Altered Gene Expression Profiles of the MDA5 Signaling Pathway in Peripheral Blood Lymphocytes of Chickens Infected with Avian Reovirus

Avian reovirus (ARV) is a member of the genus Orthoreovirus in the family Reoviridae and causes a severe syndrome including viral arthritis that leads to considerable losses in the poultry industry. Innate immunity plays a significant role in host defense against ARV. Here, we explored the interaction between ARV and the host innate immune system by measuring mRNA expression levels of several genes associated with the MDA5 signaling pathway. The results showed that expression peaks for MDA5, MAVS, TRAF3, TRAF6, IRF7, IKKɛ, TBK1 and NF-κB occurred at 3 days postinfection (dpi). Moreover, type I IFN (IFN-α, IFN-β) and IL-12 expression levels peaked at 3 dpi, while type II IFN (IFN-γ), IL-6, IL-17 and IL-18 expression reached a maximum level at 1 dpi. IL-8 changed at 5 dpi, and IL-1β and TNF-α changed at 7 dpi. Interestingly, several key IFN-stimulated genes (ISGs), including IFITM1, IFITM2, IFITM5, Mx1 and OASL, were simultaneously upregulated and reached maximum values at 3 dpi. These data indicate that the MDA5 signaling pathway and innate immune cytokines were induced after ARV infection, which would contribute to the ARV-host interaction, especially at the early infection stage.