No abstract

Animals with a chronic infection of the parasite Toxoplasma gondii are protected against lethal secondary infection with other pathogens. Our group previously determined that soluble T. gondii antigens (STAg) can mimic this protection and be used as a treatment against several lethal pathogens. Because treatments are limited for the parasite Cryptosporidium parvum , we tested STAg as a C. parvum therapeutic. We determined that STAg treatment reduced C. parvum Iowa II oocyst shedding in IFNγ-KO mice. Murine intestinal sections were then sequenced to define the IFNγ independent transcriptomic response to C. parvum infection. Gene Ontology and transcript abundance comparisons showed host immune response and metabolism changes. Transcripts for type I interferon responsive genes were more abundant in C. parvum infected mice treated with STAg. Comparisons between PBS or STAg treatments showed no significant differences in C. parvum gene expression. C. parvum transcript abundance was highest in the ileum and mucin-like glycoproteins and the GDP-fucose transporter were among the most abundant. These results will assist the field in determining both host- and parasite-directed future therapeutic targets.

Background: Protective immune responses to Cryptosporidium parvum, a zoonotic, gastrointestinal parasite, are primarily dependent on the presence of interferon-gamma (IFNγ). We discovered that treatment with soluble T. gondii antigen (STAg) reduces Cryptosporidium parvum shedding in the absence of IFNγ. To identify the protective IFNγ independent responses elicited by STAg, we conducted a transcriptomic analysis of intestinal sections of IFNγ-deleted, C. parvum infected or uninfected mice treated with STAg or PBS. Results: STAg treatment reduced oocyst shedding in C. parvum infected IFNγ deleted mice. Gene ontology analysis of the intestinal transcriptomes suggested that both C. parvum infection and STAg treatment changes the transcript abundance of genes involved in the host cell membrane, intracellular and extracellular transport, and immune responses. We found in high abundance 37 genes related to IFN type I response in infected mice treated with STAg. Among these genes, members of the oligoadenylate synthetase and Schlafen family were identified. Conclusions: STAg treatment of C. parvum infected mice induced both host immune and metabolism changes associated with a reduction in shedding. Several components of the type I interferon immune response were more abundant in the ileum of C. parvum infected in IFNγ-deleted mice. Future studies will explore the role of type I IFN mediated immune responses in controlling C. parvum infections. STAg treatment appears to only affects the host transcriptome while the parasite transcriptome remains unaffected. Several C. parvum genes, including mucin genes, are more abundant during infection of animals, which opens new avenues in C. parvum research.

Infection with parasites from the Entamoeba genus are significantly underreported causes of diarrheal disease that disproportionally impact tropical regions. There are several species of Entamoeba that infect humans to cause a range of symptoms from asymptomatic colonization of the intestinal tract to invasive disease with dissemination.

There are several Entamoeba species that colonize humans, but only Entamoeba histolytica causes severe disease. E. histolytica is transmitted through the fecal-oral route to colonize the intestinal tract of 50 million people worldwide. The current mouse model to study E. histolytica intestinal 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 murine Entamoeba colonizer via a pan-Entamoeba PCR targeting the 18S ribosomal gene. We determined that C57BL/6 mice were chronically colonized by Entamoeba muris. This amoeba is closely related to E. histolytica, as determined by 18S sequencing and cross-reactivity with an E. histolytica-specific antibody. In contrast, outbred Swiss Webster (SW) mice were not chronically colonized by E. muris. We orally challenged SW mice with 1x105E. muris cysts 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 by E. muris. Within the intestinal tract, E. muris localizes exclusively to the cecum and colon. Purified E. muris cysts treated with bovine bile in vitro excyst into mobile, pre-trophozoite stages. Overall, this work describes a novel fecal-oral mouse model for the important global pathogen E. histolytica.