How does the parasite causing amoebiasis (Entamoeba histolytica) manage to invade through the intestine?

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The intestinal parasite Entamoeba histolytica is one of the most important human parasites. Life-threatening amoebic liver abscess (ALA) formation continues to be a common complication of intestinal E. histolytica infections with about 11.300 deaths per year mainly in tropical and subtropical regions with poor hygienic conditions. Usually, E. histolytica colonizes the human intestine without causing severe symptoms. However, these protozoa can penetrate the intestinal wall and lead to ulcerative, bloody intestinal inflammation or induce ALA. The lack of a suitable model system led to the unsatisfactory situation that despite substantial research efforts, the mechanisms of tissue invasion and destruction by E. histolytica and the mechanisms that allow the bypass of the host's immune response are still not well understood. With the proposed project we would like to fill this gap of knowledge and elucidate the mechanisms underlying the invasion process of the protozoan parasite E. histolytica into the host’s intestine. In addition, the response of different host cells to contact with E. histolytica should be studied. This goal will be achieved with the help of E. histolytica clones that are exclusively available to our lab. These clones differ in their ability to form ALAs, but are derived from the same isolate and thus have the same genetic background. In addition, we also have developed a method to manipulate amoebae genetically. With the help of comparative analyses of the clones and their genetic manipulation, we recently have succeeded in identifying a new pathogenicity factor, which will also be subject of the present study. Hypotheses- Pathogenic amoebae and non-pathogenic amoebae can invade tissue similarly effective. However, pathogenic amoebae are more resistant to the immune system, while they induce a more pronounced immunopathology.- Pathogenic amoebae can switch its gene expression faster and thus adapt more quickly to changing conditions during an infection compared to non-pathogenic ones.- The host reacts differently to infection with pathogenic and non-pathogenic amoebae, respectively.- Pathogenic and non-pathogenic amoebae differently regulate the composition of the intestinal microbiome Aim: Understanding the complex interplay between E. histolytica and its host during the process of tissue invasion.Three different experimental models (in vitro intestinal model, self-renewing organoid-derived intestinal cell monolayer model, CBA/J mice intracecal inoculation model) with different levels of complexity will be used to test our hypotheses. In all systems, the interaction of host cells with amoebae with different pathogenicity will be analysed over time using High-Resolution Microscopy and Next Generation Sequencing.