# The role of toxins in Clostridioides difficile infection pathogenesis.

> **NIH VA I01** · VETERANS HEALTH ADMINISTRATION · 2024 · —

## Abstract

Project Summary
 Clostridioides difficile is a Gram-positive, spore-forming anaerobe, a leading cause of nosocomial
infection in the United States, and a significant problem for Veterans receiving care in Veterans Health
Administration (VHA) facilities. The disease state is most often preceded by disruption of the host microbiome in
response to antibiotic treatment and is characterized by mild to severe (and often recurrent) diarrhea. Left
untreated, C. difficile infection (CDI) can be life threatening with sequelae that include antibiotic-associated
pseudomembranous colitis, toxic megacolon, and sepsis.
 CDI is dependent on the secretion of one or more AB-type toxins: toxin A (TcdA), toxin B (TcdB), and the
C. difficile transferase toxin (CDT, or binary toxin). While TcdA and TcdB are considered the primary virulence
factors, multiple studies suggest that CDT increases the severity of CDI. The increasing prevalence of CDT
containing clinical isolates and the potential for developing CDT as an effective vaccine antigen necessitate a
deeper understanding of the CDT mechanism of action.
 CDT consists of two proteins: a cell binding and pore-forming protein (CdtB) which guides the delivery of
an ADP-ribosyltransferase (CdtA) into the host cytosol. CdtA-mediated disruption of actin cytoskeletal structure
has been associated with the formation of microtubule protrusions that could play a role in C. difficile adherence
to the epithelium. CDT is also associated with the suppression of an otherwise protective eosinophil response,
although the mechanism for this function is unclear.
 The over-arching goal for this project is to provide the mechanistic foundation for understanding
the role of CDT function in pathogenesis and the tools to advance this knowledge into effective vaccine
development strategies. The first aim and step toward achieving this goal is to define the dynamics of toxin
production and C. difficile adherence in a mouse model of CDI. We are developing quantitative capture ELISA
assays that allow for the quantification of TcdA, TcdB, CdtA, and CdtB protein levels in stool. We will leverage
these assays to monitor toxin levels over the time course of murine infection. We will also leverage these
reagents for the generation of sensitive and specific toxin imaging reagents. This will allow us to visualize toxin
production over the length of the intestinal tract and ultimately identify the cell types affected in the context of
infection. The second aim is to define the role of CDT in the context of CDI pathogenesis. We will evaluate a
panel of defined and isogenic toxin deletion strains in a murine model of infection. We will examine hypotheses
from the published literature and our preliminary data, with a directed focus on the possible role of CDT in
promoting C. difficile adherence, inflammasome activation, and mucosal-associated invariant T cell activation.
We will focus on understanding the dynamic changes occurring in the early stages of ...

## Key facts

- **NIH application ID:** 10801618
- **Project number:** 2I01BX002943-09
- **Recipient organization:** VETERANS HEALTH ADMINISTRATION
- **Principal Investigator:** Dana Borden Lacy
- **Activity code:** I01 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2024
- **Award amount:** —
- **Award type:** 2
- **Project period:** 2015-10-01 → 2028-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10801618

## Citation

> US National Institutes of Health, RePORTER application 10801618, The role of toxins in Clostridioides difficile infection pathogenesis. (2I01BX002943-09). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10801618. Licensed CC0.

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