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Electron microscopic study of the development of Theiler's murine encephalomyelitis viruses propagated in vitro
Abstract:
The changes occurring in the nuclei and cytoplasms of BHK21 cells during infection with the two subgroups of Theiler's murine encephalomyelitis viruses were studied by electron microscopy. The nuclear alterations include: formation of clumps and margination of chromatin, enlargement of perinuclear spaces, deformation and displacement of the nucleus. The cytoplasmic alterations include: increase in the number of ribosomes, extensive proliferation of smooth membranes at the centrosphere of infected cells, appearance of electron-dense bodies, and decrease in number and swelling of mitochondria. At late stages of infection, GDVII and FA viruses which represent the virulent subgroup, form crystalline arrays in the cytoplasm of infected cells. A few mechanisms by which these crystals may be formed are discussed. The later stages of TO viruses infection, which cause a persistent infection in mice, differed markedly from those of GDVII and FA viruses. TO viruses were found to be arranged in a single file between two sheets of membranes. A model for this unique structure is presented.
Insights
Electron microscopy revealed distinct cellular changes in BHK21 cells infected with Theiler's murine encephalomyelitis viruses. Virulent strains formed cytoplasmic crystals, while persistent strains exhibited unique membrane-bound viral arrays.
Area of Science:
- Virology
- Cell Biology
- Microscopy
Background:
- Theiler's murine encephalomyelitis viruses (TMEV) are known to cause neurological diseases in mice.
- Understanding the cellular mechanisms of TMEV infection is crucial for developing antiviral strategies.
Purpose of the Study:
- To investigate and compare the ultrastructural changes in BHK21 cells infected with two subgroups of TMEV.
- To elucidate the distinct cytopathic effects induced by virulent (GDVII, FA) and persistent (TO) TMEV strains.
Main Methods:
- Transmission electron microscopy was employed to examine infected BHK21 cells.
- Detailed morphological analysis of nuclear and cytoplasmic alterations was performed.
Main Results:
- Nuclear alterations included chromatin changes, perinuclear space enlargement, and nuclear deformation.
- Cytoplasmic changes involved increased ribosomes, smooth membrane proliferation, electron-dense bodies, and altered mitochondria.
- Virulent GDVII and FA viruses formed crystalline arrays in the cytoplasm.
- Persistent TO viruses displayed unique single-file arrangements within membrane sheets.
Conclusions:
- TMEV infection induces significant and distinct ultrastructural changes in host cells.
- Virulent and persistent TMEV strains exhibit markedly different replication and assembly strategies.
- The formation of viral crystals and membrane-bound arrays represents unique viral adaptations.