���˴�Ƭ-�����ۺ���-���޳�������

A therapeutic against C. Difficile infection in patients, patients with recurrent infections and livestock

Background

Clostridioides (formerly Clostridium) difficile (CD) is the leading cause of hospital-associated diarrhea and infectious colitis. CD is responsible for > 500,000 infections and >30,000 deaths annually in North America alone. Furthermore, CD infections are the number one cause of infectious colitis in farm animals including piglets. CD infection (CDI) results in a range of symptoms from mild diarrhea to pseudomembranous colitis, and toxic megacolon. The pathophysiology of CD disease is complex and is linked to the disruption of the bacterial community in the gastrointestinal (GI) tract, which facilitates CD GI coloniziation. Following colonization, as of yet unclear mechanisms result in the CD bacteria initiate the production of two primary toxins; Toxin A (TcdA) and Toxin B (TcdB), both have been implicated in the development of CD disease. CD strains that do not contain TcdA and TcdB gene loci do not cause human disease. TcdA is an enterotoxin and induces inflammation, cytokine release, and fluid secretion leading to the hallmark of CD disease; diarrhea. TcdB is a cytotoxin and disrupts the cytoskeletal architecture of colonic and epithelial cells catalyzing the glycosylation and inactivation of human Rho-GTPases resulting in cytoskeletal changes and cell death. Both toxins work synergistically and induce cell rounding and cytoskeletal rearrangement at picomolar concentrations in cell culture.

Technology Overview

The pathophysiology of CDI is linked closely to disturbances of the GI microbial community. Events or interventions that perturb the GI bacterial community are associated with increased risk of developing CDI including the use of antibiotics. First line treatments for CDI is antibiotic therapy, antimicrobial based CD treatments are associated with a 25-40% risk of recurrence within 30 days of therapy completion. Noting the central role of a disruption to the GI microbial community, treatments restoring the disrupted GI microbiota have been shown to be highly efficacious and have recently been incorporated into clinical guidelines. The use of human stool from “healthy” non-CD infected individuals, called fecal microbial transplants (FMT’s), has been used to replenish microbial populations in CD patients. However, the widespread adoption of FMTs has been impeded by challenges linked to finding appropriate “healthy” CD-free donors and the variability in the performance of stool between donors. Donor-based differences have been linked to the lack of compatibility of bacterial strains found in the donor and recipient stool and other unidentified causes. Present and past members of our research group circumvented the donor-to-donor variability and the challenges of finding appropriate donors by developing a defined microbial community (DMC) that was cultured in a controlled laboratory environment from a healthy donor called MET-1. 

MET-1 has been studied in mouse models of CDI and has been used clinically in patients with recurrent CDI with >90% efficacy. Additional DMC’s have since been developed to combat CD disease with excellent efficacy in patients including the recently published clinical trial using SER-109 for the treatment of recurrent CDI. The use of DMCs, like MET-1 and SER-109, provide exciting options in the battle against CDI. However, it is still unclear how these interventions work on a mechanistic level. Early hypotheses following stool transplant studies suggested that the GI tract of CD patients were recolonized by diverse microbes following FMT’s or treatment with DMC’s, however, studies using sterile fecal filtrates have demonstrated that bacteria-free components in donor stool also provide protection from CDI recurrence, suggesting that soluble derived factors may be involved in providing protection against CD.

Recent studies in Queen’s lab have identified a bacterial protease that proteolyzes and neutralizes the activity of TcdA and TcdB toxins in vitro and in vivo. The data demonstrated that oral gavage of a bacterial protease derived from commensal bacteria protected mice from developing CD disease.