Avian Interferon-Inducible Transmembrane Protein Family Effectively Restricts Avian Tembusu Virus Infection

Chen, Shilong; Wang, Long; Chen, Jieying; Zhang, Lanlan; Wang, Song; Goraya, Mohsan U.; Chi, Xiaojuan; Na, Yang; Shao, Wenhan; Yang, Zhou; Zeng, Xiancheng; Chen, Shaoying; Chen, Ji-Long

Type I and Type III IFNs bind to their receptors, which stimulates the JAK-STAT pathway that triggers various ISG expression. Expression of IFITMs is strongly induced by IFNs (Smith et al., 2013) . Consistent with previous studies (Smith et al., 2013) , our data showed that stimulation of DF-1 cells with chicken IFNs significantly enhanced the expression of IFITMs. Interestingly, we observed that IFITM1 in ATMUV infected DEFs had a faster kinetic response than ATMUV-induced IFNs. Thus, we assessed whether IFITMs expression is totally IFN-dependent. For this, siRNA specifically targeting chicken interferon alpha/beta receptor 1 (chIFNAR1-siRNA) and negative control siRNA (NC-siRNA) were employed in this study. 100 nM chIFNAR1-siRNA or NC-siRNA was transfected into DF-1 cell. Twenty-four hours post-transfection, the cells were infected with ATMUV and harvested at 24 hpi. Interestingly, disruption of endogenous IFNAR1 by siRNA greatly reduced IFITM2 mRNA expression, but only caused modest downregulation of IFITM1 and IFITM3 (Supplementary Figure 6) . The data suggest that chIFITM2 may not share the same IFN-dependent pathways with chIFITM1 and chIFITM3. Previous study has found that murine IFITM3 expression was not only induced by increased expression of type I or II IFNs, but also upregulated by other cytokines such as IL-6 (Bailey et al., 2012) . Other groups also found that expression of IFI-56K, IFI-54K, and ISG56 was induced directly by virus and then triggered secondarily through virus-induced IFNs (Wathelet et al., 1988; Holzinger et al., 2007) . These findings indicate that multiple signaling pathways might be involved in regulation of IFITM expression during the viral infection.