examination-of-pyroptosis-by-flow-cytometry

Examination of Pyroptosis by Flow Cytometry

Pyroptosis is an inflammatory type of programmed cell death predominantly driven by the formation of plasma membrane pores by the N-terminus generated ...

National Key Laboratory of Veterinary Public Health Security

Animal Epidemiology of the Ministry of Agriculture

China Agricultural University

Chicken infectious anemia virus (CIAV) infection induces immunosuppression or subclinical immunosuppression in chickens. CIAV infection has been reported to repress type I interferon (IFN-I) expression, but the underlying mechanisms are not yet understood. Here we reported that VP1, the capsid protein of CIAV, the major immunogenic protein that triggers the production of neutralizing antibodies in chickens, inhibited type I interferon (IFN-I) expression induced by cGAS-STING signaling. We showed that VP1 inhibited TBK1 phosphorylation and down stream signal transduction, leading to the inhibition of IFN-I expression. Subsequently, we demonstrated that VP1 interacted with TBK1. Finally, we clarified that aa 120-150 in VP1 was essential for VP1 to interact with TBK1 and inhibit cGAS-STING signaling. These findings will help us further understand the pathogenesis of CIAV in chickens.

Chicken infectious anemia virus (CIAV) VP1 antagonizes type I interferon (IFN-I) production by inhibiting TBK1 phosphorylation.

Infectious bursal disease virus (IBDV) is an immunosuppressive pathogen causing enormous economic losses to the poultry industry across the globe. As a double-stranded RNA virus, IBDV undergoes genetic mutation or recombination in replication during circulation among flocks, leading to the generation and spread of variant or recombinant strains. In particular, the recent emergence of variant IBDV causes severe immunosuppression in chickens, affecting the efficacy of other vaccines. It seems that the genetic mutation of IBDV during the battle against host response is an effective strategy to help itself to survive. Therefore, a comprehensive understanding of the viral genome diversity will definitely help to develop effective measures for prevention and control of infectious bursal disease (IBD). In recent years, considerable progress has been made in understanding the relation of genetic mutation and genomic recombination of IBDV to its pathogenesis using the reverse genetic technique. Therefore, this review focuses on our current genetic insight into the IBDV's genetic typing and viral genomic variation.

Genetic Insight into the Interaction of IBDV with Host-A Clue to the Development of Novel IBDV Vaccines.

Hepatitis-pericardial syndrome (HHS) is an acute highly infectious avian disease caused by fowl adenovirus serotype 4 (FAdV-4), characterized by fulminant hepatitis and hydropericardium in broilers. Since 2015, a widespread epidemic has occurred in China due to the emergence of hypervirulent FAdV-4 (HPFAdV-4), causing huge losses to the stakeholders. However, the pathogenesis of HPFAdV-4 and the host responses to its infection remain elusive. Here, we show that infection of leghorn male hepatocellular (LMH) cells by HPFAdV-4 induced complete autophagy in cells and that the autophagy induced by recombinant HPFAdV-4-ON1 (rHPFAdV-4-ON1), a viral strain generated by replacing the  gene of wild-type HPFAdV-4 (HPFAdV-4-WT) with the one of nonpathogenic strain FAdV-4-ON1, was remarkably mitigated compared to that of the rHPFAdV-4-WT control, suggesting that HPFAdV-4 hexon is responsible for virus-induced autophagy. Importantly, we found that hexon interacted with a cellular protein, BAG3, a host protein that initiates autophagy, and that BAG3 expression increased in cells infected with HPFAdV-4. Furthermore, knockdown of BAG3 by RNA interference (RNAi) significantly inhibited HPFAdV-4- or hexon-induced autophagy and suppressed viral replication. On the contrary, expression of hexon markedly upregulated the expression of BAG3 via activating the P38 signaling pathway, triggering autophagy. Thus, these findings reveal that HPFAdV-4 hexon interacts with the host protein BAG3 and promotes BAG3 expression by activating P38 signaling pathway, thereby inducing autophagy and enhancing viral proliferation, which immensely furthers our understanding of the pathogenesis of HPFAdV-4 infection.  HHS, mainly caused by HPFAdV-4, has caused large economic losses to the stakeholders in recent years. Infection of leghorn male hepatocellular (LMH) cells by HPFAdV-4 induced complete autophagy that is essential for HPFAdV-4 replication. By a screening strategy, the viral protein hexon was found responsible for virus-induced autophagy in cells. Importantly, hexon was identified as a factor promoting viral replication by interaction with BAG3, an initiator of host cell autophagy. These findings will help us to better understand the host response to HPFAdV-4 infection, providing a novel insight into the pathogenesis of HPFAdV-4 infection.

Critical Role of Viral Protein Hexon in Hypervirulent Fowl Adenovirus Serotype-4-Induced Autophagy by Interaction with BAG3 and Promotion of Viral Replication in LMH Cells.

Nuclear receptors are ligand-activated transcription factors that play an important role in regulating innate antiviral immunity and other biological processes. However, the role of nuclear receptors in the host response to infectious bursal disease virus (IBDV) infection remains elusive. In this study, we show that IBDV infection or poly(I·C) treatment of DF-1 or HD11 cells markedly decreased nuclear receptor subfamily 2 group F member 2 (NR2F2) expression. Surprisingly, knockdown, knockout, or inhibition of NR2F2 expression in host cells remarkably inhibited IBDV replication and promoted IBDV/poly(I·C)-induced type I interferon and interferon-stimulated genes expression. Furthermore, our data show that NR2F2 negatively regulates the antiviral innate immune response by promoting the suppressor of cytokine signaling 5 (SOCS5) expression. Thus, reduced NR2F2 expression in the host response to IBDV infection inhibited viral replication by enhancing the expression of type I interferon by targeting SOCS5. These findings reveal that NR2F2 plays a crucial role in antiviral innate immunity, furthering our understanding of the mechanism underlying the host response to viral infection.  Infectious bursal disease (IBD) is an immunosuppressive disease causing considerable economic losses to the poultry industry worldwide. Nuclear receptors play an important role in regulating innate antiviral immunity. However, the role of nuclear receptors in the host response to IBD virus (IBDV) infection remains elusive. Here, we report that NR2F2 expression decreased in IBDV-infected cells, which consequently reduced SOCS5 expression, promoted type I interferon expression, and suppressed IBDV infection. Thus, NR2F2 serves as a negative factor in the host response to IBDV infection by regulating SOCS5 expression, and intervention in the NR2F2-mediated host response by specific inhibitors might be employed as a strategy for prevention and treatment of IBD.

Reduced NR2F2 Expression in the Host Response to Infectious Bursal Disease Virus Infection Suppressed Viral Replication by Enhancing Type I Interferon Expression by Targeting SOCS5.

Article	Year
Chicken infectious anemia virus (CIAV) VP1 antagonizes type I interferon (IFN-I) production by inhibiting TBK1 phosphorylation. Virus research\| PubMed ID: 36809820	2023
Genetic Insight into the Interaction of IBDV with Host-A Clue to the Development of Novel IBDV Vaccines. International journal of molecular sciences\| PubMed ID: 37175960	2023
Critical Role of Viral Protein Hexon in Hypervirulent Fowl Adenovirus Serotype-4-Induced Autophagy by Interaction with BAG3 and Promotion of Viral Replication in LMH Cells. Journal of virology\| PubMed ID: 37255472	2023
Reduced NR2F2 Expression in the Host Response to Infectious Bursal Disease Virus Infection Suppressed Viral Replication by Enhancing Type I Interferon Expression by Targeting SOCS5. Journal of virology\| PubMed ID: 37358466	2023

Li Gao

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