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Replication and morphogenesis of avian coronavirus in Vero cells and their inhibition by monensin
Abstract:
Avian infectious bronchitis virus (IBV) was adapted to Vero cells by serial passage. No significant inhibition of IBV replication was observed when infected Vero cells were treated with alpha-amanitin or actinomycin D. In thin sections of infected cells, assembly of IBV was observed at the rough endoplasmic reticulum (RER), and mature IBV particles were located in dilated cisternae of the RER as well as in smooth cytoplasmic vesicles. In addition to typical IBV particles, enveloped particles containing numerous ribosomes were identified at later times postinfection. Monensin, a sodium ionophore which blocks glycoprotein transport to plasma membranes at the level of the Golgi complex, was found to inhibit the formation of infectious IBV. In thin sections of infected Vero cells treated with the ionophore, IBV particles were located in dilated cytoplasmic vesicles, but fewer particles were found when compared to controls. A similar pattern of virus-specific proteins was detected in control or monensin-treated IBV-infected cells, which included two glycoproteins (170 000 and 24 000 daltons) and a polypeptide of 52 000 daltons. These results suggest that the ionophore inhibits assembly of a virus which matures at intracellular membranes.
Insights
Avian infectious bronchitis virus (IBV) adapted to cell culture showed assembly at the endoplasmic reticulum. Monensin treatment inhibited infectious IBV formation, suggesting intracellular membrane maturation is key.
Area of Science:
- Virology
- Cell Biology
- Biochemistry
Background:
- Avian infectious bronchitis virus (IBV) is a significant pathogen in poultry.
- Understanding IBV replication and assembly is crucial for developing control strategies.
Purpose of the Study:
- To investigate the replication and assembly mechanisms of IBV in Vero cells.
- To determine the effect of monensin on IBV maturation and infectivity.
Main Methods:
- Serial passage of IBV in Vero cells.
- Treatment of infected cells with alpha-amanitin, actinomycin D, and monensin.
- Thin section electron microscopy to visualize viral assembly.
- Analysis of virus-specific proteins using SDS-PAGE.
Main Results:
- IBV assembly was observed at the rough endoplasmic reticulum (RER).
- Mature IBV particles were found in RER cisternae and cytoplasmic vesicles.
- Monensin inhibited the formation of infectious IBV, with fewer particles observed in vesicles.
- Similar viral protein patterns were detected in control and monensin-treated cells.
Conclusions:
- IBV maturation occurs at intracellular membranes, likely the RER.
- Monensin interferes with a post-assembly step involving intracellular transport or budding.
- The study provides insights into the intracellular trafficking and assembly of IBV.