Dynamics Of IL-17and Related Cytokines In Chickens Infected With Cryptosporidium Baileyi

Cryptosporidium spp. are intracellular protozoan parasites that inhabit epithelial cells inthe digestive and respiratory tracts of a wide range of vertebrates, causing cryptosporidiosis,which is a zoonotic disease. Now, there are24valid Cryptosporidium species and more than70Cryptosporidium genotypes in human, birds, mammals, fish, and reptiles since the firstCryptosporidium sp. was recognized in mice by Tyzzer in1907. However, there is noeffective drug or vaccine for cryptosporidiosis, which is a severe threat to human health andresults in significant economic losses. Understanding the pathogenic mechanisms ofCryptosporidium and mechanisms of host immune defense will provide important foundationfor prevention and treatment of cryptosporidiosis. The present study examined expression ofthe IL-17and related cytokines (IL-1β, IL-6, TGF-β and STAT3) in transcription levels intrachea and spleen of C. baileyi-infected chickens at different time points and used these datato speculate the roles of these cytokines during Cryptosporidium infection and clearance.1. In order to obtain C. baileyi oocysts from feces to establish proper infection model,oocysts were isolated from trachea and spleen tissues of mixed oocyst infected chickens basedon the different parasitic sites of parasite species. The results showed that Cryptosporidiumoocysts were found in fecal samples, trachea and spleen tissues of infected chickens, andcoccidian oocysts were also detected in fecal samples. Then Cryptosporidium oocysts wereisolated from trachea and spleen tissues of mixed oocyst infected chickens by using enzymedigesting tissue method.2. To further identify Cryptosporidium species, morphology and molecular methods wereused to identify the Cryptosporidium oocysts isolated from feces and tissues of infectedchicken. Both of the results showed that the Cryptosporidium species was C. baileyi.3. To establish proper infection model, Roman chicks and Arbor Acre (AA) chicks wereinoculated orally with1×105C. baileyi oocysts. The results showed that AA chicks inoculatedorally with a dose of1×105oocysts were more proper for further study, and the symptoms andoocyst shedding in these chickens were obvious and short.4. Expression of the IL-17and related cytokines in transcription levels in trachea andspleen of C. baileyi-infected chickens at different time points were examined by usingreal-time quantitative PCR (qPCR). Data of qPCR showed that all detected cytokines in trachea were up-regulated in the infected chickens compared with the uninfected controlduring the C. baileyi infection. Significantly increased IL-17mRNA expression in tracheawas observed as early as12h pi (post infection), peaking at24h pi and10d pi, and decliningthereafter. And the transcription levels of IL-17and relative cytokines in spleen also showedsignificant increase at different time points during the infections. These results suggested thatthe IL-17may participate in the immune responses against C. baileyi infection.