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Cassona CP, Ramalhete S, Amara K, Candela T, Kansau I, Denève-Larrazet C, Janoir-Jouveshomme C, Mota LJ, Dupuy B, Serrano M, Henriques AO. Spores of Clostridioides difficile are toxin delivery vehicles. Commun Biol 2024; 7:839. [PMID: 38987278 PMCID: PMC11237016 DOI: 10.1038/s42003-024-06521-x] [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: 05/08/2023] [Accepted: 06/28/2024] [Indexed: 07/12/2024] Open
Abstract
Clostridioides difficile causes a wide range of intestinal diseases through the action of two main cytotoxins, TcdA and TcdB. Ingested spores germinate in the intestine establishing a population of cells that produce toxins and spores. The pathogenicity locus, PaLoc, comprises several genes, including those coding for TcdA/B, for the holin-like TcdE protein, and for TcdR, an auto-regulatory RNA polymerase sigma factor essential for tcdA/B and tcdE expression. Here we show that tcdR, tcdA, tcdB and tcdE are expressed in a fraction of the sporulating cells, in either the whole sporangium or in the forespore. The whole sporangium pattern is due to protracted expression initiated in vegetative cells by σD, which primes the TcdR auto-regulatory loop. In contrast, the forespore-specific regulatory proteins σG and SpoVT control TcdR production and tcdA/tcdB and tcdE expression in this cell. We detected TcdA at the spore surface, and we show that wild type and ΔtcdA or ΔtcdB spores but not ΔtcdR or ΔtcdA/ΔtcdB spores are cytopathic against HT29 and Vero cells, indicating that spores may serve as toxin-delivery vehicles. Since the addition of TcdA and TcdB enhance binding of spores to epithelial cells, this effect may occur independently of toxin production by vegetative cells.
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Affiliation(s)
- Carolina P Cassona
- Instituto de Tecnologia Química e Biológica, NOVA University Lisbon, Oeiras, Portugal
| | - Sara Ramalhete
- Instituto de Tecnologia Química e Biológica, NOVA University Lisbon, Oeiras, Portugal
| | - Khira Amara
- Instituto de Tecnologia Química e Biológica, NOVA University Lisbon, Oeiras, Portugal
| | - Thomas Candela
- Micalis Institute, Université Paris-Saclay, INRAE, AgroParisTech, Jouy-en-Josas, France
| | - Imad Kansau
- Micalis Institute, Université Paris-Saclay, INRAE, AgroParisTech, Jouy-en-Josas, France
| | | | | | - Luís Jaime Mota
- Associate Laboratory i4HB, Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal
- UCIBIO, Applied Molecular Biosciences Unit, Department of Life Sciences, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal
| | - Bruno Dupuy
- Institut Pasteur, Université Paris-Cité, UMR-CNRS 6047, Laboratoire Pathogenèse des Bactéries Anaérobies, F-75015, Paris, France
| | - Mónica Serrano
- Instituto de Tecnologia Química e Biológica, NOVA University Lisbon, Oeiras, Portugal
| | - Adriano O Henriques
- Instituto de Tecnologia Química e Biológica, NOVA University Lisbon, Oeiras, Portugal.
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Kroh HK, Chandrasekaran R, Rosenthal K, Woods R, Jin X, Ohi MD, Nyborg AC, Rainey GJ, Warrener P, Spiller BW, Lacy DB. Use of a neutralizing antibody helps identify structural features critical for binding of Clostridium difficile toxin TcdA to the host cell surface. J Biol Chem 2017; 292:14401-14412. [PMID: 28705932 DOI: 10.1074/jbc.m117.781112] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Revised: 07/05/2017] [Indexed: 12/17/2022] Open
Abstract
Clostridium difficile is a clinically significant pathogen that causes mild-to-severe (and often recurrent) colon infections. Disease symptoms stem from the activities of two large, multidomain toxins known as TcdA and TcdB. The toxins can bind, enter, and perturb host cell function through a multistep mechanism of receptor binding, endocytosis, pore formation, autoproteolysis, and glucosyltransferase-mediated modification of host substrates. Monoclonal antibodies that neutralize toxin activity provide a survival benefit in preclinical animal models and prevent recurrent infections in human clinical trials. However, the molecular mechanisms involved in these neutralizing activities are unclear. To this end, we performed structural studies on a neutralizing monoclonal antibody, PA50, a humanized mAb with both potent and broad-spectrum neutralizing activity, in complex with TcdA. Electron microscopy imaging and multiangle light-scattering analysis revealed that PA50 binds multiple sites on the TcdA C-terminal combined repetitive oligopeptides (CROPs) domain. A crystal structure of two PA50 Fabs bound to a segment of the TcdA CROPs helped define a conserved epitope that is distinct from previously identified carbohydrate-binding sites. Binding of TcdA to the host cell surface was directly blocked by either PA50 mAb or Fab and suggested that receptor blockade is the mechanism by which PA50 neutralizes TcdA. These findings highlight the importance of the CROPs C terminus in cell-surface binding and a role for neutralizing antibodies in defining structural features critical to a pathogen's mechanism of action. We conclude that PA50 protects host cells by blocking the binding of TcdA to cell surfaces.
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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
| | | | - Rob Woods
- MedImmune LLC, Gaithersburg, Maryland 20878-2204
| | - Xiaofang Jin
- MedImmune LLC, Gaithersburg, Maryland 20878-2204
| | - Melanie D Ohi
- the Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee 37232-8240
| | | | | | | | - Benjamin W Spiller
- From the Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2363, .,the 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, .,the Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee 37212-2637
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Epitopes and Mechanism of Action of the Clostridium difficile Toxin A-Neutralizing Antibody Actoxumab. J Mol Biol 2017; 429:1030-1044. [PMID: 28232034 DOI: 10.1016/j.jmb.2017.02.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 02/14/2017] [Accepted: 02/14/2017] [Indexed: 12/17/2022]
Abstract
The exotoxins toxin A (TcdA) and toxin B (TcdB) are produced by the bacterial pathogen Clostridium difficile and are responsible for the pathology associated with C. difficile infection (CDI). The antitoxin antibodies actoxumab and bezlotoxumab bind to and neutralize TcdA and TcdB, respectively. Bezlotoxumab was recently approved by the FDA for reducing the recurrence of CDI. We have previously shown that a single molecule of bezlotoxumab binds to two distinct epitopes within the TcdB combined repetitive oligopeptide (CROP) domain, preventing toxin binding to host cells. In this study, we characterize the binding of actoxumab to TcdA and examine its mechanism of toxin neutralization. Using a combination of approaches including a number of biophysical techniques, we show that there are two distinct actoxumab binding sites within the CROP domain of TcdA centered on identical amino acid sequences at residues 2162-2189 and 2410-2437. Actoxumab binding caused the aggregation of TcdA especially at higher antibody:toxin concentration ratios. Actoxumab prevented the association of TcdA with target cells demonstrating that actoxumab neutralizes toxin activity by inhibiting the first step of the intoxication cascade. This mechanism of neutralization is similar to that observed with bezlotoxumab and TcdB. Comparisons of the putative TcdA epitope sequences across several C. difficile ribotypes and homologous repeat sequences within TcdA suggest a structural basis for observed differences in actoxumab binding and/or neutralization potency. These data provide a mechanistic basis for the protective effects of the antibody in vitro and in vivo, including in various preclinical models of CDI.
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Leng CH, Liu SJ, Chen HW, Chong P. Recombinant bacterial lipoproteins as vaccine candidates. Expert Rev Vaccines 2015; 14:1623-32. [PMID: 26420467 DOI: 10.1586/14760584.2015.1091732] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Recombinant bacterial lipoproteins (RLP) with built-in immuno-stimulating properties for novel subunit vaccine development are reviewed. This platform technology offers the following advantages: easily converts antigens into highly immunogenic RLP using a fusion sequence containing lipobox; the lipid moiety of RLP is recognized as the danger signals in the immune system through the Toll-like receptor 2, so both innate and adaptive immune responses can be induced by RLP; serves as an efficient and cost-effective bioprocess for producing RLP in Escherichia coli and the feasibility and safety of this core platform technology has been successfully demonstrated in animal model studies including meningococcal group B subunit vaccine, dengue subunit vaccine, novel subunit vaccine against Clostridium difficile-associated diseases and HPV-based immunotherapeutic vaccines.
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Affiliation(s)
- Chih-Hsiang Leng
- a Vaccine R&D Center, National Health Research Institutes, Zhunan Town, Miaoli 350, Taiwan
| | - Shih-Jen Liu
- a Vaccine R&D Center, National Health Research Institutes, Zhunan Town, Miaoli 350, Taiwan
| | - Hsin-Wei Chen
- a Vaccine R&D Center, National Health Research Institutes, Zhunan Town, Miaoli 350, Taiwan
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Huang JH, Wu CW, Lien SP, Leng CH, Hsiao KN, Liu SJ, Chen HW, Siu LK, Chong P. Recombinant lipoprotein-based vaccine candidates against C. difficile infections. J Biomed Sci 2015; 22:65. [PMID: 26245825 PMCID: PMC4527207 DOI: 10.1186/s12929-015-0171-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 07/29/2015] [Indexed: 12/18/2022] Open
Abstract
Background Opportunistically nosocomial infections in hospitalized patients are often related to Clostridium difficile infections (CDI) due to disruption of the intestinal micro-flora by antibiotic therapies during hospitalization. Clostridial exotoxins A and B (TcdA and TcdB) specifically bind to unknown glycoprotein(s) in the host intestine, disrupt the intestinal barrier leading to acute inflammation and diarrhea. The C-terminal receptor binding domain of TcdA (A-rRBD) has been shown to elicit antibody responses that neutralize TcdA toxicity in Vero cell cytotoxicity assays, but not effectively protect hamsters against a lethal dose challenge of C. difficile spores. To develop an effective recombinant subunit vaccine against CDI, A-rRBD was lipidated (rlipoA-RBD) as a rational design to contain an intrinsic adjuvant, a toll-like receptor 2 agonist and expressed in Escherichia coli. Results The purified rlipoA-RBD was characterized immunologically and found to have the following properties: (a) mice, hamsters and rabbits vaccinated with 3 μg of rlipoA-RBD produced strong antibody responses that neutralized TcdA toxicity in Vero cell cytotoxicity assays; furthermore, the neutralization titer was comparable to those obtained from antisera immunized either with 10 μg of TcdA toxoid or 30 μg of A-rRBD; (b) rlipoA-RBD elicited immune responses and protected mice from TcdA challenge, but offered insignificant protection (10 to 20 %) against C. difficile spores challenge in hamster models; (c) only rlipoA-RBD formulated with B-rRBD consistently confers protection (90 to 100 %) in the hamster challenge model; and (d) rlipoA-RBD was found to be 10-fold more potent than A-rRBD as an adjuvant to enhancing immune responses against a poor antigen such as ovalbumin. Conclusion These results indicate that rlipoA-RBD formulated with B-rRBD could be an excellent vaccine candidate for preclinical studies and future clinical trials.
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Affiliation(s)
- Jui-Hsin Huang
- Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan. .,Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan.
| | - Chia-Wei Wu
- Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan.
| | - Shu-Pei Lien
- Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan.
| | - Chih-Hsiang Leng
- Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan.
| | - Kuang-Nan Hsiao
- Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan.
| | - Shih-Jen Liu
- Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan.
| | - Hsin-Wei Chen
- Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan.
| | - Leung-Kei Siu
- Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan.
| | - Pele Chong
- Vaccine R&D Center, National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Zhunan Town, Miaoli County, Taiwan. .,Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan. .,Graduate Institute of Immunology, China Medical University, Taichung, Taiwan.
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