Chicken Interferon-induced Protein with Tetratricopeptide Repeats 5 Antagonizes Replication of RNA Viruses

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.

Antiviral responses against chicken respiratory infections: Focus on avian influenza virus and infectious bronchitis virus

“…In addition, chIFIT5 can specifically antagonize with negative-sense viral RNA structures carrying 5′-ppp portion. A previous study in chickens demonstrated the interaction between AIV and IFIT5 and subsequent reduction of AIV replication by using a lentivirus-mediated IFIT5-stable chicken fibroblast model [110]. Furthermore, the kinetics of AIV replication in transgenic chicken embryos (expressing chIFIT5 protein or knocked-down for endogenous chIFIT5 gene) showed the potential antiviral activity of chIFIT5 against AIV in ovo [110].…”

“…IFITs are a group of IFN-effectors that directly engage with 5′-ppp viral RNA [110,111]. IFIT5 is the only IFIT gene that has been identified in chickens [112].…”

“…A previous study in chickens demonstrated the interaction between AIV and IFIT5 and subsequent reduction of AIV replication by using a lentivirus-mediated IFIT5-stable chicken fibroblast model [110]. Furthermore, the kinetics of AIV replication in transgenic chicken embryos (expressing chIFIT5 protein or knocked-down for endogenous chIFIT5 gene) showed the potential antiviral activity of chIFIT5 against AIV in ovo [110]. Infection of different chicken tissues (liver, kidney, spleen, beak, trachea, lungs, and duodenum) with H9N2 avian influenza virus strain showed higher levels of chIFIT5 expression and it seems that AIV infection positively regulates the transcriptional dynamics of chIFIT5 in chickens [110].…”

Genome-Wide Classification of Type I, Type II and Type III Interferon-Stimulated Genes in Chicken Fibroblasts

“…Innate immunity defines the first line of host defense, and interferons (IFNs) play central roles in mediating host resistance against viruses, bacteria, fungi and parasites by directly and indirectly regulating multiple immune cells [1]. IFNs are part of the class II cytokine family and are divided into three types (I, II and III) based on their receptor specificity, sequence homology, evolutionary relatedness, functional activity of these cytokines and nature of interferon-stimulated genes (ISGs) induction [2,3]. The ISGs display a spectrum of cellular functions and the cumulative actions of these ISGs define the antiviral state of the hosts.…”

“…Given the fact that chicken differs fundamentally from other mammals in innate immunity, majority of current concepts are mainly based on assumptions. Some out of many examples include absence of RIG-I, IRF9 and IRF3 homologues, lack of anti-viral roles of chicken Mx, absence of many essential molecules in the innate immune signalling pathways such as IFIT1/2/3, shorter versions of ZC3HAV1 and many of the DNA sensors [2,3]. Intriguingly, despite the absence of these key components, chickens respond to highly pathogenic avian influenza (HPAIVs) and other viruses, and mount potent type I IFN responses [14-16] highlighting the presence of yet unknown and evolutionary compensatory mechanisms in chicken.…”