1
|
Ward JS, Schreiber KJ, Tam J, Youn JY, Melnyk RA. Mapping C. difficile TcdB interactions with host cell-surface and intracellular factors using proximity-dependent biotinylation labeling. mBio 2025; 16:e0333624. [PMID: 39818874 PMCID: PMC11796423 DOI: 10.1128/mbio.03336-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2024] [Accepted: 12/17/2024] [Indexed: 01/19/2025] Open
Abstract
Many bacterial toxins exert their cytotoxic effects by enzymatically inactivating one or more cytosolic targets in host cells. To reach their intracellular targets, these toxins possess functional domains or subdomains that interact with and exploit various host factors and biological processes. Despite great progress in identifying many of the key host factors involved in the uptake of toxins, significant knowledge gaps remain as to how partially characterized and newly discovered microbial toxins exploit host factors or processes to intoxicate target cells. Proximity-dependent biotinylation (e.g., BioID) is a powerful method to identify nearby host factors in living cells, offering the potential to identify host targets of microbial toxins. Here, we used BioID to interrogate proximal interactors of the multi-domain Clostridioides difficile TcdB toxin. Expressed fusions of TurboID to different fragments of TcdB identified several high-confidence proteins in the cytosol, including members of the Rho GTPase signaling network and the actin cytoskeletal network. Additionally, we developed an extracellular proximity labeling method using recombinant TurboID-toxin chimeras, which uncovered a limited number of cell-surface targets including LRP1, which was previously identified as a cell-surface receptor of TcdB. Our work reveals surface receptors and intracellular components exploited by bacterial toxins, highlighting key vulnerabilities in host cells.IMPORTANCEBacterial toxins are the causative agents of many human diseases. Further characterizing the intoxication mechanisms of these proteins is important for the development of vaccines and treatments for toxin-mediated disease. Proximity-dependent biotinylation approaches offer an orthogonal approach to complement genetic screens. Here, we evaluate the potential of this method to identify host-toxin interactions on the cell surface and in the cytosol, where the toxin modifies essential host targets. Critically, we have highlighted several limitations of this method as applied to protein toxins, which are important for researchers to weigh when considering this technique for exotoxin studies.
Collapse
Affiliation(s)
- Jennifer S. Ward
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Molecular Medicine Program, The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada
| | - Karl J. Schreiber
- Molecular Medicine Program, The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada
| | - John Tam
- Molecular Medicine Program, The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada
| | - Ji-Young Youn
- Molecular Medicine Program, The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Roman A. Melnyk
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Molecular Medicine Program, The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada
| |
Collapse
|
2
|
Rodrigues Rodrigues R, Alves MLF, Bilhalva MA, Kremer FS, Junior CM, Ferreira MRA, Galvão CC, Quatrin PHDN, Conceição FR. Large Clostridial Toxins: A Brief Review and Insights into Antigen Design for Veterinary Vaccine Development. Mol Biotechnol 2024:10.1007/s12033-024-01303-6. [PMID: 39472390 DOI: 10.1007/s12033-024-01303-6] [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: 08/12/2024] [Accepted: 10/08/2024] [Indexed: 12/18/2024]
Abstract
The group of large clostridial toxins (LCTs) includes toxins A (TcdA) and B (TcdB) from Clostridioides difficile, hemorrhagic and lethal toxins from Paeniclostridium sordellii, alpha toxin from Clostridium novyi (TcnA), and cytotoxin from Clostridium perfringens. These toxins are associated with severe pathologies in livestock, including gas gangrene (P. sordellii and C. novyi), infectious necrotic hepatitis (C. novyi), avian necrotic enteritis (C. perfringens), and enterocolitis (C. difficile). Immunoprophylaxis is crucial for controlling these diseases, but traditional vaccines face production challenges, such as labor-intensive processes, and often exhibit low immunogenicity. This has led to increased interest in recombinant vaccines. While TcdA and TcdB are well-studied for human immunization, other LCTs remain poorly characterized and require further investigation. Therefore, this study emphasizes the importance of understanding lesser-explored toxins and proposes using immunoinformatics to identify their immunodominant regions. By mapping these regions using silico tools and considering their homology with TcdA and TcdB, the study aims to guide future research in veterinary vaccinology. It also explores alternatives to overcome the limitations of conventional and recombinant vaccines, offering guidelines for developing more effective vaccination strategies against severe infections in animals.
Collapse
Affiliation(s)
- Rafael Rodrigues Rodrigues
- Centro de Desenvolvimento Tecnológico, Biotecnologia, Universidade Federal de Pelotas - Campus Universitário, Capão do Leão, Rio Grande Do Sul, CEP 96160-000, Brazil.
| | - Mariliana Luiza Ferreira Alves
- Centro de Desenvolvimento Tecnológico, Biotecnologia, Universidade Federal de Pelotas - Campus Universitário, Capão do Leão, Rio Grande Do Sul, CEP 96160-000, Brazil
- Instituto Federal Sul-Rio-Grandense, IFSul, Campus Pelotas, Pelotas, Rio Grande Do Sul, Brasil
| | - Miguel Andrade Bilhalva
- Centro de Desenvolvimento Tecnológico, Biotecnologia, Universidade Federal de Pelotas - Campus Universitário, Capão do Leão, Rio Grande Do Sul, CEP 96160-000, Brazil
| | - Frederico Schmitt Kremer
- Centro de Desenvolvimento Tecnológico, Biotecnologia, Universidade Federal de Pelotas - Campus Universitário, Capão do Leão, Rio Grande Do Sul, CEP 96160-000, Brazil
| | - Clóvis Moreira Junior
- Centro de Desenvolvimento Tecnológico, Biotecnologia, Universidade Federal de Pelotas - Campus Universitário, Capão do Leão, Rio Grande Do Sul, CEP 96160-000, Brazil
| | - Marcos Roberto Alves Ferreira
- Centro de Desenvolvimento Tecnológico, Biotecnologia, Universidade Federal de Pelotas - Campus Universitário, Capão do Leão, Rio Grande Do Sul, CEP 96160-000, Brazil
| | - Cleideanny Cancela Galvão
- Centro de Desenvolvimento Tecnológico, Biotecnologia, Universidade Federal de Pelotas - Campus Universitário, Capão do Leão, Rio Grande Do Sul, CEP 96160-000, Brazil
| | - Pedro Henrique Dala Nora Quatrin
- Centro de Desenvolvimento Tecnológico, Biotecnologia, Universidade Federal de Pelotas - Campus Universitário, Capão do Leão, Rio Grande Do Sul, CEP 96160-000, Brazil
| | - Fabricio Rochedo Conceição
- Centro de Desenvolvimento Tecnológico, Biotecnologia, Universidade Federal de Pelotas - Campus Universitário, Capão do Leão, Rio Grande Do Sul, CEP 96160-000, Brazil
| |
Collapse
|
3
|
Ramos CP, Siqueira WF, Viana LA, Cunha JLR, Fujiwara RT, Amarante VS, Souza TGV, Silva ROS. Development of two recombinant vaccines against Clostridioides difficile infection and immunogenicity in pregnant sows and neonatal piglets. Anaerobe 2024; 89:102896. [PMID: 39127403 DOI: 10.1016/j.anaerobe.2024.102896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 06/11/2024] [Accepted: 08/06/2024] [Indexed: 08/12/2024]
Abstract
INTRODUCTION Clostridioides difficile is the main cause of antibiotic-associated diarrhea in humans and is a major enteropathogen in several animal species. In newborn piglets, colonic lesions caused by C. difficile A and B toxins (TcdA and TcdB, respectively) cause diarrhea and significant production losses. OBJECTIVE The present study aimed to develop two recombinant vaccines from immunogenic C-terminal fragments of TcdA and TcdB and evaluate the immune response in rabbits and in breeding sows. Two vaccines were produced: bivalent (rAB), consisting of recombinant fragments of TcdA and TcdB, and chimeric (rQAB), corresponding to the synthesis of the same fragments in a single protein. Groups of rabbits were inoculated with 10 or 50 μg of proteins adjuvanted with aluminum or 0.85 % sterile saline in a final volume of 1 mL/dose. Anti-TcdA and anti-TcdB IgG antibodies were detected in rabbits and sows immunized with both rAB and rQAB vaccines by ELISA. The vaccinated sows were inoculated intramuscularly with 20 μg/dose using a prime-boost approach. RESULTS Different antibody titers (p ≤ 0.05) were observed among the vaccinated groups of sows (rAB and rQAB) and control. Additionally, newborn piglets from vaccinated sows were also positive for anti-TcdA and anti-TcdB IgGs, in contrast to control piglets (p ≤ 0.05). Immunization of sows with the rQAB vaccine conferred higher anti-TcdA and anti-TcdB responses in piglets, suggesting the superiority of this compound over rAB. CONCLUSION The synthesized recombinant proteins were capable of inducing antibody titers against C. difficile toxins A and B in sows, and were passively transferred to piglets through colostrum.
Collapse
Affiliation(s)
- Carolina P Ramos
- Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Williane F Siqueira
- Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Laila A Viana
- Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - João L R Cunha
- York Biomedical Research Institute, Department of Biology, University of York, York, UK
| | - Ricardo T Fujiwara
- Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Victor S Amarante
- Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Thayanne G V Souza
- Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Rodrigo O S Silva
- Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
| |
Collapse
|
4
|
Kempher ML, Shadid TM, Larabee JL, Ballard JD. A sequence invariable region in TcdB2 is required for toxin escape from Clostridioides difficile. J Bacteriol 2024; 206:e0009624. [PMID: 38888328 PMCID: PMC11323933 DOI: 10.1128/jb.00096-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Accepted: 05/23/2024] [Indexed: 06/20/2024] Open
Abstract
Sequence differences among the subtypes of Clostridioides difficile toxin TcdB (2,366 amino acids) are broadly distributed across the entire protein, with the notable exception of 76 residues at the protein's carboxy terminus. This sequence invariable region (SIR) is identical at the DNA and protein level among the TcdB variants, suggesting this string of amino acids has undergone selective pressure to prevent alterations. The functional role of the SIR domain in TcdB has not been determined. Analysis of a recombinantly constructed TcdB mutant lacking the SIR domain did not identify changes in TcdB's enzymatic or cytopathic activities. To further assess the SIR region, we constructed a C. difficile strain with the final 228 bp deleted from the tcdB gene, resulting in the production of a truncated form of TcdB lacking the SIR (TcdB2∆2291-2366). Using a combination of approaches, we found in the absence of the SIR sequence TcdB2∆2291-2366 retained cytotoxic activity but was not secreted from C. difficile. TcdB2∆2291-2366 was not released from the cell under autolytic conditions, indicating the SIR is involved in a more discrete step in toxin escape from the bacterium. Fractionation experiments combined with antibody detection found that TcdB2∆2291-2366 accumulates at the cell membrane but is unable to complete steps in secretion beyond this point. These data suggest conservation of the SIR domain across variants of TcdB could be influenced by the sequence's role in efficient escape of the toxin from C. difficile. IMPORTANCE Clostridioides difficile is a leading cause of antibiotic associated disease in the United States. The primary virulence factors produced by C. difficile are two large glucosylating toxins TcdA and TcdB. To date, several sequence variants of TcdB have been identified that differ in various functional properties. Here, we identified a highly conserved region among TcdB subtypes that is required for release of the toxin from C. difficile. This study reveals a putative role for the longest stretch of invariable sequence among TcdB subtypes and provides new details regarding toxin release into the extracellular environment. Improving our understanding of the functional roles of the conserved regions of TcdB variants aids in the development of new, broadly applicable strategies to treat CDI.
Collapse
Affiliation(s)
- Megan L. Kempher
- Department of
Microbiology and Immunology, University of Oklahoma Health Sciences
Center, Oklahoma City,
Oklahoma, USA
- Department of
Chemistry and Biochemistry, University of
Oklahoma, Norman,
Oklahoma, USA
| | - Tyler M. Shadid
- Department of
Microbiology and Immunology, University of Oklahoma Health Sciences
Center, Oklahoma City,
Oklahoma, USA
| | - Jason L. Larabee
- Department of
Microbiology and Immunology, University of Oklahoma Health Sciences
Center, Oklahoma City,
Oklahoma, USA
| | - Jimmy D. Ballard
- Department of
Microbiology and Immunology, University of Oklahoma Health Sciences
Center, Oklahoma City,
Oklahoma, USA
| |
Collapse
|
5
|
Zheng Y, Yang Q, Luo J, Zhang Y, Li X, He L, Ma C, Tao L. Identification of a hemorrhagic determinant in Clostridioides difficile TcdA and Paeniclostridium sordellii TcsH. Microbiol Spectr 2024; 12:e0035424. [PMID: 38709085 PMCID: PMC11237598 DOI: 10.1128/spectrum.00354-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Accepted: 04/18/2024] [Indexed: 05/07/2024] Open
Abstract
Paeniclostridium sordellii hemorrhagic toxin (TcsH) and Clostridioides difficile toxin A (TcdA) are two major members of the large clostridial toxin (LCT) family. These two toxins share ~87% similarity and are known to cause severe hemorrhagic pathology in animals. Yet, the pathogenesis of their hemorrhagic toxicity has been mysterious for decades. Here, we examined the liver injury after systemic exposure to different LCTs and found that only TcsH and TcdA induce overt hepatic hemorrhage. By investigating the chimeric and truncated toxins, we demonstrated that the enzymatic domain of TcsH alone is not sufficient to determine its potent hepatic hemorrhagic toxicity in mice. Likewise, the combined repetitive oligopeptide (CROP) domain of TcsH/TcdA alone also failed to explain their strong hemorrhagic activity in mice. Lastly, we showed that disrupting the first two short repeats of CROPs in TcsH and TcdA impaired hemorrhagic toxicity without causing overt changes in cytotoxicity and lethality. These findings lead to a deeper understanding of toxin-induced hemorrhage and the pathogenesis of LCTs and could be insightful in developing therapeutic avenues against clostridial infections. IMPORTANCE Paeniclostridium sordellii and Clostridioides difficile infections often cause hemorrhage in the affected tissues and organs, which is mainly attributed to their hemorrhagic toxins, TcsH and TcdA. In this study, we demonstrate that TcsH and TcdA, but not other related toxins. including Clostridioides difficile toxin B and TcsL, induce severe hepatic hemorrhage in mice. We further determine that a small region in TcsH and TcdA is critical for the hemorrhagic toxicity but not cytotoxicity or lethality of these toxins. Based on these results, we propose that the hemorrhagic toxicity of TcsH and TcdA is due to an uncharacterized mechanism, such as the presence of an unknown receptor, and future studies to identify the interactive host factors are warranted.
Collapse
Affiliation(s)
- Yangling Zheng
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
- Research Center for Industries of the Future and Key Laboratory of Multi-omics in Infection and Immunity of Zhejiang Province, School of Medicine, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China
| | - Qi Yang
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
- Research Center for Industries of the Future and Key Laboratory of Multi-omics in Infection and Immunity of Zhejiang Province, School of Medicine, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China
| | - Jianhua Luo
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
- Research Center for Industries of the Future and Key Laboratory of Multi-omics in Infection and Immunity of Zhejiang Province, School of Medicine, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China
| | - Yuanyuan Zhang
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
- Research Center for Industries of the Future and Key Laboratory of Multi-omics in Infection and Immunity of Zhejiang Province, School of Medicine, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China
| | - Xingxing Li
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
- Research Center for Industries of the Future and Key Laboratory of Multi-omics in Infection and Immunity of Zhejiang Province, School of Medicine, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China
| | - Liuqing He
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
- Research Center for Industries of the Future and Key Laboratory of Multi-omics in Infection and Immunity of Zhejiang Province, School of Medicine, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China
| | - Chao Ma
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
- Research Center for Industries of the Future and Key Laboratory of Multi-omics in Infection and Immunity of Zhejiang Province, School of Medicine, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China
| | - Liang Tao
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China
- Research Center for Industries of the Future and Key Laboratory of Multi-omics in Infection and Immunity of Zhejiang Province, School of Medicine, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang, China
| |
Collapse
|
6
|
Doyle DA, DeAngelis PL, Ballard JD. CSPG4-dependent cytotoxicity for C. difficile TcdB is influenced by extracellular calcium and chondroitin sulfate. mSphere 2024; 9:e0009424. [PMID: 38470254 PMCID: PMC11036797 DOI: 10.1128/msphere.00094-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 02/21/2024] [Indexed: 03/13/2024] Open
Abstract
TcdB is an intracellular bacterial toxin indispensable to Clostridioides difficile infections. The ability to use chondroitin sulfate proteoglycan 4 (CSPG4) as a primary cell surface receptor is evolutionarily conserved by the two major variants of TcdB. As CSPG4 does not typically undergo receptor-mediated endocytosis, we sought to identify environmental factors that stabilize interactions between TcdB and CSPG4 to promote cell binding and entry into the cytosol. Using a series of TcdB receptor-binding mutants and cell lines with various receptor expression profiles, we discovered that extracellular Ca2+ promotes receptor-specific interactions with TcdB. Specifically, TcdB exhibits preferential binding to CSPG4 in the presence of Ca2+, with the absence of Ca2+ resulting in CSPG4-independent cell surface interactions. Furthermore, Ca2+ did not enhance TcdB binding to chondroitin sulfate (CS), the sole glycosaminoglycan of CSPG4. Instead, CS was found to impact the rate of cell entry by TcdB. Collectively, results from this study indicate that Ca2+ enhances cell binding by TcdB and CS interactions contribute to subsequent steps in cell entry. IMPORTANCE Clostridioides difficile is a leading cause of antibiotic-associated gastrointestinal illness, and many disease pathologies are caused by the toxin TcdB. TcdB engages multiple cell surface receptors, with receptor tropisms differing among the variants of the toxin. Chondroitin sulfate proteoglycan 4 (CSPG4) is a critical receptor for multiple forms of TcdB, and insights into TcdB-CSPG4 interactions are applicable to many disease-causing strains of C. difficile. CSPG4 is modified by chondroitin sulfate (CS) and contains laminin-G repeats stabilized by Ca2+, yet the relative contributions of CS and Ca2+ to TcdB cytotoxicity have not been determined. This study demonstrates distinct roles in TcdB cell binding and cell entry for Ca2+ and CS, respectively. These effects are specific to CSPG4 and contribute to the activities of a prominent isoform of TcdB that utilizes this receptor. These findings advance an understanding of factors contributing to TcdB's mechanism of action and contribution to C. difficile disease.
Collapse
Affiliation(s)
- D. Annie Doyle
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Paul L. DeAngelis
- Department of Biochemistry and Physiology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Jimmy D. Ballard
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| |
Collapse
|
7
|
Kinsolving J, Bous J, Kozielewicz P, Košenina S, Shekhani R, Grätz L, Masuyer G, Wang Y, Stenmark P, Dong M, Schulte G. Structural and functional insight into the interaction of Clostridioides difficile toxin B and FZD 7. Cell Rep 2024; 43:113727. [PMID: 38308843 DOI: 10.1016/j.celrep.2024.113727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 01/12/2024] [Accepted: 01/15/2024] [Indexed: 02/05/2024] Open
Abstract
The G protein-coupled receptors of the Frizzled (FZD) family, in particular FZD1,2,7, are receptors that are exploited by Clostridioides difficile toxin B (TcdB), the major virulence factor responsible for pathogenesis associated with Clostridioides difficile infection. We employ a live-cell assay examining the affinity between full-length FZDs and TcdB. Moreover, we present cryoelectron microscopy structures of TcdB alone and in complex with full-length FZD7, which reveal that large structural rearrangements of the combined repetitive polypeptide domain are required for interaction with FZDs and other TcdB receptors, constituting a first step for receptor recognition. Furthermore, we show that bezlotoxumab, an FDA-approved monoclonal antibody to treat Clostridioides difficile infection, favors the apo-TcdB structure and thus disrupts binding with FZD7. The dynamic transition between the two conformations of TcdB also governs the stability of the pore-forming region. Thus, our work provides structural and functional insight into how conformational dynamics of TcdB determine receptor binding.
Collapse
Affiliation(s)
- Julia Kinsolving
- Karolinska Institutet, Department Physiology & Pharmacology, Sec. Receptor Biology & Signaling, Biomedicum, 17165 Stockholm, Sweden
| | - Julien Bous
- Karolinska Institutet, Department Physiology & Pharmacology, Sec. Receptor Biology & Signaling, Biomedicum, 17165 Stockholm, Sweden
| | - Pawel Kozielewicz
- Karolinska Institutet, Department Physiology & Pharmacology, Sec. Receptor Biology & Signaling, Biomedicum, 17165 Stockholm, Sweden
| | - Sara Košenina
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Rawan Shekhani
- Karolinska Institutet, Department Physiology & Pharmacology, Sec. Receptor Biology & Signaling, Biomedicum, 17165 Stockholm, Sweden
| | - Lukas Grätz
- Karolinska Institutet, Department Physiology & Pharmacology, Sec. Receptor Biology & Signaling, Biomedicum, 17165 Stockholm, Sweden
| | - Geoffrey Masuyer
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Yuankai Wang
- Department of Urology, Boston Children's Hospital, Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Pål Stenmark
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Min Dong
- Department of Urology, Boston Children's Hospital, Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Gunnar Schulte
- Karolinska Institutet, Department Physiology & Pharmacology, Sec. Receptor Biology & Signaling, Biomedicum, 17165 Stockholm, Sweden.
| |
Collapse
|
8
|
Papatheodorou P, Minton NP, Aktories K, Barth H. An Updated View on the Cellular Uptake and Mode-of-Action of Clostridioides difficile Toxins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1435:219-247. [PMID: 38175478 DOI: 10.1007/978-3-031-42108-2_11] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Research on the human gut pathogen Clostridioides (C.) difficile and its toxins continues to attract much attention as a consequence of the threat to human health posed by hypervirulent strains. Toxin A (TcdA) and Toxin B (TcdB) are the two major virulence determinants of C. difficile. Both are single-chain proteins with a similar multidomain architecture. Certain hypervirulent C. difficile strains also produce a third toxin, namely binary toxin CDT (C. difficile transferase). C. difficile toxins are the causative agents of C. difficile-associated diseases (CDADs), such as antibiotics-associated diarrhea and pseudomembranous colitis. For that reason, considerable efforts have been expended to unravel their molecular mode-of-action and the cellular mechanisms responsible for their uptake. Many of these studies have been conducted in European laboratories. Here, we provide an update on our previous review (Papatheodorou et al. Adv Exp Med Biol, 2018) on important advances in C. difficile toxins research.
Collapse
Affiliation(s)
- Panagiotis Papatheodorou
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Ulm, Germany.
| | - Nigel P Minton
- BBSRC/EPSRC Synthetic Biology Research Centre, University of Nottingham, Nottingham, UK
| | - Klaus Aktories
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany
| | - Holger Barth
- Institute of Experimental and Clinical Pharmacology, Toxicology and Pharmacology of Natural Products, Ulm University Medical Center, Ulm, Germany
| |
Collapse
|
9
|
Zhou Y, Zhan X, Luo J, Li D, Zhou R, Zhang J, Pan Z, Zhang Y, Jia T, Zhang X, Li Y, Tao L. Structural dynamics of the CROPs domain control stability and toxicity of Paeniclostridium sordellii lethal toxin. Nat Commun 2023; 14:8426. [PMID: 38114525 PMCID: PMC10730571 DOI: 10.1038/s41467-023-44169-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 12/04/2023] [Indexed: 12/21/2023] Open
Abstract
Paeniclostridium sordellii lethal toxin (TcsL) is a potent exotoxin that causes lethal toxic shock syndrome associated with fulminant bacterial infections. TcsL belongs to the large clostridial toxin (LCT) family. Here, we report that TcsL with varied lengths of combined repetitive oligopeptides (CROPs) deleted show increased autoproteolysis as well as higher cytotoxicity. We next present cryo-EM structures of full-length TcsL, at neutral (pH 7.4) and acidic (pH 5.0) conditions. The TcsL at neutral pH exhibits in the open conformation, which resembles reported TcdB structures. Low pH induces the conformational change of partial TcsL to the closed form. Two intracellular interfaces are observed in the closed conformation, which possibly locks the cysteine protease domain and hinders the binding of the host receptor. Our findings provide insights into the structure and function of TcsL and reveal mechanisms for CROPs-mediated modulation of autoproteolysis and cytotoxicity, which could be common across the LCT family.
Collapse
Affiliation(s)
- Yao Zhou
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310024, China
| | - Xiechao Zhan
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China.
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China.
| | - Jianhua Luo
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310024, China
| | - Diyin Li
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310024, China
| | - Ruoyu Zhou
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Jiahao Zhang
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Zhenrui Pan
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Yuanyuan Zhang
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Tianhui Jia
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310024, China
| | - Xiaofeng Zhang
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Yanyan Li
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China
| | - Liang Tao
- Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, 310024, China.
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang, 310024, China.
- Westlake Institute for Advanced Study, Hangzhou, Zhejiang, 310024, China.
- Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang, 310024, China.
| |
Collapse
|
10
|
Liu S, Wang W, Jia T, Xin L, Xu TT, Wang C, Xie G, Luo K, Li J, Kong J, Zhang Q. Vibrio parahaemolyticus becomes lethal to post-larvae shrimp via acquiring novel virulence factors. Microbiol Spectr 2023; 11:e0049223. [PMID: 37850796 PMCID: PMC10714935 DOI: 10.1128/spectrum.00492-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 09/05/2023] [Indexed: 10/19/2023] Open
Abstract
IMPORTANCE As a severe emerging shrimp disease, TPD has heavily impacted the shrimp aquaculture industry and resulted in serious economic losses in China since spring 2020. This study aimed to identify the key virulent factors and related genes of the Vp TPD, for a better understanding of its pathogenicity of the novel highly lethal infectious pathogen, as well as its molecular epidemiological characteristics in China. The present study revealed that a novel protein, Vibrio high virulent protein-2 (MW >100 kDa), is responsible to the lethal virulence of V. parahaemolyticus to shrimp post-larvae. The results are essential for effectively diagnosing and monitoring novel pathogenic bacteria, like Vp TPD, in aquaculture shrimps and would be beneficial to the fisheries department in early warning of Vp TPD emergence and developing prevention strategies to reduce economic losses due to severe outbreaks of TPD. Elucidation of the key virulence genes and genomics of Vp TPD could also provide valuable information on the evolution and ecology of this emerging pathogen in aquaculture environments.
Collapse
Affiliation(s)
- Shuang Liu
- State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, Shandong, China
- Key Laboratory of Marine Aquaculture Disease Control, Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
| | - Wei Wang
- State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, Shandong, China
| | - Tianchang Jia
- State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, Shandong, China
| | - Lusheng Xin
- State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, Shandong, China
- Key Laboratory of Marine Aquaculture Disease Control, Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
| | - Ting-ting Xu
- State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, Shandong, China
- Key Laboratory of Marine Aquaculture Disease Control, Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
| | - Chong Wang
- State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, Shandong, China
| | - Guosi Xie
- State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, Shandong, China
- Key Laboratory of Marine Aquaculture Disease Control, Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
| | - Kun Luo
- State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, Shandong, China
| | - Jun Li
- School of Sciences and Medicine, Lake Superior State University, Sault Ste. Marie, Michigan, USA
| | - Jie Kong
- State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, Shandong, China
- Key Laboratory of Marine Aquaculture Disease Control, Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
| | - Qingli Zhang
- State Key Laboratory of Mariculture Biobreeding and Sustainable Goods, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, Shandong, China
- Key Laboratory of Marine Aquaculture Disease Control, Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, Shandong, China
| |
Collapse
|
11
|
Kordus SL, Kroh HK, Rodríguez RC, Shrem RA, Peritore-Galve FC, Shupe JA, Wadzinski BE, Lacy DB, Spiller BW. Nanobodies against C. difficile TcdA and TcdB reveal unexpected neutralizing epitopes and provide a toolkit for toxin quantitation in vivo. PLoS Pathog 2023; 19:e1011496. [PMID: 37871122 PMCID: PMC10621975 DOI: 10.1371/journal.ppat.1011496] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 11/02/2023] [Accepted: 10/07/2023] [Indexed: 10/25/2023] Open
Abstract
Clostridioides difficile is a leading cause of antibiotic-associated diarrhea and nosocomial infection in the United States. The symptoms of C. difficile infection (CDI) are associated with the production of two homologous protein toxins, TcdA and TcdB. The toxins are considered bona fide targets for clinical diagnosis as well as the development of novel prevention and therapeutic strategies. While there are extensive studies that document these efforts, there are several gaps in knowledge that could benefit from the creation of new research tools. First, we now appreciate that while TcdA sequences are conserved, TcdB sequences can vary across the span of circulating clinical isolates. An understanding of the TcdA and TcdB epitopes that drive broadly neutralizing antibody responses could advance the effort to identify safe and effective toxin-protein chimeras and fragments for vaccine development. Further, an understanding of TcdA and TcdB concentration changes in vivo can guide research into how host and microbiome-focused interventions affect the virulence potential of C. difficile. We have developed a panel of alpaca-derived nanobodies that bind specific structural and functional domains of TcdA and TcdB. We note that many of the potent neutralizers of TcdA bind epitopes within the delivery domain, a finding that could reflect roles of the delivery domain in receptor binding and/or the conserved role of pore-formation in the delivery of the toxin enzyme domains to the cytosol. In contrast, neutralizing epitopes for TcdB were found in multiple domains. The nanobodies were also used for the creation of sandwich ELISA assays that allow for quantitation of TcdA and/or TcdB in vitro and in the cecal and fecal contents of infected mice. We anticipate these reagents and assays will allow researchers to monitor the dynamics of TcdA and TcdB production over time, and the impact of various experimental interventions on toxin production in vivo.
Collapse
Affiliation(s)
- Shannon L. Kordus
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Heather K. Kroh
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Rubén Cano Rodríguez
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Rebecca A. Shrem
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, United States of America
| | - F. Christopher Peritore-Galve
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - John A. Shupe
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Brian E. Wadzinski
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, United States of America
| | - D. Borden Lacy
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Benjamin W. Spiller
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, United States of America
| |
Collapse
|
12
|
Raeisi H, Azimirad M, Asadzadeh Aghdaei H, Zarnani AH, Abdolalizadeh J, Yadegar A, Zali MR. Development and characterization of phage display-derived anti-toxin antibodies neutralizing TcdA and TcdB of Clostridioides difficile. Microbiol Spectr 2023; 11:e0531022. [PMID: 37668373 PMCID: PMC10580902 DOI: 10.1128/spectrum.05310-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Accepted: 06/08/2023] [Indexed: 09/06/2023] Open
Abstract
TcdA and TcdB are known as the major virulence attributes of Clostridioides difficile. Hence, neutralizing the TcdA and TcdB activities can be considered as an efficient therapeutic approach against C. difficile infection (CDI). In this work, we utilized phage display technique to select single-chain fragment variable (scFv) fragments as recombinant antibodies displayed on the surface of phages, which specifically target native TcdA, or TcdB (nTcdA and nTcdB), and their recombinant C-terminal combined repetitive oligopeptide (CROP) domains (rTcdA and rTcdB). After three rounds of biopanning, abundance of phage clones displaying high reactivity with TcdA or TcdB was quantified through enzyme-linked immunosorbent assay (ELISA). Furthermore, selected scFvs were characterized by cell viability and neutralization assays. The gene expression of immunological markers, IL-8 and TNF-α, was examined in treated Caco-2 cells by RT-qPCR. The epitopes of neutralizing scFvs were also identified by molecular docking. Totally, 18 scFv antibodies (seven for TcdA and 11 for TcdB) were identified by ELISA. Among selected scFvs, two clones for TcdA (rA-C2, A-C9) and three clones for TcdB (rB-B4, B-F5, B-F11) exhibited the highest neutralizing activity in Caco-2 and Vero cells. Moreover, the cocktail of anti-TcdA and anti-TcdB antibodies notably decreased the mRNA expression of TNF-α and IL-8 in Caco-2 cells. Molecular docking revealed that the interaction between scFv and toxin was mostly restricted to CROP domain of TcdA or TcdB. Our results collectively provided more insights for the development of neutralizing scFvs against C. difficile toxins using phage display. Further research is needed to meticulously evaluate the potential of scFvs as an alternative treatment for CDI using animal models and clinical trials.IMPORTANCETargeting the major toxins of Clostridioides difficile by neutralizing antibodies is a novel therapeutic approach for CDI. Here, we report a panel of new anti-TcdA (rA-C2, A-C9) and anti-TcdB (rB-B4, B-F5, and B-F11) recombinant antibody fragments (scFvs) isolated from Tomlinson I and J libraries using phage display technique. These scFv antibodies were capable of neutralizing their respective toxin and showed promise as potential therapeutics against TcdA and TcdB of C. difficile in different in vitro models. In addition, in silico analysis showed that at least two neutralization mechanisms, including inhibiting cell surface binding of toxins and inhibiting toxin internalization can be proposed for the isolated scFvs in this work. These findings provide more insights for the applicability of specific scFvs toward C. difficile toxins at in vitro level. However, further research is required to evaluate the potential application of these scFvs as therapeutic agents for CDI treatment in clinical setting.
Collapse
Affiliation(s)
- Hamideh Raeisi
- Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Masoumeh Azimirad
- Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Hamid Asadzadeh Aghdaei
- Basic and Molecular Epidemiology of Gastrointestinal Disorders Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Amir-Hassan Zarnani
- Department of Immunology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Jalal Abdolalizadeh
- Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Abbas Yadegar
- Foodborne and Waterborne Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad Reza Zali
- Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| |
Collapse
|
13
|
Chen P, Jin R. Receptor binding mechanisms of Clostridioides difficile toxin B and implications for therapeutics development. FEBS J 2023; 290:962-969. [PMID: 34862749 PMCID: PMC9344982 DOI: 10.1111/febs.16310] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 11/19/2021] [Accepted: 12/02/2021] [Indexed: 12/29/2022]
Abstract
Clostridioides difficile is classified as an urgent antibiotic resistance threat by the Centers for Disease Control and Prevention (CDC). C. difficile infection (CDI) is mainly caused by the C. difficile exotoxin TcdB, which invades host cells via receptor-mediated endocytosis. However, many natural variants of TcdB have been identified including some from the hypervirulent strains, which pose significant challenges for developing effective CDI therapies. Here, we review the recent research progress on the molecular mechanisms by which TcdB recognizes Frizzed proteins (FZDs) and chondroitin sulfate proteoglycan 4 (CSPG4) as two major host receptors. We suggest that the receptor-binding sites and several previously identified neutralizing epitopes on TcdB are ideal targets for the development of broad-spectrum inhibitors to protect against diverse TcdB variants.
Collapse
Affiliation(s)
- Peng Chen
- Department of Physiology and Biophysics, University of California Irvine, Irvine, California, 92697, USA
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California Irvine, Irvine, California, 92697, USA
| |
Collapse
|
14
|
Cherny KE, Balaji A, Mukherjee J, Goo YA, Hauser AR, Ozer E, Satchell KJF, Bachta KER, Kochan TJ, Mitra SD, Kociolek LK. Identification of Clostridium innocuum hypothetical protein that is cross-reactive with C. difficile anti-toxin antibodies. Anaerobe 2022; 75:102555. [PMID: 35367613 PMCID: PMC9197939 DOI: 10.1016/j.anaerobe.2022.102555] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/25/2022] [Accepted: 03/28/2022] [Indexed: 11/01/2022]
Abstract
OBJECTIVES Previously considered solely an opportunistic pathogen, Clostridium innocuum (CI) was recently reported in Taiwan to be an emerging cause of antibiotic-associated diarrhea and clinically indistinguishable from Clostridioides difficile (CD) infection. We previously identified CI culture supernatant being cross-reactive with commercial CD toxin enzyme immunoassays. We aimed to identify and characterize the cross-reacting protein and determine whether it functioned as a human toxin. METHODS We performed western blots using CI culture supernatants and CD anti-toxin antibodies and identified interacting bands. We identified protein(s) using tandem mass spectrometry and evaluated them by cytotoxicity assays. RESULTS CI, but not CD, was isolated from stool of 12 children and adults with diarrhea. Culture supernatant from 6/12 CI isolates, and an ATCC reference strain, tested positive for CD toxins (total 7/13 isolates) by commercial EIA. Using two of these isolates, we identified two ∼40 kDa hypothetical proteins, CI_01447 and CI_01448, and confirmed cross-reactivity with CD anti-toxin antibodies by enzyme immunoassay and Western blot. Whole-genome sequencing confirmed all 13 isolates contained both genes, which were highly conserved. We observed no cytopathic or cytotoxic effects to HeLa cells when treated with these proteins. We identified amino acid sequence similarity to the NlpC/P60 family of proteins. CONCLUSIONS Our findings do not suggest CI proteins CI_01448 and CI_01447, which cross-react with antibodies against CD toxins A and B, are toxic to HeLa cells. Further studies are needed to determine the function of these cross-reacting proteins and the potential virulence factors that could be responsible for CI diarrheal disease.
Collapse
Affiliation(s)
- K E Cherny
- Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, USA; Northwestern University, Feinberg School of Medicine, Chicago, IL, USA.
| | - A Balaji
- Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, USA
| | - J Mukherjee
- Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, USA
| | - Y A Goo
- Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - A R Hauser
- Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - E Ozer
- Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - K J F Satchell
- Northwestern University, Feinberg School of Medicine, Chicago, IL, USA; Center for Structural Genomics of Infectious Diseases, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - K E R Bachta
- Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - T J Kochan
- Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - S D Mitra
- Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - L K Kociolek
- Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, USA; Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| |
Collapse
|
15
|
Kordus SL, Thomas AK, Lacy DB. Clostridioides difficile toxins: mechanisms of action and antitoxin therapeutics. Nat Rev Microbiol 2022; 20:285-298. [PMID: 34837014 PMCID: PMC9018519 DOI: 10.1038/s41579-021-00660-2] [Citation(s) in RCA: 92] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/21/2021] [Indexed: 01/03/2023]
Abstract
Clostridioides difficile is a Gram-positive anaerobe that can cause a spectrum of disorders that range in severity from mild diarrhoea to fulminant colitis and/or death. The bacterium produces up to three toxins, which are considered the major virulence factors in C. difficile infection. These toxins promote inflammation, tissue damage and diarrhoea. In this Review, we highlight recent biochemical and structural advances in our understanding of the mechanisms that govern host-toxin interactions. Understanding how C. difficile toxins affect the host forms a foundation for developing novel strategies for treatment and prevention of C. difficile infection.
Collapse
Affiliation(s)
- Shannon L. Kordus
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA,Center for Structural Biology, Vanderbilt University, Nashville, TN, USA,These authors contributed equally: Shannon L. Kordus, Audrey K. Thomas
| | - Audrey K. Thomas
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA,Center for Structural Biology, Vanderbilt University, Nashville, TN, USA,These authors contributed equally: Shannon L. Kordus, Audrey K. Thomas
| | - D. Borden Lacy
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA,Center for Structural Biology, Vanderbilt University, Nashville, TN, USA,The Veterans Affairs, Tennessee Valley Healthcare, System, Nashville, TN, USA,
| |
Collapse
|
16
|
Luo J, Yang Q, Zhang X, Zhang Y, Wan L, Zhan X, Zhou Y, He L, Li D, Jin D, Zhen Y, Huang J, Li Y, Tao L. TFPI is a colonic crypt receptor for TcdB from hypervirulent clade 2 C. difficile. Cell 2022; 185:980-994.e15. [PMID: 35303428 DOI: 10.1016/j.cell.2022.02.010] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 01/11/2022] [Accepted: 02/08/2022] [Indexed: 12/14/2022]
Abstract
The emergence of hypervirulent clade 2 Clostridioides difficile is associated with severe symptoms and accounts for >20% of global infections. TcdB is a dominant virulence factor of C. difficile, and clade 2 strains exclusively express two TcdB variants (TcdB2 and TcdB4) that use unknown receptors distinct from the classic TcdB. Here, we performed CRISPR/Cas9 screens for TcdB4 and identified tissue factor pathway inhibitor (TFPI) as its receptor. Using cryo-EM, we determined a complex structure of the full-length TcdB4 with TFPI, defining a common receptor-binding region for TcdB. Residue variations within this region divide major TcdB variants into 2 classes: one recognizes Frizzled (FZD), and the other recognizes TFPI. TFPI is highly expressed in the intestinal glands, and recombinant TFPI protects the colonic epithelium from TcdB2/4. These findings establish TFPI as a colonic crypt receptor for TcdB from clade 2 C. difficile and reveal new mechanisms for CDI pathogenesis.
Collapse
Affiliation(s)
- Jianhua Luo
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Qi Yang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Xiaofeng Zhang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Yuanyuan Zhang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China; School of Food Science and Biotechnology Engineering, Zhejiang Gongshang University, Hangzhou, Zhejiang 310018, China
| | - Li Wan
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Xiechao Zhan
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Yao Zhou
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Liuqing He
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, 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; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Dazhi Jin
- Center 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 310014, China
| | - Ying Zhen
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Jing Huang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Yanyan Li
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China.
| | - Liang Tao
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China.
| |
Collapse
|
17
|
Abstract
![]()
The paradigm of antivirulence
therapy dictates that bacterial pathogens
are specifically disarmed but not killed by neutralizing their virulence
factors. Clearance of the invading pathogen by the immune system is
promoted. As compared to antibiotics, the pathogen-selective antivirulence
drugs hold promise to minimize collateral damage to the beneficial
microbiome. Also, selective pressure for resistance is expected to
be lower because bacterial viability is not directly affected. Antivirulence
drugs are being developed for stand-alone prophylactic and therapeutic
treatments but also for combinatorial use with antibiotics. This Review
focuses on drug modalities that target bacterial exotoxins after the
secretion or release-upon-lysis. Exotoxins have a significant and
sometimes the primary role as the disease-causing virulence factor,
and thereby they are attractive targets for drug development. We describe
the key pre-clinical and clinical trial data that have led to the
approval of currently used exotoxin-targeted drugs, namely the monoclonal
antibodies bezlotoxumab (toxin B/TcdB, Clostridioides difficile), raxibacumab (anthrax toxin, Bacillus anthracis), and obiltoxaximab (anthrax toxin, Bacillus anthracis), but also to challenges with some of the promising leads. We also
highlight the recent developments in pre-clinical research sector
to develop exotoxin-targeted drug modalities, i.e., monoclonal antibodies,
antibody fragments, antibody mimetics, receptor analogs, neutralizing
scaffolds, dominant-negative mutants, and small molecules. We describe
how these exotoxin-targeted drug modalities work with high-resolution
structural knowledge and highlight their advantages and disadvantages
as antibiotic alternatives.
Collapse
Affiliation(s)
- Moona Sakari
- Institute of Biomedicine, Research Unit for Infection and Immunity, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland
| | - Arttu Laisi
- Institute of Biomedicine, Research Unit for Infection and Immunity, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland
| | - Arto T. Pulliainen
- Institute of Biomedicine, Research Unit for Infection and Immunity, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland
| |
Collapse
|
18
|
Chaves-Cordero C, Quesada-Gómez C, Chaves-Olarte E, Barquero-Calvo E. Human neutrophils are resistant to Clostridioides difficile toxin B. Anaerobe 2022; 74:102553. [DOI: 10.1016/j.anaerobe.2022.102553] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 03/18/2022] [Accepted: 03/21/2022] [Indexed: 02/08/2023]
|
19
|
Aminzadeh A, Larsen CE, Boesen T, Jørgensen R. High-resolution structure of native toxin A from Clostridioides difficile. EMBO Rep 2022; 23:e53597. [PMID: 34817920 PMCID: PMC8728606 DOI: 10.15252/embr.202153597] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 11/09/2021] [Accepted: 11/10/2021] [Indexed: 01/07/2023] Open
Abstract
Clostridioides difficile infections have emerged as the leading cause of healthcare-associated infectious diarrhea. Disease symptoms are mainly caused by the virulence factors, TcdA and TcdB, which are large homologous multidomain proteins. Here, we report a 2.8 Å resolution cryo-EM structure of native TcdA, unveiling its conformation at neutral pH. The structure uncovers the dynamic movement of the CROPs domain which is induced in response to environmental acidification. Furthermore, the structure reveals detailed information about the interaction area between the CROPs domain and the tip of the delivery and receptor-binding domain, which likely serves to shield the C-terminal part of the hydrophobic pore-forming region from solvent exposure. Similarly, extensive interactions between the globular subdomain and the N-terminal part of the pore-forming region suggest that the globular subdomain shields the upper part of the pore-forming region from exposure to the surrounding solvent. Hence, the TcdA structure provides insights into the mechanism of preventing premature unfolding of the pore-forming region at neutral pH, as well as the pH-induced inter-domain dynamics.
Collapse
Affiliation(s)
- Aria Aminzadeh
- Department of Bacteria, Parasites and FungiStatens Serum InstitutCopenhagenDenmark
| | - Christian Engelbrecht Larsen
- Interdisciplinary Nanoscience Center (iNANO)Aarhus UniversityAarhusDenmark
- Department of Molecular Biology and GeneticsAarhus UniversityAarhusDenmark
| | - Thomas Boesen
- Interdisciplinary Nanoscience Center (iNANO)Aarhus UniversityAarhusDenmark
- Department of Molecular Biology and GeneticsAarhus UniversityAarhusDenmark
| | - René Jørgensen
- Department of Bacteria, Parasites and FungiStatens Serum InstitutCopenhagenDenmark
- Department of Science and EnvironmentUniversity of RoskildeRoskildeDenmark
| |
Collapse
|
20
|
Orrell KE, Melnyk RA. Translocation expands the scope of the large clostridial toxin family. Trends Biochem Sci 2021; 46:953-959. [PMID: 34429235 DOI: 10.1016/j.tibs.2021.07.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 07/20/2021] [Accepted: 07/30/2021] [Indexed: 10/20/2022]
Abstract
Large clostridial toxins (LCTs) are a family of six homologous disease-causing proteins characterised by their large size (>200 kDa) and conserved multidomain architectures. Using their central translocation and receptor-binding domain (T domain), LCTs bind host cell receptors and translocate their upstream glycosyltransferase and cysteine protease domain across the endosomal membrane and into the cytosol. The recent discovery of hundreds of LCT-like T domains in diverse genomic contexts and domain architectures from bacteria other than clostridia has provided significant new insights into the enigmatic process of LCT translocation, but also has put the definition of what constitutes an LCT into question. In this opinion article, we discuss how these findings have expanded our understanding of LCT translocation and reshaped the scope of the LCT family.
Collapse
Affiliation(s)
- Kathleen E Orrell
- Molecular Medicine Program, The Hospital for Sick Children Research Institute, Toronto M5G 0A4, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto M5S 1A8, Ontario, Canada
| | - Roman A Melnyk
- Molecular Medicine Program, The Hospital for Sick Children Research Institute, Toronto M5G 0A4, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto M5S 1A8, Ontario, Canada.
| |
Collapse
|
21
|
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: 42] [Impact Index Per Article: 10.5] [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.
Collapse
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.
| |
Collapse
|
22
|
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.
Collapse
|
23
|
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: 29] [Impact Index Per Article: 7.3] [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.
Collapse
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)
| |
Collapse
|
24
|
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: 4.0] [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.
Collapse
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:
| |
Collapse
|
25
|
Schöttelndreier D, Langejürgen A, Lindner R, Genth H. Low Density Lipoprotein Receptor-Related Protein-1 (LRP1) Is Involved in the Uptake of Clostridioides difficile Toxin A and Serves as an Internalizing Receptor. Front Cell Infect Microbiol 2020; 10:565465. [PMID: 33194803 PMCID: PMC7604483 DOI: 10.3389/fcimb.2020.565465] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 09/28/2020] [Indexed: 01/24/2023] Open
Abstract
Toxin producing Clostridioides difficile strains cause gastrointestinal infections with the large glucosylating protein toxins A (TcdA) and B (TcdB) being major virulence factors responsible for the onset of symptoms. TcdA and TcdB enter their target cells via receptor-mediated endocytosis. Inside the cell, the toxins glucosylate and thereby inactivate small GTPases of the Rho-/Ras subfamilies resulting in actin reorganization and cell death. The receptors of TcdA are still elusive, glycoprotein 96 (gp96), the low density lipoprotein receptor family (LDLR) and sulfated glycosaminoglycans (sGAGs) have most recently been suggested as receptors for TcdA. In this study, we provide evidence on rapid endocytosis of Low density lipoprotein Receptor-related Protein-1 (LRP1) into fibroblasts and Caco-2 cells by exploiting biotinylation of cell surface proteins. In contrast, gp96 was not endocytosed either in the presence or absence of TcdA. The kinetics of internalization of TfR and LRP1 were comparable in the presence and the absence of TcdA, excluding that TcdA facilitates its internalization by triggering internalization of its receptors. Exploiting fibroblasts with a genetic deletion of LRP1, TcdA was about one order of magnitude less potent in LRP1-deficient cells as compared to the corresponding control cells. In contrast, TcdB exhibited a comparable potency in LRP1-proficient and -deficient fibroblasts. These findings suggested a role of LRP1 in the cellular uptake of TcdA but not of TcdB. Correspondingly, binding of TcdA to the cell surface of LRP1-deficient fibroblasts was reduced as compared with LRP1-proficient fibroblasts. Finally, TcdA bound to LRP1 ligand binding type repeat cluster II (amino acid 786–1,165) and cluster IV (amino acid 3332-3779). In conclusion, LRP1 appears to serve as an endocytic receptor and gp96 as a non-endocytic receptor for TcdA.
Collapse
Affiliation(s)
| | - Anna Langejürgen
- Institutes for Toxicology, Hannover Medical School, Hannover, Germany
| | - Robert Lindner
- Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany
| | - Harald Genth
- Institutes for Toxicology, Hannover Medical School, Hannover, Germany
| |
Collapse
|
26
|
Martins CS, Costa DVS, Lima BB, Leitäo RFC, Freire GE, Silva GFM, Pacífico DM, Abreu JG, Brito GAC. Clostridioides difficile Toxin A-Induced Wnt/β-Catenin Pathway Inhibition Is Mediated by Rac1 Glucosylation. Front Microbiol 2020; 11:1998. [PMID: 32983019 PMCID: PMC7483921 DOI: 10.3389/fmicb.2020.01998] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 07/28/2020] [Indexed: 11/13/2022] Open
Abstract
Clostridioides difficile toxin A (TcdA) has been shown to inhibit cellular Wnt signaling, the major driving force behind the proliferation of epithelial cells in colonic crypts, likely through the inhibition of β-catenin nuclear translocation. Herein, we aimed to advance the understanding of this mechanism by replicating the findings in vivo and by investigating the specific role of Rac1, a member of the Rho GTPase family, on the inhibition of the Wnt-induced β-catenin nuclear translocation triggered by TcdA. To investigate the effects of TcdA on the Wnt/β-catenin pathway in vivo, we injected the ileal loops of C57BL/6 mice with TcdA [phosphate-buffered saline (PBS) as the control] to induce C. difficile disease-like ileitis. After 4 h post-injection, we obtained ileum tissue samples to assess Wnt signaling activation and cell proliferation through Western blotting, immunohistochemistry, and qPCR. To assess the role of Rac1 on Wnt signaling inhibition by TcdA, we transfected rat intestinal epithelial cells (IEC-6) with either a constitutively active Rac1 plasmid (pcDNA3-EGFP-Rac1-Q61L) or an empty vector, which served as the control. We incubated these cells with Wnt3a-conditioned medium (Wnt3a-CM) to induce Wnt/β-catenin pathway activation, and then challenged the cells with TcdA. We assessed Wnt signaling activation in vitro with TOP/FOPflash luciferase assays, determined nuclear β-catenin translocation by immunofluorescence, measured cyclin D1 protein expression by Western blotting, and quantified cell proliferation by Ki67 immunostaining. In vivo, TcdA decreased β-catenin, cyclin D1, and cMYC expression and inhibited the translocation of β-catenin into the nucleus in the ileum epithelial cells. In addition, TcdA suppressed cell proliferation and increased Wnt3a expression, but did not alter Rac1 gene expression in the ileum tissue. In vitro, constitutively active Rac1 prevented Wnt signaling inhibition by enabling the β-catenin nuclear translocation that had been blocked by TcdA. Our results show that TcdA inhibits Wnt/β-catenin pathway in vivo and demonstrate that this inhibition is likely caused by a Rac1-mediated mechanism.
Collapse
Affiliation(s)
- Conceição S Martins
- Postgraduate Program in Morphofunctional Sciences, Department of Morphology, School of Medicine, Federal University of Ceará, Fortaleza, Brazil
| | - Deiziane V S Costa
- Department of Physiology and Pharmacology, School of Medicine, Federal University of Ceará, Fortaleza, Brazil
| | - Bruno B Lima
- Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, GA, United States
| | - Renata F C Leitäo
- Postgraduate Program in Morphofunctional Sciences, Department of Morphology, School of Medicine, Federal University of Ceará, Fortaleza, Brazil
| | - Gildênio E Freire
- Postgraduate Program in Morphofunctional Sciences, Department of Morphology, School of Medicine, Federal University of Ceará, Fortaleza, Brazil
| | - Guilherme F M Silva
- Department of Medical Sciences, School of Medicine, Federal University of Ceará, Fortaleza, Brazil
| | - Dvison M Pacífico
- Department of Medical Sciences, School of Medicine, Federal University of Ceará, Fortaleza, Brazil
| | - José G Abreu
- Department of Anatomy, Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Gerly A C Brito
- Postgraduate Program in Morphofunctional Sciences, Department of Morphology, School of Medicine, Federal University of Ceará, Fortaleza, Brazil.,Department of Physiology and Pharmacology, School of Medicine, Federal University of Ceará, Fortaleza, Brazil
| |
Collapse
|
27
|
Giacobbe DR, Dettori S, Di Bella S, Vena A, Granata G, Luzzati R, Petrosillo N, Bassetti M. Bezlotoxumab for Preventing Recurrent Clostridioides difficile Infection: A Narrative Review from Pathophysiology to Clinical Studies. Infect Dis Ther 2020; 9:481-494. [PMID: 32632582 PMCID: PMC7452994 DOI: 10.1007/s40121-020-00314-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Indexed: 12/17/2022] Open
Abstract
Clostridioides difficile infection (CDI) and recurrent CDI (rCDI) remain associated with a reduction in the patients' quality of life and with increased healthcare costs. Bezlotoxumab is a monoclonal antibody against toxin B of C. difficile, approved for prevention of rCDI. In this narrative review, we briefly discuss the pathophysiology of CDI and the mechanism of action of bezlotoxumab, as well as the available evidence from investigational and observational studies in terms of efficacy, effectiveness, and safety of bezlotoxumab for the prevention of rCDI. Overall, bezlotoxumab has proved efficacious in reducing the burden of rCDI, thereby providing clinicians with an important novel strategy to achieve sustained cure. Nonetheless, experiences outside randomized controlled trials (RCTs) remain scant, and mostly represented by case series without a control group. Along with the conduction of RCTs to directly compare bezlotoxumab with faecal microbiota transplantation (or to precisely evaluate the role of their combined use), further widening our post-marketing experience remains paramount to firmly guide the use of bezlotoxumab outside RCTs, and to clearly identify those real-life settings where its preventive benefits can be exploited most.
Collapse
Affiliation(s)
- Daniele Roberto Giacobbe
- Infectious Diseases Unit, Ospedale Policlinico San Martino, IRCCS, Genoa, Italy.
- Department of Health Sciences, University of Genoa, Genoa, Italy.
| | - Silvia Dettori
- Infectious Diseases Unit, Ospedale Policlinico San Martino, IRCCS, Genoa, Italy
- Department of Health Sciences, University of Genoa, Genoa, Italy
| | - Stefano Di Bella
- Clinical Department of Medical, Surgical and Health Sciences, Trieste University, Trieste, Italy
| | - Antonio Vena
- Infectious Diseases Unit, Ospedale Policlinico San Martino, IRCCS, Genoa, Italy
| | - Guido Granata
- Clinical and Research Department for Infectious Diseases, Severe and Immunedepression-Associated Infections Unit, National Institute for Infectious Diseases L. Spallanzani, IRCCS, Rome, Italy
| | - Roberto Luzzati
- Clinical Department of Medical, Surgical and Health Sciences, Trieste University, Trieste, Italy
| | - Nicola Petrosillo
- Clinical and Research Department for Infectious Diseases, Severe and Immunedepression-Associated Infections Unit, National Institute for Infectious Diseases L. Spallanzani, IRCCS, Rome, Italy
| | - Matteo Bassetti
- Infectious Diseases Unit, Ospedale Policlinico San Martino, IRCCS, Genoa, Italy
- Department of Health Sciences, University of Genoa, Genoa, Italy
| |
Collapse
|
28
|
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: 31] [Impact Index Per Article: 6.2] [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.
Collapse
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.
| |
Collapse
|
29
|
Engevik MA, Danhof HA, Chang-Graham AL, Spinler JK, Engevik KA, Herrmann B, Endres BT, Garey KW, Hyser JM, Britton RA, Versalovic J. Human intestinal enteroids as a model of Clostridioides difficile-induced enteritis. Am J Physiol Gastrointest Liver Physiol 2020; 318:G870-G888. [PMID: 32223302 PMCID: PMC7272722 DOI: 10.1152/ajpgi.00045.2020] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Clostridioides difficile is an important nosocomial pathogen that produces toxins to cause life-threatening diarrhea and colitis. Toxins bind to epithelial receptors and promote the collapse of the actin cytoskeleton. C. difficile toxin activity is commonly studied in cancer-derived and immortalized cell lines. However, the biological relevance of these models is limited. Moreover, no model is available for examining C. difficile-induced enteritis, an understudied health problem. We hypothesized that human intestinal enteroids (HIEs) express toxin receptors and provide a new model to dissect C. difficile cytotoxicity in the small intestine. We generated biopsy-derived jejunal HIE and Vero cells, which stably express LifeAct-Ruby, a fluorescent label of F-actin, to monitor actin cytoskeleton rearrangement by live-cell microscopy. Imaging analysis revealed that toxins from pathogenic C. difficile strains elicited cell rounding in a strain-dependent manner, and HIEs were tenfold more sensitive to toxin A (TcdA) than toxin B (TcdB). By quantitative PCR, we paradoxically found that HIEs expressed greater quantities of toxin receptor mRNA and yet exhibited decreased sensitivity to toxins when compared with traditionally used cell lines. We reasoned that these differences may be explained by components, such as mucins, that are present in HIEs cultures, that are absent in immortalized cell lines. Addition of human-derived mucin 2 (MUC2) to Vero cells delayed cell rounding, indicating that mucus serves as a barrier to toxin-receptor binding. This work highlights that investigation of C. difficile infection in that HIEs can provide important insights into the intricate interactions between toxins and the human intestinal epithelium.NEW & NOTEWORTHY In this article, we developed a novel model of Clostridioides difficile-induced enteritis using jejunal-derived human intestinal enteroids (HIEs) transduced with fluorescently tagged F-actin. Using live-imaging, we identified that jejunal HIEs express high levels of TcdA and CDT receptors, are more sensitive to TcdA than TcdB, and secrete mucus, which delays toxin-epithelial interactions. This work also optimizes optically clear C. difficile-conditioned media suitable for live-cell imaging.
Collapse
Affiliation(s)
- Melinda A. Engevik
- 1Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas,2Department of Pathology, Texas Children’s Hospital, Houston, Texas
| | - Heather A. Danhof
- 3Alkek Center for Metagenomic and Microbiome Research, Baylor College of Medicine, Houston, Texas,4Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | | | - Jennifer K. Spinler
- 1Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas,2Department of Pathology, Texas Children’s Hospital, Houston, Texas
| | - Kristen A. Engevik
- 3Alkek Center for Metagenomic and Microbiome Research, Baylor College of Medicine, Houston, Texas,4Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Beatrice Herrmann
- 1Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas,2Department of Pathology, Texas Children’s Hospital, Houston, Texas
| | - Bradley T. Endres
- 5Department of Pharmacy Practice and Translational Research, University of Houston College of Pharmacy, Houston, Texas
| | - Kevin W. Garey
- 5Department of Pharmacy Practice and Translational Research, University of Houston College of Pharmacy, Houston, Texas
| | - Joseph M. Hyser
- 1Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas,2Department of Pathology, Texas Children’s Hospital, Houston, Texas
| | - Robert A. Britton
- 3Alkek Center for Metagenomic and Microbiome Research, Baylor College of Medicine, Houston, Texas,4Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - James Versalovic
- 1Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas,2Department of Pathology, Texas Children’s Hospital, Houston, Texas
| |
Collapse
|
30
|
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: 24] [Impact Index Per Article: 4.8] [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.
Collapse
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.
| |
Collapse
|
31
|
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: 75] [Impact Index Per Article: 15.0] [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.
Collapse
|
32
|
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: 54] [Impact Index Per Article: 10.8] [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.
Collapse
|
33
|
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: 19] [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.
Collapse
|
34
|
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: 19] [Impact Index Per Article: 3.2] [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.
Collapse
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
| |
Collapse
|
35
|
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: 61] [Impact Index Per Article: 10.2] [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.
Collapse
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.
| |
Collapse
|
36
|
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: 24] [Impact Index Per Article: 4.0] [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.
Collapse
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
| |
Collapse
|
37
|
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: 5] [Impact Index Per Article: 0.8] [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.
Collapse
|
38
|
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: 8] [Impact Index Per Article: 1.3] [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.
Collapse
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.
| |
Collapse
|
39
|
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: 2.5] [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.
Collapse
|
40
|
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: 2.0] [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.
Collapse
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
| |
Collapse
|
41
|
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: 2.1] [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.
Collapse
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
| |
Collapse
|
42
|
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: 2.6] [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.
Collapse
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
| |
Collapse
|
43
|
Johnson S, Gerding DN. Bezlotoxumab. Clin Infect Dis 2018; 68:699-704. [DOI: 10.1093/cid/ciy577] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 07/10/2018] [Indexed: 01/05/2023] Open
Affiliation(s)
- Stuart Johnson
- Hines Veterans Affairs Hospital, Hines, Illinois
- Loyola University Medical Center, Maywood, Illinois
| | | |
Collapse
|
44
|
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: 14] [Impact Index Per Article: 2.0] [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.
Collapse
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
| |
Collapse
|
45
|
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: 1.0] [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.
Collapse
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
| |
Collapse
|
46
|
Chen P, Tao L, Wang T, Zhang J, He A, Lam KH, Liu Z, He X, Perry K, Dong M, Jin R. Structural basis for recognition of frizzled proteins by Clostridium difficile toxin B. Science 2018; 360:664-669. [PMID: 29748286 PMCID: PMC6231499 DOI: 10.1126/science.aar1999] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 04/04/2018] [Indexed: 12/12/2022]
Abstract
Clostridium difficile infection is the most common cause of antibiotic-associated diarrhea in developed countries. The major virulence factor, C. difficile toxin B (TcdB), targets colonic epithelia by binding to the frizzled (FZD) family of Wnt receptors, but how TcdB recognizes FZDs is unclear. Here, we present the crystal structure of a TcdB fragment in complex with the cysteine-rich domain of human FZD2 at 2.5-angstrom resolution, which reveals an endogenous FZD-bound fatty acid acting as a co-receptor for TcdB binding. This lipid occupies the binding site for Wnt-adducted palmitoleic acid in FZDs. TcdB binding locks the lipid in place, preventing Wnt from engaging FZDs and signaling. Our findings establish a central role of fatty acids in FZD-mediated TcdB pathogenesis and suggest strategies to modulate Wnt signaling.
Collapse
Affiliation(s)
- Peng Chen
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Liang Tao
- Department of Urology, Boston Children's Hospital, Department of Microbiology and Immunobiology and Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Tianyu Wang
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Jie Zhang
- Department of Urology, Boston Children's Hospital, Department of Microbiology and Immunobiology and Department of Surgery, Harvard Medical School, Boston, MA, USA
| | - Aina He
- Department of Urology, Boston Children's Hospital, Department of Microbiology and Immunobiology and Department of Surgery, Harvard Medical School, Boston, MA, USA
- Department of Oncology, Affiliated Sixth People's Hospital, Shanghai Jiaotong University, No. 600, Yishan Road, 200233 Shanghai, PRC
| | - 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
| | - Xi He
- F. M. Kirby Neurobiology Center, Boston Children's Hospital, Department of Neurology, Harvard Medical School, Boston, MA, USA
| | - Kay Perry
- NE-CAT and Department of Chemistry and Chemical Biology, Cornell University, Argonne National Laboratory, Argonne, IL, USA
| | - Min Dong
- Department of Urology, Boston Children's Hospital, Department of Microbiology and Immunobiology and Department of Surgery, Harvard Medical School, Boston, MA, USA.
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA.
| |
Collapse
|
47
|
Kroh HK, Chandrasekaran R, Zhang Z, Rosenthal K, Woods R, Jin X, Nyborg AC, Rainey GJ, Warrener P, Melnyk RA, Spiller BW, Lacy DB. A neutralizing antibody that blocks delivery of the enzymatic cargo of Clostridium difficile toxin TcdB into host cells. J Biol Chem 2017; 293:941-952. [PMID: 29180448 DOI: 10.1074/jbc.m117.813428] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 11/08/2017] [Indexed: 12/14/2022] Open
Abstract
Clostridium difficile infection is the leading cause of hospital-acquired diarrhea and is mediated by the actions of two toxins, TcdA and TcdB. The toxins perturb host cell function through a multistep process of receptor binding, endocytosis, low pH-induced pore formation, and the translocation and delivery of an N-terminal glucosyltransferase domain that inactivates host GTPases. Infection studies with isogenic strains having defined toxin deletions have established TcdB as an important target for therapeutic development. Monoclonal antibodies that neutralize TcdB function have been shown to protect against C. difficile infection in animal models and reduce recurrence in humans. Here, we report the mechanism of TcdB neutralization by PA41, a humanized monoclonal antibody capable of neutralizing TcdB from a diverse array of C. difficile strains. Through a combination of structural, biochemical, and cell functional studies, involving X-ray crystallography and EM, we show that PA41 recognizes a single, highly conserved epitope on the TcdB glucosyltransferase domain and blocks productive translocation and delivery of the enzymatic cargo into the host cell. Our study reveals a unique mechanism of C. difficile toxin neutralization by a monoclonal antibody, which involves targeting a process that is conserved across the large clostridial glucosylating toxins. The PA41 antibody described here provides a valuable tool for dissecting the mechanism of toxin pore formation and translocation across the endosomal membrane.
Collapse
Affiliation(s)
- Heather K Kroh
- From the Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2363
| | - Ramyavardhanee Chandrasekaran
- From the Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2363
| | - Zhifen Zhang
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | | | - Rob Woods
- MedImmune LLC, Gaithersburg, Maryland 20878-2204
| | - Xiaofang Jin
- MedImmune LLC, Gaithersburg, Maryland 20878-2204
| | | | | | | | - Roman A Melnyk
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - Benjamin W Spiller
- From the Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2363.,Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232-6600, and
| | - D Borden Lacy
- From the Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2363, .,Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee 37212-2637
| |
Collapse
|
48
|
Chandrasekaran R, Lacy DB. The role of toxins in Clostridium difficile infection. FEMS Microbiol Rev 2017; 41:723-750. [PMID: 29048477 PMCID: PMC5812492 DOI: 10.1093/femsre/fux048] [Citation(s) in RCA: 232] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 10/10/2017] [Indexed: 02/06/2023] Open
Abstract
Clostridium difficile is a bacterial pathogen that is the leading cause of nosocomial antibiotic-associated diarrhea and pseudomembranous colitis worldwide. The incidence, severity, mortality and healthcare costs associated with C. difficile infection (CDI) are rising, making C. difficile a major threat to public health. Traditional treatments for CDI involve use of antibiotics such as metronidazole and vancomycin, but disease recurrence occurs in about 30% of patients, highlighting the need for new therapies. The pathogenesis of C. difficile is primarily mediated by the actions of two large clostridial glucosylating toxins, toxin A (TcdA) and toxin B (TcdB). Some strains produce a third toxin, the binary toxin C. difficile transferase, which can also contribute to C. difficile virulence and disease. These toxins act on the colonic epithelium and immune cells and induce a complex cascade of cellular events that result in fluid secretion, inflammation and tissue damage, which are the hallmark features of the disease. In this review, we summarize our current understanding of the structure and mechanism of action of the C. difficile toxins and their role in disease.
Collapse
Affiliation(s)
- Ramyavardhanee Chandrasekaran
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - D. Borden Lacy
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
- The Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN 37232, USA
| |
Collapse
|