The role of intestinal Enterococcus faecalis and its virulence factors in multigenerational microbiota-humanized mouse models of primary sclerosing cholangitis and in bacteriophage therapy

• Applicant: Dr. Burcin Özdirik
• Subject Area: Gastroenterology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 527410864

Primary sclerosing cholangitis (PSC) is an immune-related cholangiopathy characterized by biliary inflammation, cholestasis, and multifocal bile duct strictures, which is associated with high rates of progression to end-stage liver disease. Currently, no effective medical treatment with beneficial impact on overall survival is available, and liver transplantation seems to be the only curative treatment option. PSC patients are characterized by compositional changes of the gut bacterial microbiota with a proportional increase in fecal microbes including Enterococcus (E.) species (spp.) (especially E. faecalis), Klebsiella spp. and Veillonella spp., suggesting a potential translocation of those microbes, which may additionally contribute to PSC pathogenesis. Cytolysin is a virulence factor secreted by E. faecalis. Targeting cytolysin-positive E. faecalis using bacteriophages (viruses that can destroy strain-specific bacteria) resulted in a reduction of disease activity in mice with alcoholic hepatitis. The role of specific bacterial virulence factors in patients with PSC remains unclear since mechanistic studies investigating gut microbiota and specific gut pathobionts are limited by the lack of in vivo models comprehensively reflecting human PSC. Therefore, our multigenerational microbiota-humanized mouse model on the background of Abcb4 deficient mice with chronic cholangiopathy better reflects aspects of the human disease. In this project, we will investigate the complex role of intestinal E. faecalis in PSC (i) by using our multigenerational microbiota-humanized mouse model including human donor samples with high and low E. faecalis abundance, (ii) by performing metagenome shotgun sequencing of stool samples from our Charité PSC cohort for validation of the impact of virulence factors such as cytolysin, (iii) by analyzing therapeutic effects of bacteriophages targeting cytolysin-positive E. faecalis and (iv) by investigating mechanistic insights of cytolysins effect in the liver employing biliary organoids. We will elucidate novel microbiota-associated disease mechanisms, which may contribute to the development of novel therapeutic approaches for the treatment of human PSC.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Dr. Bernd Schnabl