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An electron microscopic study of MDBK cells persistently infected with Newcastle disease virus
Abstract:
Ultrastructural examination of a line of MDBK cells persistently infected with Newcastle disease virus (MDBKpi cells) revealed the presence of cytoplasmic aggregates of both smooth and granular nucleocapsids. Only granular nucleocapsids aligned under modified areas of plasma membrane and were incorporated into virus particles. On the grounds of morphogenesis, there was no apparent explanation for the persistent, not-cytocidal nature of the infection. Both nuclear and cytoplasmic aggregates of smooth nucleocapsids were present in MDBKpi cells which had been held without subculture for between 40 and 130 days (aged MDBKpi cells). Modified areas of plasma membrane with associated alignment of nucleocapsids were not present in aged MDBKpi cells, and neither budding nor released virus particles were observed, indicating a block in virus maturation. It is suggested that the granular material coating granular nucleocapsids allows them to interact with modified areas of plasma membrane, thereby inducing virus budding. A deficiency of this material, as apparently occurs in aged MDBKpi cells, would therefore cause a block in virus maturation. The nature of this granular material is discussed, and we suggest that it consists of M protein.
Insights
Persistent Newcastle disease virus (NDV) infection in MDBK cells involves cytoplasmic nucleocapsid aggregates. Aged cells show a maturation block, suggesting granular material on nucleocapsids is crucial for virus budding.
Area of Science:
- Virology
- Cell Biology
- Microbiology
Background:
- Persistent viral infections can alter cell behavior and virus-host interactions.
- Newcastle disease virus (NDV) can establish persistent infections in cell lines.
- Understanding the mechanisms of persistent viral infections is crucial for disease control.
Purpose of the Study:
- To investigate the ultrastructural characteristics of MDBK cells persistently infected with NDV (MDBKpi cells).
- To elucidate the role of nucleocapsid morphology and plasma membrane interactions in persistent NDV infection.
- To identify potential blocks in virus maturation during prolonged cell culture.
Main Methods:
- Ultrastructural examination using electron microscopy of MDBKpi cells.
- Comparison of MDBKpi cells with aged MDBKpi cells (cultured without subculture for extended periods).
- Analysis of nucleocapsid aggregation and association with plasma membrane modifications.
Main Results:
- Cytoplasmic aggregates of smooth and granular nucleocapsids were observed in MDBKpi cells.
- Only granular nucleocapsids aligned with modified plasma membranes and were incorporated into virus particles.
- Aged MDBKpi cells showed a block in virus maturation, with no membrane modifications or virus budding observed.
- A deficiency in granular material on nucleocapsids in aged cells is proposed as the cause of the maturation block.
Conclusions:
- The granular material on NDV nucleocapsids appears essential for interaction with modified plasma membranes, facilitating virus budding.
- A deficiency in this granular material, potentially M protein, leads to a block in virus maturation in aged MDBKpi cells.
- The findings provide insights into the morphogenesis and persistence of NDV infections.