Abstract
The intracellular actions of interferon (IFN)-regulated proteins, including IFN-induced proteins with tetratricopeptide repeats (IFITs), attribute a major component of the protective antiviral host defense. Here we applied genomics approaches to annotate the chicken IFIT locus and currently identified a single IFIT (chIFIT5) gene. The profound transcriptional level of this effector of innate immunity was mapped within its unique cis-acting elements. This highly virus- and IFN-responsive chIFIT5 protein interacted with negative sense viral RNA structures that carried a triphosphate group on its 5′ terminus (ppp-RNA). This interaction reduced the replication of RNA viruses in lentivirus-mediated IFIT5-stable chicken fibroblasts whereas CRISPR/Cas9-edited chIFIT5 gene knockout fibroblasts supported the replication of RNA viruses. Finally, we generated mosaic transgenic chicken embryos stably expressing chIFIT5 protein or knocked-down for endogenous chIFIT5 gene. Replication kinetics of RNA viruses in these transgenic chicken embryos demonstrated the antiviral potential of chIFIT5 in ovo. Taken together, these findings propose that IFIT5 specifically antagonize RNA viruses by sequestering viral nucleic acids in chickens, which are unique in innate immune sensing and responses to viruses of both poultry and human health significance.
Highlights
IFN-induced proteins with tetratricopeptide repeats (IFITs) genes are evolutionary conserved and are originated possibly by gene duplication[6]
Several pseudogenes have been identified in different animal species including IFIT1B, IFIT1C, IFIT3-like and IFIT5-like gene
Since IFIT5 was the only identified IFIT protein in chickens, we aimed to explore whether chicken IFIT5 (chIFIT5) interacts with RNA in a similar mechanism reported for huIFIT5 or chIFIT5-RNA interaction is redundant to other members of IFIT family
Summary
IFIT genes are evolutionary conserved and are originated possibly by gene duplication[6]. Viral genomic and subgenomic RNA of negative sense single-stranded viruses such as influenza A viruses (IAV) and Newcastle disease viruses (NDV) bear triphosphate at the 5′-termini[14] These PAMPs are sensed by cellular PRRs and initiate innate immune responses, which restrict virus growth[1,5]. Employing the RCAS-based retroviral gene transfer vector system[20], we generated transgenic chicken embryos expressing chIFIT5 and demonstrated its antiviral potential in ovo These findings were further evaluated by RCAS-mediated gene silencing in developing transgenic chicken embryos by assessing the replication kinetics of RNA viruses. These analyses provide evidence of the presence of a functional homologue of IFIT5 and expand our understanding on the breaths and dynamics of nucleic acid sensing in chicken
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