The impact of TcdB conformational dynamics on vaccination against Clostridioides difficile
- 1Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
- 2Department of Molecular Microbiology and Immunology, University of Texas at San Antonio, San Antonio, Texas, United States of America
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.
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BibTeX
@article{kempher2026impact,
title = {{The impact of TcdB conformational dynamics on vaccination against Clostridioides difficile}},
author = {Megan L. Kempher and Tyler M. Shadid and Gillian A. Lang and Sydney T. Honold and Jordan N. May and Elizabeth J. Hall and Jason L. Larabee and Mark L. Lang and Jimmy D. Ballard},
journal = {PLOS Pathogens},
year = {2026},
month = sep,
doi = {10.1371/journal.ppat.1014627},
url = {https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014627},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - The impact of TcdB conformational dynamics on vaccination against Clostridioides difficile
AU - Megan L. Kempher
AU - Tyler M. Shadid
AU - Gillian A. Lang
AU - Sydney T. Honold
AU - Jordan N. May
AU - Elizabeth J. Hall
AU - Jason L. Larabee
AU - Mark L. Lang
AU - Jimmy D. Ballard
PY - 2026
DA - 2026/09/18
JO - PLOS Pathogens
DO - 10.1371/journal.ppat.1014627
UR - https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014627
AB - 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.
SN - 1553-7374
ER -