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Clostridioides difficile Toxin B subverts germinal center formation and antibody recall responses by stimulating a drug-treatable CXCR4-dependent mechanism

ABSTRACT: Recurrent Clostridioides difficile infection (CDI) results in significant morbidity and mortality. We previously established that CDI in mice did not protect against reinfection and was associated with poor pathogen-specific B cell memory (Bmem), recapitulating our observations with human Bmem. Herein, we demonstrate that the secreted toxin TcdB2 is responsible for subversion of Bmem responses. TcdB2 from an endemic C. difficile strain delayed IgG class switch following vaccination, attenuated IgG recall to a vaccine booster, and prevented germinal center formation. The mechanism of TcdB2 action included increased B cell CXCR4 expression and responsiveness to its ligand CXCL12, accounting for altered cell migration and a failure of germinal center-dependent Bmem. These results were reproduced in a C. difficile infection model and an FDA-approved CXCR4-blocking drug rescued germinal center formation. We therefore provide mechanistic insights into C. difficile-associated pathogenesis and illuminate a target for clinical intervention to limit recurrent disease.

ORGANISM(S): Mus musculus

PROVIDER: GSE263792 | GEO | 2024/04/25

REPOSITORIES: GEO

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Project description:A major risk factor for Clostridioides difficile infection (CDI) is the perturbation of the gut microbiota by antibiotic administration, and antibiotic therapy, the standard treatment option for CDI, exacerbates the imbalance of the gut microbiota, leading to a very high recurrent CDI (rCDI) incidence rate. Therefore, CDI treatment based on live biotherapeutic products (LBPs) has recently emerged for long-term CDI management and preventive treatment However, there is limited research and understanding of how these LBPs improve CDI symptoms, which raises the need to elucidate the therapeutic mechanisms of LBPs. To fill this knowledge gap, here, we holistically analyzed and investigated the mechanisms involved in the inhibitory effect of probiotics on C. difficile at the molecular level through a multiomics approach on screened strain from probiotics that inhibit C. difficile growth. First, Bifidobacterium species were co-cultured with C. difficile, and B. longum was screened based on its ability to inhibit the growth of C. difficile. Then, the antimicrobial activity of B. longum against C. difficile was confirmed by spot-on-lawn assay and organic acid quantification. Next, we performed proteomic and metabolomic analysis on C. difficile co-cultured with B. longum, and observed physiological changes associated with the inhibition of C. difficile growth and toxin production. It was found that lactate produced by B. longum up-regulated the lactate dehydrogenase complex of C. difficile, leading to a decrease in intracellular ATP synthesis and a subsequent decrease in (deoxy)ribonucleoside triphosphate synthesis. Furthermore, proteinaceous stress induced by B. longum was also identified through the up-regulation of ribosomal proteins, molecular chaperones, and chaperonins, and the down-regulation of translation-related proteins. Finally, we found that B. longum suppressed butyrate metabolism and toxin production by producing and replenishing proline consumed by C. difficile. Therefore, this study will not only expand our understanding of the mechanisms of probiotics' inhibition of C. difficile, but also contribute to the development of LBPs based on molecular mechanisms for treating CDI.

Project description:Clostridium difficile is an anaerobic spore-forming rod-shaped gram-positive bacterium that can infect both humans and animals. Most studies on the pathogenesis of C. difficile have focused on its toxins and their effect on the host cells. Recently, we utilized microarrays to identify conserved and divergent genes associated with virulence in C. difficile isolates from humans and animals. Our data provided the first clue toward a complex mechanism underlying host adaptation and pathogenesis. Microarray technology offers an efficient high-throughput tool to study the transcriptional profiles of pathogens and infected host cells. Transcriptomes of C. difficile after exposure to environmental and antibiotic stresses and those of human epithelial colorectal Caco-2 cells upon TcdA treatment have been analyzed. To our knowledge, there are still no reports on the transcriptomic study of host-pathogen interactions for C. difficile infection (CDI). In vitro analyses of interplay between host and pathogen are essential to unravel the mechanisms of infection and to investigate the host response to infection. We therefore employed microarrays to study both bacterial and human cellular transcriptome kinetics during CDI to Caco-2 cells. Here we present a large-scale analysis of transcriptional profiles to reveal molecular determinants playing a role in C. difficile pathogenesis and the host response. We found that there were 254 and 224 differentially-expressed genes after CDI in C. difficile and Caco-2 cells, respectively. These genes are clustered according to their functional categories and their potential roles in pathogenesis and host response are discussed. Our results will not only increase our understanding on the host-pathogen interaction, but may also provide targets for drug development. Clostridium difficile: Control vs Infection (time course) mRNA with genomic DNA of tested and reference strains Caco-2 cells: Control vs Infected with Clostridium difficile Time-course experiments of Caco-2 cells infected with C. difficile for 30, 60 and 120 min

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Clostridioides difficile Toxin B subverts germinal center formation and antibody recall responses by stimulating a drug-treatable CXCR4-dependent mechanism

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