A Drosophila Model for Clostridium difficile Toxin CDT Reveals Interactions with Multiple Effector Pathways

Abstract

Clostridium difficile infections (CDIs) cause severe and occasionally life-threatening diarrhea. Hypervirulent strains produce CDT, a toxin that ADP-ribosylates actin monomers and inhibits actin polymerization. We created transgenic Drosophila lines expressing the catalytic subunit CDTa to investigate its interaction with host signaling pathways in vivo. When expressed in the midgut, CDTa reduces body weight and fecal output and compromises survival, suggesting severe impairment of digestive functions. At the cellular level, CDTa induces F-actin network collapse, elimination of the intestinal brush border, and disruption of intercellular junctions. We confirm toxin-dependent redistribution of Rab11 to enterocytes' apical surface and observe suppression of CDTa phenotypes by a Dominant-Negative form of Rab11 or RNAi of the dedicated Rab11GEF Crag (DENND4). We also report that Calmodulin (Cam) is required to mediate CDTa activity. In parallel, chemical inhibition of the Cam/Calcineurin pathway by Cyclosporin A or FK506 also reduces CDTa phenotypes, potentially opening new avenues for treating CDIs.

Probiotics: insights and new opportunities for Clostridioides difficile intervention

“…For example, the expression of the catalytic subunit of the C. difficile toxin, CDTa, in the Drosophila midgut reduces body weight, fecal output, and overall survival. Mechanistically, the Drosophila enterocytes are informative to illustrate that CDTa induces F-actin network collapse, eliminates the intestinal brush border, and disrupts intercellular junctions by re-distributing Rab11 to the enterocytes' apical surface and the activation of the calmodulin/calcineurin pathway[170].Thus, non-vertebrate or vertebrate model hosts can be used complementary to clinical development. Drosophila or mice exposed to with C. difficile secreted factors in multidimensional screens involving microbiota, prebiotics, and probiotics and the study of host epithelium response can teach us about the plasticity of C. difficile pathogenicity.…”

“…Drosophila or mice exposed to with C. difficile secreted factors in multidimensional screens involving microbiota, prebiotics, and probiotics and the study of host epithelium response can teach us about the plasticity of C. difficile pathogenicity. Modulating host epithelium genetics or metabolism to alter the impact of CDI or virulence factors on the host is also a viable option, since genetic inhibition of Rab11 or chemical inhibition of the calmodulin/calcineurin pathway by cyclosporin A or FK506 reduces CDTa phenotypes[170].…”

Clostridioides difficile in Non-hospital Sources (Animals, Food, and Environment) in Asian Countries: A Literature Review

“…Nearly all toxigenic forms of C. difficile release toxins, and a few clinically relevant strains secrete only toxin B in a colonic environment. Another toxin was discovered in some C. difficile strains, named binary toxin (cdt), associated with intensive symptoms (5,6). Significant mortality related to the virulence properties of PCR ribotypes 027 and 078 of C. difficile has been highlighted in clinical epidemiology (7).…”