Novel, non-colonizing, single-strain live biotherapeutic product ADS024 protects against Clostridioides difficile infection challenge in vivo

ARTICLE HIGHLIGHTS

Research background

Clostridioides difficile (C. difficile) is a Gram positive pathogen that causes C. difficile infection (CDI). It infects millions of people worldwide, causing potentially life-threatening gastrointestinal disease in individuals with disrupted gut microbiomes. Following successful antibiotic treatment, recurrent CDI (rCDI) can occur in cured patients. Therefore, development of a therapeutic product for preventing rCDI following successful standard-of-care antibiotic therapy is of vital importance.

Research motivation

C. difficile, a major cause of infectious disease death in the United States, causes inflammation of the colon and potentially deadly diarrhea. ADS024, a Bacillus velezensis strain, has previously demonstrated direct in vitro bactericidal activity against C. difficile, without affecting other members of the gut microbiota. In this study, we investigated the efficacy of ADS024 against CDI challenge in vivo. Following our findings, further investigation of ADS024 as a single-strain, live biotherapeutic product (SS-LBP) for prevention of rCDI following successful standard-of-care antibiotic therapy is warranted.

Research objectives

The objectives of the research were to investigate: (1) The in vivo efficacy of B. velezensis ADS024 in protecting against CDI challenge in mouse models; (2) the capability of ADS024 to colonize the GI tract; and (3) the impact of ADS024 on the gut microbiome, finding that it was efficacious against CDI challenge without colonization, and with minimal effects on the gut microbiome, thus supporting further development of ADS024 as an SS-LBP for prevention of rCDI.

Research methods

Mouse models were used to determine: (1) The in vivo efficacy against CDI challenge; and (2) colonization status of ADS024 (in conjunction with miniature swine). Human distal colon model and miniature swine were utilized to determine the effects of ADS024 on the gut microbiome. To mimic disruption of the gut microbiota, the mice and miniature swine were exposed to vancomycin prior to dosing with ADS024. To model the human distal colon, an anerobic fecal fermentation system was used.

Research results

Single oral daily doses of ADS024, similarly to multiple doses, demonstrated efficacy in protecting against subsequent challenge by C. difficile in a mouse model of CDI challenge. ADS024 showed no colonization based on lack of recovery ADS024 colonies in fecal samples 24 h after single doses in mice, 72 h after single doses in miniature swine, or a 28-d repeat-dose study in miniature swine. Phylogenetic analysis in the human distal colon model and in vivo studies performed in miniature swine demonstrated a selective impact of ADS024 on the healthy human colonic microbiota.

Research conclusions

In vivo efficacy of ADS024 in protecting against CDI challenge and minimal effects on the gut microbiome support development of ADS024 as an SS-LBP in preventing rCDI following standard antibiotic treatment.

Research perspectives

In vivo investigation of ADS024 is compatible with previous in vitro studies that showed efficacy against C. difficile and maintenance of gut microbiota diversity. Altogether, findings from these studies support initiation of clinical trials to evaluate the safety and efficacy of ADS024 in patients recovering from CDI.