Recapitulating the life cycle of the global pathogenEntamoebain mice

Abstract

AbstractThere are severalEntamoebaspecies that colonize humans, but onlyEntamoeba histolyticacauses severe disease.E. histolyticais transmitted through the fecal-oral route to colonize the intestinal tract of 50 million people worldwide. The current mouse model to studyE. histolyticaintestinal infection directly delivers the parasite into the surgically exposed cecum, which circumvents the natural route of infection and does not produce infectious cysts. To develop a fecal-oral mouse model, we screened our vivarium for a natural murineEntamoebacolonizer via a pan-EntamoebaPCR targeting the 18S ribosomal gene. We determined that C57BL/6 mice were chronically colonized byEntamoeba muris. This amoeba is closely related toE. histolytica, as determined by 18S sequencing and cross-reactivity with anE. histolytica-specific antibody. In contrast, outbred Swiss Webster (SW) mice were not chronically colonized byE. muris. We orally challenged SW mice with 1×105E. muriscysts and discovered they were susceptible to infection, with peak cyst shedding occurring between 5-7 days post-infection. Most infected SW mice did not lose weight significantly but trended toward decreased weight gain throughout the experiment when compared to mock-infected controls. Infected mice treated with paromomycin, an antibiotic used against non-invasive intestinal disease, do not become colonized byE. muris. Within the intestinal tract,E. murislocalizes exclusively to the cecum and colon. PurifiedE. muriscysts treated with bovine bilein vitroexcyst into mobile, pre-trophozoite stages. Overall, this work describes a novel fecal-oral mouse model for the important global pathogenE. histolytica.ImportanceInfection with parasites from theEntamoebagenus are significantly underreported causes of diarrheal disease that disproportionally impact tropical regions. There are several species ofEntamoebathat infect humans to cause a range of symptoms from asymptomatic colonization of the intestinal tract to invasive disease with dissemination. AllEntamoebaspecies are spread via the fecal-oral route in contaminated food and water. Studying the life cycle ofEntamoeba, from host colonization to infectious fecal cyst production, can provide targets for vaccine and drug development. Because there is not an oral challenge rodent model, we screened for a mouseEntamoebaspecies and identifiedEntamoeba murisas a natural colonizer. We determine the peak of infection after an oral challenge, the efficacy of paromomycin treatment, the intestinal tract localization, and the cues that trigger excystation. This oral infection mouse model will be valuable for the development of novel therapeutic options forEntamoebainfections.