Fusion of Infectious Bronchitis Virus with Host Cell Activated by Low pH

2006 ◽  
Vol 1 (5) ◽  
pp. 243-243
Keyword(s):  
Host Cell ◽  
Infectious Bronchitis Virus ◽  
Low Ph ◽  
Infectious Bronchitis

scholarly journals The Avian Coronavirus Infectious Bronchitis Virus Undergoes Direct Low-pH-Dependent Fusion Activation during Entry into Host Cells

2006 ◽  
Vol 80 (7) ◽  
pp. 3180-3188 ◽  
Author(s):  
Victor C. Chu ◽  
Lisa J. McElroy ◽  
Vicky Chu ◽  
Beverley E. Bauman ◽  
Gary R. Whittaker
Keyword(s):  
Cell Fusion ◽  
Conformational Changes ◽  
Infectious Bronchitis Virus ◽  
Fusion Reaction ◽  
Low Ph ◽  
Surface Proteins ◽  
Host Cells ◽  
Dependent Manner ◽  
Infectious Bronchitis ◽  
Ph Dependent

ABSTRACT Coronaviruses are the causative agents of respiratory disease in humans and animals, including severe acute respiratory syndrome. Fusion of coronaviruses is generally thought to occur at neutral pH, although there is also evidence for a role of acidic endosomes during entry of a variety of coronaviruses. Therefore, the molecular basis of coronavirus fusion during entry into host cells remains incompletely defined. Here, we examined coronavirus-cell fusion and entry employing the avian coronavirus infectious bronchitis virus (IBV). Virus entry into cells was inhibited by acidotropic bases and by other inhibitors of pH-dependent endocytosis. We carried out fluorescence-dequenching fusion assays of R18-labeled virions and show that for IBV, coronavirus-cell fusion occurs in a low-pH-dependent manner, with a half-maximal rate of fusion occurring at pH 5.5. Fusion was reduced, but still occurred, at lower temperatures (20°C). We observed no effect of inhibitors of endosomal proteases on the fusion event. These data are the first direct measure of virus-cell fusion for any coronavirus and demonstrate that the coronavirus IBV employs a direct, low-pH-dependent virus-cell fusion activation reaction. We further show that IBV was not inactivated, and fusion was unaffected, by prior exposure to pH 5.0 buffer. Virions also showed evidence of reversible conformational changes in their surface proteins, indicating that aspects of the fusion reaction may be reversible in nature.

scholarly journals Infectious bronchitis virus attaches to lipid rafts and enters cells via clathrin mediated endocytosis

2018 ◽  
Author(s):  
Huan Wang ◽  
Yingjie Sun ◽  
Xiang Mao ◽  
Chunchun Meng ◽  
Lei Tan ◽  
...  
Keyword(s):  
Lipid Rafts ◽  
Infectious Bronchitis Virus ◽  
Time Course ◽  
Molecular Mechanisms ◽  
Low Ph ◽  
Infection Process ◽  
Late Endosome ◽  
Poultry Industry ◽  
Infectious Bronchitis ◽  
Late Endosomes

ABSTRACTDue to its economic importance to in poultry industry, the biology and pathogenesis of infectious bronchitis virus (IBV) have been investigated extensively. However, the molecular mechanisms involved in IBV entry are not well characterized. In this study, systematic approaches were used to dissect IBV entry process in various susceptible cells. First, we observed that lipid rafts were involved in IBV attachment. Second, low pH in intracyplasmic vesicles was required for virus entry. By using the specific clathrin mediated endocytosis (CME) inhibitor or knock down of clathrin heavy chain (CHC), we demonstrated that IBV mainly utilized the CME for its entry. Furthermore, GTPase dynamin1 was involved in virus containing vesicle scission and internalization. Surprisingly, CME adaptor Eps15 had no effect on IBV internalization. Third, the penetration of IBV into cells led to active cytoskeleton rearrangement. After internalization, virus particles moved along with the classical endosome/lysosome track, as evidenced by co-localization of R18 labeled IBV with vehicle markers Rab5/Rab7/LAMP1 along with the infection time course. Functional inactivation of Rab5 and Rab7 significantly inhibited IBV infection. VCP, a protein helps early endosome maturation, was involved virus trafficking. Finally, by using the dual R18/DiOC labeled IBV, we observed that membrane fusion with late endosome/lysosome membranes was induced between 2-3 h.p.i.. Taken together, our findings demonstrate that IBV virions attach to lipid rafts and are internalized into cells via CME, move along with early/late endosomes-lysosomes, finally fuse with late endosome-lysosome membranes, release virus genome into cytoplasm. This study provides comprehensive images of IBV attachment-internalization-trafficking-fusion steps.IMPORTANCEIBV, the avian coronavirus isolated in 1937, infects chicken and causes economic loss in poultry industry. It has been reported that the entry of IBV requires low pH. However, the molecular mechanisms underlying IBV internalization and trafficking remain to be clarified. Therefore, we employed multiple chemical and molecular approaches to dissect the entry mechanisms of IBV in susceptible cells. Our results showed IBV entry was significantly inhibited when clathrin-mediated endocytosis (CME) was blocked by chemical inhibitor or depletion of clathrin protein. Moreover, by using R18-labeled IBV, we found that IBV particles attached to lipid rafts, led to actin rearrangement, and moved along with the entire endosomal system. R18/DiOC labeling method showed that IBV fused with late endosomes or lysosomes. This is the first report to describe the entire entry process of IBV, allowing for a better understanding of the infection process of group III avian coronavirus.

scholarly journals Comparative Analysis of Gene Expression in Virulent and Attenuated Strains of Infectious Bronchitis Virus at Subcodon Resolution

2019 ◽  
Vol 93 (18) ◽  
Author(s):  
Adam M. Dinan ◽  
Sarah Keep ◽  
Erica Bickerton ◽  
Paul Britton ◽  
Andrew E. Firth ◽  
...  
Keyword(s):  
Gene Expression ◽  
Comparative Analysis ◽  
Virus Infection ◽  
Host Cell ◽  
Infectious Bronchitis Virus ◽  
Cell Response ◽  
Gene Networks ◽  
Infectious Bronchitis ◽  
Host Cell Response ◽  
Cellular Genes

ABSTRACTLike all coronaviruses, avian infectious bronchitis virus (IBV) possesses a long, single-stranded, positive-sense RNA genome (∼27 kb) and has a complex replication strategy that includes the production of a nested set of subgenomic mRNAs (sgmRNAs). Here, we used whole-transcriptome sequencing (RNASeq) and ribosome profiling (RiboSeq) to delineate gene expression in the IBV M41-CK and Beau-R strains at subcodon resolution. RNASeq facilitated a comparative analysis of viral RNA synthesis and revealed two novel transcription junction sites in the attenuated Beau-R strain, one of which would generate a sgmRNA encoding a ribosomally occupied open reading frame (dORF) located downstream of the nucleocapsid coding region. RiboSeq permitted quantification of the translational efficiency of virus gene expression and identified, for the first time, sites of ribosomal pausing on the genome. Quantification of reads flanking the programmed ribosomal frameshifting (PRF) signal at the genomic RNA ORF1a/ORF1b junction revealed that PRF in IBV is highly efficient (33 to 40%). Triplet phasing of RiboSeq data allowed precise determination of reading frames and revealed the translation of two ORFs (ORF4b and ORF4c on sgmRNA IR), which are widely conserved across IBV isolates. Analysis of differential gene expression in infected primary chick kidney cells indicated that the host cell response to IBV occurs primarily at the level of transcription, with global upregulation of immune-related mRNA transcripts following infection and comparatively modest changes in the translation efficiencies of host genes. Cellular genes and gene networks differentially expressed during virus infection were also identified, giving insights into the host cell response to IBV infection.IMPORTANCEIBV is a major avian pathogen and presents a substantial economic burden to the poultry industry. Improved vaccination strategies are urgently needed to curb the global spread of this virus, and the development of suitable vaccine candidates will be aided by an improved understanding of IBV molecular biology. Our high-resolution data have enabled a precise study of transcription and translation in cells infected with both pathogenic and attenuated forms of IBV and expand our understanding of gammacoronaviral gene expression. We demonstrate that gene expression shows considerable intraspecies variation, with single nucleotide polymorphisms being associated with altered production of sgmRNA transcripts, and our RiboSeq data sets enabled us to uncover novel ribosomally occupied ORFs in both strains. The numerous cellular genes and gene networks found to be differentially expressed during virus infection provide insights into the host cell response to IBV infection.

scholarly journals Comparative analysis of gene expression in virulent and attenuated strains of infectious bronchitis virus at sub-codon resolution

2019 ◽  
Author(s):  
Adam M. Dinan ◽  
Sarah Keep ◽  
Erica Bickerton ◽  
Paul Britton ◽  
Andrew E. Firth ◽  
...  
Keyword(s):  
Gene Expression ◽  
Host Cell ◽  
Infectious Bronchitis Virus ◽  
Gene Networks ◽  
Ribosome Profiling ◽  
Species Variation ◽  
Messenger Rnas ◽  
High Resolution Data ◽  
Infectious Bronchitis

ABSTRACTInfectious bronchitis virus (IBV) is a member of the genusGammacoronavirusand the causative agent of avian infectious bronchitis. IBV has a single-stranded, positive-sense RNA genome ~27 kb in length and, like all coronaviruses, produces a set of sub-genomic messenger RNAs (sgmRNAs) synthesised via the viral polymerase. Here, we used RNA sequencing (RNASeq) and ribosome profiling (RiboSeq) to delineate gene expression in the IBV M41-CK and Beau-CK strains at sub-codon resolution. Quantification of reads flanking the programmed ribosomal frameshifting (PRF) signal at the genomic RNA ORF1a/ORF1b junction revealed that PRF in IBV is highly efficient (33–40%), consistent within vitromeasurements. Triplet phasing of the profiling data allowed precise determination of reading frames and revealed the translation of two intergenic genes (4b and 4c on sgmRNA4), which are widely conserved across IBV isolates. RNASeq revealed two novel transcription junction sites in the attenuated Beau-CK strain, one of which would generate a sgmRNA encoding a ribosomally occupied ORF in the viral 3’ untranslated region (dORF). Within IBV transcripts, the nucleocapsid (N) protein was unexpectedly found to be inefficiently translated, despite being an abundant structural component of mature IBV virions. Finally, we demonstrate that the host cell response to IBV occurs primarily at the level of transcription, with a global up-regulation of immune-related mRNA transcripts following infection, and comparatively modest changes in the translation efficiencies of host genes.IMPORTANCEIBV is a major avian pathogen and presents a substantial economic burden to the poultry industry. Improved vaccination strategies are urgently needed to curb the global spread of this pathogen, and the development of suitable vaccine candidates will be aided by an improved understanding of IBV molecular biology. Our high-resolution data have enabled a precise study of transcription and translation in both pathogenic and attenuated forms of IBV, and expand our understanding of gammacoronaviral gene expression. We demonstrate that gene expression shows considerable intra-species variation, with single nucleotide polymorphisms associated with altered production of sgmRNA transcripts, and our RiboSeq data sets enabled us to uncover novel ribosomally occupied ORFs in both strains. We also identify numerous cellular genes and gene networks that are differentially expressed during virus infection, giving insights into the host cell reponse to IBV infection.

Sign in / Sign up

Export Citation Format

Share Document