Dual role of the colonization factor CD2831 in Clostridium difficile pathogenesis

Vanessa Arato,Maria Scarselli,Gianmarco Gasperini,Rosanna Leuzzi,Ilaria Ferlenghi,Fabiola Giusti

doi:10.1038/s41598-019-42000-8

Abstract

Clostridium difficile is a Gram-positive, anaerobic bacterium and the leading cause of antibiotic-associated diarrhea and pseudomembranous colitis. C. difficile modulates its transition from a motile to a sessile lifestyle through a mechanism of riboswitches regulated by cyclic diguanosine monophosphate (c-di-GMP). Previously described as a sortase substrate positively regulated by c-di-GMP, CD2831 was predicted to be a collagen-binding protein and thus potentially involved in sessility. By overexpressing CD2831 in C. difficile and heterologously expressing it on the surface of Lactococcus lactis, here we further demonstrated that CD2831 is a collagen-binding protein, able to bind to immobilized collagen types I, III and V as well as native collagen produced by human fibroblasts. We also observed that the overexpression of CD2831 raises the ability to form biofilm on abiotic surface in both C. difficile and L. lactis. Notably, we showed that CD2831 binds to the collagen-like domain of the human complement component C1q, suggesting a role in preventing complement cascade activation via the classical pathway. This functional characterization places CD2831 in the Microbial Surface Components Recognizing Adhesive Matrix Molecule (MSCRAMMs) family, a class of virulence factors with a dual role in adhesion to collagen-rich tissues and in host immune evasion by binding to human complement components.

Highlights

The sporogenic, anaerobic rod Clostridium difficile is a Gram-positive enteropathogen causing C. difficile Infection (CDI)
The collagen-binding domains (CBDs) are followed by a region of 110 amino acids rich in Proline that has been showed to be targeted by ZmpI/PPEP-144,45
Bacterial infections involve binding of pathogens to ligands expressed on the surface of host cells and in the ECM53–55

Summary

Introduction

The sporogenic, anaerobic rod Clostridium difficile is a Gram-positive enteropathogen causing C. difficile Infection (CDI). Adhesion to the host epithelial cells is the first crucial step to the bacterial settlement in the gut mucosa This step involves C. difficile adhesion to the epithelium mucosa and multiplication, with concomitant evasion of the host immune system. The surface proteins known to mediate adhesion to ECM are designated as Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs). Their role could be crucial in C. difficile pathogenesis as the disruption of epithelial barriers caused by the toxins determines the accessibility to the underlying matrix and favors bacterial colonization. A second role for MSCRAMMs has been identified in the host immune system evasion with the binding to the complement component C1q. C-di-GMP controls bacterial physiology and virulence by modulating the expression levels of tcdA and tcdB, as well as that of tcdR, which encodes an alternative sigma factor that activates tcdA and tcdB expression[27,28]

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Conclusion