Differential expression of Toll-like receptors and associated cytokines in the bursa of Eimeria tenella infected chickens

Abstract

Chicken coccidiosis, caused by Eimeria spp., is an economically important disease of commercial poultry. Innate immunity ensures an immediate response to invading parasites, and Toll-like receptors (TLRs) are major components of the innate immune system. However, few systematic studies have been reported on the roles of TLRs in chickens infected with Eimeria. In the present study, 14-day-old chickens were infected orally with 50,000 E. tenella oocysts and the bursa of Fabricius was dissected at different time points. Expression profiles of 10 chicken TLRs (chTLRs) and associated cytokines were determined by quantitative real-time PCR. The results showed that chTLR1a and chTLR2a peaked significantly at 3 h post-infection (p < 0.05), while other chTLRs displayed different expression profiles; chTLR1b, chTLR2b, chTLR5, and chTLR15 peaked at 48 h post-infection, while chTLR4, chTLR7, and chTLR21 peaked at 144 h post-infection. ChTLR3 expression was the highest among chTLRs, peaking at 96 h post-infection (p < 0.05). For cytokines, interleukin (IL)-6, IL-12, IL-17, and interferon-γ peaked at 12 h post-infection, while IL-4 peaked at 24 h post-infection. The results provide a valuable overview of the expression profiles of innate immune molecules during E. tenella infection in chicken bursa, and indicate that innate immune responses may mediate resistance to chicken coccidiosis.