Effects of infectious bursal disease virus infection on interferon and antiviral gene expression in layer chicken bursa

Molecular analysis of chicken interferon-alpha inducible protein 6 gene and transcriptional regulation

Interferon-alpha inducible protein 6 (IFI6) is an interferon-stimulated gene (ISG), belonging to the FAM14 family of proteins and is localized in the mitochondrial membrane, where it plays a role in apoptosis. Transcriptional regulation of this gene is poorly understood in the context of inflammation by intracellular nucleic acid-sensing receptors and pathological conditions caused by viral infection. In this study, chicken IFI6 (chIFI6) was identified and studied for its molecular features and transcriptional regulation in chicken cells and tissues, i.e., lungs, spleens, and tracheas from highly pathogenic avian influenza virus (HPAIV)-infected chickens. The chIFI6-coding sequences contained 1638 nucleotides encoding 107 amino acids in three exons, whereas the duck IFI6-coding sequences contained 495 nucleotides encoding 107 amino acids. IFI6 proteins from chickens, ducks, and quail contain an IF6/IF27-like superfamily domain. Expression of chIFI6 was higher in HPAIV-infected White Leghorn chicken lungs, spleens, and tracheas than in mock-infected controls. TLR3 signals regulate the transcription of chIFI6 in chicken DF-1 cells via the NF-κB and JNK signaling pathways, indicating that multiple signaling pathways differentially contribute to the transcription of chIFI6. Further research is needed to unravel the molecular mechanisms underlying IFI6 transcription, as well as the involvement of chIFI6 in the pathogenesis of HPAIV in chickens.

Chicken TAX1BP1 suppresses type I interferon production via degrading chicken MAVS and facilitates infectious bursal diseases virus replication

Mammalian TAX1BP1 (TAX1 binding protein 1), originally identified as a partner of the HTLV-1 viral oncoprotein, functions in regulation of cellular cytokine production. TAX1BP1 plays an important signal transduction regulator, specifically modulating innate immune signaling pathways including NF-B and IRF3. The function of TAX1BP1, which regulates the innate immune response in mammals, has been well studied in previous reports, but the role of chicken TAX1BP1 (chTAX1) in IFN regulation and infectious bursal disease virus (IBDV) replication is still unclear. In this report, chTAX1 was successfully cloned and sub-inserted into a eukaryotic expression vector. The critical regions of chTAX1, such as LC3 binding motif, ubiquitin binding motif, are highly conserved compared to other organisms. We also found that chTAX1 inhibits IFN expression by promoting degradation of chicken MAVS (chMAVS). In addition, the distribution of chTAX1 altered and translocated to co-localize with both VP1 and VP3 after IBDV infection. Overexpression of chTAX1 promotes IBDV replication and knockdown of chTAX1 by RNA interference suppresses IBDV replication. In summary, our data initially indicate that chTAX1 is a suppressor of IFN expression as well as a promoter of IBDV replication.

Molecular characterization, expression profile, and antiviral activity of redlip mullet (Liza haematocheila) viperin

Viperin is known to exhibit activity against RNA viral infection. Viral hemorrhagic septicemia virus (VHSV) is a negative-sense single-stranded RNA virus that causes severe loss in aquaculture species. Susceptible species include redlip mullets (Liza haematocheila), which has become an economically important euryhaline mugilid species in offshore aquaculture along the west coast of Korea. Although interferon-stimulated genes are suspected to act against VHSV, specific pathways or mechanisms of these antiviral actions in redlip mullets have not yet been established. In silico studies of the mullet viperin (Lhrsad2) revealed an S-adenosyl methionine binding conserved domain containing the ⁷⁷CNYKCGFC⁸⁴ sequence. In the tissue distribution, the highest levels of lhrsad2 expression were observed in the blood. When injected with poly(I:C), an approximately 17-fold upregulation (compared to the control) of viperin was detected in the blood after 24 h. Furthermore, non-viral immune stimuli, including Lactococcus garvieae (L. garvieae) and lipopolysaccharide (LPS), that were injected into redlip mullets were not found to induce considerable levels of viperin expression. Subcellular analysis revealed that Lhrsad2 localized to the endoplasmic reticulum (ER). To investigate Lhrsad2's antiviral effects against VHSV, cells overexpressing lhrsad2 were infected with VHSV, and then the viral titer and viral gene expression were analyzed. Both assays revealed the potential of Lhrsad2 to significantly reduce VHSV transcription and replication. In brief, the current study illustrates the remarkable ability of viperin to weaken VHSV in redlip mullet.

Chicken Heat Shock Protein 70 Is an Essential Host Protein for Infectious Bursal Disease Virus Infection In Vitro

Infectious bursal disease virus (IBDV) infection causes pathogenicity and mortality in chickens, leading to huge economic losses in the poultry industry worldwide. Studies of host-virus interaction can help us to better understand the viral pathogenicity. As a highly conservative host factor, heat shock protein 70 (Hsp70) is observed to be involved in numerous viral infections. However, there is little information about the role of chicken Hsp70 (cHsp70) in IBDV infection. In the present study, the increased expression of cHsp70 was observed during IBDV-infected DF-1 cells. Further studies revealed that Hsp70 had similar locations with the viral double-stranded RNA (dsRNA), and the result of pull-down assay showed the direct interaction between cHsp70 with dsRNA, viral proteins (vp)2 and 3, indicating that maybe cHsp70 participates in the formation of the replication and transcription complex. Furthermore, overexpression of cHsp70 promoted IBDV production and knockdown of cHsp70 using small interfering RNAs (siRNA) and reducedviral production, implying the necessity of cHsp70 in IBDV infection. These results reveal that cHsp70 is essential for IBDV infection in DF-1 cells, suggesting that targeting cHsp70 may be applied as an antiviral strategy.

Tandem Mass Tag-Based Quantitative Proteomic Analysis of Chicken Bursa of Fabricius Infected With Reticuloendotheliosis Virus

Reticuloendotheliosis virus (REV) is a type C avian retrovirus that causes immunosuppression, dwarf syndrome, and lymphoma in infected hosts. In this study, we used tandem mass tag (TMT) labeling and liquid chromatography–tandem mass spectrometry (LC-MS/MS) to characterize protein alterations in chicken bursa of Fabricius, before and after REV infection at 7, 14, 21, and 28 days. Our data showed that 1,127, 999, 910, and 1,138 differentially expressed proteins were significantly altered at 7, 14, 21, and 28 days after REV infection, respectively. Morphological analysis showed that REV infection reduced in cortical lymphocytes, bursal follicle atrophy, and nuclear damage. Bioinformatics analysis indicated these proteins were mainly involved with immune responses, energy metabolism, cellular processes, biological regulation, metabolic processes, response to stimuli, and multicellular organismal process. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway cluster analysis showed that post-infection, proteins were enriched in the cell cycle, Wnt signaling, antigen processing and presentation, cytokine receptor interaction, adenosine 3′,5′-cyclic monophosphate signaling pathway, and NF-κB signaling. In addition, we observed that peroxiredoxin 4 (PRDX4), peroxiredoxin 6 (PRDX6), glutathione peroxidase 3 (GPX3), catalase (CAT), and peroxidasin (PXDN) were involved in oxidative stress. Some heat shock protein (HSP) family members such as HSPH1, DNAJA4, HSPA8, and HSPA4L also changed significantly after REV infection. These findings help clarify interactions between REV and the host and provides mechanistic insights on REV-induced host immunosuppression.