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

• Applicant: Professorin Dr. Iris Bruchhaus
• Subject Area: Parasitology and Biology of Tropical Infectious Disease Pathogens
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 444520224

Despite improved hygiene, 500,000 million people worldwide are still infected with Entamoeba histolytica and around 25,000 people die from this infection every year. E. histolytica is an intestinal protozoan that can become invasive in 10% of cases, i.e. it penetrates the intestinal mucosa, which can lead to the development of colitis, or the amoebae enter the bloodstream and from there into the liver, which can lead to the development of amoebic liver abscesses (ALAs). There is a sexual dimorphism in amoebiasis, meaning that males are more likely to suffer from ALA than females. Far less is known about the pathogenesis of amoebic colitis than that of ALA, and many aspects remain speculative or poorly documented. One of the main reasons for this unsatisfactory situation is the lack of suitable animal models. The use of organoid-derived monolayers has the potential to fill this gap in the experimental analysis of amoebic colitis. For our studies, we have two genetically almost identical clones of the E. histolytica isolate HM-1:IMSS (clone A1np: non-pathogenic / clone B2p: pathogenic), which differ in their ability to form ALAs. Using these clones, we were able to show that B2p trophozoites destroy a colonoid-derived monolayer (CDM) significantly faster and induce a stronger immune response than A1np trophozoites. In addition, B2p trophozoites are more responsive to confrontation with colonic cells than A1np trophozoites. We have also shown that extracellular vesicles (EVs) from A1np and B2p trophozoites induce a pro-inflammatory response in male and female mouse monocytes. Based on these results, the following hypotheses will be tested in this proposal: I. B2p trophozoites penetrate the CDM of male probands better and induce a more pronounced immune response compared to the CDM of female probands. This increases the likelihood of trophozoites entering the liver and forming ALAs. II. Different cell types in the colon respond differently to A1np and B2p trophozoites. III. EVs secreted by A1np and B2p stimulate colonic cells in a similar way to A1np and B2p trophozoites. IV. Since colon cells are hardly stimulated by co-incubation with A1np trophozoites, in contrast to co-incubation with B2p trophozoites, the presence of immune cells (e.g. monocytes) only increases the destruction of the CDM in the presence of B2p trophozoites. V. Silencing of the virulence factor EhHP127 in B2p trophozoites reduces their ability to invade the CDM. The studies planned here will contribute to a more complete understanding of the processes involved in the intestinal invasion of E. histolytica and will elucidate the mechanisms underlying sexual dimorphism in this infection.

• DFG Programme: Research Grants