Molecular cloning, expression and mimicking antiviral activity analysis of retinoic acid-inducible gene-I in duck (Anas platyrhynchos)

Intracellular double-stranded RNA (dsRNA) is a chief sign of replication for many viruses. Pattern recognition receptors (PRRs) of the innate immune system detected the dsRNA and initiate the antiviral responses. Retinoic acid-inducible gene I (RIG-I), a member of PRRs, plays an essential regulatory role in dsRNA-induced signalling. In this study, the full-length complementary DNA (cDNA) of duck RIG-I (duRIG-I) was cloned using the reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of the cDNA ends (RACE). The cDNA of duRIG-I contained 97-bp 50 UTR, 141-bp 30 -UTR and 2802 bp complete open-reading frame (ORF) encoding 933 amino acids. Multiple sequence alignments showed that duRIG-I shared high similarity with RIG-I from other vertebrates. Quantitative real-time PCR (qRT-PCR) analysis revealed that duRIG-I mRNA was expressed in all tested tissues, with high levels in the liver, heart, spleen, kidney and thymus, while lower in the duodenum. duRIG-I could be induced by treatment with poly(I:C). Further, overexpression of duRIG-I significantly activated the transcription of poly(I:C)-induced IFN-b, IRF7, TRIF, Mx, STAT1 and STAT2 mRNA, and duRIG-I knockdown showed the opposite results. Overall, our results suggested that duRIG-I could be an important receptor for mimicking antiviral state in duck, which warrant further studies to show the possible mechanism.

Up-regulation of NLRC5 and NF-кB signaling pathway in carrier chickens challenged with Salmonella enterica Serovar Pullorum at different persistence periods.

The immune performance, SNPs and expression levels of candidate genes (IL1-β, Nramp1, TLR4, MyD88, NF-кB and NLRC5) were analyzed in carrier chickens of a Chinese indigenous breed infected with Salmonella enterica Serovar Pullorum at different persistence periods (12, 19 and 24 weeks of age). Carrier birds at 19 weeks of age presented significant difference in most immune parameters, as compared to carriers at 12 and 24 weeks of age, while no significant difference in most immune parameters was observed between carriers at 12 and 24 weeks of age. The genotype distributions of IL1-β and TLR4 presented significant differences between carriers and healthy birds. The expression levels of most candidate genes in carriers at 19 weeks of age were significantly higher than that in carriers at 12, 24 weeks of age and healthy birds and reached 1% level of significance between carriers at 19 weeks of age and healthy birds. The expression patterns of all genes, but IL-1β and NLRC5 between carriers at 12 and 24 weeks of age in all tissues were similar. Compared with carriers at 12 weeks of age, IL1-β was significantly down-regulated, but NLRC5 was significantly up-regulated in carriers at 24 weeks of age. Our study demonstrated that immune performance of carrier birds was severely impaired at age of sexual maturation and NLRC5 might play as a negative mediator of NF-кB pathway involved in immune response to asymptomatic infection by S. Pullorum. The TLR4/MyD88/NF-кB pathway might be suitable for study on S. Pullorum infection in Chinese indigenous breeds.