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Coronavirus (JHM) replication within the retina: analysis of cell tropism in mouse retinal cell cultures
1Immunology & Virology Section, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892.
Abstract:
The murine coronavirus, mouse hepatitis virus, JHM strain, induces a retinal degenerative disease in adult BALB/c mice. Coronavirus infections are highly species specific with virus exhibiting a strong tissue and cell specificity. In this report we evaluated the cellular basis of JHM virus retinal tropism. Retinal cultures and retinal pigment epithelial (RPE)-retinal mixed cell cultures were prepared from eyes obtained from Balb/c mice. The ability of JHM virus to infect and replicate in these retinal cultures was evaluated by light microscopy, immunofluorescent staining, electron microscopy, and virus isolation. Cytopathology was not observed and virus could not be detected in supernatant fluid in retinal cultures. However, low levels of infectious virus could be detected within the cells for the first 4 days. This observation suggested that cell-to-cell interactions may be critical since virus particles and virus antigens can be seen in vivo within the neural retina and the RPE. In contrast to the retinal cultures, retinal-RPE mixed cultures were supportive to JHM virus replication. Syncytial cytopathology was observed for the first 4 days and virus was isolated from supernatant fluids. By electron microscopy, virus was found intracellularly within vacuoles and extracellularly at the plasma membrane. After Day 4, a persistent virus infection was established in which cells produced virus for 5 weeks without cytopathic effects or cell death. Double-labeling immunofluorescent studies of retinal-RPE mixed cultures showed that the virus antigen was co-expressed with a Muller cell marker, glutamine synthetase. This cell is the most prominent glial element in the retina. These studies demonstrate that JHM virus is capable of establishing a persistent virus infection in mixed retinal (Muller)-RPE cell cultures. Moreover, these data suggest that cell-to-cell interactions influence the establishment of coronavirus infections in the retina.
Insights
Mouse hepatitis virus (JHM strain) establishes persistent retinal infections, particularly in Muller cells and retinal pigment epithelial cells. Cell-to-cell interactions are crucial for this coronavirus tropism in the eye.
Area of Science:
- Virology
- Ophthalmology
- Neuroscience
Background:
- Murine coronavirus (JHM strain) causes retinal degeneration in mice.
- Coronaviruses exhibit species, tissue, and cell specificity.
- Understanding JHM virus retinal tropism is key to its pathogenesis.
Purpose of the Study:
- To investigate the cellular basis of JHM virus retinal tropism.
- To evaluate JHM virus infection and replication in retinal cultures.
- To determine the role of cell-to-cell interactions in viral tropism.
Main Methods:
- Preparation of retinal and retinal pigment epithelial (RPE)-retinal mixed cell cultures from Balb/c mice.
- Infection of cultures with JHM virus.
- Evaluation using light microscopy, immunofluorescent staining, electron microscopy, and virus isolation.
- Double-labeling immunofluorescent studies with Muller cell markers.
Main Results:
- JHM virus did not cause cytopathology or release virus in pure retinal cultures but persisted intracellularly.
- Retinal-RPE mixed cultures supported JHM virus replication, syncytial cytopathology, and virus release.
- Persistent infection (5 weeks) without cell death was established in mixed cultures.
- Viral antigens co-expressed with Muller cell marker (glutamine synthetase) in mixed cultures.
Conclusions:
- JHM virus can establish persistent infections in mixed retinal (Muller)-RPE cell cultures.
- Cell-to-cell interactions significantly influence the establishment of coronavirus infections in the retina.
- Muller cells and RPE cells are implicated in JHM virus retinal tropism.