Transcriptomic Analysis of the Chicken MDA5 Response Genes

RIG-I and MDA5 are two key pattern recognition receptors that sense RNA virus invasion, but RIG-I is absent in chickens. Although chickens have intact MDA5, the genes downstream of chicken MDA5 (chMDA5) that may mediate antiviral response are not well studied. We compared the transcriptional profile of chicken embryonic fibroblasts (DF1) transfected with chMDA5, and poly(I:C), using RNA-seq. Transfected chMDA5 and poly(I:C) in DF1 cells were associated with the marked induction of many antiviral innate immune genes compared with control. Interestingly, nine interferon-stimulated genes (ISGs) were listed in the top 15 upregulated genes by chMDA5 and poly(I:C) transfection. We used real-time PCR to confirm the upregulation of the nine ISGs, namely, MX1, IFI6, IFIT5, RSAD2, OASL, CMPK2, HELZ2, EPSTI1, and OLFML1, by chMDA5 and poly(I:C) transfection in DF1 cells. However, avian influenza virus H5N6 infection only increased MX1, IFI6, IFIT5, RSAD2, and OASL expression levels. Further study showed that the overexpression of these five genes could significantly inhibit H5N6 virus replication. These results provide some insights into the gene expression pattern induced by chMDA5, which would be beneficial for understanding and identifying innate immune genes of chicken that may lead to new antiviral therapies.