Dynamics Of Th17 Associating Cytokines In Cryptosporidium Parvum Infecting Mice

Cryptosporidium parvum is an intracellular protozoan parasite that inhabits in epithelial cells in the digestive tracts of a wide range of vertebrates, causing cryptosporidiosis, which is a zoonotic disease. Now, there are 27 valid Cryptosporidium species infecting all five classes of vertebrates including human, since the first Cryptosporidium sp. was recognized in mice by Tyzzer in 1907. Cryptosporidiosis, which is caused by C. parvum, mainly leads to cattle, sheep and goats with diarrhea. However, there are no effective drugs or vaccines for cryptosporidiosis, which is a severe threat to human health and results in significant economic losses. Understanding the pathogenic mechanism of Cryptosporidium and mechanism of host immune defense will provide important foundation for prevention and treatment of cryptosporidiosis. The present study identified two different Ⅱd isolates of C. parvum oocysts and chose one to establish the infection model in BALB/c mice. Subsequently, this work examined the expression pattern of the IL-17 and related cytokines in transcriptional levels in small intestinals and spleens of C. parvum-infecting BALB/c mice at different time points and used these data to speculate the roles of these cytokines during Cryptosporidium infection and clearance.1. In order to establish proper infection model, two different isolates of C. parvum were identified and chose ⅡdA15G2R1 subtype to infected BALB/c mice with orally 1×106 oocysts per mouse.Thereafter, the mice continuously excreted oocysts from post infection 1 d to 20 d. The oocysts also showed good genetic stability which were examined by PCR using 18 S rRNA gene.2. Using quantitative real time PCR, the Th17 cell differentiation relative cytokines were examined during C. parvum infection at different time points in spleen and gut-associated lymphoid tissue(GALT) of BALB/c mice. Th17 cell differentiation relative cytokines, including the promoters(IL-6 and TGF-β), the signal transducer(STAT-3) and the transcription factor(RORγt) were up-regulated at different degrees in the course of C. parvum infection.3. To examine the role of Th17 cell during C. parvum infection, the effector cytokines(IL-17, IL-22 and TNF-α) and the maintenance factor(IL-23) were detected at different time points in spleens and GALT of BALB/c mice. In addition, the protein level of IL-17 was also examined by ELISA. Both the mRNA and protein levels of IL-17 were highly expressed in infected mice in early and meta-phase of the infection, and the mRNA levels of effector cytokines were increased in almost all the examined time in infected groups.