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Costa DVS, Moura-Neto V, Bolick DT, Guerrant RL, Fawad JA, Shin JH, Medeiros PHQS, Ledwaba SE, Kolling GL, Martins CS, Venkataraman V, Warren CA, Brito GAC. S100B Inhibition Attenuates Intestinal Damage and Diarrhea Severity During Clostridioides difficile Infection by Modulating Inflammatory Response. Front Cell Infect Microbiol 2021; 11:739874. [PMID: 34568098 PMCID: PMC8461106 DOI: 10.3389/fcimb.2021.739874] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 08/11/2021] [Indexed: 12/12/2022] Open
Abstract
The involvement of the enteric nervous system, which is a source of S100B, in Clostridioides difficile (C. difficile) infection (CDI) is poorly understood although intestinal motility dysfunctions are known to occur following infection. Here, we investigated the role of S100B in CDI and examined the S100B signaling pathways activated in C. difficile toxin A (TcdA)- and B (TcdB)-induced enteric glial cell (EGC) inflammatory response. The expression of S100B was measured in colon tissues and fecal samples of patients with and without CDI, as well as in colon tissues from C. difficile-infected mice. To investigate the role of S100B signaling in IL-6 expression induced by TcdA and TcdB, rat EGCs were used. Increased S100B was found in colonic biopsies from patients with CDI and colon tissues from C. difficile-infected mice. Patients with CDI-promoted diarrhea exhibited higher levels of fecal S100B compared to non-CDI cases. Inhibition of S100B by pentamidine reduced the synthesis of IL-1β, IL-18, IL-6, GMCSF, TNF-α, IL-17, IL-23, and IL-2 and downregulated a variety of NFκB-related genes, increased the transcription (SOCS2 and Bcl-2) of protective mediators, reduced neutrophil recruitment, and ameliorated intestinal damage and diarrhea severity in mice. In EGCs, TcdA and TcdB upregulated S100B-mediated IL-6 expression via activation of RAGE/PI3K/NFκB. Thus, CDI appears to upregulate colonic S100B signaling in EGCs, which in turn augment inflammatory response. Inhibition of S100B activity attenuates the intestinal injury and diarrhea caused by C. difficile toxins. Our findings provide new insight into the role of S100B in CDI pathogenesis and opens novel avenues for therapeutic interventions.
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Affiliation(s)
- Deiziane V S Costa
- Department of Physiology and Pharmacology, Faculty of Medicine, Federal University of Ceará, Fortaleza, Brazil.,Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, VA, United States.,Department of Morphology, Faculty of Medicine, Federal University of Ceará, Fortaleza, Brazil
| | - Vivaldo Moura-Neto
- Paulo Niemeyer Brain Institute, Federal University of Rio de Janeiro, UFRJ, Rio de Janeiro, Brazil
| | - David T Bolick
- Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, VA, United States
| | - Richard L Guerrant
- Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, VA, United States
| | - Jibraan A Fawad
- Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, VA, United States
| | - Jae H Shin
- Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, VA, United States
| | - Pedro H Q S Medeiros
- Department of Microbiology, Faculty of Medicine, Federal University of Ceará, Fortaleza, Brazil
| | - Solanka E Ledwaba
- Department of Biochemistry and Microbiology, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa
| | - Glynis L Kolling
- Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, VA, United States
| | - Conceição S Martins
- Department of Physiology and Pharmacology, Faculty of Medicine, Federal University of Ceará, Fortaleza, Brazil
| | - Venkat Venkataraman
- Department of Cell Biology and Neuroscience, Rowan University School of Osteopathic Medicine, Stratford, NJ, United States.,Department of Rehabilitation Medicine, Rowan University School of Osteopathic Medicine, Stratford, NJ, United States
| | - Cirle A Warren
- Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, VA, United States
| | - Gerly A C Brito
- Department of Physiology and Pharmacology, Faculty of Medicine, Federal University of Ceará, Fortaleza, Brazil.,Department of Morphology, Faculty of Medicine, Federal University of Ceará, Fortaleza, Brazil
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52
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Fettucciari K, Marconi P, Marchegiani A, Fruganti A, Spaterna A, Bassotti G. Invisible steps for a global endemy: molecular strategies adopted by Clostridioides difficile. Therap Adv Gastroenterol 2021; 14:17562848211032797. [PMID: 34413901 PMCID: PMC8369858 DOI: 10.1177/17562848211032797] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Accepted: 06/26/2021] [Indexed: 02/06/2023] Open
Abstract
Clostridioides difficile infection (CDI) is on the rise worldwide and is associated with an increase in deaths and socio-health burden. C. difficile has become ubiquitous in anthropized environments because of the extreme resistance of its spores. Based on the epidemiological data and knowledge of molecular pathogenesis of C. difficile, it is possible to predict its progressive colonization of the human population for the following reasons: first, its global spread is unstoppable; second, the toxins (Tcds) produced by C. difficile, TcdA and TcdB, mainly cause cell death by apoptosis, but the surviving cells acquire a senescence state that favours persistence of C. difficile in the intestine; third, proinflammatory cytokines, tumour necrosis factor-α and interferon-γ, induced during CDI, enhance the cytotoxicity of Tcds and can increase the survival of senescent cells; fourth, Tcds block mobility and induce apoptosis in immune cells recruited at the infection site; and finally, after remission from primary infection or relapse, C. difficile causes functional abnormalities in the enteric glial cell (EGC) network that can result in irritable bowel syndrome, characterized by a latent inflammatory response that contributes to C. difficile survival and enhances the cytotoxic activity of low doses of TcdB, thus favouring further relapses. Since a 'global endemy' of C. difficile seems inevitable, it is necessary to develop an effective vaccine against Tcds for at-risk individuals, and to perform a prophylaxis/selective therapy with bacteriophages highly specific for C. difficile. We must be aware that CDI will become a global health problem in the forthcoming years, and we must be prepared to face this menace.
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Affiliation(s)
- Katia Fettucciari
- Biosciences & Medical Embryology Section, Department of Medicine and Surgery, University of Perugia, Medical School -Piazza Lucio Severi 1, Edificio B - IV piano; Sant’Andrea delle Fratte, Perugia, 06132, Italy
| | - Pierfrancesco Marconi
- Biosciences & Medical Embryology Section, Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - Andrea Marchegiani
- School of Biosciences and Veterinary Medicine, University of Camerino, Macerata, Italy
| | - Alessandro Fruganti
- School of Biosciences and Veterinary Medicine, University of Camerino, Macerata, Italy
| | - Andrea Spaterna
- School of Biosciences and Veterinary Medicine, University of Camerino, Macerata, Italy
| | - Gabrio Bassotti
- Gastroenterology, Hepatology & Digestive Endoscopy Section, Department of Medicine and Surgery, University of Perugia, Perugia, Italy
- Gastroenterology & Hepatology Unit, Santa Maria della Misericordia Hospital, Perugia, Italy
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53
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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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54
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Chen P, Zeng J, Liu Z, Thaker H, Wang S, Tian S, Zhang J, Tao L, Gutierrez CB, Xing L, Gerhard R, Huang L, Dong M, Jin R. Structural basis for CSPG4 as a receptor for TcdB and a therapeutic target in Clostridioides difficile infection. Nat Commun 2021; 12:3748. [PMID: 34145250 PMCID: PMC8213806 DOI: 10.1038/s41467-021-23878-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 05/19/2021] [Indexed: 12/13/2022] Open
Abstract
C. difficile is a major cause of antibiotic-associated gastrointestinal infections. Two C. difficile exotoxins (TcdA and TcdB) are major virulence factors associated with these infections, and chondroitin sulfate proteoglycan 4 (CSPG4) is a potential receptor for TcdB, but its pathophysiological relevance and the molecular details that govern recognition remain unknown. Here, we determine the cryo-EM structure of a TcdB–CSPG4 complex, revealing a unique binding site spatially composed of multiple discontinuous regions across TcdB. Mutations that selectively disrupt CSPG4 binding reduce TcdB toxicity in mice, while CSPG4-knockout mice show reduced damage to colonic tissues during C. difficile infections. We further show that bezlotoxumab, the only FDA approved anti-TcdB antibody, blocks CSPG4 binding via an allosteric mechanism, but it displays low neutralizing potency on many TcdB variants from epidemic hypervirulent strains due to sequence variations in its epitopes. In contrast, a CSPG4-mimicking decoy neutralizes major TcdB variants, suggesting a strategy to develop broad-spectrum therapeutics against TcdB. Chondroitin sulfate proteoglycan 4 (CSPG4) is a potential receptor for C. difficile toxin B (TcdB) during C. difficile infections (CDIs). Here, the cryo-EM structure of a TcdB–CSPG4 complex and CDI mouse models offer insights into CSPG4 role in CDIs and suggest a therapeutic strategy targeting TcdB.
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Affiliation(s)
- Peng Chen
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA
| | - Ji Zeng
- Department of Urology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.,Department of Microbiology, Harvard Medical School, Boston, MA, USA.,Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Zheng Liu
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA
| | - Hatim Thaker
- Department of Urology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.,Department of Microbiology, Harvard Medical School, Boston, MA, USA.,Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Siyu Wang
- Department of Urology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.,Department of Microbiology, Harvard Medical School, Boston, MA, USA.,Department of Surgery, Harvard Medical School, Boston, MA, USA.,Department of Gastrointestinal, Colorectal and Anal Surgery, China-Japan Union Hospital of Jilin University, Changchun, China
| | - Songhai Tian
- Department of Urology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.,Department of Microbiology, Harvard Medical School, Boston, MA, USA.,Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Jie Zhang
- Department of Urology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.,Department of Microbiology, Harvard Medical School, Boston, MA, USA.,Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Liang Tao
- Center for Infectious Disease Research, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China
| | - Craig B Gutierrez
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA
| | - Li Xing
- UC Irvine Materials Research Institute (IMRI), University of California, Irvine, CA, USA
| | - Ralf Gerhard
- Institute of Toxicology, Hannover Medical School, Hannover, Germany
| | - Lan Huang
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA
| | - Min Dong
- Department of Urology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA. .,Department of Microbiology, Harvard Medical School, Boston, MA, USA. .,Department of Surgery, Harvard Medical School, Boston, MA, USA.
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA.
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55
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Abstract
Large clostridial toxins (LCTs) are a family of bacterial exotoxins that infiltrate and destroy target cells. Members of the LCT family include Clostridioides difficile toxins TcdA and TcdB, Paeniclostridium sordellii toxins TcsL and TcsH, Clostridium novyi toxin TcnA, and Clostridium perfringens toxin TpeL. Since the 19th century, LCT-secreting bacteria have been isolated from the blood, organs, and wounds of diseased individuals, and LCTs have been implicated as the primary virulence factors in a variety of infections, including C. difficile infection and some cases of wound-associated gas gangrene. Clostridia express and secrete LCTs in response to various physiological signals. LCTs invade host cells by binding specific cell surface receptors, ultimately leading to internalization into acidified vesicles. Acidic pH promotes conformational changes within LCTs, which culminates in translocation of the N-terminal glycosyltransferase and cysteine protease domain across the endosomal membrane and into the cytosol, leading first to cytopathic effects and later to cytotoxic effects. The focus of this review is on the role of LCTs in infection and disease, the mechanism of LCT intoxication, with emphasis on recent structural work and toxin subtyping analysis, and the genomic discovery and characterization of LCT homologues. We provide a comprehensive review of these topics and offer our perspective on emerging questions and future research directions for this enigmatic family of toxins.
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56
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Faden H. Review and Commentary on the Importance of Bile Acids in the Life Cycle of Clostridioides difficile in Children and Adults. J Pediatric Infect Dis Soc 2021; 10:659-664. [PMID: 33626138 DOI: 10.1093/jpids/piaa150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 11/18/2020] [Indexed: 12/16/2022]
Abstract
Clostridioides difficile, a spore-forming anaerobe, resides in the intestine. The life cycle of C. difficile illustrates an interdependent relationship between bile acids, commensal microbiota, and C. difficile. Primary bile acids are critical for the germination of C. difficile spores in the small intestine, while secondary bile acids serve as a counterbalance to inhibit the growth of the organism in the colon. Many commensal bacteria especially Clostridium spp. are responsible for transforming primary bile acids into secondary bile acids. Antibiotics eliminate bacteria that convert primary bile acids into secondary bile acids and, thus, allow C. difficile to flourish and cause diarrhea. In children younger than 2 years of age, who normally only produce primary bile acids, colonization with toxin-producing C. difficile is exceedingly common. The reason for the absence of C. difficile diarrhea in the children remains unexplained.
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Affiliation(s)
- Howard Faden
- Department of Pediatrics, Division of Infectious Diseases, Jacobs School of Medicine and Biomedical Sciences, State University of New York, Buffalo, New York, USA
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57
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Sulfated glycosaminoglycans and low-density lipoprotein receptor mediate the cellular entry of Clostridium novyi alpha-toxin. Cell Res 2021; 31:935-938. [PMID: 33972749 PMCID: PMC8107810 DOI: 10.1038/s41422-021-00510-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Accepted: 04/10/2021] [Indexed: 11/13/2022] Open
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58
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Asadpoor M, Ithakisiou GN, Henricks PAJ, Pieters R, Folkerts G, Braber S. Non-Digestible Oligosaccharides and Short Chain Fatty Acids as Therapeutic Targets against Enterotoxin-Producing Bacteria and Their Toxins. Toxins (Basel) 2021; 13:175. [PMID: 33668708 PMCID: PMC7996226 DOI: 10.3390/toxins13030175] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 02/08/2021] [Accepted: 02/17/2021] [Indexed: 02/07/2023] Open
Abstract
Enterotoxin-producing bacteria (EPB) have developed multiple mechanisms to disrupt gut homeostasis, and provoke various pathologies. A major part of bacterial cytotoxicity is attributed to the secretion of virulence factors, including enterotoxins. Depending on their structure and mode of action, enterotoxins intrude the intestinal epithelium causing long-term consequences such as hemorrhagic colitis. Multiple non-digestible oligosaccharides (NDOs), and short chain fatty acids (SCFA), as their metabolites produced by the gut microbiota, interact with enteropathogens and their toxins, which may result in the inhibition of the bacterial pathogenicity. NDOs characterized by diverse structural characteristics, block the pathogenicity of EPB either directly, by inhibiting bacterial adherence and growth, or biofilm formation or indirectly, by promoting gut microbiota. Apart from these abilities, NDOs and SCFA can interact with enterotoxins and reduce their cytotoxicity. These anti-virulent effects mostly rely on their ability to mimic the structure of toxin receptors and thus inhibiting toxin adherence to host cells. This review focuses on the strategies of EPB and related enterotoxins to impair host cell immunity, discusses the anti-pathogenic properties of NDOs and SCFA on EPB functions and provides insight into the potential use of NDOs and SCFA as effective agents to fight against enterotoxins.
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Affiliation(s)
- Mostafa Asadpoor
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands; (M.A.); (G.-N.I.); (P.A.J.H.); (G.F.)
| | - Georgia-Nefeli Ithakisiou
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands; (M.A.); (G.-N.I.); (P.A.J.H.); (G.F.)
| | - Paul A. J. Henricks
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands; (M.A.); (G.-N.I.); (P.A.J.H.); (G.F.)
| | - Roland Pieters
- Division of Medicinal Chemistry and Chemical Biology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands;
| | - Gert Folkerts
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands; (M.A.); (G.-N.I.); (P.A.J.H.); (G.F.)
| | - Saskia Braber
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands; (M.A.); (G.-N.I.); (P.A.J.H.); (G.F.)
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59
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Pan Z, Zhang Y, Luo J, Li D, Zhou Y, He L, Yang Q, Dong M, Tao L. Functional analyses of epidemic Clostridioides difficile toxin B variants reveal their divergence in utilizing receptors and inducing pathology. PLoS Pathog 2021; 17:e1009197. [PMID: 33507919 PMCID: PMC7842947 DOI: 10.1371/journal.ppat.1009197] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 11/30/2020] [Indexed: 02/06/2023] Open
Abstract
Clostridioides difficile toxin B (TcdB) is a key virulence factor that causes C. difficile associated diseases (CDAD) including diarrhea and pseudomembranous colitis. TcdB can be divided into multiple subtypes/variants based on their sequence variations, of which four (TcdB1-4) are dominant types found in major epidemic isolates. Here, we find that these variants are highly diverse in their receptor preference: TcdB1 uses two known receptors CSPG4 and Frizzled (FZD) proteins, TcdB2 selectively uses CSPG4, TcdB3 prefers to use FZDs, whereas TcdB4 uses neither CSPG4 nor FZDs. By creating chimeric toxins and systematically switching residues between TcdB1 and TcdB3, we determine that regions in the N-terminal cysteine protease domain (CPD) are involved in CSPG4-recognition. We further evaluate the pathological effects induced by TcdB1-4 with a mouse intrarectal installation model. TcdB1 leads to the most severe overall symptoms, followed by TcdB2 and TcdB3. When comparing the TcdB2 and TcdB3, TcdB2 causes stronger oedema while TcdB3 induces severer inflammatory cell infiltration. These findings together demonstrate divergence in the receptor preference and further lead to colonic pathology for predominant TcdB subtypes. Clostridioides difficile is a major cause of nosocomial and community-associated gastrointestinal infections. The bacterium produces three exotoxins including TcdA, TcdB, and CDT, of which TcdB is known as a key virulence factor causing the diseases. Since C. difficile was first linked to antibiotic-associated infections in 1978, a large number of clinically relevant strains were characterized and many of them were found to harbor some variant forms of TcdB. In this study, we examined four predominant TcdB variants from epidemic C. difficile strains. We found that these variants are highly diverse in preference to the known receptors, CSPG4 and Frizzled proteins. By conducting a systematically designed mutagenesis study, we determined that TcdB interacts with CSPG4 via regions across multiple domains. We also found that TcdB variants could induce distinguishable pathological phenotypes in a mouse model, suggesting C. difficile strains harboring divergent TcdB variants might exhibit different disease progression. Our study provides new insights into the toxicology and pathology of C. difficile toxin variants.
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Affiliation(s)
- Zhenrui Pan
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Yuanyuan Zhang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Jianhua Luo
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Danyang Li
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Yao Zhou
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Liuqing He
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Qi Yang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Min Dong
- Department of Urology, Boston Children’s Hospital, Boston, Massechusetts, United States of America
- Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, Massechusetts, United States of America
- * E-mail: (MD); (LT)
| | - Liang Tao
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
- * E-mail: (MD); (LT)
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60
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Extra-Intestinal Effects of C. difficile Toxin A and B: An In Vivo Study Using the Zebrafish Embryo Model. Cells 2020; 9:cells9122575. [PMID: 33271969 PMCID: PMC7760802 DOI: 10.3390/cells9122575] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/27/2020] [Accepted: 11/29/2020] [Indexed: 12/18/2022] Open
Abstract
C.difficile infection (CDI) is not a merely “gut-confined” disease as toxemia could drive the development of CDI-related extra-intestinal effects. These effects could explain the high CDI-associated mortality, not just justified by diarrhea and dehydration. Here, the extra-intestinal effects of toxin A (TcdA) and B (TcdB) produced by C. difficile have been studied in vivo using the zebrafish embryo model. Noteworthy, protective properties of human serum albumin (HSA) towards toxins-induced extra-intestinal effects were also addressed. Zebrafish embryos were treated with TcdA, TcdB and/or HSA at 24 h post-fertilization. Embryos were analyzed for 48 h after treatment to check vital signs and morphological changes. Markers related to cardio-vascular damage and inflammation were evaluated by Real-Time quantitative PCR and/or western blotting. Both toxins induced cardiovascular damage in zebrafish embryos by different mechanisms: (i) direct toxicity (i.e., pericardial edema, cardiac chambers enlargement, endothelial alteration); (ii) increased hormonal production and release (i.e., atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP)), (iii) alteration of the vascular system through the increase of the vascular endothelial growth factor (VEGF-A) levels, as well as of its receptors, (iv) pro-inflammatory response through high cytokines production (i.e., CXCL8, IL1B, IL6 and TNFα) and (v) cell-mediated damage due to the increase in neutrophils number. In addition to cardiovascular damage, we observe skin alteration and inflammation. Finally, our data indicate a protective effect of HSA toward the toxins induced extra-intestinal effects. Together, our findings can serve as a starting point for humans’ studies to substantiate and understand the extra-intestinal effects observed in CDI patients.
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Henkel D, Tatge H, Schöttelndreier D, Tao L, Dong M, Gerhard R. Receptor Binding Domains of TcdB from Clostridioides difficile for Chondroitin Sulfate Proteoglycan-4 and Frizzled Proteins Are Functionally Independent and Additive. Toxins (Basel) 2020; 12:toxins12120736. [PMID: 33255261 PMCID: PMC7759879 DOI: 10.3390/toxins12120736] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 11/18/2020] [Accepted: 11/19/2020] [Indexed: 02/06/2023] Open
Abstract
Toxin B (TcdB) produced by Clostridioides difficile is a main pathogenicity factor that affects a variety of different cell types within the colonic mucosa. TcdB is known to utilize frizzled-1,2,7 and chondroitin sulfate proteoglycan-4 (CSPG4) as protein receptors. By using human cervical cancer cell line HeLa CSPG4 knockout (CSPG4−/−) cells as well as TcdB mutants which do not bind to either CSPG4 or frizzled-1,2,7, or both, we evaluated the impact of the individual receptors for cytopathic and cytotoxic effects of TcdB. We compared TcdB from the reference strain VPI10463 (TcdBVPI) and the endemic strain R20291 (TcdBR20) which does not interact with frizzled-1,2,7. TcdBVPI devoid of CSPG4 binding (TcdBVPI ΔCROP) shows identical cytopathic potency as full-length TcdB in HeLa CSPG4−/− cells, indicating that interaction with frizzled proteins is not affected in the presence of the C-terminal CROP domain. We validated CSPG4 as cellular receptor for both TcdB toxinotypes in HeLa and HEp-2 cells. By exchange of a single phenylalanine residue, 1597 with serine, we generated a mutated TcdBVPI variant (TcdBVPI F1597S) that in accordance with TcdBR20 lacks binding to frizzled-1,2,7 and showed identical potency as TcdBR20 on HeLa cells. This enabled us to estimate the respective share of CSPG4 and frizzled-1,2,7 in the cytotoxic and cytopathic effect induced by TcdB. Our data reveal that binding to frizzled-1,2,7 and to CSPG4 occurs independently and in an additive manner.
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Affiliation(s)
- Daniel Henkel
- Institute of Toxicology, Hannover Medical School, 30625 Hannover, Germany; (D.H.); (H.T.); (D.S.)
| | - Helma Tatge
- Institute of Toxicology, Hannover Medical School, 30625 Hannover, Germany; (D.H.); (H.T.); (D.S.)
| | - Dennis Schöttelndreier
- Institute of Toxicology, Hannover Medical School, 30625 Hannover, Germany; (D.H.); (H.T.); (D.S.)
| | - Liang Tao
- Department of Urology, Boston Children’s Hospital, Boston, MA 02115, USA; (L.T.); (M.D.)
- Departments of Surgery and Microbiology, Harvard Medical School, Boston, MA 02115, USA
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Westlake University Hangzhou, Hangzhou 310000, China
| | - Min Dong
- Department of Urology, Boston Children’s Hospital, Boston, MA 02115, USA; (L.T.); (M.D.)
- Departments of Surgery and Microbiology, Harvard Medical School, Boston, MA 02115, USA
| | - Ralf Gerhard
- Institute of Toxicology, Hannover Medical School, 30625 Hannover, Germany; (D.H.); (H.T.); (D.S.)
- Correspondence:
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62
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Danz HR, Lee S, Chapman-Bonofiglio SP, Ginese M, Beamer G, Girouard DJ, Tzipori S. The Impact of Actotoxumab Treatment of Gnotobiotic Piglets Infected With Different Clostridium difficile Isogenic Mutants. J Infect Dis 2020; 221:276-284. [PMID: 31495879 DOI: 10.1093/infdis/jiz459] [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: 05/17/2019] [Accepted: 09/06/2019] [Indexed: 11/14/2022] Open
Abstract
Nosocomial infections with Clostridium difficile are on the rise in the Unites States, attributed to emergence of antibiotic-resistant and hypervirulent strains associated with greater likelihood of recurrent infections. In addition to antibiotics, treatment with Merck anti-toxin B (TcdB) antibody bezlotoxumab is reported to reduce recurrent infections. However, treatment with anti-toxin A (TcdA) antibody actotoxumab was associated with dramatically increased disease severity and mortality rates in humans and gnotobiotic piglets. Using isogenic mutants of C. difficile strain NAPI/BI/027 deficient in TcdA (A-B+) or TcdB (A+B-), and the wild type, we investigated how and why treatment of infected animals with anti-TcdA dramatically increased disease severity. Contrary to the hypothesis, among piglets treated with anti-TcdA, those with A+B- infection were disease free, in contrast to the disease enhancement seen in those with wild-type or A-B+ infection. It seems that the lack of TcdA, through either deletion or neutralization with anti-TcdA, reduces a competitive pressure, allowing TcdB to freely exert its profound effect, leading to increased mucosal injury and disease severity.
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Affiliation(s)
- Hillary R Danz
- Department of Infectious Diseases and Global Health, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts, USA
| | - Sangun Lee
- Department of Infectious Diseases and Global Health, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts, USA
| | - Susan P Chapman-Bonofiglio
- Department of Infectious Diseases and Global Health, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts, USA
| | - Melanie Ginese
- Department of Infectious Diseases and Global Health, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts, USA
| | - Gillian Beamer
- Department of Infectious Diseases and Global Health, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts, USA
| | - Donald J Girouard
- Department of Infectious Diseases and Global Health, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts, USA
| | - Saul Tzipori
- Department of Infectious Diseases and Global Health, Cummings School of Veterinary Medicine at Tufts University, North Grafton, Massachusetts, USA
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63
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Bilverstone TW, Garland M, Cave RJ, Kelly ML, Tholen M, Bouley DM, Kaye P, Minton NP, Bogyo M, Kuehne SA, Melnyk RA. The glucosyltransferase activity of C. difficile Toxin B is required for disease pathogenesis. PLoS Pathog 2020; 16:e1008852. [PMID: 32960931 PMCID: PMC7531778 DOI: 10.1371/journal.ppat.1008852] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 10/02/2020] [Accepted: 08/03/2020] [Indexed: 01/01/2023] Open
Abstract
Enzymatic inactivation of Rho-family GTPases by the glucosyltransferase domain of Clostridioides difficile Toxin B (TcdB) gives rise to various pathogenic effects in cells that are classically thought to be responsible for the disease symptoms associated with C. difficile infection (CDI). Recent in vitro studies have shown that TcdB can, under certain circumstances, induce cellular toxicities that are independent of glucosyltransferase (GT) activity, calling into question the precise role of GT activity. Here, to establish the importance of GT activity in CDI disease pathogenesis, we generated the first described mutant strain of C. difficile producing glucosyltransferase-defective (GT-defective) toxin. Using allelic exchange (AE) technology, we first deleted tcdA in C. difficile 630Δerm and subsequently introduced a deactivating D270N substitution in the GT domain of TcdB. To examine the role of GT activity in vivo, we tested each strain in two different animal models of CDI pathogenesis. In the non-lethal murine model of infection, the GT-defective mutant induced minimal pathology in host tissues as compared to the profound caecal inflammation seen in the wild-type and 630ΔermΔtcdA (ΔtcdA) strains. In the more sensitive hamster model of CDI, whereas hamsters in the wild-type or ΔtcdA groups succumbed to fulminant infection within 4 days, all hamsters infected with the GT-defective mutant survived the 10-day infection period without primary symptoms of CDI or evidence of caecal inflammation. These data demonstrate that GT activity is indispensable for disease pathogenesis and reaffirm its central role in disease and its importance as a therapeutic target for small-molecule inhibition.
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Affiliation(s)
- Terry W. Bilverstone
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, Centre for Biomolecular Sciences, The University of Nottingham, Nottingham, United kingdom
| | - Megan Garland
- Cancer Biology Program, Stanford School of Medicine, Stanford, CA, United States of America
- Department of Pathology, Stanford School of Medicine, Stanford, CA, United States of America
| | - Rory J. Cave
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, Centre for Biomolecular Sciences, The University of Nottingham, Nottingham, United kingdom
| | - Michelle L. Kelly
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, Centre for Biomolecular Sciences, The University of Nottingham, Nottingham, United kingdom
| | - Martina Tholen
- Department of Pathology, Stanford School of Medicine, Stanford, CA, United States of America
| | - Donna M. Bouley
- Department of Comparative Medicine, Stanford School of Medicine, Stanford, CA, United States of America
| | - Philip Kaye
- Department of Histopathology, Nottingham University Hospitals and University of Nottingham NDDC NIHR BRC, Nottingham, United Kingdom
| | - Nigel P. Minton
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre, School of Life Sciences, Centre for Biomolecular Sciences, The University of Nottingham, Nottingham, United kingdom
- NIHR Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust and the University of Nottingham, Nottingham, United Kingdom
| | - Matthew Bogyo
- Department of Pathology, Stanford School of Medicine, Stanford, CA, United States of America
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, CA, United States of America
| | - Sarah A. Kuehne
- Oral Microbiology Group, School of Dentistry and Institute of Microbiology and Infection, College of Medical and Dental Sciences, The University of Birmingham, Birmingham, United Kingdom
| | - Roman A. Melnyk
- Department of Biochemistry, University of Toronto, and Program in Molecular Medicine, The Hospital for Sick Children, Toronto, ON, Canada
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64
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Lee H, Beilhartz GL, Kucharska I, Raman S, Cui H, Lam MHY, Liang H, Rubinstein JL, Schramek D, Julien JP, Melnyk RA, Taipale M. Recognition of Semaphorin Proteins by P. sordellii Lethal Toxin Reveals Principles of Receptor Specificity in Clostridial Toxins. Cell 2020; 182:345-356.e16. [PMID: 32589945 PMCID: PMC7316060 DOI: 10.1016/j.cell.2020.06.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 05/06/2020] [Accepted: 06/01/2020] [Indexed: 01/03/2023]
Abstract
Pathogenic clostridial species secrete potent toxins that induce severe host tissue damage. Paeniclostridium sordellii lethal toxin (TcsL) causes an almost invariably lethal toxic shock syndrome associated with gynecological infections. TcsL is 87% similar to C. difficile TcdB, which enters host cells via Frizzled receptors in colon epithelium. However, P. sordellii infections target vascular endothelium, suggesting that TcsL exploits another receptor. Here, using CRISPR/Cas9 screening, we establish semaphorins SEMA6A and SEMA6B as TcsL receptors. We demonstrate that recombinant SEMA6A can protect mice from TcsL-induced edema. A 3.3 Å cryo-EM structure shows that TcsL binds SEMA6A with the same region that in TcdB binds structurally unrelated Frizzled. Remarkably, 15 mutations in this evolutionarily divergent surface are sufficient to switch binding specificity of TcsL to that of TcdB. Our findings establish semaphorins as physiologically relevant receptors for TcsL and reveal the molecular basis for the difference in tissue targeting and disease pathogenesis between highly related toxins.
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Affiliation(s)
- Hunsang Lee
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Greg L Beilhartz
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Iga Kucharska
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Swetha Raman
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Hong Cui
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Mandy Hiu Yi Lam
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Huazhu Liang
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - John L Rubinstein
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada
| | - Daniel Schramek
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Jean-Philippe Julien
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Immunology, University of Toronto, Toronto, ON M5S 1A8, Canada; Molecular Architecture of Life Program, Canadian Institute for Advanced Research (CIFAR), Toronto, ON M5G 1M1, Canada.
| | - Roman A Melnyk
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - Mikko Taipale
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON M5S 3E1, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada; Molecular Architecture of Life Program, Canadian Institute for Advanced Research (CIFAR), Toronto, ON M5G 1M1, Canada.
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65
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Shen E, Zhu K, Li D, Pan Z, Luo Y, Bian Q, He L, Song X, Zhen Y, Jin D, Tao L. Subtyping analysis reveals new variants and accelerated evolution of Clostridioides difficile toxin B. Commun Biol 2020; 3:347. [PMID: 32620855 PMCID: PMC7335066 DOI: 10.1038/s42003-020-1078-y] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 06/16/2020] [Indexed: 02/06/2023] Open
Abstract
Clostridioides difficile toxins (TcdA and TcdB) are major exotoxins responsible for C. difficile infection (CDI) associated diseases. The previously reported TcdB variants showed distinct biological features, immunoactivities, and potential pathogenicity in disease progression. Here, we performed global comparisons of amino acid sequences of both TcdA and TcdB from 3,269 C. difficile genomes and clustered them according to the evolutionary relatedness. We found that TcdB was much diverse and could be divided into eight subtypes, of which four were first described. Further analysis indicates that the tcdB gene undergoes accelerated evolution to maximize diversity. By tracing TcdB subtypes back to their original isolates, we found that the distribution of TcdB subtypes was not completely aligned with the phylogeny of C. difficile. These findings suggest that the tcdB genes not only frequently mutate, but also continuously transfer and exchange among C. difficile strains. Shen et al. compare the amino acid sequences of bacterial toxins TcdA and TcdB from 3,269 Clostridioides difficile genomes to identify four new TcdB subtypes. They find that TcdB was more diverse in amino acid sequence than TcdA. This study suggests that the tcdB genes not only frequently mutate, but they also continuously transfer and exchange among C. difficile strains.
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Affiliation(s)
- Enhui Shen
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Kangli Zhu
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Danyang Li
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Zhenrui Pan
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Yun Luo
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, 310051, China.,School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Qiao Bian
- School of Medicine, Ningbo University, Ningbo, Zhejiang, 315211, China
| | - Liuqing He
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Xiaojun Song
- Centre of Laboratory Medicine, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, Zhejiang, 310014, China
| | - Ying Zhen
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Dazhi Jin
- Centre of Laboratory Medicine, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, Zhejiang, 310014, China.,School of Laboratory Medicine, Hangzhou Medical College, Hangzhou, Zhejiang, 310053, China
| | - Liang Tao
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China. .,Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China.
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66
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Li Z, Lee K, Rajyaguru U, Jones CH, Janezic S, Rupnik M, Anderson AS, Liberator P. Ribotype Classification of Clostridioides difficile Isolates Is Not Predictive of the Amino Acid Sequence Diversity of the Toxin Virulence Factors TcdA and TcdB. Front Microbiol 2020; 11:1310. [PMID: 32636819 PMCID: PMC7318873 DOI: 10.3389/fmicb.2020.01310] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 05/25/2020] [Indexed: 12/18/2022] Open
Abstract
Clostridioides (Clostridium) difficile is the most commonly recognized cause of infectious diarrhea in healthcare settings. Currently there is no vaccine to prevent initial or recurrent C. difficile infection (CDI). Two large clostridial toxins, TcdA and TcdB, are the primary virulence factors for CDI. Immunological approaches to prevent CDI include antibody-mediated neutralization of the cytotoxicity of these toxins. An understanding of the sequence diversity of the two toxins expressed by disease causing isolates is critical for the interpretation of the immune response to the toxins. In this study, we determined the whole genome sequence (WGS) of 478 C. difficile isolates collected in 12 countries between 2004 and 2018 to probe toxin variant diversity. A total of 44 unique TcdA variants and 37 unique TcdB variants were identified. The amino acid sequence conservation among the TcdA variants (≥98%) is considerably greater than among the TcdB variants (as low as 86.1%), suggesting that different selection pressures may have contributed to the evolution of the two toxins. Phylogenomic analysis of the WGS data demonstrate that isolates grouped together based on ribotype or MLST code for multiple different toxin variants. These findings illustrate the importance of determining not only the ribotype but also the toxin sequence when evaluating strain coverage using vaccine strategies that target these virulence factors. We recommend that toxin variant type and sequence type (ST), be used together with ribotype data to provide a more comprehensive strain classification scheme for C. difficile surveillance during vaccine development objectives.
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Affiliation(s)
- Zhenghui Li
- Vaccine Research and Development, Pfizer Inc., Pearl River, NY, United States
| | - Kwok Lee
- Vaccine Research and Development, Pfizer Inc., Pearl River, NY, United States
| | - Urvi Rajyaguru
- Vaccine Research and Development, Pfizer Inc., Pearl River, NY, United States
| | - C Hal Jones
- Vaccine Research and Development, Pfizer Inc., Pearl River, NY, United States
| | - Sandra Janezic
- National Laboratory for Health, Environment and Food, Maribor, Slovenia.,Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | - Maja Rupnik
- National Laboratory for Health, Environment and Food, Maribor, Slovenia.,Faculty of Medicine, University of Maribor, Maribor, Slovenia
| | | | - Paul Liberator
- Vaccine Research and Development, Pfizer Inc., Pearl River, NY, United States
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67
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Varela-Chavez C, Blondel A, Popoff MR. Bacterial intracellularly active toxins: Membrane localisation of the active domain. Cell Microbiol 2020; 22:e13213. [PMID: 32353188 DOI: 10.1111/cmi.13213] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 04/06/2020] [Accepted: 04/17/2020] [Indexed: 12/31/2022]
Abstract
Numerous bacterial toxins exert their activity by inactivating or modulating a specific intracellular host target. For this purpose, these toxins have developed efficient strategies to overcome the different host cell defences including specific binding to cell surface, internalisation, passage through the endosome or plasma membrane, exploiting intracellular trafficking and addressing to intracellular targets. Several intracellularly active toxins deliver an active domain into the cytosol that interacts with a target localised to the inner face of the plasma membrane. Thus, the large clostridial glucosylating toxins (LCGTs) target Rho/Ras-GTPases, certain virulence factors of Gram negative bacteria, Rho-GTPases, while Pasteurella multocida toxin (PMT) targets trimeric G-proteins. Others such as botulinum neurotoxins and tetanus neurotoxin have their substrate on synaptic vesicle membrane. LCGTs, PMT, and certain virulence factors from Vibrio sp. show a particular structure constituted of a four-helix bundle membrane (4HBM) protruding from the catalytic site that specifically binds to the membrane phospholipids and then trap the catalytic domain at the proximity of the membrane anchored substrate. Structural and functional analysis indicate that the 4HBM tip of the Clostridium sordellii lethal toxin (TcsL) from the LCGT family contain two loops forming a cavity that mediates the binding to phospholipids and more specifically to phosphatidylserine.
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Affiliation(s)
| | - Arnaud Blondel
- Unité de Bio-Informatique Structurale, Institut Pasteur, Paris, France
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68
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Identification of the role of toxin B in the virulence of Clostridioides difficile based on integrated bioinformatics analyses. Int Microbiol 2020; 23:575-587. [PMID: 32388701 DOI: 10.1007/s10123-020-00128-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 03/03/2020] [Accepted: 04/13/2020] [Indexed: 02/08/2023]
Abstract
PURPOSE Clostridioides difficile toxin B (TcdB) plays a critical role in C. difficile infection (CDI), a common and costly healthcare-associated disease. The aim of the current study was to explore the intracellular and potent systemic effects of TcdB on human colon epithelial cells utilizing Gene Expression Omnibus and bioinformatic methods. METHODS Two datasets (GSE63880 and GSE29008) were collected to extract data components of mRNA of TcdB-treated human colon epithelial cells; "limma" package of "R" software was used to screen the differential genes, and "pheatmap" package was applied to construct heat maps for the differential genes; Metascape website was utilized for protein-protein interaction network and Molecular Complex Detection analysis, and Genome Ontology (GO) was used to analyze the selected differential genes. Quantitative real-time PCR (qRT-PCR) and Western blot were performed to validate the expression of hub genes. RESULTS GO terms involved in DNA replication and cell cycle were identified significantly enriched in TcdB-treated human colon epithelial cells. Moreover, the decreased expression of DNA replication-related genes, MCM complex, and CDC45 in C. difficile (TcdA-/TcdB+)-infected Caco-2 cells were validated via qRT-PCR and Western blot assays. CONCLUSIONS In conclusion, the integrated analysis of different gene expression datasets allowed us to identify a set of genes and GO terms underlying the mechanisms of CDI induced by TcdB. It would aid in understanding of the molecular mechanisms underlying TcdB-exposed colon epithelial cells and provide the basis for developing diagnosis biomarkers, treatment, and prevention strategies.
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69
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Tian S, Liu Y, Wu H, Liu H, Zeng J, Choi MY, Chen H, Gerhard R, Dong M. Genome-Wide CRISPR Screen Identifies Semaphorin 6A and 6B as Receptors for Paeniclostridium sordellii Toxin TcsL. Cell Host Microbe 2020; 27:782-792.e7. [PMID: 32302524 DOI: 10.1016/j.chom.2020.03.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 02/04/2020] [Accepted: 03/11/2020] [Indexed: 01/21/2023]
Abstract
The exotoxin TcsL is a major virulence factor in Paeniclostridium (Clostridium) sordellii and responsible for the high lethality rate associated with P. sordellii infection. Here, we present a genome-wide CRISPR-Cas9-mediated screen using a human lung carcinoma cell line and identify semaphorin (SEMA) 6A and 6B as receptors for TcsL. Disrupting SEMA6A/6B expression in several distinct human cell lines and primary human endothelial cells results in reduced TcsL sensitivity, while SEMA6A/6B over-expression increases their sensitivity. TcsL recognizes the extracellular domain (ECD) of SEMA6A/6B via a region homologous to the receptor-binding site in Clostridioides difficile toxin B (TcdB), which binds the human receptor Frizzled. Exchanging the receptor-binding interfaces between TcsL and TcdB switches their receptor-binding specificity. Finally, administration of SEMA6A-ECD proteins protects human cells from TcsL toxicity and reduces TcsL-induced damage to lung tissues and the lethality rate in mice. These findings establish SEMA6A and 6B as pathophysiologically relevant receptors for TcsL.
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Affiliation(s)
- Songhai Tian
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA; Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA
| | - Yang Liu
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA; Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA; Department of Nephrology, The First Hospital of Jilin University, Changchun 130012, China
| | - Hao Wu
- The Vascular Biology Program, Department of Surgery, Boston Children's Hospital and Harvard Medical School, MA 02115, USA
| | - Hao Liu
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA; Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA
| | - Ji Zeng
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA; Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA
| | - Mei Yuk Choi
- Division of Genetics, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Hong Chen
- The Vascular Biology Program, Department of Surgery, Boston Children's Hospital and Harvard Medical School, MA 02115, USA
| | - Ralf Gerhard
- Institute of Toxicology, Hannover Medical School, Hannover, 30625, Germany
| | - Min Dong
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA; Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA.
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70
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Clostridioides difficile infection damages colonic stem cells via TcdB, impairing epithelial repair and recovery from disease. Proc Natl Acad Sci U S A 2020; 117:8064-8073. [PMID: 32198200 DOI: 10.1073/pnas.1915255117] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Gastrointestinal infections often induce epithelial damage that must be repaired for optimal gut function. While intestinal stem cells are critical for this regeneration process [R. C. van der Wath, B. S. Gardiner, A. W. Burgess, D. W. Smith, PLoS One 8, e73204 (2013); S. Kozar et al., Cell Stem Cell 13, 626-633 (2013)], how they are impacted by enteric infections remains poorly defined. Here, we investigate infection-mediated damage to the colonic stem cell compartment and how this affects epithelial repair and recovery from infection. Using the pathogen Clostridioides difficile, we show that infection disrupts murine intestinal cellular organization and integrity deep into the epithelium, to expose the otherwise protected stem cell compartment, in a TcdB-mediated process. Exposure and susceptibility of colonic stem cells to intoxication compromises their function during infection, which diminishes their ability to repair the injured epithelium, shown by altered stem cell signaling and a reduction in the growth of colonic organoids from stem cells isolated from infected mice. We also show, using both mouse and human colonic organoids, that TcdB from epidemic ribotype 027 strains does not require Frizzled 1/2/7 binding to elicit this dysfunctional stem cell state. This stem cell dysfunction induces a significant delay in recovery and repair of the intestinal epithelium of up to 2 wk post the infection peak. Our results uncover a mechanism by which an enteric pathogen subverts repair processes by targeting stem cells during infection and preventing epithelial regeneration, which prolongs epithelial barrier impairment and creates an environment in which disease recurrence is likely.
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71
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Intestinal bile acids directly modulate the structure and function of C. difficile TcdB toxin. Proc Natl Acad Sci U S A 2020; 117:6792-6800. [PMID: 32152097 DOI: 10.1073/pnas.1916965117] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Intestinal bile acids are known to modulate the germination and growth of Clostridioides difficile Here we describe a role for intestinal bile acids in directly binding and neutralizing TcdB toxin, the primary determinant of C. difficile disease. We show that individual primary and secondary bile acids reversibly bind and inhibit TcdB to varying degrees through a mechanism that requires the combined oligopeptide repeats region to which no function has previously been ascribed. We find that bile acids induce TcdB into a compact "balled up" conformation that is no longer able to bind cell surface receptors. Lastly, through a high-throughput screen designed to identify bile acid mimetics we uncovered nonsteroidal small molecule scaffolds that bind and inhibit TcdB through a bile acid-like mechanism. In addition to suggesting a role for bile acids in C. difficile pathogenesis, these findings provide a framework for development of a mechanistic class of C. difficile antitoxins.
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72
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The C. difficile toxin B membrane translocation machinery is an evolutionarily conserved protein delivery apparatus. Nat Commun 2020; 11:432. [PMID: 31974369 PMCID: PMC6978384 DOI: 10.1038/s41467-020-14306-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 12/19/2019] [Indexed: 12/13/2022] Open
Abstract
Large Clostridial Toxins (LCTs) are a family of six homologous protein toxins that are implicated in severe disease. LCTs infiltrate host cells using a translocation domain (LCT-T) that contains both cell-surface receptor binding sites and a membrane translocation apparatus. Despite much effort, LCT translocation remains poorly understood. Here we report the identification of 1104 LCT-T homologs, with 769 proteins from bacteria outside of clostridia. Sequences are widely distributed in pathogenic and host-associated species, in a variety of contexts and architectures. Consistent with these homologs being functional toxins, we show that a distant LCT-T homolog from Serratia marcescens acts as a pH-dependent translocase to deliver its effector into host cells. Based on evolutionary footprinting of LCT-T homologs, we further define an evolutionarily conserved translocase region that we show is an autonomous translocase capable of delivering heterologous cargo into host cells. Our work uncovers a broad class of translocating toxins and provides insights into LCT translocation. Large Clostridial toxins infiltrate host cells using a translocation domain (LCT-T). Here, using a genomics-driven approach and functional assays, the authors uncover the presence of distant LCT-T homologs in bacteria outside clostridia and provide evidence for a toxic effector function in the gammaproteobacterium Serratia marcescens.
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73
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Zhang X, Yue D, Wang Y, Zhou Y, Liu Y, Qiu Y, Tian F, Yu Y, Zhou Z, Wei W. PASTMUS: mapping functional elements at single amino acid resolution in human cells. Genome Biol 2019; 20:279. [PMID: 31842968 PMCID: PMC6913009 DOI: 10.1186/s13059-019-1897-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 11/22/2019] [Indexed: 11/10/2022] Open
Abstract
Identification of functional elements for a protein of interest is important for achieving a mechanistic understanding. However, it remains cumbersome to assess each and every amino acid of a given protein in relevance to its functional significance. Here, we report a strategy, PArsing fragmented DNA Sequences from CRISPR Tiling MUtagenesis Screening (PASTMUS), which provides a streamlined workflow and a bioinformatics pipeline to identify critical amino acids of proteins in their native biological contexts. Using this approach, we map six proteins-three bacterial toxin receptors and three cancer drug targets, and acquire their corresponding functional maps at amino acid resolution.
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Affiliation(s)
- 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
| | - Di Yue
- 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
| | - Yinan Wang
- 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
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Yuexin 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
| | - Ying 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
| | - Yeting Qiu
- 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
| | - Feng Tian
- 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
| | - Ying Yu
- 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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74
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Immunogenicity and Protection from Receptor-Binding Domains of Toxins as Potential Vaccine Candidates for Clostridium difficile. Vaccines (Basel) 2019; 7:vaccines7040180. [PMID: 31717334 PMCID: PMC6963439 DOI: 10.3390/vaccines7040180] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 11/04/2019] [Accepted: 11/06/2019] [Indexed: 01/05/2023] Open
Abstract
The receptor-binding domains (RBDs) located in toxin A and toxin B of Clostridium difficile are known to be nontoxic and immunogenic. We need to develop a new type vaccine based on RBDs. In this study, we expressed and purified recombinant proteins (named RBD-TcdA and RBD-TcdB) as vaccine candidates containing the RBDs of toxin A and toxin B, respectively, from the C. difficile reference strain VPI10463. The immunogenicity and protection of the vaccine candidates RBD-TcdA, RBD-TcdB, and RBD-TcdA/B was evaluated by ELISA and survival assays. The data indicated that mice immunized with all vaccine candidates displayed potent levels of RBD-specific serum IgG. Following intramuscular immunization of mice with RBD-TcdA and/or RBD-TcdB, these vaccine candidates triggered immune responses that protected mice compared to mice immunized with aluminum hydroxide alone. Taken together, the results of this study reveal that recombinant proteins containing RBDs of C. difficile toxins can be used for vaccine development. Additionally, we found that an RBD-TcdA/B vaccine can elicit a stronger humoral immune response and provide better immunoprotection than the univalent vaccines. This RBD vaccine candidate conferred significant protection against disease symptoms and death caused by toxins from a wild-type C. difficile strain.
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75
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Peng Z, Simeon R, Mitchell SB, Zhang J, Feng H, Chen Z. Designed Ankyrin Repeat Protein (DARPin) Neutralizers of TcdB from Clostridium difficile Ribotype 027. mSphere 2019; 4:e00596-19. [PMID: 31578248 PMCID: PMC6796971 DOI: 10.1128/msphere.00596-19] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 09/11/2019] [Indexed: 02/08/2023] Open
Abstract
Clostridium difficile infection (CDI) is a leading cause of hospital-acquired diarrhea. In recent decades, the emergence of the "hypervirulent" BI/NAP1/027 strains of C. difficile significantly increased the morbidity and mortality of CDI. The pathogenesis of CDI is primarily mediated by the action of two toxins, TcdA and TcdB, with TcdB being the major virulent factor in humans. In this report, we describe the engineering of a panel of designed ankyrin repeat proteins (DARPins) that potently neutralize TcdB from the BI/NAP1/027 strains (e.g., TcdBUK1). The most effective DARPin, D16, inhibits TcdBUK1 with a 50% effective concentration (EC50) of 0.5 nM, which is >66-fold lower than that of the FDA-approved anti-TcdB antibody bezlotoxumab (EC50, ∼33 nM). Competitive enzyme-linked immunosorbent assays (ELISAs) showed that D16 blocks interactions between TcdB and its receptor, chondroitin sulfate proteoglycan 4 (CSPG4). The dimeric DARPin U3D16, which pairs D16 with DARPin U3, a disrupter of the interaction of TcdB with Frizzled 1/2/7 receptor, exhibits 10-fold-to-20-fold-enhanced neutralization potency against TcdB from C. difficile strains VPI 10463 (laboratory strain) and M68 (CF/NAP9/017) but identical activity against TcdBUK1 relative to D16. Subsequent ELISAs revealed that TcdBUK1 did not significantly interact with Frizzled 1/2/7. Computation modeling revealed 4 key differences at the Frizzled 1/2/7 binding interface which are likely responsible for the significantly reduced binding affinity.IMPORTANCE We report the engineering and characterization of designed ankyrin proteins as potent neutralizers of TcdB toxin secreted by a hypervirulent ribotype 027 strain of Clostridium difficile We further show that although TcdB toxins from both ribotype 027 and VPI 10461 interact efficiently with TcdB receptors CSPG4 and Pvrl3, TcdB027 lacks significant ability to bind the only known physiologically relevant TcdB receptor, Frizzled 1/2/7.
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Affiliation(s)
- Zeyu Peng
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, College Station, Texas, USA
| | - Rudo Simeon
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, College Station, Texas, USA
| | - Samuel B Mitchell
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, College Station, Texas, USA
| | - Junjie Zhang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | - Hanping Feng
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, Maryland, USA
| | - Zhilei Chen
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, College Station, Texas, USA
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76
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Silva-García O, Valdez-Alarcón JJ, Baizabal-Aguirre VM. Wnt/β-Catenin Signaling as a Molecular Target by Pathogenic Bacteria. Front Immunol 2019; 10:2135. [PMID: 31611869 PMCID: PMC6776594 DOI: 10.3389/fimmu.2019.02135] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 08/27/2019] [Indexed: 12/31/2022] Open
Abstract
The Wnt/β-catenin signaling pathway is crucial to regulate cell proliferation and polarity, cell determination, and tissue homeostasis. The activation of Wnt/β-catenin signaling is based on the interaction between Wnt glycoproteins and seven transmembrane receptors-Frizzled (Fzd). This binding promotes recruitment of the scaffolding protein Disheveled (Dvl), which results in the phosphorylation of the co-receptor LRP5/6. The resultant molecular complex Wnt-Fzd-LRP5/6-Dvl forms a structural region for Axin interaction that disrupts Axin-mediated phosphorylation/degradation of the transcriptional co-activator β-catenin, thereby allowing it to stabilize and accumulate in the nucleus where it activates the expression of Wnt-dependent genes. Due to the prominent physiological function, the Wnt/β-catenin signaling must be strictly controlled because its dysregulation, which is caused by different stimuli, may lead to alterations in cell proliferation, apoptosis, and inflammation-associated cancer. The virulence factors from pathogenic bacteria such as Salmonella enterica sv Typhimurium, Helicobacter pylori, Mycobacterium tuberculosis, Pseudomonas aeruginosa, Citrobacter rodentium, Clostridium difficile, Bacteroides fragilis, Escherichia coli, Haemophilus parasuis, Lawsonia intracellularis, Shigella dysenteriae, and Staphylococcus epidermidis employ a variety of molecular strategies to alter the appropriate functioning of diverse signaling pathways. Among these, Wnt/β-catenin has recently emerged as an important target of several virulence factors produced by bacteria. The mechanisms used by these factors to interfere with the activity of Wnt/β-catenin is diverse and include the repression of Wnt inhibitors' expression by the epigenetic modification of histones, blocking Wnt-Fzd ligand binding, activation or inhibition of β-catenin nuclear translocation, down- or up-regulation of Wnt family members, and inhibition of Axin-1 expression that promotes β-catenin activity. Such a variety of mechanisms illustrate an evolutionary co-adaptation of eukaryotic molecular signaling to a battery of soluble or structural components synthesized by pathogenic bacteria. This review gathers the recent efforts to elucidate the mechanistic details through which bacterial virulence factors modulate Wnt/β-catenin signaling and its physiological consequences concerning the inflammatory response and cancer.
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Affiliation(s)
| | - Juan J Valdez-Alarcón
- Centro Multidisciplinario de Estudios en Biotecnología, Facultad de Medicina Veterinaria y Zootecnia, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Mexico
| | - Víctor M Baizabal-Aguirre
- Centro Multidisciplinario de Estudios en Biotecnología, Facultad de Medicina Veterinaria y Zootecnia, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Mexico
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77
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Chen P, Lam KH, Liu Z, Mindlin FA, Chen B, Gutierrez CB, Huang L, Zhang Y, Hamza T, Feng H, Matsui T, Bowen ME, Perry K, Jin R. Structure of the full-length Clostridium difficile toxin B. Nat Struct Mol Biol 2019; 26:712-719. [PMID: 31308519 PMCID: PMC6684407 DOI: 10.1038/s41594-019-0268-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 06/07/2019] [Indexed: 01/07/2023]
Abstract
Clostridium difficile is an opportunistic pathogen that establishes in the colon when the gut microbiota are disrupted by antibiotics or disease. C. difficile infection (CDI) is largely caused by two virulence factors, TcdA and TcdB. Here, we report a 3.87-Å-resolution crystal structure of TcdB holotoxin that captures a unique conformation of TcdB at endosomal pH. Complementary biophysical studies suggest that the C-terminal combined repetitive oligopeptides (CROPs) domain of TcdB is dynamic and can sample open and closed conformations that may facilitate modulation of TcdB activity in response to environmental and cellular cues during intoxication. Furthermore, we report three crystal structures of TcdB-antibody complexes that reveal how antibodies could specifically inhibit the activities of individual TcdB domains. Our studies provide novel insight into the structure and function of TcdB holotoxin and identify intrinsic vulnerabilities that could be exploited to develop new therapeutics and vaccines for the treatment of CDI.
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Affiliation(s)
- Peng Chen
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Kwok-Ho Lam
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Zheng Liu
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Frank A Mindlin
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Baohua Chen
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Craig B Gutierrez
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Lan Huang
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Yongrong Zhang
- Department of Microbial Pathogenesis, University of Maryland Baltimore, Baltimore, MD, USA
| | - Therwa Hamza
- Department of Microbial Pathogenesis, University of Maryland Baltimore, Baltimore, MD, USA
| | - Hanping Feng
- Department of Microbial Pathogenesis, University of Maryland Baltimore, Baltimore, MD, USA
| | - Tsutomu Matsui
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, USA
| | - Mark E Bowen
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Kay Perry
- NE-CAT and Department of Chemistry and Chemical Biology, Cornell University, Argonne National Laboratory, Argonne, IL, USA
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA.
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López-Ureña D, Orozco-Aguilar J, Chaves-Madrigal Y, Ramírez-Mata A, Villalobos-Jimenez A, Ost S, Quesada-Gómez C, Rodríguez C, Papatheodorou P, Chaves-Olarte E. Toxin B Variants from Clostridium difficile Strains VPI 10463 and NAP1/027 Share Similar Substrate Profile and Cellular Intoxication Kinetics but Use Different Host Cell Entry Factors. Toxins (Basel) 2019; 11:toxins11060348. [PMID: 31212980 PMCID: PMC6628394 DOI: 10.3390/toxins11060348] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 05/14/2019] [Indexed: 02/07/2023] Open
Abstract
Clostridium difficile induces antibiotic-associated diarrhea due to the release of toxin A (TcdA) and toxin B (TcdB), the latter being its main virulence factor. The epidemic strain NAP1/027 has an increased virulence attributed to different factors. We compared cellular intoxication by TcdBNAP1 with that by the reference strain VPI 10463 (TcdBVPI). In a mouse ligated intestinal loop model, TcdBNAP1 induced higher neutrophil recruitment, cytokine release, and epithelial damage than TcdBVPI. Both toxins modified the same panel of small GTPases and exhibited similar in vitro autoprocessing kinetics. On the basis of sequence variations in the frizzled-binding domain (FBD), we reasoned that TcdBVPI and TcdBNAP1 might have different receptor specificities. To test this possibility, we used a TcdB from a NAP1 variant strain (TcdBNAP1v) unable to glucosylate RhoA but with the same receptor-binding domains as TcdBNAP1. Cells were preincubated with TcdBNAP1v to block cellular receptors, prior to intoxication with either TcdBVPI or TcdBNAP1. Preincubation with TcdBNAP1v blocked RhoA glucosylation by TcdBNAP1 but not by TcdBVPI, indicating that the toxins use different host factors for cell entry. This crucial difference might explain the increased biological activity of TcdBNAP1 in the intestine, representing a contributing factor for the increased virulence of the NAP1/027 strain.
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Affiliation(s)
- Diana López-Ureña
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - Josué Orozco-Aguilar
- Facultad de Farmacia and Laboratorio de Ensayos Biológicos, Escuela de Medicina, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - Yendry Chaves-Madrigal
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - Andrea Ramírez-Mata
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - Amanda Villalobos-Jimenez
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - Stefan Ost
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany.
| | - Carlos Quesada-Gómez
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | - César Rodríguez
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
| | | | - Esteban Chaves-Olarte
- Facultad de Microbiología and Centro de Investigación en Enfermedades Tropicales, Universidad de Costa Rica, 10101 San José, Costa Rica.
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79
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Sulfated glycosaminoglycans and low-density lipoprotein receptor contribute to Clostridium difficile toxin A entry into cells. Nat Microbiol 2019; 4:1760-1769. [PMID: 31160825 PMCID: PMC6754795 DOI: 10.1038/s41564-019-0464-z] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 04/19/2019] [Indexed: 12/18/2022]
Abstract
Clostridium difficile toxin A (TcdA) is a major exotoxin contributing to disruption of the colonic epithelium during C. difficile infection. TcdA contains a carbohydrate-binding combined repetitive oligopeptides (CROPs) domain that mediates its attachment to cell surfaces, but recent data suggest the existence of CROPs-independent receptors. Here, we carried out genome-wide clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9)-mediated screens using a truncated TcdA lacking the CROPs, and identified sulfated glycosaminoglycans (sGAGs) and low-density lipoprotein receptor (LDLR) as host factors contributing to binding and entry of TcdA. TcdA recognizes the sulfation group in sGAGs. Blocking sulfation and glycosaminoglycan synthesis reduces TcdA binding and entry into cells. Binding of TcdA to the colonic epithelium can be reduced by surfen, a small molecule that masks sGAGs, by GM-1111, a sulfated heparan sulfate analogue, and by sulfated cyclodextrin, a sulfated small molecule. Cells lacking LDLR also show reduced sensitivity to TcdA, although binding between LDLR and TcdA are not detected, suggesting that LDLR may facilitate endocytosis of TcdA. Finally, GM-1111 reduces TcdA-induced fluid accumulation and tissue damage in the colon in a mouse model in which TcdA is injected into the caecum. These data demonstrate in vivo and pathological relevance of TcdA-sGAGs interactions, and reveal a potential therapeutic approach of protecting colonic tissues by blocking these interactions.
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80
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Differential effects of Clostridium difficile toxins on ion secretion and cell integrity in human intestinal cells. Pediatr Res 2019; 85:1048-1054. [PMID: 30851723 DOI: 10.1038/s41390-019-0365-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 02/04/2019] [Accepted: 02/27/2019] [Indexed: 11/08/2022]
Abstract
BACKGROUND Toxin A (TcdA), toxin B (TcdB), and binary toxin (CDT) produced by Clostridium difficile (CD) are thought to play a key role in inducing diarrhea. The aim of this study was to investigate the individual and combined roles of CD toxins in inducing enterotoxic and cytotoxic effect. METHODS Ion secretion and epithelial damage were evaluated in the Ussing chambers as measure of enterotoxic or cytotoxic effect, respectively, in human-derived intestinal cells. RESULTS When added to the mucosal side of Caco-2 cells, TcdB, but not TcdA, induced ion secretion and its effects increased in the presence of TcdA. CDT also induced ion secretion when added to either the mucosal or serosal compartment. Serosal addition of TcdB induced epithelial damage consistent with its cytotoxic effect. However, mucosal addition of TcdB had similar effects, but only in the presence of TcdA. CDT induced epithelial damage when added to the serosal side of cell monolayers, and this was associated with a late onset but prolonged effect. All data were replicated using human colon biopsies. CONCLUSIONS These data indicate that CD, through the combined and direct activity of its three toxins, induces integrated and synergic enterotoxic and cytotoxic effects on the intestinal epithelium.
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Simeon R, Jiang M, Chamoun-Emanuelli AM, Yu H, Zhang Y, Meng R, Peng Z, Jakana J, Zhang J, Feng H, Chen Z. Selection and characterization of ultrahigh potency designed ankyrin repeat protein inhibitors of C. difficile toxin B. PLoS Biol 2019; 17:e3000311. [PMID: 31233493 PMCID: PMC6590788 DOI: 10.1371/journal.pbio.3000311] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 05/20/2019] [Indexed: 12/18/2022] Open
Abstract
Clostridium difficile infection (CDI) is a major nosocomial disease associated with significant morbidity and mortality. The pathology of CDI stems primarily from the 2 C. difficile-secreted exotoxins-toxin A (TcdA) and toxin B (TcdB)-that disrupt the tight junctions between epithelial cells leading to the loss of colonic epithelial barrier function. Here, we report the engineering of a series of monomeric and dimeric designed ankyrin repeat proteins (DARPins) for the neutralization of TcdB. The best dimeric DARPin, DLD-4, inhibited TcdB with a half maximal effective concentration (EC50) of 4 pM in vitro, representing an approximately 330-fold higher potency than the Food and Drug Administration (FDA)-approved anti-TcdB monoclonal antibody bezlotoxumab in the same assay. DLD-4 also protected mice from a toxin challenge in vivo. Cryo-electron microscopy (cryo-EM) studies revealed that the 2 constituent DARPins of DLD-4-1.4E and U3-bind the central and C-terminal regions of the delivery domain of TcdB. Competitive enzyme-linked immunosorbent assay (ELISA) studies showed that the DARPins 1.4E and U3 interfere with the interaction between TcdB and its receptors chondroitin sulfate proteoglycan 4 (CSPG4) and frizzled class receptor 2 (FZD2), respectively. Our cryo-EM studies revealed a new conformation of TcdB (both apo- and DARPin-bound at pH 7.4) in which the combined repetitive oligopeptides (CROPS) domain points away from the delivery domain. This conformation of the CROPS domain is in stark contrast to that seen in the negative-stain electron microscopy (EM) structure of TcdA and TcdB at the same pH, in which the CROPS domain bends toward and "kisses" the delivery domain. The ultrapotent anti-TcdB molecules from this study serve as candidate starting points for CDI drug development and provide new biological tools for studying the pathogenicity of C. difficile. The structural insights regarding both the "native" conformation of TcdB and the putative sites of TcdB interaction with the FZD2 receptor, in particular, should help accelerate the development of next-generation anti-C. difficile toxin therapeutics.
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Affiliation(s)
- Rudo Simeon
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, College Station, Texas, United States of America
| | - Mengqiu Jiang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
| | - Ana M. Chamoun-Emanuelli
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, College Station, Texas, United States of America
| | - Hua Yu
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, Maryland, United Sates of America
| | - Yongrong Zhang
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, Maryland, United Sates of America
| | - Ran Meng
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
| | - Zeyu Peng
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, College Station, Texas, United States of America
| | - Joanita Jakana
- National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Junjie Zhang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
| | - Hanping Feng
- Department of Microbial Pathogenesis, University of Maryland Dental School, Baltimore, Maryland, United Sates of America
| | - Zhilei Chen
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, College Station, Texas, United States of America
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Deletion of a 19-Amino-Acid Region in Clostridioides difficile TcdB2 Results in Spontaneous Autoprocessing and Reduced Cell Binding and Provides a Nontoxic Immunogen for Vaccination. Infect Immun 2019; 87:IAI.00210-19. [PMID: 31138612 DOI: 10.1128/iai.00210-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 05/17/2019] [Indexed: 11/20/2022] Open
Abstract
Clostridioides difficile toxin B (TcdB) is an intracellular toxin responsible for many of the pathologies of C. difficile infection. The two variant forms of TcdB (TcdB1 and TcdB2) share 92% sequence identity but have reported differences in rates of cell entry, autoprocessing, and overall toxicity. This 2,366-amino-acid, multidomain bacterial toxin glucosylates and inactivates small GTPases in the cytosol of target cells, ultimately leading to cell death. Successful cell entry and intoxication by TcdB are known to involve various conformational changes in the protein, including a proteolytic autoprocessing event. Previous studies found that amino acids 1753 to 1852 influence the conformational states of the proximal carboxy-terminal domain of TcdB and could contribute to differences between TcdB1 and TcdB2. In the current study, a combination of approaches was used to identify sequences within the region from amino acids 1753 to 1852 that influence the conformational integrity and cytotoxicity of TcdB2. Four deletion mutants with reduced cytotoxicity were identified, while one mutant, TcdB2Δ1769-1787, exhibited no detectable cytotoxicity. TcdB2Δ1769-1787 underwent spontaneous autoprocessing and was unable to interact with CHO-K1 or HeLa cells, suggesting a potential change in the conformation of the mutant protein. Despite the putative alteration in structural stability, vaccination with TcdB2Δ1769-1787 induced a TcdB2-neutralizing antibody response and protected against C. difficile disease in a mouse model. These findings indicate that the 19-amino-acid region spanning residues 1769 to 1787 in TcdB2 is crucial to cytotoxicity and the structural regulation of autoprocessing and that TcdB2Δ1769-1787 is a promising candidate for vaccination.
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Cole LE, Li L, Jetley U, Zhang J, Pacheco K, Ma F, Zhang J, Mundle S, Yan Y, Barone L, Rogers C, Beltraminelli N, Quemeneur L, Kleanthous H, Anderson SF, Anosova NG. Deciphering the domain specificity of C. difficile toxin neutralizing antibodies. Vaccine 2019; 37:3892-3901. [PMID: 31122858 DOI: 10.1016/j.vaccine.2019.05.040] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 04/10/2019] [Accepted: 05/13/2019] [Indexed: 12/21/2022]
Abstract
Clostridium difficile infection (CDI) is the principal cause of nosocomial diarrhea and pseudomembranous colitis associated with antibiotic therapy. The pathological effects of CDI are primarily attributed to toxins A (TcdA) and B (TcdB). Adequate toxin-specific antibody responses are associated with asymptomatic carriage, whereas insufficient humoral responses are associated with recurrent CDI. While the data supporting the importance of anti-toxin antibodies are substantial, clarity about the toxin domain specificity of these antibodies is more limited. To investigate this matter, combinations of human mAbs targeting multiple domains of TcdB were assessed using toxin neutralization assays. These data revealed that a combination of mAbs specific to all major toxin domains had improved neutralizing potency when compared to equivalent concentrations of a single mAb or a combination of mAbs against one or two domains. The function and toxin domain binding specificity of serum antibodies elicited by immunization of hamsters with a toxoid vaccine candidate was also assessed. Immunization with a toxoid vaccine candidate provoked toxin neutralizing antibodies specific to multiple domains of both TcdA and TcdB. When assessed in a toxin neutralization assay, polyclonal sera displayed greater activity against elevated concentrations of toxins than equivalent concentrations of individual mAbs. These data suggest a potential benefit of any antibody based therapeutic or prophylactic treatment that targets multiple toxin domains.
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Affiliation(s)
- Leah E Cole
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA
| | - Lu Li
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA
| | - Utsav Jetley
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA; Momenta Pharmaceuticals, INC., Research, 675 W Kendall St, Cambridge, MA 02142, USA
| | - Jinrong Zhang
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA
| | - Kristl Pacheco
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA
| | - Fuqin Ma
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA
| | - Jianxin Zhang
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA
| | - Sophia Mundle
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA
| | - Yanhua Yan
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA
| | - Lucianna Barone
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA; Harvard Vanguard Medical Associates, 230 Worcester Street, Wellesley, MA 02481, USA
| | - Christopher Rogers
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA; Maine Medical Center, Department of Pediatrics, 22 Bramhall Street, Portland, ME 04102, USA
| | - Nicola Beltraminelli
- BliNK Biomedical SAS, R&D, Gerland Plaza Techsud, 70, rue Saint Jean de Dieu, 69007 Lyon, France
| | - Laurence Quemeneur
- Sanofi Pasteur, Research Europe, 1541, Avenue Marcel Mérieux, 68280 Marcy l'Etoile, France
| | - Harry Kleanthous
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA
| | - Stephen F Anderson
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA; Anokion US, Inc., Development and Analytics, 50 Hampshire Street, Cambridge, MA 02139, USA
| | - Natalie G Anosova
- Sanofi Pasteur, Research North America, 38 Sidney Street, Cambridge, MA 02139, USA.
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Mileto S, Das A, Lyras D. Enterotoxic Clostridia: Clostridioides difficile Infections. Microbiol Spectr 2019; 7:10.1128/microbiolspec.gpp3-0015-2018. [PMID: 31124432 PMCID: PMC11026080 DOI: 10.1128/microbiolspec.gpp3-0015-2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Indexed: 12/17/2022] Open
Abstract
Clostridioides difficile is a Gram-positive, anaerobic, spore forming pathogen of both humans and animals and is the most common identifiable infectious agent of nosocomial antibiotic-associated diarrhea. Infection can occur following the ingestion and germination of spores, often concurrently with a disruption to the gastrointestinal microbiota, with the resulting disease presenting as a spectrum, ranging from mild and self-limiting diarrhea to severe diarrhea that may progress to life-threating syndromes that include toxic megacolon and pseudomembranous colitis. Disease is induced through the activity of the C. difficile toxins TcdA and TcdB, both of which disrupt the Rho family of GTPases in host cells, causing cell rounding and death and leading to fluid loss and diarrhea. These toxins, despite their functional and structural similarity, do not contribute to disease equally. C. difficile infection (CDI) is made more complex by a high level of strain diversity and the emergence of epidemic strains, including ribotype 027-strains which induce more severe disease in patients. With the changing epidemiology of CDI, our understanding of C. difficile disease, diagnosis, and pathogenesis continues to evolve. This article provides an overview of the current diagnostic tests available for CDI, strain typing, the major toxins C. difficile produces and their mode of action, the host immune response to each toxin and during infection, animal models of disease, and the current treatment and prevention strategies for CDI.
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Affiliation(s)
- S Mileto
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Victoria, Australia, 3800
| | - A Das
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Victoria, Australia, 3800
| | - D Lyras
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Victoria, Australia, 3800
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85
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Lectin Activity of the TcdA and TcdB Toxins of Clostridium difficile. Infect Immun 2019; 87:IAI.00676-18. [PMID: 30530621 PMCID: PMC6386544 DOI: 10.1128/iai.00676-18] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 12/04/2018] [Indexed: 02/06/2023] Open
Abstract
Clostridium difficile is a major cause of hospital-acquired antibiotic-associated diarrhea. C. difficile produces two cytotoxins, TcdA and TcdB; both toxins are multidomain proteins that lead to cytotoxicity through the modification and inactivation of small GTPases of the Rho/Rac family. Previous studies have indicated that host glycans are targets for TcdA and TcdB, with interactions thought to be with both α- and β-linked galactose. In the current study, screening of glycan arrays with different domains of TcdA and TcdB revealed that the binding regions of both toxins interact with a wider range of host glycoconjugates than just terminal α- and β-linked galactose, including blood groups, Lewis antigens, N-acetylglucosamine, mannose, and glycosaminoglycans. The interactions of TcdA and TcdB with ABO blood group and Lewis antigens were assessed by surface plasmon resonance (SPR). The blood group A antigen was the highest-affinity ligand for both toxins. Free glycans alone or in combination were unable to abolish Vero cell cytotoxicity by TcdB. SPR competition assays indicate that there is more than one glycan binding site on TcdB. Host glycoconjugates are common targets of bacterial toxins, but typically this binding is to a specific structure or related structures. The binding of TcdA and TcdB is to a wide range of host glycans providing a wide range of target cells and tissues in vivo.
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86
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Zhu S, Cao Z, Liu Z, He Y, Wang Y, Yuan P, Li W, Tian F, Bao Y, Wei W. Guide RNAs with embedded barcodes boost CRISPR-pooled screens. Genome Biol 2019; 20:20. [PMID: 30678704 PMCID: PMC6345036 DOI: 10.1186/s13059-019-1628-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 01/11/2019] [Indexed: 01/08/2023] Open
Abstract
We report a new method using re-designed guide RNAs with internal barcodes (iBARs) embedded in their loop regions. Our iBAR approach outperforms the conventional method by producing screening results with much lower false-positive and false-negative rates especially with a high multiplicity of infection (MOI). Importantly, the iBAR approach reduces the starting cells at high MOI significantly with greatly improved efficiency and accuracy compared with the canonical CRISPR screens at a low MOI. This new system is particularly useful when the source of cells is limited or when it is difficult to control viral infection for in vivo screening.
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Affiliation(s)
- Shiyou Zhu
- Biomedical Pioneering Innovation Center (BIOPIC), 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
| | - Zhongzheng Cao
- Biomedical Pioneering Innovation Center (BIOPIC), 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
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Zhiheng Liu
- Biomedical Pioneering Innovation Center (BIOPIC), 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
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Yuan He
- Biomedical Pioneering Innovation Center (BIOPIC), 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
| | - Yinan Wang
- Biomedical Pioneering Innovation Center (BIOPIC), 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
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Pengfei Yuan
- EdiGene Inc, Life Science Park, 22 KeXueYuan Road, Changping District, Beijing, 102206, China
| | - Wei Li
- Center for Genetic Medicine Research, Children's National Health System, Washington, DC, 20010, USA
- Department of Genomics and Precision Medicine, The George Washington School of Medicine and Health Sciences, Washington, DC, 20010, USA
| | - Feng Tian
- Biomedical Pioneering Innovation Center (BIOPIC), 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
| | - Ying Bao
- Biomedical Pioneering Innovation Center (BIOPIC), 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 (BIOPIC), 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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87
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Brander S, Jank T, Hugel T. AFM Imaging Suggests Receptor-Free Penetration of Lipid Bilayers by Toxins. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:365-371. [PMID: 30565941 DOI: 10.1021/acs.langmuir.8b03146] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A crucial step of exotoxin action is the attack on the membrane. Many exotoxins show an architecture following the AB model, where a binding subunit translocates an "action" subunit across a cell membrane. Atomic force microscopy is an ideal technique to study these systems because of its ability to provide structural as well as dynamic information at the same time. We report first images of toxins Photorhabdus luminescens TcdA1 and Clostridium difficile TcdB on a supported lipid bilayer. A significant amount of toxin binds to the bilayer at neutral pH in the absence of receptors. Lack of diffusion indicates that toxin particles penetrate the membrane. This observation is supported by fluorescence recovery after photobleaching measurements. We mimic endocytosis by acidification while imaging the particles over time; however, we see no large conformational change. We therefore conclude that the toxin particles we imaged in neutral conditions had already formed a pore and speculate that there is no "pre-pore" state in our imaging conditions (i.e., in the absence of receptor).
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88
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Papatheodorou P, Song S, López-Ureña D, Witte A, Marques F, Ost GS, Schorch B, Chaves-Olarte E, Aktories K. Cytotoxicity of Clostridium difficile toxins A and B requires an active and functional SREBP-2 pathway. FASEB J 2018; 33:4883-4892. [PMID: 30592645 DOI: 10.1096/fj.201801440r] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Clostridium difficile is associated with antibiotic-associated diarrhea and pseudomembranous colitis in humans. Its 2 major toxins, toxins A and B, enter host cells and inactivate GTPases of the Ras homologue/rat sarcoma family by glucosylation. Pore formation of the toxins in the endosomal membrane enables the translocation of their glucosyltransferase domain into the cytosol, and membrane cholesterol is crucial for this process. Here, we asked whether the activity of the sterol regulatory element-binding protein 2 (SREBP-2) pathway, which regulates the cholesterol content in membranes, affects the susceptibility of target cells toward toxins A and B. We show that the SREBP-2 pathway is crucial for the intoxication process of toxins A and B by using pharmacological inhibitors (PF-429242, 25-hydroxycholesterol) and cells that are specifically deficient in SREBP-2 pathway signaling. SREBP-2 pathway inhibition disturbed the cholesterol-dependent pore formation of toxin B in cellular membranes. Preincubation with the cholesterol-lowering drug simvastatin protected cells from toxin B intoxication. Inhibition of the SREBP-2 pathway was without effect when the enzyme portion of toxin B was introduced into target cells via the cell delivery property of anthrax protective antigen. Taken together, these findings allowed us to identify the SREBP-2 pathway as a suitable target for the development of antitoxin therapeutics against C. difficile toxins A and B.-Papatheodorou, P., Song, S., López-Ureña, D., Witte, A., Marques, F., Ost, G. S., Schorch, B., Chaves-Olarte, E., Aktories, K. Cytotoxicity of Clostridium difficile toxins A and B requires an active and functional SREBP-2 pathway.
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Affiliation(s)
- Panagiotis Papatheodorou
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Shuo Song
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Diana López-Ureña
- Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Alexander Witte
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Felícia Marques
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Gerhard Stefan Ost
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Björn Schorch
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
| | - Esteban Chaves-Olarte
- Centro de Investigación en Enfermedades Tropicales, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Klaus Aktories
- Institut für Experimentelle and Klinische Pharmakologie und Toxikologie, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany; and
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89
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Naran K, Nundalall T, Chetty S, Barth S. Principles of Immunotherapy: Implications for Treatment Strategies in Cancer and Infectious Diseases. Front Microbiol 2018; 9:3158. [PMID: 30622524 PMCID: PMC6308495 DOI: 10.3389/fmicb.2018.03158] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 12/05/2018] [Indexed: 12/13/2022] Open
Abstract
The advances in cancer biology and pathogenesis during the past two decades, have resulted in immunotherapeutic strategies that have revolutionized the treatment of malignancies, from relatively non-selective toxic agents to specific, mechanism-based therapies. Despite extensive global efforts, infectious diseases remain a leading cause of morbidity and mortality worldwide, necessitating novel, innovative therapeutics that address the current challenges of increasing antimicrobial resistance. Similar to cancer pathogenesis, infectious pathogens successfully fashion a hospitable environment within the host and modulate host metabolic functions to support their nutritional requirements, while suppressing host defenses by altering regulatory mechanisms. These parallels, and the advances made in targeted therapy in cancer, may inform the rational development of therapeutic interventions for infectious diseases. Although "immunotherapy" is habitually associated with the treatment of cancer, this review accentuates the evolving role of key targeted immune interventions that are approved, as well as those in development, for various cancers and infectious diseases. The general features of adoptive therapies, those that enhance T cell effector function, and ligand-based therapies, that neutralize or eliminate diseased cells, are discussed in the context of specific diseases that, to date, lack appropriate remedial treatment; cancer, HIV, TB, and drug-resistant bacterial and fungal infections. The remarkable diversity and versatility that distinguishes immunotherapy is emphasized, consequently establishing this approach within the armory of curative therapeutics, applicable across the disease spectrum.
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Affiliation(s)
- Krupa Naran
- Medical Biotechnology and Immunotherapy Unit, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Trishana Nundalall
- Medical Biotechnology and Immunotherapy Unit, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Shivan Chetty
- Medical Biotechnology and Immunotherapy Unit, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Stefan Barth
- Medical Biotechnology and Immunotherapy Unit, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
- South African Research Chair in Cancer Biotechnology, Department of Integrative Biomedical Sciences, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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90
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Hussack G, Ryan S, van Faassen H, Rossotti M, MacKenzie CR, Tanha J. Neutralization of Clostridium difficile toxin B with VHH-Fc fusions targeting the delivery and CROPs domains. PLoS One 2018; 13:e0208978. [PMID: 30540857 PMCID: PMC6291252 DOI: 10.1371/journal.pone.0208978] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Accepted: 11/28/2018] [Indexed: 02/08/2023] Open
Abstract
An increasing number of antibody-based therapies are being considered for controlling bacterial infections, including Clostridium difficile by targeting toxins A and B. In an effort to develop novel C. difficile immunotherapeutics, we previously isolated several single-domain antibodies (VHHs) capable of toxin A neutralization through recognition of the extreme C-terminal combined repetitive oligopeptides (CROPs) domain, but failed at identifying neutralizing VHHs that bound a similar region on toxin B. Here we report the isolation of a panel of 29 VHHs targeting at least seven unique epitopes on a toxin B immunogen composed of a portion of the central delivery domain and the entire CROPs domain. Despite monovalent affinities as high as KD = 70 pM, none of the VHHs tested were capable of toxin B neutralization; however, modest toxin B inhibition was observed with VHH-VHH dimers and to a much greater extent with VHH-Fc fusions, reaching the neutralizing potency of the recently approved anti-toxin B monoclonal antibody bezlotoxumab in in vitro assays. Epitope binning revealed that several VHH-Fcs bound toxin B at sites distinct from the region recognized by bezlotoxumab, while other VHH-Fcs partially competed with bezlotoxumab for toxin binding. Therefore, the VHHs described here are effective at toxin B neutralization when formatted as bivalent VHH-Fc fusions by targeting toxin B at regions both similar and distinct from the bezlotoxumab binding site.
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Affiliation(s)
- Greg Hussack
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
- * E-mail:
| | - Shannon Ryan
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
| | - Henk van Faassen
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
| | - Martin Rossotti
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
| | - C. Roger MacKenzie
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
| | - Jamshid Tanha
- Human Health Therapeutics Research Centre, National Research Council Canada, Ottawa, Ontario, Canada
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada
- School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada
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91
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Fühner V, Heine PA, Helmsing S, Goy S, Heidepriem J, Loeffler FF, Dübel S, Gerhard R, Hust M. Development of Neutralizing and Non-neutralizing Antibodies Targeting Known and Novel Epitopes of TcdB of Clostridioides difficile. Front Microbiol 2018; 9:2908. [PMID: 30574127 PMCID: PMC6291526 DOI: 10.3389/fmicb.2018.02908] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 11/13/2018] [Indexed: 12/18/2022] Open
Abstract
Clostridioides difficile is the causative bacterium in 15-20% of all antibiotic associated diarrheas. The symptoms associated with C. difficile infection (CDI) are primarily induced by the two large exotoxins TcdA and TcdB. Both toxins enter target cells by receptor-mediated endocytosis. Although different toxin receptors have been identified, it is no valid therapeutic option to prevent receptor endocytosis. Therapeutics, such as neutralizing antibodies, directly targeting both toxins are in development. Interestingly, only the anti-TcdB antibody bezlotoxumab but not the anti-TcdA antibody actoxumab prevented recurrence of CDI in clinical trials. In this work, 31 human antibody fragments against TcdB were selected by antibody phage display from the human naive antibody gene libraries HAL9/10. These antibody fragments were further characterized by in vitro neutralization assays. The epitopes of the neutralizing and non-neutralizing antibody fragments were analyzed by domain mapping, TcdB fragment phage display, and peptide arrays, to identify neutralizing and non-neutralizing epitopes. A new neutralizing epitope within the glucosyltransferase domain of TcdB was identified, providing new insights into the relevance of different toxin regions in respect of neutralization and toxicity.
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Affiliation(s)
- Viola Fühner
- Department Biotechnology, Institute for Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Philip Alexander Heine
- Department Biotechnology, Institute for Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Saskia Helmsing
- Department Biotechnology, Institute for Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Sebastian Goy
- Institute for Toxicology, Hannover Medical School, Hannover, Germany
| | - Jasmin Heidepriem
- Department Synthetic Array Technologies, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
| | - Felix F. Loeffler
- Department Synthetic Array Technologies, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
| | - Stefan Dübel
- Department Biotechnology, Institute for Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Ralf Gerhard
- Institute for Toxicology, Hannover Medical School, Hannover, Germany
| | - Michael Hust
- Department Biotechnology, Institute for Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Braunschweig, Germany
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92
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Liu Y, Cao Z, Wang Y, Guo Y, Xu P, Yuan P, Liu Z, He Y, Wei W. Genome-wide screening for functional long noncoding RNAs in human cells by Cas9 targeting of splice sites. Nat Biotechnol 2018; 36:nbt.4283. [PMID: 30395134 DOI: 10.1038/nbt.4283] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 08/27/2018] [Indexed: 12/17/2022]
Abstract
The functions of many long noncoding RNAs (lncRNAs) in the human genome remain unknown owing to the lack of scalable loss-of-function screening tools. We previously used pairs of CRISPR-Cas9 (refs. 1, 2, 3) single guide RNAs (sgRNAs) for small-scale functional screening of lncRNAs. Here we demonstrate genome-wide screening of lncRNA function using sgRNAs to target splice sites and achieve exon skipping or intron retention. Splice-site targeting outperformed a conventional CRISPR library in a negative selection screen targeting 79 ribosomal genes. Using a genome-scale library of splicing-targeting sgRNAs, we performed a screen covering 10,996 lncRNAs and identified 230 that are essential for cellular growth of chronic myeloid leukemia K562 cells. Screening GM12878 lymphoblastoid cells and HeLa cells with the same library identified cell-type-specific differences in lncRNA essentiality. Extensive validation confirmed the robustness of our approach.
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Affiliation(s)
- Ying Liu
- Biomedical Pioneering Innovation Center (BIOPIC), 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, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Zhongzheng Cao
- Biomedical Pioneering Innovation Center (BIOPIC), 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, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Yinan Wang
- Biomedical Pioneering Innovation Center (BIOPIC), 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, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Yu Guo
- Biomedical Pioneering Innovation Center (BIOPIC), 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, China
| | - Ping Xu
- Biomedical Pioneering Innovation Center (BIOPIC), 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, China
| | - Pengfei Yuan
- Biomedical Pioneering Innovation Center (BIOPIC), 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, China
| | - Zhiheng Liu
- Biomedical Pioneering Innovation Center (BIOPIC), 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, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Yuan He
- Biomedical Pioneering Innovation Center (BIOPIC), 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, China
| | - Wensheng Wei
- Biomedical Pioneering Innovation Center (BIOPIC), 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, China
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93
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Chen P, Tao L, Liu Z, Dong M, Jin R. Structural insight into Wnt signaling inhibition by Clostridium difficile toxin B. FEBS J 2018; 286:874-881. [PMID: 30347517 DOI: 10.1111/febs.14681] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 10/09/2018] [Accepted: 10/17/2018] [Indexed: 12/17/2022]
Abstract
The incidence of Clostridium difficile infection (CDI) has increased significantly worldwide, causing substantial morbidity and mortality. One of the major virulence factor, TcdB, manages to enter the colonic epithelia via the human frizzled proteins (FZDs), which are physiological receptors for Wnt morphogens. Binding of TcdB to FZDs inhibits Wnt signaling, which may contribute to pathogenesis of CDI. Here, we review the structural mechanism by which TcdB exploits to recognize FZDs for cell entry and inhibiting Wnt signaling, which reveals new strategies to modulate Wnt signaling for therapeutic interventions.
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Affiliation(s)
- Peng Chen
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA
| | - Liang Tao
- Department of Urology, Boston Children's Hospital, Boston, MA, USA.,Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA.,Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Zheng Liu
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA
| | - Min Dong
- Department of Urology, Boston Children's Hospital, Boston, MA, USA.,Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA.,Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA
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94
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Chung SY, Schöttelndreier D, Tatge H, Fühner V, Hust M, Beer LA, Gerhard R. The Conserved Cys-2232 in Clostridioides difficile Toxin B Modulates Receptor Binding. Front Microbiol 2018; 9:2314. [PMID: 30416488 PMCID: PMC6212469 DOI: 10.3389/fmicb.2018.02314] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 09/11/2018] [Indexed: 12/14/2022] Open
Abstract
Clostridioides difficile toxins TcdA and TcdB are large clostridial glucosyltransferases which are the main pathogenicity factors in C. difficile-associated diseases. Four highly conserved cysteines are present in all large clostridial glucosyltransferases. In this study we focused on the conserved cysteine 2232 within the combined repetitive oligopeptide domain of TcdB from reference strain VPI10463 (clade I). Cysteine 2232 is not present in TcdB from hypervirulent strain R20291 (clade II), where a tyrosine is found instead. Replacement of cysteine 2232 by tyrosine in TcdBV PI10463 reduced binding to the soluble fragments of the two known TcdB receptors, frizzled-2 (FZD2) and poliovirus receptor-like protein-3/nectin-3 (PVRL3). In line with this, TcdBR20291 showed weak binding to PVRL3 in pull-down assays which was increased when tyrosine 2232 was exchanged for cysteine. Surprisingly, we did not observe binding of TcdBR20291 to FZD2, indicating that this receptor is less important for this toxinotype. Competition assay with the receptor binding fragments (aa 1101–1836) of TcdBV PI10463 and TcdBR20291, as well as antibodies newly developed by antibody phage display, revealed different characteristics of the yet poorly described delivery domain of TcdB harboring the second receptor binding region. In summary, we found that conserved Cys-2232 in TcdB indirectly contributes to toxin–receptor interaction.
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Affiliation(s)
- Soo-Young Chung
- Institute of Toxicology, Hannover Medical School, Hanover, Germany
| | | | - Helma Tatge
- Institute of Toxicology, Hannover Medical School, Hanover, Germany
| | - Viola Fühner
- Department of Biotechnology, Institute for Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Michael Hust
- Department of Biotechnology, Institute for Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Braunschweig, Germany
| | | | - Ralf Gerhard
- Institute of Toxicology, Hannover Medical School, Hanover, Germany
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95
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The chaperonin TRiC/CCT is essential for the action of bacterial glycosylating protein toxins like Clostridium difficile toxins A and B. Proc Natl Acad Sci U S A 2018; 115:9580-9585. [PMID: 30181275 DOI: 10.1073/pnas.1807658115] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Various bacterial protein toxins, including Clostridium difficile toxins A (TcdA) and B (TcdB), attack intracellular target proteins of host cells by glucosylation. After receptor binding and endocytosis, the toxins are translocated into the cytosol, where they modify target proteins (e.g., Rho proteins). Here we report that the activity of translocated glucosylating toxins depends on the chaperonin TRiC/CCT. The chaperonin subunits CCT4/5 directly interact with the toxins and enhance the refolding and restoration of the glucosyltransferase activities of toxins after heat treatment. Knockdown of CCT5 by siRNA and HSF1A, an inhibitor of TRiC/CCT, blocks the cytotoxic effects of TcdA and TcdB. In contrast, HSP90, which is involved in the translocation and uptake of ADP ribosylating toxins, is not involved in uptake of the glucosylating toxins. We show that the actions of numerous glycosylating toxins from various toxin types and different species depend on TRiC/CCT. Our data indicate that the TRiC/CCT chaperonin system is specifically involved in toxin uptake and essential for the action of various glucosylating protein toxins acting intracellularly on target proteins.
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96
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Marine glycosaminoglycan-like carbohydrates as potential drug candidates for infectious disease. Biochem Soc Trans 2018; 46:919-929. [PMID: 30026370 DOI: 10.1042/bst20170404] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 04/27/2018] [Accepted: 05/21/2018] [Indexed: 12/15/2022]
Abstract
Glycosaminoglycans (GAGs), present in the extracellular matrix, are exploited by numerous, distinct microbes for cellular attachment, adhesion, invasion and evasion of the host immune system. Glycosaminoglycans, including the widely used, clinical anticoagulant heparin and semi-synthetic analogues thereof, have been reported to inhibit and disrupt interactions between microbial proteins and carbohydrates present on the surface of host cells. However, the anticoagulant properties of unmodified, pharmaceutical heparin preparations preclude their capabilities as therapeutics for infectious disease states. Here, unique Glycosaminoglycan-like saccharides from various, distinct marine species are reported for their potential use as therapeutics against infectious diseases; many of which possess highly attenuated anticoagulant activities, while retaining significant antimicrobial properties.
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97
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Schöttelndreier D, Seeger K, Grassl GA, Winny MR, Lindner R, Genth H. Expression and (Lacking) Internalization of the Cell Surface Receptors of Clostridioides difficile Toxin B. Front Microbiol 2018; 9:1483. [PMID: 30022975 PMCID: PMC6039548 DOI: 10.3389/fmicb.2018.01483] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 06/14/2018] [Indexed: 12/30/2022] Open
Abstract
Toxin-producing strains of Clostridioides difficile and Clostridium perfringens cause infections of the gastrointestinal tract in humans and ruminants, with the toxins being major virulence factors, essential for the infection, and responsible for the onset of severe symptoms. C. difficile toxin A (TcdA) and toxin B (TcdB), and the large cytotoxin (TpeL) from C. perfringens are single chain bacterial protein toxins with an AB-like toxin structure. The C-terminal delivery domain mediates cell entry of the N-terminal glycosyltransferase domain by receptor-mediated endocytosis. Several cell surface proteins have been proposed to serve as toxin receptors, including chondroitin-sulfate proteoglycan 4 (CSPG4), poliovirus receptor-like 3 (PVRL3), and frizzled-1/2/7 (FZD1/2/7) for TcdB and LDL-receptor-related protein-1 (LRP1) for TpeL. The expression of the TcdB receptors was investigated in human intestinal organoids (HIOs) and in cultured cell lines. HIOs from four human donors exhibited a comparable profile of receptor expression, with PVRL3, LRP1, and FZD7 being expressed and CSPG4 and FZD2 not being expressed. In human epithelial Caco-2 cells and HT29 cells as well as in immortalized murine fibroblasts, either receptor FZD2/7, CSPG4, PVRL3, and LRP1 was expressed. The question whether the toxins take advantage of the normal turnover of their receptors (i.e., constitutive endocytosis and recycling) from the cell surface or whether the toxins activity induce the internalization of their receptors has not yet been addressed. For the analysis of receptor internalization, temperature-induced uptake of biotinylated toxin receptors into immortalized mouse embryonic fibroblasts (MEFs) and Caco-2 cells was exploited. Solely LRP1 exhibited constitutive endocytosis from the plasma membrane to the endosome, which might be abused by TpeL (and possibly TcdB as well) for cell entry. Furthermore, internalization of CSPG4, PVRL3, FZD2, and FZD7 was observed neither in MEFs nor in Caco-2 cells. FZD2/7, CSPG4, and PVRL3 did thus exhibit no constitutive recycling. The presence of TcdB and the p38 activation induced by anisomycin were not able to induce or enhance CSPG4 or PVRL3 uptake in MEFs. In conclusion, FZD2/7, CSPG4, and PVRL3 seem to serve as cell surface binding receptors rather than internalizing receptors of TcdB.
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Affiliation(s)
| | - Katrin Seeger
- Institute of Medical Microbiology and Hospital Epidemiology and DZIF Partner Site Hannover-Braunschweig, Hannover Medical School, Hanover, Germany
| | - Guntram A Grassl
- Institute of Medical Microbiology and Hospital Epidemiology and DZIF Partner Site Hannover-Braunschweig, Hannover Medical School, Hanover, Germany
| | - Markus R Winny
- Department of General, Visceral and Transplantation Surgery, Hannover Medical School, Hanover, Germany
| | - Robert Lindner
- Neuroanatomy and Cell Biology, Hannover Medical School, Hanover, Germany
| | - Harald Genth
- Institute for Toxicology, Hannover Medical School, Hanover, Germany
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98
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Popoff MR. Clostridium difficile and Clostridium sordellii toxins, proinflammatory versus anti-inflammatory response. Toxicon 2018; 149:54-64. [DOI: 10.1016/j.toxicon.2017.11.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 11/07/2017] [Accepted: 11/09/2017] [Indexed: 12/17/2022]
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99
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Beer LA, Tatge H, Reich N, Tenspolde M, Olling A, Goy S, Rottner K, Alekov AK, Gerhard R. Early cell death induced by Clostridium difficile TcdB: Uptake and Rac1-glucosylation kinetics are decisive for cell fate. Cell Microbiol 2018; 20:e12865. [PMID: 29904993 DOI: 10.1111/cmi.12865] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 05/23/2018] [Accepted: 05/26/2018] [Indexed: 12/29/2022]
Abstract
Toxin A and Toxin B (TcdA/TcdB) are large glucosyltransferases produced by Clostridium difficile. TcdB but not TcdA induces reactive oxygen species-mediated early cell death (ECD) when applied at high concentrations. We found that nonglucosylated Rac1 is essential for induction of ECD since inhibition of Rac1 impedes this effect. ECD only occurs when TcdB is rapidly endocytosed. This was shown by generation of chimeras using the trunk of TcdB from a hypervirulent strain. TcdB from hypervirulent strain has been described to translocate from endosomes at higher pH values and thus, meaning faster than reference type TcdB. Accordingly, intracellular delivery of the glucosyltransferase domain of reference TcdB by the trunk of TcdB from hypervirulent strain increased ECD. Furthermore, proton transporters such as sodium/proton exchanger (NHE) or the ClC-5 anion/proton exchanger, both of which contribute to endosomal acidification, also affected cytotoxic potency of TcdB: Specific inhibition of NHE reduced cytotoxicity, whereas transfection of cells with the endosomal anion/proton exchanger ClC-5 increased cytotoxicity of TcdB. Our data suggest that both the uptake rate of TcdB into the cytosol and the status of nonglucosylated Rac1 are key determinants that are decisive for whether ECD or delayed apoptosis is triggered.
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Affiliation(s)
| | - Helma Tatge
- Institute of Toxicology, Hannover Medical School, Hannover, Germany
| | - Nicole Reich
- Institute of Toxicology, Hannover Medical School, Hannover, Germany
| | - Michel Tenspolde
- Institute of Toxicology, Hannover Medical School, Hannover, Germany
| | - Alexandra Olling
- Institute of Toxicology, Hannover Medical School, Hannover, Germany
| | - Sebastian Goy
- Institute of Toxicology, Hannover Medical School, Hannover, Germany
| | - Klemens Rottner
- Division of Molecular Cell Biology, Zoological Institute, Braunschweig, Germany.,Molecular Cell Biology Group, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | | | - Ralf Gerhard
- Institute of Toxicology, Hannover Medical School, Hannover, Germany
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100
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Uzal FA, Navarro MA, Li J, Freedman JC, Shrestha A, McClane BA. Comparative pathogenesis of enteric clostridial infections in humans and animals. Anaerobe 2018; 53:11-20. [PMID: 29883627 DOI: 10.1016/j.anaerobe.2018.06.002] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 06/03/2018] [Accepted: 06/04/2018] [Indexed: 02/06/2023]
Abstract
Several enteric clostridial diseases can affect humans and animals. Of these, the enteric infections caused by Clostridium perfringens and Clostridium difficile are amongst the most prevalent and they are reviewed here. C. perfringens type A strains encoding alpha toxin (CPA) are frequently associated with enteric disease of many animal mammalian species, but their role in these diseased mammals remains to be clarified. C. perfringens type B encoding CPA, beta (CPB) and epsilon (ETX) toxins causes necro-hemorrhagic enteritis, mostly in sheep, and these strains have been recently suggested to be involved in multiple sclerosis in humans, although evidence of this involvement is lacking. C. perfringens type C strains encode CPA and CPB and cause necrotizing enteritis in humans and animals, while CPA and ETX producing type D strains of C. perfringens produce enterotoxemia in sheep, goats and cattle, but are not known to cause spontaneous disease in humans. The role of C. perfringens type E in animal or human disease remains poorly defined. The newly revised toxinotype F encodes CPA and enterotoxin (CPE), the latter being responsible for food poisoning in humans, and the less prevalent antibiotic associated and sporadic diarrhea. The role of these strains in animal disease has not been fully described and remains controversial. Another newly created toxinotype, G, encodes CPA and necrotic enteritis toxin B-like (NetB), and is responsible for avian necrotic enteritis, but has not been associated with human disease. C. difficile produces colitis and/or enterocolitis in humans and multiple animal species. The main virulence factors of this microorganism are toxins A, B and an ADP-ribosyltransferase (CDT). Other clostridia causing enteric diseases in humans and/or animals are Clostridium spiroforme, Clostridium piliforme, Clostridium colinum, Clostridium sordellii, Clostridium chauvoei, Clostridium septicum, Clostridium botulinum, Clostridium butyricum and Clostridium neonatale. The zoonotic transmission of some, but not all these clostridsial species, has been demonstrated.
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Affiliation(s)
- Francisco A Uzal
- California Animal Health and Food Safety Laboratory System, San Bernardino Branch, University of California, Davis, CA, USA.
| | - Mauricio A Navarro
- California Animal Health and Food Safety Laboratory System, San Bernardino Branch, University of California, Davis, CA, USA
| | - Jihong Li
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - John C Freedman
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Archana Shrestha
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Bruce A McClane
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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