Response of human intestinal cells and structures to Bacillus cereus enterotoxins

• Applicant: Dr. Nadja Jeßberger
• Subject Area: Medical Microbiology and Mycology, Hygiene, Molecular Infection Biology ; Public Health, Healthcare Research, Social and Occupational Medicine ; Cell Biology
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 407925087

In the preceding project the mode of action of the three-component pore forming enterotoxin haemolysin BL (Hbl) from Bacillus cereus was characterized in detail. The results obtained in this successful project are published in three original research articles, two PhD theses and two review articles. They also contributed to four further original research articles and a book chapter. Obviously, we also raised a multitude of further questions, especially regarding the effects on human intestinal target cells and structures. The goal of the proposed follow-up project is the continuation of the detailed characterization of the fascinating interaction between the enterotoxins (extended to both Hbl and Nhe) and the host. Open questions are: - How do intestinal cells respond to B. cereus and its pore forming enterotoxins? - Are there differences between the two enterotoxins? - Do these toxins generally induce apoptosis, or do cellular repair mechanisms take place? - How does the bacterium survive, proliferate, and produce toxins inside the human intestine? We will address these important issues in six work packages. First, our target cell model, a co-culture of human enterocyte-like CaCo-2 and mucus-producing HT29-MTX goblet cells, will be exposed to lethal and sublethal enterotoxin concentrations. Changes in ionic currents and membrane resistance, cellular response on a transcriptional level and activation of apoptotic signalling pathways will be monitored. Further, we will also determine the conditions necessary for cellular repair and survival (toxin concentrations and exposure times, signalling pathways, etc.). We will further simulate these processes in more detail using human intestinal organoids derived from human induced pluripotent stem cells. Together with our cooperation partner Prof. Seeger, we will monitor organoid maintenance or loss of structural integrity and a possible transcriptional and post-transcriptional response (including the activation of cellular signalling pathways). In a second approach, we will modify the amounts of enterocytes and further cell types in the organoid, which will lead to the identification of preferred target cell types. Next to the enterotoxins, we will also investigate the fate of the pathogen itself in the intestinal organoids (spore germination, survival, proliferation, etc.). Supported by our cooperation partner Dr. Dietrich, we will determine the amounts of enterotoxins produced by the pathogen inside the intestinal organoids. Finally, we will expand the experiments to further B. cereus toxins and virulence factors, such as haemolysin II, sphingomyelinase or secreted proteases. Altogether, the proposed project will provide important information about onset and course of the gastrointestinal disease induced by the B. cereus pore-forming enterotoxins. New knowledge will be gained about the variable processes favoring this toxico-infection.

• DFG Programme: Research Grants
• Co-Investigator: Professorin Dr. Bettina Seeger