Eimeria tenella: expression profiling of toll-like receptors and associated cytokines in the cecum of infected day-old and three-week old SPF chickens.

Coccidiosis is an economically important protozoan disease worldwide caused by Eimeria parasites. Toll-like receptors (TLRs), a family of highly conserved proteins, are involved in pathogen detection by initiating host responses, and play important roles in the reduction and clearance of pathogens. Little is known about the roles of chicken TLRs during Eimeria tenella infection. We detected the dynamic changes in the expression of TLRs and associated cytokines in the cecum of E. tenella-infected chickens during the early stage of infection. Day-old (Experiment 1) and three-week-old (Experiment 2) chickens were orally gavaged with 10,000 oocysts (30 chickens each experiment), and their cecum intraepithelial lymphocytes were collected at 3, 6, 12, 24, 48, and 72h post-infection (hpi). Expression profiling of TLR1LA, TLR4, TLR5, TLR7, TLR21, and IFN-α, IFN-β, IFN-γ, IL-1β, IL-12 genes were analyzed using quantitative real-time polymerase chain reaction. Almost all TLR transcripts were transiently increased at 3hpi in Experiment 1. In three-week-old chickens, TLR1LA, TLR4, TLR5, TLR7, and TLR21 expression was upregulated at 12hpi, and TLR1LA, TLR5, and TLR21 were highly expressed at 72hpi. In day-old chickens, IFN-α, IFN-β, IFN-γ, IL-1β, and IL-12 expression was significantly upregulated at 3hpi (156.1-1117.1-fold change), in comparison to the different peak level times and relatively small changes for these cytokines in the three-week-old chickens. Our results provide a valuable overview for the expression pattern of TLRs and associated cytokines during the early stage of E. tenella infection in chickens.