Strategies of the protozoan parasite Entamoeba histolytica to evade the innate immune responses of intestinal epithelial cells

Molecules expressed by the pathogenic ameoba Entamoeba histolytica but weakly expressed or absent from the non-pathogenic ameoba Entamoeba dispar could be used by intestinal epithelial cells to discriminate between the two species and to initiate an appropriate inflammatory response. Among the possible molecules involved in this identification are the Gal/GalNac lectin and the lipophosphoglycan. Once the inflammatory response is initiated, E. histolytica trophozoites have to protect themselves against reactive nitrogen intermediates produced by intestinal epithelial cells, oxygen intermediates, and cytotoxic molecules released by activated neutrophils. By screening the E. histolytica genome, we have identified proteins that may play a role in the defence strategy of the parasite. One of these proteins, a serine proteinase inhibitor, inhibits human neutrophil cathepsin G, a key component of the host defence.