{ "abstract": "Clostridioides difficile TcdB is a multidomain ~270 kDa protein that adopts at least two distinct structural conformations influencing receptor binding, sensitivity to bile salts, and antibody reactivity. Data from the current study suggest TcdB may benefit from conformational flexibility by avoiding neutralization by vaccine induced antibodies. Experiments further demonstrate that targeting a single TcdB conformation overcomes the toxin’s ability to evade antibody neutralization. In the first series of experiments, mice were administered TcdB engineered with a 19 amino acid deletion and two site specific mutations that, in combination, brought toxicity to undetectable levels. This TcdB formulation drove robust antibody and recall responses that protected mice from weight loss but not damage to the intestines. Though all the treated mice generated similar anti-TcdB titers, only about half of the mice produced detectable neutralizing antibodies to TcdB’s open conformation. In the second part of this study, we sought to overcome this limitation to vaccine effectiveness by designing and testing an inactive form of TcdB modified to adopt only the open conformation. Treatment with this constitutively open form of TcdB resulted in an effective neutralizing antibody response in all the experimental mice. Vaccination reduced weight loss, preserved colon length and reduced selected measures of inflammatory-cell infiltration. These findings provide structure-based insights into the rational design of next generation vaccines that overcome TcdB’s conformational dynamics. Author summary: Clostridioides difficile is a major cause of severe gastrointestinal infections. Much of the damage caused during infection is driven by the large multidomain toxin, TcdB, making it a worthwhile target for vaccine and therapeutic development. However, TcdB exhibits extensive conformational flexibility, transitioning between open and closed forms, and the impact of these structural changes on the neutralizing ability of vaccine induced antibodies is not well understood. Here, we evaluated the immune response and protective ability of a detoxified TcdB vaccine candidate against infection. Despite eliciting a strong antibody response, vaccination provided only limited protection against infection. We further found these vaccine-induced antibodies poorly neutralized a TcdB mutant unable to adopt the closed conformation. In contrast, immunization with this conformationally restricted toxin generated broadly neutralizing antibodies and improved protection against inflammatory-cell infiltration. Our data raise the possibility that TcdB conformational flexibility could be a potential immune evasion strategy that could diminish antibody mediated protection and vaccine efficacy.", "abstract_shown": true, "affiliations": [ "Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America", "Department of Molecular Microbiology and Immunology, University of Texas at San Antonio, San Antonio, Texas, United States of America" ], "article_type": "Research Article", "arxiv": null, "author_total": 9, "authors": [ { "affs": [ 0 ], "name": "Megan L. Kempher" }, { "affs": [ 1 ], "name": "Tyler M. Shadid" }, { "name": "Gillian A. Lang" }, { "name": "Sydney T. Honold" }, { "name": "Jordan N. May" }, { "name": "Elizabeth J. Hall" }, { "name": "Jason L. Larabee" }, { "name": "Mark L. Lang" }, { "name": "Jimmy D. Ballard" } ], "bibtex": "https://research.draconitic.com/paper/1g5matfnsc2rt.bib", "cited_by": 0, "doi": "10.1371/journal.ppat.1014627", "fulltext_url": "https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014627", "id": "1g5matfnsc2rt", "issns": [ "1553-7374" ], "landing_url": "https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014627", "language": null, "licence": "CC-BY-4.0", "licence_label": "CC BY 4.0", "licence_source": "journal", "licence_url": "https://creativecommons.org/licenses/by/4.0/", "metadata_licence": null, "native_subjects": [ [ "openalex", "2725|Clostridium difficile and Clostridium perfringens research" ], [ "plos", "/Biology and life sciences/Biochemistry/Proteins/Immune system proteins/Antibodies" ], [ "plos", "/Biology and life sciences/Immunology/Immune response/Antibody response" ], [ "plos", "/Biology and life sciences/Immunology/Immune system proteins/Antibodies" ], [ "plos", "/Biology and life sciences/Immunology/Vaccination and immunization" ], [ "plos", "/Biology and life sciences/Immunology/Vaccination and immunization/Vaccine development" ], [ "plos", "/Biology and life sciences/Physiology/Immune physiology/Antibodies" ], [ "plos", "/Biology and life sciences/Toxicology/Toxic agents/Toxins" ], [ "plos", "/Medicine and health sciences/Immunology/Immune response/Antibody response" ], [ "plos", "/Medicine and health sciences/Immunology/Immune system proteins/Antibodies" ], [ "plos", "/Medicine and health sciences/Immunology/Vaccination and immunization" ], [ "plos", "/Medicine and health sciences/Immunology/Vaccination and immunization/Vaccine development" ], [ "plos", "/Medicine and health sciences/Medical conditions/Infectious diseases/Infectious disease control/Vaccines" ], [ "plos", "/Medicine and health sciences/Pathology and laboratory medicine/Toxicology/Toxic agents/Toxins" ], [ "plos", "/Medicine and health sciences/Public and occupational health/Preventive medicine/Vaccination and immunization" ], [ "plos", "/Medicine and health sciences/Public and occupational health/Preventive medicine/Vaccination and immunization/Vaccine development" ], [ "plos", "/Research and analysis methods/Animal studies/Experimental organism systems/Animal models/Mouse models" ], [ "plos", "/Research and analysis methods/Animal studies/Experimental organism systems/Model organisms/Mouse models" ], [ "plos", "/Research and analysis methods/Immunologic techniques/Immunoassays/Enzyme-linked immunoassays" ], [ "plos", "/Research and analysis methods/Model organisms/Mouse models" ] ], "openalex": "W7213550918", "pdf_url": "https://journals.plos.org/plospathogens/article/file?id=10.1371/journal.ppat.1014627&type=printable", "pmcid": null, "pmid": null, "published": "2026-09-18", "publisher": "Public Library of Science", "ris": "https://research.draconitic.com/paper/1g5matfnsc2rt.ris", "sources": [ { "first_seen": "2026-10-30T12:17:49Z", "native_id": "10.1371/journal.ppat.1014627", "source": "plos", "url": "https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014627" } ], "subjects": [ { "field": "biology", "origin": "plos:immunology", "subfield": "immunology" } ], "title": "The impact of TcdB conformational dynamics on vaccination against Clostridioides difficile", "title_text": "The impact of TcdB conformational dynamics on vaccination against Clostridioides difficile", "type": "peer-reviewed", "updated_at": "2026-10-30T12:17:49Z", "url": "https://research.draconitic.com/paper/1g5matfnsc2rt", "venue": "PLOS Pathogens", "versions": [] }