024-46394-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 02/26/2024] [Indexed: 03/06/2024] Open
Abstract
Hemorrhagic toxin (TcsH) is a major virulence factor produced by Paeniclostridium sordellii, which is a non-negligible threat to women undergoing childbirth or abortions. Recently, Transmembrane Serine Protease 2 (TMPRSS2) was identified as a host receptor of TcsH. Here, we show the cryo-EM structures of the TcsH-TMPRSS2 complex and uncover that TcsH binds to the serine protease domain (SPD) of TMPRSS2 through the CROP unit-VI. This receptor binding mode is unique among LCTs. Five top surface loops of TMPRSS2SPD, which also determine the protease substrate specificity, constitute the structural determinants recognized by TcsH. The binding of TcsH inhibits the proteolytic activity of TMPRSS2, whereas its implication in disease manifestations remains unclear. We further show that mutations selectively disrupting TMPRSS2-binding reduce TcsH toxicity in the intestinal epithelium of the female mice. These findings together shed light on the distinct molecular basis of TcsH-TMPRSS2 interactions, which expands our knowledge of host recognition mechanisms employed by LCTs and provides novel targets for developing therapeutics against P. sordellii infections.
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Affiliation(s)
- Ruoyu Zhou
- College of Life Sciences, Fudan University, Shanghai, 200433, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, 310024, China
| | - Liuqing He
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, 310024, China
- Research Center for Industries of the Future, Westlake University, Hangzhou, 310024, China
| | - Jiahao Zhang
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, 310024, China
| | - Xiaofeng Zhang
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, 310024, China
| | - Yanyan Li
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, 310024, China
| | - Xiechao Zhan
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, 310024, China.
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, 310024, China.
- Westlake Institute for Advanced Study, Hangzhou, 310024, China.
| | - Liang Tao
- College of Life Sciences, Fudan University, Shanghai, 200433, China.
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, 310024, China.
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, 310024, China.
- Westlake Institute for Advanced Study, Hangzhou, 310024, China.
- Research Center for Industries of the Future, Westlake University, Hangzhou, 310024, China.
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4
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Zhou Y, Zhan X, Luo J, Li D, Zhou R, Zhang J, Pan Z, Zhang Y, Jia T, Zhang X, Li Y, Tao L. Structural dynamics of the CROPs domain control stability and toxicity of Paeniclostridium sordellii lethal toxin. Nat Commun 2023; 14:8426. [PMID: 38114525 PMCID: PMC10730571 DOI: 10.1038/s41467-023-44169-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 12/04/2023] [Indexed: 12/21/2023] Open
Abstract
Paeniclostridium sordellii lethal toxin (TcsL) is a potent exotoxin that causes lethal toxic shock syndrome associated with fulminant bacterial infections. TcsL belongs to the large clostridial toxin (LCT) family. Here, we report that TcsL with varied lengths of combined repetitive oligopeptides (CROPs) deleted show increased autoproteolysis as well as higher cytotoxicity. We next present cryo-EM structures of full-length TcsL, at neutral (pH 7.4) and acidic (pH 5.0) conditions. The TcsL at neutral pH exhibits in the open conformation, which resembles reported TcdB structures. Low pH induces the conformational change of partial TcsL to the closed form. Two intracellular interfaces are observed in the closed conformation, which possibly locks the cysteine protease domain and hinders the binding of the host receptor. Our findings provide insights into the structure and function of TcsL and reveal mechanisms for CROPs-mediated modulation of autoproteolysis and cytotoxicity, which could be common across the LCT family.
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Affiliation(s)
- Yao Zhou
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310024, China
| | - Xiechao Zhan
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China.
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China.
| | - Jianhua Luo
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310024, China
| | - Diyin Li
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310024, China
| | - Ruoyu Zhou
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Jiahao Zhang
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Zhenrui Pan
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Yuanyuan Zhang
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Tianhui Jia
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310024, China
| | - Xiaofeng Zhang
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Yanyan Li
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Liang Tao
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China.
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China.
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310024, China.
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5
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Schumacher J, Nienhaus A, Heber S, Matylitsky J, Chaves-Olarte E, Rodríguez C, Barth H, Papatheodorou P. Exploring the inhibitory potential of the antiarrhythmic drug amiodarone against Clostridioides difficile toxins TcdA and TcdB. Gut Microbes 2023; 15:2256695. [PMID: 37749884 PMCID: PMC10524773 DOI: 10.1080/19490976.2023.2256695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 09/05/2023] [Indexed: 09/27/2023] Open
Abstract
The intestinal pathogen Clostridioides difficile is the leading cause of antibiotic-associated diarrhea and pseudomembranous colitis in humans. The symptoms of C. difficile-associated diseases (CDADs) are directly associated with the pathogen's toxins TcdA and TcdB, which enter host cells and inactivate Rho and/or Ras GTPases by glucosylation. Membrane cholesterol is crucial during the intoxication process of TcdA and TcdB, and likely involved during pore formation of both toxins in endosomal membranes, a key step after cellular uptake for the translocation of the glucosyltransferase domain of both toxins from endosomes into the host cell cytosol. The licensed drug amiodarone, a multichannel blocker commonly used in the treatment of cardiac dysrhythmias, is also capable of inhibiting endosomal acidification and, as shown recently, cholesterol biosynthesis. Thus, we were keen to investigate in vitro with cultured cells and human intestinal organoids, whether amiodarone preincubation protects from TcdA and/or TcdB intoxication. Amiodarone conferred protection against both toxins independently and in combination as well as against toxin variants from the clinically relevant, epidemic C. difficile strain NAP1/027. Further mechanistic studies suggested that amiodarone's mode-of-inhibition involves also interference with the translocation pore of both toxins. Our study opens the possibility of repurposing the licensed drug amiodarone as a novel pan-variant antitoxin therapeutic in the context of CDADs.
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Affiliation(s)
- Judith Schumacher
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Ulm, Germany
| | - Astrid Nienhaus
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Ulm, Germany
| | - Sebastian Heber
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Ulm, Germany
| | - Jauheni Matylitsky
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Ulm, Germany
| | - Esteban Chaves-Olarte
- Centro de Investigación en Enfermedades Tropicales and Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - César Rodríguez
- Centro de Investigación en Enfermedades Tropicales and Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Holger Barth
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Ulm, Germany
| | - Panagiotis Papatheodorou
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Ulm, Germany
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6
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Papatheodorou P, Kindig S, Badilla-Lobo A, Fischer S, Durgun E, Thuraisingam T, Witte A, Song S, Aktories K, Chaves-Olarte E, Rodríguez C, Barth H. The Compound U18666A Inhibits the Intoxication of Cells by Clostridioides difficile Toxins TcdA and TcdB. Front Microbiol 2021; 12:784856. [PMID: 34912322 PMCID: PMC8667575 DOI: 10.3389/fmicb.2021.784856] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 11/01/2021] [Indexed: 11/13/2022] Open
Abstract
The intestinal pathogen Clostridioides (C.) difficile is a major cause of diarrhea both in hospitals and outpatient in industrialized countries. This bacterium produces two large exotoxins, toxin A (TcdA) and toxin B (TcdB), which are directly responsible for the onset of clinical symptoms of C. difficile-associated diseases (CDADs), such as antibiotics-associated diarrhea and the severe, life-threatening pseudomembranous colitis. Both toxins are multidomain proteins and taken up into host eukaryotic cells via receptor-mediated endocytosis. Within the cell, TcdA and TcdB inactivate Rho and/or Ras protein family members by glucosylation, which eventually results in cell death. The cytotoxic mode of action of the toxins is the main reason for the disease. Thus, compounds capable of inhibiting the cellular uptake and/or mode-of-action of both toxins are of high therapeutic interest. Recently, we found that the sterol regulatory element-binding protein 2 (SREBP-2) pathway, which regulates cholesterol content in membranes, is crucial for the intoxication of cells by TcdA and TcdB. Furthermore, it has been shown that membrane cholesterol is required for TcdA- as well as TcdB-mediated pore formation in endosomal membranes, which is a key step during the translocation of the glucosyltransferase domain of both toxins from endocytic vesicles into the cytosol of host cells. In the current study, we demonstrate that intoxication by TcdA and TcdB is diminished in cultured cells preincubated with the compound U18666A, an established inhibitor of cholesterol biosynthesis and/or intracellular transport. U18666A-pretreated cells were also less sensitive against TcdA and TcdB variants from the epidemic NAP1/027 C. difficile strain. Our study corroborates the crucial role of membrane cholesterol for cell entry of TcdA and TcdB, thus providing a valuable basis for the development of novel antitoxin strategies in the context of CDADs.
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Affiliation(s)
| | - Selina Kindig
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
| | - Adriana Badilla-Lobo
- Centro de Investigación en Enfermedades Tropicales and Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Stephan Fischer
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
| | - Ebru Durgun
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
| | - Tharani Thuraisingam
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
| | - Alexander Witte
- Institute of Experimental and Clinical Pharmacology and Toxicology, Albert Ludwig University Freiburg, Freiburg, Germany
| | - Shuo Song
- Institute of Experimental and Clinical Pharmacology and Toxicology, Albert Ludwig University Freiburg, Freiburg, Germany
| | - Klaus Aktories
- Institute of Experimental and Clinical Pharmacology and Toxicology, Albert Ludwig University Freiburg, Freiburg, Germany
| | - Esteban Chaves-Olarte
- Centro de Investigación en Enfermedades Tropicales and Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - César Rodríguez
- Centro de Investigación en Enfermedades Tropicales and Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Holger Barth
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm, Germany
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7
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Guo S, Chen Y, Liu J, Zhang X, Liu Z, Zhou Z, Wei W. Low-density lipoprotein receptor-related protein 1 is a CROPs-associated receptor for Clostridioides difficile toxin B. SCIENCE CHINA-LIFE SCIENCES 2021; 65:107-118. [PMID: 34279819 DOI: 10.1007/s11427-021-1943-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 04/28/2021] [Indexed: 12/23/2022]
Abstract
As the leading cause of worldwide hospital-acquired infection, Clostridioides difficile (C. difficile) infection has caused heavy economic and hospitalized burden, while its pathogenesis is not fully understood. Toxin B (TcdB) is one of the major virulent factors of C. difficile. Recently, CSPG4 and FZD2 were reported to be the receptors that mediate TcdB cellular entry. However, genetic ablation of genes encoding these receptors failed to completely block TcdB entry, implicating the existence of alternative receptor(s) for this toxin. Here, by employing the CRISPR-Cas9 screen in CSPG4-deficient HeLa cells, we identified LDL receptor-related protein-1 (LRP1) as a novel receptor for TcdB. Knockout of LRP1 in both CSPG4-deficient HeLa cells and colonic epithelium Caco2 cells conferred cells with increased TcdB resistance, while LRP1 overexpression sensitized cells to TcdB at a low concentration. Co-immunoprecipitation assay showed that LRP1 interacts with full-length TcdB. Moreover, CROPs domain, which is dispensable for TcdB's interaction with CSPG4 and FZD2, is sufficient for binding to LRP1. As such, our study provided evidence for a novel mechanism of TcdB entry and suggested potential therapeutic targets for treating C. diff.
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Affiliation(s)
- Shengjie Guo
- Biomedical Pioneering Innovation Center, Beijing Advanced Innovation Center for Genomics, Peking-Tsinghua Center for Life Sciences, Peking University Genome Editing Research Center, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, 100871, China
| | - Yiou Chen
- Biomedical Pioneering Innovation Center, Beijing Advanced Innovation Center for Genomics, Peking-Tsinghua Center for Life Sciences, Peking University Genome Editing Research Center, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, 100871, China
| | - Jingze Liu
- Biomedical Pioneering Innovation Center, Beijing Advanced Innovation Center for Genomics, Peking-Tsinghua Center for Life Sciences, Peking University Genome Editing Research Center, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, 100871, China
| | - Xinyi Zhang
- Biomedical Pioneering Innovation Center, Beijing Advanced Innovation Center for Genomics, Peking-Tsinghua Center for Life Sciences, Peking University Genome Editing Research Center, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, 100871, China
| | - Zhiheng Liu
- Biomedical Pioneering Innovation Center, Beijing Advanced Innovation Center for Genomics, Peking-Tsinghua Center for Life Sciences, Peking University Genome Editing Research Center, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, 100871, China
| | - Zhuo Zhou
- Biomedical Pioneering Innovation Center, Beijing Advanced Innovation Center for Genomics, Peking-Tsinghua Center for Life Sciences, Peking University Genome Editing Research Center, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, 100871, China.
| | - Wensheng Wei
- Biomedical Pioneering Innovation Center, Beijing Advanced Innovation Center for Genomics, Peking-Tsinghua Center for Life Sciences, Peking University Genome Editing Research Center, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, 100871, China.
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8
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Development and verification of an enzyme-linked immunosorbent assay for the quantification of toxoid A and toxoid B from Clostridioides difficile. J Immunol Methods 2020; 488:112917. [PMID: 33221460 DOI: 10.1016/j.jim.2020.112917] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 10/14/2020] [Accepted: 11/15/2020] [Indexed: 11/23/2022]
Abstract
Clostridioides difficile (C. difficile) is the most common cause of nosocomial antibiotic associated diarrhoea. The incidence of C. difficile infection (CDI) has been rising worldwide over the last 20 years with consequent rises in morbidity, mortality and healthcare costs, although the incidence has fallen in the UK over the last few years. Confirmation of diagnosis and early intervention are critical to the management of CDI. The standard treatment for CDI is the administration of antibiotics. However, vaccination has been recognized as the most cost-effective treatment for the prevention and possible long-term protection against CDI episode. There are several promising vaccine candidates in various stages of development. Many of these vaccines have displayed good efficacy for CDI under laboratory conditions or in clinical trials. With the emergence of vaccines against C. difficile, here we describe the development and verification of an Enzyme Linked Immunosorbent Assay (ELISA) that can be used for the quality control testing of candidate vaccines against C. difficile through the measurement of vaccine antigen content. Verification of the assay was performed by assessment of specificity, sensitivity, intermediate precision and relative accuracy. The ELISAs were specific for the toxoids being detected and the detection limit of the assay for toxoid A was 4.88 ng/mL and 3.91 ng/mL for toxoid B. The geometric coefficients of variation for intermediate precision did not exceed 25% and relative accuracy was within 77-130%. We therefore conclude that the ELISA described here is sufficiently sensitive, specific, precise and accurate for use for the quality control testing of candidate C. difficile vaccines.
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9
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Fischer S, Ückert AK, Landenberger M, Papatheodorou P, Hoffmann-Richter C, Mittler AK, Ziener U, Hägele M, Schwan C, Müller M, Kleger A, Benz R, Popoff MR, Aktories K, Barth H. Human peptide α-defensin-1 interferes with Clostridioides difficile toxins TcdA, TcdB, and CDT. FASEB J 2020; 34:6244-6261. [PMID: 32190927 DOI: 10.1096/fj.201902816r] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 12/23/2019] [Accepted: 02/27/2020] [Indexed: 12/15/2022]
Abstract
The human pathogenic bacterium Clostridioides difficile produces two exotoxins TcdA and TcdB, which inactivate Rho GTPases thereby causing C. difficile-associated diseases (CDAD) including life-threatening pseudomembranous colitis. Hypervirulent strains produce additionally the binary actin ADP-ribosylating toxin CDT. These strains are hallmarked by more severe forms of CDAD and increased frequency and severity. Once in the cytosol, the toxins act as enzymes resulting in the typical clinical symptoms. Therefore, targeting and inactivation of the released toxins are of peculiar interest. Prompted by earlier findings that human α-defensin-1 neutralizes TcdB, we investigated the effects of the defensin on all three C. difficile toxins. Inhibition of TcdA, TcdB, and CDT was demonstrated by analyzing toxin-induced changes in cell morphology, substrate modification, and decrease in transepithelial electrical resistance. Application of α-defensin-1 protected cells and human intestinal organoids from the cytotoxic effects of TcdA, TcdB, CDT, and their combination which is attributed to a direct interaction between the toxins and α-defensin-1. In mice, the application of α-defensin-1 reduced the TcdA-induced damage of intestinal loops in vivo. In conclusion, human α-defensin-1 is a specific and potent inhibitor of the C. difficile toxins and a promising agent to develop novel therapeutic options against C. difficile infections.
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Affiliation(s)
- Stephan Fischer
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany
| | - Anna-Katharina Ückert
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany
| | - Marc Landenberger
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany
| | | | | | - Ann-Katrin Mittler
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany
| | - Ulrich Ziener
- Institute of Organic Chemistry III, Ulm University, Ulm, Germany
| | - Marlen Hägele
- Department of Internal Medicine I, University of Ulm Medical Center, Ulm, Germany
| | - Carsten Schwan
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany
| | - Martin Müller
- Department of Internal Medicine I, University of Ulm Medical Center, Ulm, Germany
| | - Alexander Kleger
- Department of Internal Medicine I, University of Ulm Medical Center, Ulm, Germany
| | - Roland Benz
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Bremen, Germany
| | - Michel R Popoff
- Department of Anaerobic Bacteria, Pasteur Institute, Paris, France
| | - Klaus Aktories
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany
| | - Holger Barth
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Ulm, Germany
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10
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Pathogenicity Locus, Core Genome, and Accessory Gene Contributions to Clostridium difficile Virulence. mBio 2017; 8:mBio.00885-17. [PMID: 28790208 PMCID: PMC5550754 DOI: 10.1128/mbio.00885-17] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Clostridium difficile is a spore-forming anaerobic bacterium that causes colitis in patients with disrupted colonic microbiota. While some individuals are asymptomatic C. difficile carriers, symptomatic disease ranges from mild diarrhea to potentially lethal toxic megacolon. The wide disease spectrum has been attributed to the infected host’s age, underlying diseases, immune status, and microbiome composition. However, strain-specific differences in C. difficile virulence have also been implicated in determining colitis severity. Because patients infected with C. difficile are unique in terms of medical history, microbiome composition, and immune competence, determining the relative contribution of C. difficile virulence to disease severity has been challenging, and conclusions regarding the virulence of specific strains have been inconsistent. To address this, we used a mouse model to test 33 clinical C. difficile strains isolated from patients with disease severities ranging from asymptomatic carriage to severe colitis, and we determined their relative in vivo virulence in genetically identical, antibiotic-pretreated mice. We found that murine infections with C. difficile clade 2 strains (including multilocus sequence type 1/ribotype 027) were associated with higher lethality and that C. difficile strains associated with greater human disease severity caused more severe disease in mice. While toxin production was not strongly correlated with in vivo colonic pathology, the ability of C. difficile strains to grow in the presence of secondary bile acids was associated with greater disease severity. Whole-genome sequencing and identification of core and accessory genes identified a subset of accessory genes that distinguish high-virulence from lower-virulence C. difficile strains. Clostridium difficile is an important cause of hospital-associated intestinal infections, and recent years have seen an increase in the number and severity of cases in the United States. A patient’s antibiotic history, immune status, and medical comorbidities determine, in part, the severity of C. difficile infection. The relative virulence of different clinical C. difficile strains, although postulated to determine disease severity in patients, has been more difficult to consistently associate with mild versus severe colitis. We tested 33 distinct clinical C. difficile isolates for their ability to cause disease in genetically identical mice and found that C. difficile strains belonging to clade 2 were associated with higher mortality. Differences in survival were not attributed to differences in toxin production but likely resulted from the distinct gene content in the various clinical isolates.
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11
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Clostridium difficile Toxins TcdA and TcdB Cause Colonic Tissue Damage by Distinct Mechanisms. Infect Immun 2016; 84:2871-7. [PMID: 27456833 PMCID: PMC5038081 DOI: 10.1128/iai.00583-16] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 07/19/2016] [Indexed: 02/04/2023] Open
Abstract
As the major cause of antibiotic-associated diarrhea, Clostridium difficile is a serious problem in health care facilities worldwide. C. difficile produces two large toxins, TcdA and TcdB, which are the primary virulence factors in disease. The respective functions of these toxins have been difficult to discern, in part because the cytotoxicity profiles for these toxins differ with concentration and cell type. The goal of this study was to develop a cell culture model that would allow a side-by-side mechanistic comparison of the toxins. Conditionally immortalized, young adult mouse colonic (YAMC) epithelial cells demonstrate an exquisite sensitivity to both toxins with phenotypes that agree with observations in tissue explants. TcdA intoxication results in an apoptotic cell death that is dependent on the glucosyltransferase activity of the toxin. In contrast, TcdB has a bimodal mechanism; it induces apoptosis in a glucosyltransferase-dependent manner at lower concentrations and glucosyltransferase-independent necrotic death at higher concentrations. The direct comparison of the responses to TcdA and TcdB in cells and colonic explants provides the opportunity to unify a large body of observations made by many independent investigators.
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12
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Vidunas E, Mathews A, Weaver M, Cai P, Koh EH, Patel-Brown S, Yuan H, Zheng ZR, Carriere M, Johnson JE, Lotvin J, Moran J. Production and Characterization of Chemically Inactivated Genetically Engineered Clostridium difficile Toxoids. J Pharm Sci 2016; 105:2032-41. [DOI: 10.1016/j.xphs.2016.04.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 04/06/2016] [Accepted: 04/15/2016] [Indexed: 12/17/2022]
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13
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Nagahama M, Ohkubo A, Kinouchi Y, Kobayashi K, Miyamoto K, Takehara M, Sakurai J. Clostridium perfringens TpeL Induces Formation of Stress Fibers via Activation of RhoA-ROCK Signaling Pathway. Biol Pharm Bull 2016; 38:732-9. [PMID: 25947919 DOI: 10.1248/bpb.b14-00842] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Clostridium perfringens TpeL belongs to a family of large clostridial glucosylating cytotoxins. TpeL modifies Rac1 and Ras subfamily proteins. Herein we report TpeL-induced formation of stress fibers via RhoA-Rho kinase (ROCK) signaling. A recombinant protein (TpeL1-525) derived from the TpeL N-terminal catalytic domain in the presence of streptolysin O (SLO) induced the formation of actin stress fibers in Madin-Darby canine kidney (MDCK) cells in a dose-dependent manner. The RhoA/ROCK pathway is known to control the formation of stress fibers. We examined the role of the RhoA/ROCK pathway in TpeL-induced formation of stress fibers. TpeL1-525-induced formation of stress fibers was inhibited by the ROCK inhibitor, Y27632 and Rho protein inhibitor, C3 transferase. TpeL1-525 activated RhoA and ROCK in a dose-dependent manner. C3 transferase blocked TpeL1-525-induced activation of RhoA and ROCK whereas Y27632 inhibited TpeL-induced activation of ROCK. These results demonstrate for the first time that TpeL induces the formation of stress fibers by activating the RhoA/ROCK signaling pathway.
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Affiliation(s)
- Masahiro Nagahama
- Department of Microbiology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University
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14
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Lobet E, Letesson JJ, Arnould T. Mitochondria: a target for bacteria. Biochem Pharmacol 2015; 94:173-85. [PMID: 25707982 DOI: 10.1016/j.bcp.2015.02.007] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 02/12/2015] [Accepted: 02/12/2015] [Indexed: 01/12/2023]
Abstract
Eukaryotic cells developed strategies to detect and eradicate infections. The innate immune system, which is the first line of defence against invading pathogens, relies on the recognition of molecular patterns conserved among pathogens. Pathogen associated molecular pattern binding to pattern recognition receptor triggers the activation of several signalling pathways leading to the establishment of a pro-inflammatory state required to control the infection. In addition, pathogens evolved to subvert those responses (with passive and active strategies) allowing their entry and persistence in the host cells and tissues. Indeed, several bacteria actively manipulate immune system or interfere with the cell fate for their own benefit. One can imagine that bacterial effectors can potentially manipulate every single organelle in the cell. However, the multiple functions fulfilled by mitochondria especially their involvement in the regulation of innate immune response, make mitochondria a target of choice for bacterial pathogens as they are not only a key component of the central metabolism through ATP production and synthesis of various biomolecules but they also take part to cell signalling through ROS production and control of calcium homeostasis as well as the control of cell survival/programmed cell death. Furthermore, considering that mitochondria derived from an ancestral bacterial endosymbiosis, it is not surprising that a special connection does exist between this organelle and bacteria. In this review, we will discuss different mitochondrial functions that are affected during bacterial infection as well as different strategies developed by bacterial pathogens to subvert functions related to calcium homeostasis, maintenance of redox status and mitochondrial morphology.
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Affiliation(s)
- Elodie Lobet
- Laboratory of Biochemistry and Cellular Biology (URBC), NAmur Research Institute for LIfe Science (NARILIS), University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium.
| | - Jean-Jacques Letesson
- Research Unit in Microorganisms Biology, University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium.
| | - Thierry Arnould
- Laboratory of Biochemistry and Cellular Biology (URBC), NAmur Research Institute for LIfe Science (NARILIS), University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium.
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15
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Critical roles of Clostridium difficile toxin B enzymatic activities in pathogenesis. Infect Immun 2014; 83:502-13. [PMID: 25404023 DOI: 10.1128/iai.02316-14] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
TcdB is one of the key virulence factors of Clostridium difficile that is responsible for causing serious and potentially fatal colitis. The toxin contains at least two enzymatic domains: an effector glucosyltransferase domain for inactivating host Rho GTPases and a cysteine protease domain for the delivery of the effector domain into host cytosol. Here, we describe a novel intrabody approach to examine the role of these enzymes of TcdB in cellular intoxication. By screening a single-domain heavy chain (V(H)H) library raised against TcdB, we identified two V(H)H antibodies, 7F and E3, that specifically inhibit TcdB cysteine protease and glucosyltransferase activities, respectively. Cytoplasmic expression of 7F intrabody in Vero cells inhibited TcdB autoprocessing and delayed cellular intoxication, whereas E3 intrabody completely blocked the cytopathic effects of TcdB holotoxin. These data also demonstrate for the first time that toxin autoprocessing occurs after cysteine protease and glucosyltransferase domains translocate into the cytosol of target cells. We further determined the role of the enzymatic activities of TcdB in in vivo toxicity using a sensitive systemic challenge model in mice. Consistent with these in vitro results, a cysteine protease noncleavable mutant, TcdB-L543A, delayed toxicity in mice, whereas glycosyltransferase-deficient TcdB demonstrated no toxicity up to 500-fold of the 50% lethal dose (LD50) when it was injected systemically. Thus, glucosyltransferase but not cysteine protease activity is critical for TcdB-mediated cytopathic effects and TcdB systemic toxicity, highlighting the importance of targeting toxin glucosyltransferase activity for future therapy.
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16
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Genth H, Pauillac S, Schelle I, Bouvet P, Bouchier C, Varela-Chavez C, Just I, Popoff MR. Haemorrhagic toxin and lethal toxin from Clostridium sordellii strain vpi9048: molecular characterization and comparative analysis of substrate specificity of the large clostridial glucosylating toxins. Cell Microbiol 2014; 16:1706-21. [PMID: 24905543 DOI: 10.1111/cmi.12321] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 05/12/2014] [Accepted: 05/29/2014] [Indexed: 12/16/2022]
Abstract
Large clostridial glucosylating toxins (LCGTs) are produced by toxigenic strains of Clostridium difficile, Clostridium perfringens, Clostridium novyi and Clostridium sordellii. While most C. sordellii strains solely produce lethal toxin (TcsL), C. sordellii strain VPI9048 co-produces both hemorrhagic toxin (TcsH) and TcsL. Here, the sequences of TcsH-9048 and TcsL-9048 are provided, showing that both toxins retain conserved LCGT features and that TcsL and TcsH are highly related to Toxin A (TcdA) and Toxin B (TcdB) from C. difficile strain VPI10463. The substrate profile of the toxins was investigated with recombinant LCGT transferase domains (rN) and a wide panel of small GTPases. rN-TcsH-9048 and rN-TcdA-10463 glucosylated preferably Rho-GTPases but also Ras-GTPases to some extent. In this respect, rN-TcsH-9048 and rN-TcdA-10463 differ from the respective full-length TcsH-9048 and TcdA-10463, which exclusively glucosylate Rho-GTPases. rN-TcsL-9048 and full length TcsL-9048 glucosylate both Rho- and Ras-GTPases, whereas rN-TcdB-10463 and full length TcdB-10463 exclusively glucosylate Rho-GTPases. Vero cells treated with full length TcsH-9048 or TcdA-10463 also showed glucosylation of Ras, albeit to a lower extent than of Rho-GTPases. Thus, in vitro analysis of substrate spectra using recombinant transferase domains corresponding to the auto-proteolytically cleaved domains, predicts more precisely the in vivo substrates than the full length toxins. Except for TcdB-1470, all LCGTs evoked increased expression of the small GTPase RhoB, which exhibited cytoprotective activity in cells treated with TcsL isoforms, but pro-apoptotic activity in cells treated with TcdA, TcdB, and TcsH. All LCGTs induced a rapid dephosphorylation of pY118-paxillin and of pS144/141-PAK1/2 prior to actin filament depolymerization indicating that disassembly of focal adhesions is an early event leading to the disorganization of the actin cytoskeleton.
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Affiliation(s)
- Harald Genth
- Institute of Toxicology, Medical School Hannover, Hannover, Germany
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17
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Development and optimization of a high-throughput assay to measure neutralizing antibodies against Clostridium difficile binary toxin. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2014; 21:689-97. [PMID: 24623624 DOI: 10.1128/cvi.00038-14] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Clostridium difficile strains producing binary toxin, in addition to toxin A (TcdA) and toxin B (TcdB), have been associated with more severe disease and increased recurrence of C. difficile infection in recent outbreaks. Binary toxin comprises two subunits (CDTa and CDTb) and catalyzes the ADP-ribosylation of globular actin (G-actin), which leads to the depolymerization of filamentous actin (F-actin) filaments. A robust assay is highly desirable for detecting the cytotoxic effect of the toxin and the presence of neutralizing antibodies in animal and human sera to evaluate vaccine efficacy. We describe here the optimization, using design-of-experiment (DOE) methodology, of a high-throughput assay to measure the toxin potency and neutralizing antibodies (NAb) against binary toxin. Vero cells were chosen from a panel of cells screened for sensitivity and specificity. We have successfully optimized the CDTa-to-CDTb molar ratio, toxin concentration, cell-seeding density, and sera-toxin preincubation time in the NAb assay using DOE methodology. This assay is robust, produces linear results across serial dilutions of hyperimmune serum, and can be used to quantify neutralizing antibodies in sera from hamsters and monkeys immunized with C. difficile binary toxin-containing vaccines. The assay will be useful for C. difficile diagnosis, for epidemiology studies, and for selecting and optimizing vaccine candidates.
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18
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Swett RJ, Cisneros GA, Feig AL. Disruption of intrinsic motions as a mechanism for enzyme inhibition. Biophys J 2014; 105:494-501. [PMID: 23870270 DOI: 10.1016/j.bpj.2013.05.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 05/14/2013] [Accepted: 05/20/2013] [Indexed: 11/17/2022] Open
Abstract
Clostridium difficile (C. diff) is one of the most common and most severe hospital-acquired infections; its consequences range from lengthened hospital stay to outright lethality. C. diff causes cellular damage through the action of two large toxins TcdA and TcdB. Recently, there has been increased effort toward developing antitoxin therapies, rather than antibacterial treatments, in hopes of mitigating the acquisition of drug resistance. To date, no analysis of the recognition mechanism of TcdA or TcdB has been attempted. Here, we use small molecule flexible docking followed by unbiased molecular dynamics to obtain a more detailed perspective on how inhibitory peptides, exemplified by two species HQSPWHH and EGWHAHT function. Using principal component analysis and generalized masked Delaunay analysis, an examination of the conformational space of TcdB in its apo form as well as forms bound to the peptides and UDP-Glucose was performed. Although both species inhibit by binding in the active site, they do so in two very different ways. The simulations show that the conformational space occupied by TcdB bound to the two peptides are quite different and provide valuable insight for the future design of toxin inhibitors and other enzymes that interact with their substrates through conformational capture mechanisms and thus work by the disruption of the protein's intrinsic motions.
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Affiliation(s)
- Rebecca J Swett
- Department of Chemistry, Wayne State University, Detroit, Michigan, USA
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19
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Diagnosis of Clostridium difficile infection: an ongoing conundrum for clinicians and for clinical laboratories. Clin Microbiol Rev 2014; 26:604-30. [PMID: 23824374 DOI: 10.1128/cmr.00016-13] [Citation(s) in RCA: 277] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Clostridium difficile is a formidable nosocomial and community-acquired pathogen, causing clinical presentations ranging from asymptomatic colonization to self-limiting diarrhea to toxic megacolon and fulminant colitis. Since the early 2000s, the incidence of C. difficile disease has increased dramatically, and this is thought to be due to the emergence of new strain types. For many years, the mainstay of C. difficile disease diagnosis was enzyme immunoassays for detection of the C. difficile toxin(s), although it is now generally accepted that these assays lack sensitivity. A number of molecular assays are commercially available for the detection of C. difficile. This review covers the history and biology of C. difficile and provides an in-depth discussion of the laboratory methods used for the diagnosis of C. difficile infection (CDI). In addition, strain typing methods for C. difficile and the evolving epidemiology of colonization and infection with this organism are discussed. Finally, considerations for diagnosing C. difficile disease in special patient populations, such as children, oncology patients, transplant patients, and patients with inflammatory bowel disease, are described. As detection of C. difficile in clinical specimens does not always equate with disease, the diagnosis of C. difficile infection continues to be a challenge for both laboratories and clinicians.
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20
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Clostridium difficile toxin B-induced necrosis is mediated by the host epithelial cell NADPH oxidase complex. Proc Natl Acad Sci U S A 2013; 110:18674-9. [PMID: 24167244 DOI: 10.1073/pnas.1313658110] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Clostridium difficile infection (CDI) is a leading cause of health care-associated diarrhea and has increased in incidence and severity over the last decade. Pathogenesis is mediated by two toxins, TcdA and TcdB, which cause fluid secretion, inflammation, and necrosis of the colonic mucosa. TcdB is a potent cytotoxin capable of inducing enzyme-independent necrosis in both cells and tissue. In this study, we show that TcdB-induced cell death depends on assembly of the host epithelial cell NADPH oxidase (NOX) complex and the production of reactive oxygen species (ROS). Treating cells with siRNAs directed against key components of the NOX complex, chemical inhibitors of NOX function, or molecules that scavenge superoxide or ROS confers protection against toxin challenge. To test the hypothesis that chemical inhibition of TcdB-induced cytotoxicity can protect against TcdB-induced tissue damage, we treated colonic explants with diphenyleneiodonium (DPI), a flavoenzyme inhibitor, or N-acetylcysteine (NAC), an antioxidant. TcdB-induced ROS production in colonic tissue was inhibited with DPI, and both DPI and NAC conferred protection against TcdB-induced tissue damage. The efficacy of DPI and NAC provides proof of concept that chemical attenuation of ROS could serve as a viable strategy for protecting the colonic mucosa of patients with CDI.
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21
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Pant C, Deshpande A, Altaf MA, Minocha A, Sferra TJ. Clostridium difficile infection in children: a comprehensive review. Curr Med Res Opin 2013; 29:967-84. [PMID: 23659563 DOI: 10.1185/03007995.2013.803058] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
OBJECTIVE To provide a comprehensive review of the literature relating to Clostridium difficile (C. difficile) infection (CDI) in the pediatric population. METHODS Two investigators conducted independent searches of PubMed, Web of Science, and Scopus until March 31st, 2013. All databases were searched using the terms 'Clostridium difficile infection', 'Clostridium difficile associated diarrhea' 'antibiotic associated diarrhea', 'C. difficile', in combination with 'pediatric' and 'paediatric'. Articles which discussed pediatric CDI were reviewed and relevant cross references also read and evaluated for inclusion. Selection bias could be a possible limitation of this approach. FINDINGS There is strong evidence for an increased incidence of pediatric CDI. Increasingly, the infection is being acquired from the community, often without a preceding history of antibiotic use. The severity of the disease has remained unchanged. Several medical conditions may be associated with the development of pediatric CDI. Infection prevention and control with antimicrobial stewardship are of paramount importance. It is important to consider the age of the child while testing for CDI. Traditional therapy with metronidazole or vancomycin remains the mainstay of treatment. Newer antibiotics such as fidaxomicin appear promising especially for the treatment of recurrent infection. Conservative surgical options may be a life-saving measure in severe or fulminant cases. CONCLUSIONS Pediatric providers should be cognizant of the increased incidence of CDI in children. Early and judicious testing coupled with the timely institution of therapy will help to secure better outcomes for this disease.
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Affiliation(s)
- Chaitanya Pant
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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22
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Upregulation of the host SLC11A1 gene by Clostridium difficile toxin B facilitates glucosylation of Rho GTPases and enhances toxin lethality. Infect Immun 2013; 81:2724-32. [PMID: 23690404 DOI: 10.1128/iai.01177-12] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Pseudomembranous enterocolitis associated with Clostridium difficile infection is an important cause of morbidity and mortality in patients being treated with antibiotics. Two closely related large protein toxins produced by C. difficile, TcdA and TcdB, which act identically but at different efficiencies to glucosylate low-molecular-weight Rho GTPases, underlie the microbe's pathogenicity. Using antisense RNA encoded by a library of human expressed sequence tags (ESTs), we randomly inactivated host chromosomal genes in HeLa cells and isolated clones that survived exposure to ordinarily lethal doses of TcdB. This phenotypic screening and subsequent analysis identified solute carrier family 11 member 1 (SLC11A1; formerly NRAMP1), a divalent cation transporter crucial to host defense against certain microbes, as an enhancer of TcdB lethality. Whereas SLC11A1 normally is poorly expressed in human cells of nonmyeloid lineage, TcdB increased SLC11A1 mRNA abundance in such cells through the actions of the RNA-binding protein HuR. We show that short hairpin RNA (shRNA) directed against SLC11A1 reduced TcdB glucosylation of small Rho GTPases and, consequently, toxin lethality. Consistent with the previously known role of SLC11A1 in cation transport, these effects were enhanced by elevation of Mn(2+) in media; conversely, they were decreased by treatment with a chelator of divalent cations. Our findings reveal an unsuspected role for SLC11A1 in determining C. difficile pathogenicity, demonstrate the novel ability of a bacterial toxin to increase its cytotoxicity, establish a mechanistic basis for these effects, and suggest a therapeutic approach to mitigate cell killing by C. difficile toxins A and B.
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23
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Development and optimization of a novel assay to measure neutralizing antibodies against Clostridium difficile toxins. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2013; 20:517-25. [PMID: 23389929 DOI: 10.1128/cvi.00549-12] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Clostridium difficile produces two major virulence toxins, toxin A (TcdA) and toxin B (TcdB). Antitoxin antibodies, especially neutralizing antibodies, have been shown to be associated with a lower incidence of C. difficile infection (CDI) recurrence, and antibody levels are predictive of asymptomatic colonization. The development of an assay to detect the presence of neutralizing antibodies in animal and human sera for the evaluation of vaccine efficacy is highly desired. We have developed such an assay, which allows for the quantification of the effect of toxins on eukaryotic cells in an automated manner. We describe here the optimization of this assay to measure toxin potency as well as neutralizing antibody (NAb) activity against C. difficile toxins using a design-of-experiment (DOE) methodology. Toxin concentration and source, cell seeding density, and serum-toxin preincubation time were optimized in the assay using Vero cells. The assay was shown to be robust and to produce linear results across a range of antibody concentrations. It can be used to quantify neutralizing antibodies in sera of monkeys and hamsters immunized with C. difficile toxoid vaccines. This assay was shown to correlate strongly with traditional assays which rely on labor-intensive methods of determining neutralizing antibody titers by visual microscopic inspection of intoxicated-cell monolayers. This assay has utility for the selection and optimization of C. difficile vaccine candidates.
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24
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Li S, Shi L, Yang Z, Feng H. Cytotoxicity of Clostridium difficile toxin B does not require cysteine protease-mediated autocleavage and release of the glucosyltransferase domain into the host cell cytosol. Pathog Dis 2013; 67:11-8. [PMID: 23620115 DOI: 10.1111/2049-632x.12016] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 11/26/2012] [Accepted: 11/29/2012] [Indexed: 01/05/2023] Open
Abstract
Clostridium difficile virulence requires secretion of two exotoxins: TcdA and TcdB. The precise mechanism of toxin uptake and delivery is undefined, but current models predict that the cysteine protease domain (CPD)-mediated autocleavage and release of glucosyltransferase domain (GTD) are crucial for intoxication. To determine the importance of CPD-mediated cleavage to TcdB cytotoxicity, we generated two mutant toxins--TcdB-C698S and TcdB-H653A--and assayed their abilities to intoxicate cells. The CPD mutants include an intact GTD but lack the cysteine protease activity. The mutants had reduced potency in that their effect on cells was delayed and required higher concentrations than wild-type TcdB. They did eventually cause cell rounding, glucosylation of Rho GTPases, and apoptosis that was indistinguishable from that caused by TcdB. Although the mutant toxins caused a complete cell rounding, they failed to release their GTD into cytosol, whereas wild-type TcdB displayed significant autocleavage and release of GTD. We conclude that the cysteine protease-mediated autocleavage and release of GTD is not a prerequisite for the cytotoxic activity of TcdB, but rather limits the potency and speed of Rho GTPase glucosylation. Our findings revise and refine the current model for the mode of the action and cellular trafficking of TcdB.
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Affiliation(s)
- Shan Li
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, MD 21201, USA
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Nassour I, Carchman EH, Simmons RL, Zuckerbraun BS. Novel management strategies in the treatment of severe Clostridium difficile infection. Adv Surg 2012; 46:111-35. [PMID: 22873036 DOI: 10.1016/j.yasu.2012.03.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
CDI is increasing in incidence and severity. Clinicians must have a low threshold to consider the diagnosis and to treat patients with the clinical syndrome and risk factors before laboratory confirmation of the diagnosis. In patients who have signs of advanced disease, escalation of care with antimicrobial strategies and multidisciplinary care including surgical consultation is necessary. Furthermore, lowering the threshold for surgery compared with traditional approaches likely results in improved survival. Novel surgical approaches may obviate total abdominal colectomy and the associated immediate and long-term morbidity in this often fragile patient population, thus allowing clinicians to embrace surgical therapy earlier in the course of severe, complicated disease.
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Affiliation(s)
- Ibrahim Nassour
- Department of Surgery, University of Pittsburgh, 200 Lothrop Street, F1200 PUH, Pittsburgh, PA 15213, USA
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Rebeaud F, Bachmann MF. Immunization strategies for Clostridium difficile infections. Expert Rev Vaccines 2012; 11:469-79. [PMID: 22551032 DOI: 10.1586/erv.12.18] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Clostridium difficile infection is a major cause of nosocomial disease in Western countries. The recent emergence of hypervirulent strains resistant to most antibiotics correlates with increasing disease incidence, severity and lethal outcomes. Current treatments rely on metronidazol and vancomycin, but the limited ability of these antibiotics to cure infection and prevent relapse highlights the need for new strategies. A better knowledge of the molecular mechanisms of the disease, the host immune response and identification of key virulence factors of Clostridium difficile now permits the development of new products specifically targeting the pathogen. Immune-based strategies relying on active vaccination or passive administration of antibody products are the focus of intense research and, today, the efficacy of monoclonal antibodies and of two vaccines are evaluated clinically. This review presents recent data, discusses the different strategies and highlights the challenges linked to the development of immunization strategies against this emerging threat.
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Affiliation(s)
- Fabien Rebeaud
- Cytos Biotechnology AG, Wagistrasse 25, 8952 Schlieren, Switzerland
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D'Urzo N, Malito E, Biancucci M, Bottomley MJ, Maione D, Scarselli M, Martinelli M. The structure of Clostridium difficile toxin A glucosyltransferase domain bound to Mn2+ and UDP provides insights into glucosyltransferase activity and product release. FEBS J 2012; 279:3085-97. [PMID: 22747490 DOI: 10.1111/j.1742-4658.2012.08688.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Clostridiumdifficile toxin A (TcdA) is a member of the large clostridial toxin family, and is responsible, together with C. difficile toxin B (TcdB), for many clinical symptoms d ring human infections. Like other large clostridial toxins, TcdA catalyzes the glucosylation of GTPases, and is able to inactivate small GTPases within the host cell. Here, we report the crystal structures of the TcdA glucosyltransferase domain (TcdA-GT) in the apo form and in the presence of Mn(2+) and hydrolyzed UDP-glucose. These structures, together with the recently reported crystal structure of TcdA-GT bound to UDP-glucose, provide a detailed understanding of the conformational changes of TcdA that occur during the catalytic cycle. Indeed, we present a new intermediate conformation of a so-called 'lid' loop (residues 510-522 in TcdA), concomitant with the absence of glucose in the catalytic domain. The recombinant TcdA was expressed in Brevibacillus in the inactive apo form. High thermal stability of wild-type TcdA was observed only after the addition of both Mn(2+) and UDP-glucose. The glucosylhydrolase activity, which is readily restored after reconstitution with both these cofactors, was similar to that reported for TcdB. Interestingly, we found that ammonium, like K(+) , is able to activate the UDP-glucose hydrolase activities of TcdA. Consequently, the presence of ammonium in the crystallization buffer enabled us to obtain the first crystal structure of TcdA-GT bound to the hydrolysis product UDP.
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Ananthakrishnan AN. Detecting and treating Clostridium difficile infections in patients with inflammatory bowel disease. Gastroenterol Clin North Am 2012; 41:339-53. [PMID: 22500522 DOI: 10.1016/j.gtc.2012.01.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The prevalence of CDI in patients with IBD has increased over the last decade. The excess morbidity and mortality associated with CDI appears to be greater in patients with IBD than in those without preexisting bowel disease. The risk factors for CDI in IBD and non-IBD populations appear similar; unique IBD-related risk factors are use of maintenance immunosuppression and extent and severity of prior colitis. Nevertheless, a significant proportion of CDI-IBD patients may have the disease without traditional risk factors (ie, antibiotic use, recent hospitalization). The absence of such risk factors must not preclude considering CDI in the differential diagnosis of IBD patients presenting with a disease flare. Vancomycin and metronidazole appear to have similar efficacy with vancomycin being the preferred agent for severe disease. Early surgical consultation is key for improving outcomes of patients with severe disease. Several gaps in research exist; prospective multicenter cohorts of CDI-IBD are essential to improve our understanding of the impact of CDI on IBD patients and define appropriate therapeutic regimens to improve patient outcomes.
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Affiliation(s)
- Ashwin N Ananthakrishnan
- Massachusetts General Hospital, Harvard Medical School, 165 Cambridge Street, 9th Floor, Boston, MA 02114, USA.
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Carroll KC, Bartlett JG. Biology of Clostridium difficile: implications for epidemiology and diagnosis. Annu Rev Microbiol 2012; 65:501-21. [PMID: 21682645 DOI: 10.1146/annurev-micro-090110-102824] [Citation(s) in RCA: 172] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Clostridium difficile is an anaerobic, spore-forming, gram-positive rod that causes a spectrum of antibiotic-associated colitis through the elaboration of two large clostridial toxins and other virulence factors. Since its discovery in 1978 as the agent responsible for pseudomembranous colitis, the organism has continued to evolve into an adaptable, aggressive, hypervirulent strain. Advances in molecular methods and improved animal models have facilitated an understanding of how this organism survives in the environment, adapts to the gastrointestinal tract of animals and humans, and accomplishes its unique pathogenesis. The advances in microbiology have been accompanied by some important clinical observations including increased rates of C. difficile infection, increased virulence, and multiple outbreaks. The major new risk is fluoroquinolone use; there is also an association with proton pump inhibitors and increased recognition of cases in outpatients, pediatric patients, and patients without recent antibiotic use. The combination of more aggressive strains with mobile genomes in a setting of an expanded pool of individuals at risk has refocused attention on and challenged assumptions regarding diagnostic gold standards. Future research is likely to build upon the advancements in phylogenetics to create novel strategies for diagnosis, treatment, and prevention.
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Affiliation(s)
- Karen C Carroll
- Division of Medical Microbiology, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21205, USA.
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Pant C, Sferra TJ, Deshpande A, Minocha A. Clinical approach to severe Clostridium difficile infection: update for the hospital practitioner. Eur J Intern Med 2011; 22:561-8. [PMID: 22075280 DOI: 10.1016/j.ejim.2011.04.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Revised: 04/17/2011] [Accepted: 04/26/2011] [Indexed: 12/18/2022]
Abstract
The rising incidence of Clostridium difficile (C. difficile) infection or CDI is now a problem of pandemic proportions. The NAP1 hypervirulent strain of C. difficile is responsible for a majority of recent epidemics and the widespread use of fluoroquinolone antibiotics may have facilitated the selective proliferation of this strain. The NAP1 strain also is more likely to cause severe and fulminant colitis characterized by marked leukocytosis, renal failure, hemodynamic instability, and toxic megacolon. No single test suffices to diagnose severe CDI, instead; the clinician must rely on a combination of clinical acumen, laboratory testing, and radiologic and endoscopic modalities. Although oral vancomycin and metronidazole are considered standard therapies in the medical management of CDI, recently it has been demonstrated that vancomycin is the more effective antibiotic in cases of severe disease. Moreover, early surgical consultation is necessary in patients who do not respond to medical therapy or who demonstrate rising white blood cell counts or hemodynamic instability indicative of fulminant colitis. Subtotal colectomy with end ileostomy is the procedure of choice for fulminant colitis. When applied to select patients in a judicious and timely fashion, surgery can be a life-saving intervention. In addition to these therapeutic approaches, several investigational treatments including novel antibiotics, fecal bacteriotherapy and immunotherapy have shown promise in the care of patients with severe CDI.
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Affiliation(s)
- Chaitanya Pant
- Department of Pediatrics, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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Retargeting Clostridium difficile Toxin B to Neuronal Cells as a Potential Vehicle for Cytosolic Delivery of Therapeutic Biomolecules to Treat Botulism. J Toxicol 2011; 2012:760142. [PMID: 21941543 PMCID: PMC3177232 DOI: 10.1155/2012/760142] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 07/13/2011] [Indexed: 12/30/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) deliver a protease to neurons which can cause a flaccid paralysis called botulism. Development of botulism antidotes will require neuronal delivery of agents that inhibit or destroy the BoNT protease. Here, we investigated the potential of engineering Clostridium difficile toxin B (TcdB) as a neuronal delivery vehicle by testing two recombinant TcdB chimeras. For AGT-TcdB chimera, an alkyltransferase (AGT) was appended to the N-terminal glucosyltransferase (GT) of TcdB. Recombinant AGT-TcdB had alkyltransferase activity, and the chimera was nearly as toxic to Vero cells as wild-type TcdB, suggesting efficient cytosolic delivery of the AGT/GT fusion. For AGT-TcdB-BoNT/A-Hc, the receptor-binding domain (RBD) of TcdB was replaced by the equivalent RBD from BoNT/A (BoNT/A-Hc). AGT-TcdB-BoNT/A-Hc was >25-fold more toxic to neuronal cells and >25-fold less toxic to Vero cells than AGT-TcdB. Thus, TcdB can be engineered for cytosolic delivery of biomolecules and improved targeting of neuronal cells.
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Current Status of Nonantibiotic and Adjunct Therapies for Clostridium difficile Infection. Curr Infect Dis Rep 2011; 13:21-7. [PMID: 21308451 DOI: 10.1007/s11908-010-0155-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Clostridium difficile infection (CDI) is a leading cause of nosocomial infections and the most important cause of health care-associated diarrhea worldwide. Standard treatment of CDI consists of modifying underlying antibiotic exposure, aggressive supportive measures, and therapy with specific antibiotics, most commonly metronidazole or vancomycin. This general approach to CDI has remained largely unchanged for decades. In an effort to improve outcomes and reduce recurrences of CDI, interest has been renewed in the development of nonantibiotic and adjunct approaches to therapy. In this review, we highlight some of these recent, resurrected, and novel nonantibiotic treatments.
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Super toxins from a super bug: structure and function of Clostridium difficile toxins. Biochem J 2011; 436:517-26. [DOI: 10.1042/bj20110106] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Clostridium difficile, a highly infectious bacterium, is the leading cause of antibiotic-associated pseudomembranous colitis. In 2009, the number of death certificates mentioning C. difficile infection in the U.K. was estimated at 3933 with 44% of certificates recording infection as the underlying cause of death. A number of virulence factors facilitate its pathogenicity, among which are two potent exotoxins; Toxins A and B. Both are large monoglucosyltransferases that catalyse the glucosylation, and hence inactivation, of Rho-GTPases (small regulatory proteins of the eukaryote actin cell cytoskeleton), leading to disorganization of the cytoskeleton and cell death. The roles of Toxins A and B in the context of C. difficile infection is unknown. In addition to these exotoxins, some strains of C. difficile produce an unrelated ADP-ribosylating binary toxin. This toxin consists of two independently produced components: an enzymatic component (CDTa) and the other, the transport component (CDTb) which facilitates translocation of CDTa into target cells. CDTa irreversibly ADP-ribosylates G-actin in target cells, which disrupts the F-actin:G-actin equilibrium leading to cell rounding and cell death. In the present review we provide a summary of the current structural understanding of these toxins and discuss how it may be used to identify potential targets for specific drug design.
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Rational design of inhibitors and activity-based probes targeting Clostridium difficile virulence factor TcdB. ACTA ACUST UNITED AC 2011; 17:1201-11. [PMID: 21095570 DOI: 10.1016/j.chembiol.2010.09.011] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 09/30/2010] [Accepted: 09/30/2010] [Indexed: 01/05/2023]
Abstract
Clostridium difficile is a leading cause of nosocomial infections. The major virulence factors of this pathogen are the multi-domain toxins TcdA and TcdB. These toxins contain a cysteine protease domain (CPD) that autoproteolytically releases a cytotoxic effector domain upon binding intracellular inositol hexakisphosphate. Currently, there are no known inhibitors of this protease. Here, we describe the rational design of covalent small molecule inhibitors of TcdB CPD. We identified compounds that inactivate TcdB holotoxin function in cells and solved the structure of inhibitor-bound protease to 2.0 Å. This structure reveals the molecular basis of CPD substrate recognition and informed the synthesis of activity-based probes for this enzyme. The inhibitors presented will guide the development of therapeutics targeting C. difficile, and the probes will serve as tools for studying the unique activation mechanism of bacterial toxin CPDs.
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Abstract
The epidemiology of Clostridium difficile infection (CDI) has changed over the past decade. There has been a dramatic worldwide increase in its incidence, and new CDI populations are emerging, such as those with community-acquired infection and no previous exposure to antibiotics, children, pregnant women and patients with IBD. Diagnosis of CDI requires identification of C. difficile toxin A or B in diarrheal stool. The accuracy of current diagnostic tests remains inadequate and the optimal diagnostic testing algorithm has not been defined. The first-line agents for CDI treatment are metronidazole and vancomycin, with the latter being the preferred agent in patients with severe disease as it has significantly superior efficacy. The incidence of metronidazole treatment failures has increased, emphasizing the need to find alternative treatment options. Disease recurrence continues to occur in 20-40% of patients and its treatment remains challenging. In patients with CDI who develop fulminant colitis, early surgical consultation is essential. Intravenous immunoglobulin and tigecycline have been used in patients with severe refractory disease but delaying surgery may be associated with worse outcomes. Infection control measures are key to prevent horizontal transmission of infection. Ongoing research into effective treatment protocols and prevention is essential.
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36
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Lin YP, Kuo CJ, Koleci X, McDonough SP, Chang YF. Manganese binds to Clostridium difficile Fbp68 and is essential for fibronectin binding. J Biol Chem 2010; 286:3957-69. [PMID: 21062746 DOI: 10.1074/jbc.m110.184523] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Clostridium difficile is an etiological agent of pseudomembranous colitis and antibiotic-associated diarrhea. Adhesion is the crucial first step in bacterial infection. Thus, in addition to toxins, the importance of colonization factors in C. difficile-associated disease is recognized. In this study, we identified Fbp68, one of the colonization factors that bind to fibronectin (Fn), as a manganese-binding protein (K(D) = 52.70 ± 1.97 nM). Furthermore, the conformation of Fbp68 changed dramatically upon manganese binding. Manganese binding can also stabilize the structure of Fbp68 as evidenced by the increased T(m) measured by thermodenatured circular dichroism and differential scanning calorimetry (CD, T(m) = 58-65 °C; differential scanning calorimetry, T(m) = 59-66 °C). In addition, enhanced tolerance to protease K also suggests greatly improved stability of Fbp68 through manganese binding. Fn binding activity was found to be dependent on manganese due to the lack of binding by manganese-free Fbp68 to Fn. The C-terminal 194 amino acid residues of Fbp68 (Fbp68C) were discovered to bind to the N-terminal domain of Fn (Fbp68C-NTD, K(D) = 233 ± 10 nM, obtained from isothermal titration calorimetry). Moreover, adhesion of C. difficile to Caco-2 cells can be partially blocked if cells are pretreated with Fbp68C, and the binding of Fbp68C on Fn siRNA-transfected cells was significantly reduced. These results raise the possibility that Fbp68 plays a key role in C. difficile adherence on host cells to initiate infection.
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Affiliation(s)
- Yi-Pin Lin
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
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Souza Dias MB, Yamashiro J, Borrasca VL, Stempliuk VA, Araújo MRE, Costa SF, Levin AS. Pseudo-outbreak of Clostridium difficile associated diarrhea (CDAD) in a tertiary-care hospital. Rev Inst Med Trop Sao Paulo 2010; 52:133-7. [PMID: 20602022 DOI: 10.1590/s0036-46652010000300004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 05/06/2010] [Indexed: 01/26/2023] Open
Abstract
The objective of this study was to describe a pseudo-outbreak of C. difficile in a hospital, following a change in the method used to detect the toxin. In February 2002, there were two cases of CDAD and in March 7 occurred, coinciding with a change of the test (from detection of toxin A to toxin A/B). An outbreak was suspected. Active surveillance and education of staff were started. A CDAD case was defined as a patient with acute onset of diarrhea (> or = three episodes of liquid stools) and a positive stool test. They were classified as hospital or community-acquired. Stool samples were also collected for C. difficile culture and isolates were typed using AP-PCR. From March 2002 through December 2003 there were 138 cases of CDAD: 70% were hospital-acquired and among the 30% with CDAD present on admission, most (81%) came directly from the community (50% had no history of hospitalization). Fifty-two percent of hospital-acquired CDAD and 94% of cases on admission had already used antibiotics. The incidence of CDAD in hospitalized patients during surveillance was 3.3 per 1000 patient-admissions. The incidence of CDAD present on admission was 6.1/1000 patients. Sixteen isolates were typed and presented 13 different profiles. In conclusion, the CDAD increase in our study occurred due to change in diagnostic methods and not due to an outbreak, as suspected initially. The incidence in hospitalized patients was much lower than in reported outbreaks. There were 13 molecular types suggesting that an outbreak did not occur. CDAD was largely community-acquired.
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Ananthakrishnan AN, Binion DG. Impact of Clostridium difficile on inflammatory bowel disease. Expert Rev Gastroenterol Hepatol 2010; 4:589-600. [PMID: 20932144 DOI: 10.1586/egh.10.55] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Clostridium difficile infection (CDI) has been increasing in incidence among those with underlying inflammatory bowel disease (IBD) and is associated with substantial morbidity, the need for surgery and even mortality. The similar clinical presentation between CDI and a flare of underlying IBD makes prompt diagnosis essential to prevent deterioration which would accompany an escalation of immunosuppression in the absence of appropriate antibiotic therapy. Classical risk factors (antibiotic or healthcare exposure) or clinical findings (pseudomembranes) may not be found in many IBD patients with CDI and should not be considered essential for entertaining the diagnosis. Enzyme immunoassays detecting both toxins A and B remain the most widely used test for diagnosis and have acceptable sensitivity, but may require testing of multiple samples in select situations. Both vancomycin and metronidazole appear to be effective and treatment with oral vancomycin is preferred in those with severe disease, including those who require hospitalization. Appropriate infection control measures are essential to restrict patient-to-patient spread within healthcare environments and to prevent recurrences. Several novel therapies are currently under study, including new antibiotic agents and monoclonal antibodies targeted against the toxins. There is a need to broaden these studies to the IBD population. There is also the need to prospectively examine whether CDI has long-term disease-modifying consequences in those with underlying IBD.
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Ng J, Hirota SA, Gross O, Li Y, Ulke-Lemee A, Potentier MS, Schenck LP, Vilaysane A, Seamone ME, Feng H, Armstrong GD, Tschopp J, Macdonald JA, Muruve DA, Beck PL. Clostridium difficile toxin-induced inflammation and intestinal injury are mediated by the inflammasome. Gastroenterology 2010; 139:542-52, 552.e1-3. [PMID: 20398664 DOI: 10.1053/j.gastro.2010.04.005] [Citation(s) in RCA: 174] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 03/23/2010] [Accepted: 04/08/2010] [Indexed: 01/05/2023]
Abstract
BACKGROUND & AIMS Clostridium difficile-associated disease (CDAD) is the leading cause of nosocomial diarrhea in the United States. C difficile toxins TcdA and TcdB breach the intestinal barrier and trigger mucosal inflammation and intestinal damage. The inflammasome is an intracellular danger sensor of the innate immune system. In the present study, we hypothesize that TcdA and TcdB trigger inflammasome-dependent interleukin (IL)-1beta production, which contributes to the pathogenesis of CDAD. METHODS Macrophages exposed to TcdA and TcdB were assessed for IL-1beta production, an indication of inflammasome activation. Macrophages deficient in components of the inflammasome were also assessed. Truncated/mutated forms of TcdB were assessed for their ability to activate the inflammasome. The role of inflammasome signaling in vivo was assessed in ASC-deficient and IL-1 receptor antagonist-treated mice. RESULTS TcdA and TcdB triggered inflammasome activation and IL-1beta secretion in macrophages and human mucosal biopsy specimens. Deletion of Nlrp3 decreased, whereas deletion of ASC completely abolished, toxin-induced IL-1beta release. TcdB-induced IL-1beta release required recognition of the full-length toxin but not its enzymatic function. In vivo, deletion of ASC significantly reduced toxin-induced inflammation and damage, an effect that was mimicked by pretreatment with the IL-1 receptor antagonist anakinra. CONCLUSIONS TcdA and TcdB trigger IL-1beta release by activating an ASC-containing inflammasome, a response that contributes to toxin-induced inflammation and damage in vivo. Pretreating mice with the IL-1 receptor antagonist anakinra afforded the same level of protection that was observed in ASC-/- mice. These data suggest that targeting inflammasome or IL-1beta signaling may represent new therapeutic targets in the treatment of CDAD.
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Affiliation(s)
- Jeffrey Ng
- Department of Medicine, University of Calgary, Calgary, Alberta, Canada
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Shen A. Autoproteolytic activation of bacterial toxins. Toxins (Basel) 2010; 2:963-77. [PMID: 22069620 PMCID: PMC3153235 DOI: 10.3390/toxins2050963] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 04/28/2010] [Accepted: 05/05/2010] [Indexed: 01/05/2023] Open
Abstract
Protease domains within toxins typically act as the primary effector domain within target cells. By contrast, the primary function of the cysteine protease domain (CPD) in Multifunctional Autoprocessing RTX-like (MARTX) and Clostridium sp. glucosylating toxin families is to proteolytically cleave the toxin and release its cognate effector domains. The CPD becomes activated upon binding to the eukaryotic-specific small molecule, inositol hexakisphosphate (InsP6), which is found abundantly in the eukaryotic cytosol. This property allows the CPD to spatially and temporally regulate toxin activation, making it a prime candidate for developing anti-toxin therapeutics. In this review, we summarize recent findings related to defining the regulation of toxin function by the CPD and the development of inhibitors to prevent CPD-mediated activation of bacterial toxins.
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Affiliation(s)
- Aimee Shen
- Department of Pathology, Stanford School of Medicine, 300 Pasteur Drive, Stanford, California, USA.
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Ananthakrishnan AN, Issa M, Binion DG. Clostridium difficile and inflammatory bowel disease. Med Clin North Am 2010; 94:135-53. [PMID: 19944802 DOI: 10.1016/j.mcna.2009.08.013] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The past decade has seen an alarming increase in the burden of disease associated with Clostridium difficile. Several studies have now demonstrated an increasing incidence of C difficile infection in patients with inflammatory bowel disease (IBD) with a more severe course of disease compared with the non-IBD population. This article summarizes the available literature on the impact of C difficile infection on IBD and discusses the various diagnostic testing and treatment options available. Also reviewed are clinical situations specific to patients with IBD that are important for the treating physician to recognize.
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Mechanistic and structural insights into the proteolytic activation of Vibrio cholerae MARTX toxin. Nat Chem Biol 2009; 5:469-78. [PMID: 19465933 PMCID: PMC2783333 DOI: 10.1038/nchembio.178] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Accepted: 03/25/2009] [Indexed: 12/11/2022]
Abstract
MARTX toxins modulate the virulence of a number of Gram-negative Vibrio species. This family of toxins is defined by the presence of a cysteine protease domain (CPD), which proteolytically activates the Vibrio cholerae MARTX toxin. Although recent structural studies of the CPD have uncovered a novel allosteric activation mechanism, the mechanism of CPD substrate recognition or toxin processing is unknown. Here, we show that interdomain cleavage of MARTXVc enhances effector domain function. We also identify the first small molecule inhibitors of this protease domain and present the 2.35 Å structure of the CPD bound to one of these inhibitors. This structure, coupled with biochemical and mutational studies of the toxin, reveals the molecular basis of CPD substrate specificity and underscores the evolutionary relationship between the CPD and the clan CD caspase proteases. These studies are likely to prove valuable for devising novel anti-toxin strategies for a number of bacterial pathogens.
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Ananthakrishnan AN, Issa M, Binion DG. Clostridium difficile and inflammatory bowel disease. Gastroenterol Clin North Am 2009; 38:711-28. [PMID: 19913210 DOI: 10.1016/j.gtc.2009.07.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The past decade has seen an alarming increase in the burden of disease associated with Clostridium difficile. Several studies have now demonstrated an increasing incidence of C difficile infection in patients with inflammatory bowel disease (IBD) with a more severe course of disease compared with the non-IBD population. This article summarizes the available literature on the impact of C difficile infection on IBD and discusses the various diagnostic testing and treatment options available. Also reviewed are clinical situations specific to patients with IBD that are important for the treating physician to recognize.
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Affiliation(s)
- Ashwin N Ananthakrishnan
- Division of Gastroenterology and Hepatology, Medical College of Wisconsin, 9200 West Wisconsin Avenue, Milwaukee, WI 53226, USA
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Pei J, Lupardus PJ, Garcia KC, Grishin NV. CPDadh: a new peptidase family homologous to the cysteine protease domain in bacterial MARTX toxins. Protein Sci 2009; 18:856-62. [PMID: 19309740 DOI: 10.1002/pro.78] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A cysteine protease domain (CPD) has been recently discovered in a group of multifunctional, autoprocessing RTX toxins (MARTX) and Clostridium difficile toxins A and B. These CPDs (referred to as CPDmartx) autocleave the toxins to release domains with toxic effects inside host cells. We report identification and computational analysis of CPDadh, a new cysteine peptidase family homologous to CPDmartx. CPDadh and CPDmartx share a Rossmann-like structural core and conserved catalytic residues. In bacteria, domains of the CPDadh family are present at the N-termini of a diverse group of putative cell-cell interaction proteins and at the C-termini of some RHS (recombination hot spot) proteins. In eukaryotes, catalytically inactive members of the CPDadh family are found in cell surface protein NELF (nasal embryonic LHRH factor) and some putative signaling proteins.
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Affiliation(s)
- Jimin Pei
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9050, USA.
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Renewed interest in a difficult disease: Clostridium difficile infections--epidemiology and current treatment strategies. Curr Opin Gastroenterol 2009; 25:24-35. [PMID: 19114771 DOI: 10.1097/mog.0b013e32831da7c4] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
PURPOSE OF REVIEW Renewed interest in Clostridium difficile infections (CDI) is stimulating research into the pathogenesis and virulence factors for this pathogen. This review summarizes recent progress in the field, particularly in relation to the changing epidemiologic trends and new investigational treatments. RECENT FINDINGS Elucidation of the role of different toxins of C. difficile (tcdA, tcdB and binary toxin) is deepening our understanding of CDI. Stain typing of C. difficile isolates is documenting the spread of an emergent strain (BI/NAP1/027) associated with large outbreaks of severe disease. Typing of isolates around the world shows global spread of this strain. Reliance upon metronidazole is questioned due to a lower response rate and newer investigational therapies are reported. SUMMARY After being considered a manageable pathogen for decades, C. difficile recently caused large outbreaks of severe disease. Refocused research is determining patients who are at risk for CDI, what methods are more effective in diagnosing CDI and what new treatments may be effective. This article reviews the recent findings in the literature regarding this difficult and challenging pathogen.
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Affiliation(s)
- Ian R. Poxton
- Centre for Infectious Diseases, University of Edinburgh College of Medicine and Veterinary Medicine, The Chancellor's Building, 49 Little France Crescent, Edinburgh EH16 4SB, UK
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