Infectious bronchitis virus nucleocapsid protein suppressed type I interferon production by interfering with the binding of MDA5-dsRNA and interacting with LGP2

Comparative proteomics analysis of kidney in chicken infected by infectious bronchitis virus

The gamma coronavirus infectious bronchitis virus (IBV) is known to cause an acute and highly contagious infectious disease in poultry. Here, this study aimed to investigate the impact of virulent or avirulent IBV infection on the avian host by conducting proteomics with data-independent acquisition mass spectrometry (DIA-MS) in the kidneys of IBV-infected chickens. The results revealed 267, 489, and 510 differentially expressed proteins (DEPs) in the chicken kidneys at 3, 5, and 7 days postinfection (dpi), respectively, when infected with the GD17/04 strain, which is a highly nephrogenic strain and belongs to the 4/91 genotype. In contrast, the attenuated 4/91 vaccine resulted in the identification of 144, 175, and 258 DEPs at 3, 5, and 7 dpi, respectively. Functional enrichment analyses indicated distinct expression profiles between the 2 IBV strains. Upon GD17/04 infection, metabolic pathways respond initially in the early stage (3 dpi) and immune-related signaling pathways respond in the middle and late stages (5 and 7 dpi). The 4/91 vaccine elicited a completely opposite response compared to the GD17/04 infection. Among all DEPs, 62 immune-related DEPs were focused on and found to be mainly enriched in the type I interferon (IFN-I) signaling pathway and involved in humoral and cellular immunity. Notably, key molecules in the IFN-I signaling pathway including MDA5, LGP2, and TBK1 may serve as regulatory targets of IBV. Overall, this study highlights similarities and discrepancies in the patterns of protein expression at different stages of infection with virulent and avirulent IBV strains, with the IFN-I signaling pathway emerging as a critical response to IBV infection.

The role of IBV PL1pro in virus replication and suppression of host innate immune responses

BACKGROUND

Coronavirus papain-like proteases (PLpros) play a crucial role in virus replication and the evasion of the host immune response. Infectious bronchitis virus (IBV) encodes a proteolytically defective remnant of PL1pro and an active PL2pro. However, the function of PL1pro in IBV remains largely unknown. This study aims to explore the effect of PL1pro on virus replication and underlying mechanisms.

RESULTS

The recombinant viruses rIBV-ΔPL1pro and rIBV-ΔPL1pro-N were obtained using reverse genetic techniques through the deletion of the IBV PL1pro domain and the N-terminal conserved sequence of PL1pro (PL1pro-N). We observed significantly lower replication of rIBV-ΔPL1pro and rIBV-ΔPL1pro-N than wild-type IBV. Further investigation revealed that the lack of PL1pro-N in IBV decreased virus resistance to interferon (IFN) while also inducing host immune response by enhancing the production of IFN-β and activating the downstream STAT1 signaling pathway of IFNs. In addition, the overexpression of PL1pro-N significantly suppressed type I IFN response by down-regulating the expressions of genes in the IFN pathway.

CONCLUSIONS

Our data demonstrated that IBV PL1pro plays a crucial role in IBV replication and the suppression of host innate immune responses, suggesting that IBV PL1pro could serve as a promising molecular target for antiviral therapy.

Genes, inflammatory response, tolerance, and resistance to virus infections in migratory birds, bats, and rodents

Normally, the host immunological response to viral infection is coordinated to restore homeostasis and protect the individual from possible tissue damage. The two major approaches are adopted by the host to deal with the pathogen: resistance or tolerance. The nature of the responses often differs between species and between individuals of the same species. Resistance includes innate and adaptive immune responses to control virus replication. Disease tolerance relies on the immune response allowing the coexistence of infections in the host with minimal or no clinical signs, while maintaining sufficient viral replication for transmission. Here, we compared the virome of bats, rodents and migratory birds and the molecular mechanisms underlying symptomatic and asymptomatic disease progression. We also explore the influence of the host physiology and environmental influences on RNA virus expression and how it impacts on the whole brain transcriptome of seemingly healthy semipalmated sandpiper (Calidris pusilla) and spotted sandpiper (Actitis macularius). Three time points throughout the year were selected to understand the importance of longitudinal surveys in the characterization of the virome. We finally revisited evidence that upstream and downstream regulation of the inflammatory response is, respectively, associated with resistance and tolerance to viral infections.