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Mouse hepatitis virus S in weanling Swiss mice following intranasal inoculation
Abstract:
Three-week-old outbred mice were inoculated intranasally with a mildly pathogenic strain of mouse hepatitis virus (MHV-S). Tissues were analyzed for distribution of infectious virus, lesions, and viral antigen at intervals up to 49 days after inoculation. Sera were tested for neutralizing antibody to MHV-S. Within the first week of infection, virus was isolated from lung and brain of most mice and liver of one mouse, but not from blood, spleen, or intestine. Microscopic lesions consisted of mild olfactory mucosal necrosis, neuronal necrosis of olfactory bulbs and tracts, lymphoplasmacytic infiltrates and vacuolation in the brain, mild nonsuppurative pulmonary perivascular lymphocyte infiltration, focal interstitial pneumonia, and focal necrotizing hepatitis. The presence and distribution of MHV antigen, as determined by indirect immunofluorescence, correlated with virus recovery and acute lesions. No virus or antigen was demonstrable beyond day 7. Serum antibody was first detected on day 10, and titers peaked on day 28 after infection.
Insights
This study tracked mouse hepatitis virus (MHV-S) infection in mice. MHV-S was found in the lungs and brain early on, with antibodies appearing later.
Area of Science:
- Virology
- Immunology
- Pathology
Background:
- Mouse hepatitis virus (MHV-S) is a common pathogen in laboratory mice.
- Understanding MHV-S pathogenesis is crucial for reliable animal research.
- Mildly pathogenic strains can still cause significant disease and impact experimental outcomes.
Purpose of the Study:
- To characterize the temporal and spatial distribution of infectious mouse hepatitis virus (MHV-S).
- To document the development and resolution of lesions and viral antigen.
- To correlate viral presence with the host's immune response, specifically neutralizing antibody production.
Main Methods:
- Outbred mice were intranasally inoculated with MHV-S.
- Tissues were analyzed for virus isolation, lesions (histopathology), and viral antigen (immunofluorescence) at multiple time points.
- Serum samples were tested for MHV-S neutralizing antibodies.
Main Results:
- Infectious MHV-S and viral antigen were primarily detected in the lung and brain within the first week post-inoculation.
- Microscopic lesions, including necrosis and inflammation, were observed in the olfactory mucosa, olfactory bulbs/tracts, brain, lungs, and liver.
- No infectious virus or antigen was detectable after day 7, while serum neutralizing antibodies appeared around day 10 and peaked by day 28.
Conclusions:
- Mildly pathogenic MHV-S establishes an acute infection predominantly in the respiratory and central nervous systems.
- Viral clearance occurs by day 7, followed by a detectable adaptive immune response.
- The findings provide insights into the pathogenesis of MHV-S and its transient nature in immunocompetent hosts.