Molecular and functional characterization of chicken interleukin 1 receptor 2 (chIL-1R2)

Interleukin-1 receptor type 2 (IL1R2) is a decoy receptor for exogenous IL-1. However, its functional role in chicken immunity is poorly understood. Herein, chicken IL-1R2 (chIL-1R2) was identified and functionally characterized in vivo and in vitro. The chIL-1R2 coding sequence includes 1,236 nucleotides encoding 412 amino acids, is highly conserved, and has a close relationship with its mammalian counterpart. Its extracellular region has three Ig-like domains but no TIR domain for intracellular signaling. Using ELISA, the recombinant chIL-1R2 protein was demonstrated to specifically bind to the chicken IL-1β. ChIL-1R2 mRNA expression was shown to be higher in the spleen, lung, kidney, small intestine, and liver. The expression of chIL-1R2 and chIL-1R1 was significantly upregulated in DF-1 cells treated with poly (I:C), but significantly downregulated in the presence of NF-κB, JNK, and MEK inhibitors, indicating that the NF-κB, JNK, and MEK signaling pathways are required for the transcriptional regulation of chIL-1R1 and chIL-1R2 expression. It is worth noting that while the p30 MAPK pathway was required for chIL-1R1 expression, it was not required for chIL-1R2 expression. Furthermore, chIL-1R2 expression increased as early as day 1, and then significantly decreased until day 3, while chIL-1R1 was dramatically upregulated in four organs of chickens infected with the highly pathogenic avian influenza virus (HPAIV). These findings indicate that chIL-1R1 and chIL-1R2 may play a crucial in innate and adaptive immune responses toward HPAIV infection. In summary the present study showed that chIL-1R2 binds to chIL-1β antibody. ChIL-1R2 expression can be induced by a viral infection, and may be regulated through NF-κB/JNK/MEK-mediated signaling pathways.