Differential analysis of IBV-infected primary chicken embryonic fibroblasts and immortalized DF-1

Abstract

Infectious bronchitis virus (IBV), the causative agent of infectious bronchitis, is responsible for major economic losses in the poultry industry worldwide. While IBVs can usually be passaged in primary chicken embryonic fibroblasts (CEFs), most of the wild ones cannot adapt to passaged cell lines. In this study, the wild strain CK/CH/MY/2020 was used to infect primary CEF and immortalize DF-1 CEF cells. Results indicated that IBV was able to cause lesions and pass onto CEF, but not DF-1. Indeed, the virus could enter DF-1 cells and synthesize the associated structural gene but could not assemble into complete viral particles for release. Furthermore, transcriptome sequencing analysis showed significant differences in gene expression between CEF and DF-1 cells after viral infection, although the corresponding antiviral responses could be activated in both cell types. The biggest difference was in terms of the amino acid biosynthesis pathway and the cytokine receptor interaction pathway, which were significantly and specifically activated in CEF. This could actually explain why intact viruses can be assembled but not in DF-1. In addition, SLBP and P2RX7 affect the replication of IBV’s structural genes to some extent. Overall, IBV can enter CEF and DF-1 cells, but the complex intracellular cytokine interactions affect the assembly and release of viral particles. The insight will be useful for the study of IBV through in vitro transmission and pathogenesis. IMPORTANCE Infectious bronchitis virus (IBV) is responsible for high morbidity and mortality as well as substantial economic losses worldwide. Transcriptome sequencing of IBV-infected chicken embryonic fibroblast and DF-1 cells revealed that the virus elicits antiviral immunity in cells after viral infection, but IBV cannot activate DF-1 cells to produce sufficient amounts of viral structures to assemble into complete virions, which may be caused by the interactions between cytokines. The study of IBV cellular adaptations is important for vaccine development and investigation of the pathogenesis of IBV.

Host Immune Response Modulation in Avian Coronavirus Infection: Tracheal Transcriptome Profiling In Vitro and In Vivo

“…Since the early 2000s, researchers have aimed to map the host gene expression patterns involved in IBV infection [ 37 , 38 , 39 ]. More recent transcriptomic studies have looked at chicken spleen tissues [ 40 , 41 , 42 ], tracheal tissues [ 43 , 44 , 45 ], lung tissues [ 41 ], human lung epithelial-like cells [ 46 ], chicken kidney tissues and cells [ 47 , 48 , 49 , 50 , 51 ], dendritic cells [ 52 , 53 ], macrophages [ 54 ], and fibroblasts [ 55 ] upon infection with various strains of IBV. Currently, there are no RNA-seq studies specifically looking at IBV infection in chicken tracheal epithelial cells (cTECs), nor using the IBV DMV/1639 strain, which has been the dominant IBV genotype circulating in Canada [ 21 , 22 ] and the United States of America (USA) in recent years [ 20 , 56 ].…”