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Prevalence of enterotropic and polytropic mouse hepatitis virus in enzootically infected mouse colonies
F R Homberger1, L Zhang, S W Barthold
1Institute of Laboratory Animal Science, University of Zurich, Switzerland.
Abstract:
Mouse hepatitis virus (MHV) causes the most prevalent viral infection in contemporary laboratory mouse colonies. According to their primary replication site, different strains of MHV segregate into two overlapping biotypes, enterotropic and polytropic. These two groups vary greatly in disease pattern, pathogenicity, immune response, and duration of infection. Historically, the polytropic MHV strains represent the extensively studied prototype strains that have minimal enterotropism, whereas enterotropic MHV strains have been less characterized. Anecdotal reports suggest that most MHV strains encountered today belong to the enterotropic biotype. We have identified 15 isolates of MHV from 19 independent enzootically infected mouse colonies. Sequencing of a variable region of the nucleoprotein (N) gene of each isolate confirmed that all were independent genetic variants. The principal tissue tropism of the new isolates was determined by experimental inoculation of infant mice and examination of intestine, liver, spleen, and brain for lesions. Nine isolates infected only intestine; four isolates infected intestine and liver; one isolate infected intestine, liver, and brain; and one isolate infected liver. These results confirm that the enterotropic MHV biotype is predominant in contemporary laboratory mouse colonies. The MHV biotype features need to be taken into consideration when dealing with MHV infections.
Insights
Enterotropic mouse hepatitis virus (MHV) strains are predominant in modern lab mice, unlike historical polytropic strains. Understanding MHV biotypes is crucial for managing infections in research settings.
Area of Science:
- Virology
- Infectious Diseases
- Laboratory Animal Science
Background:
- Mouse hepatitis virus (MHV) is a common viral infection in laboratory mice.
- MHV strains are classified into enterotropic and polytropic biotypes based on replication site, differing in disease characteristics.
- Enterotropic strains are anecdotally reported as more prevalent currently, but less characterized than polytropic strains.
Purpose of the Study:
- To investigate the predominant biotype of current Mouse hepatitis virus (MHV) isolates in laboratory mouse colonies.
- To characterize the tissue tropism of newly identified MHV isolates.
Main Methods:
- 15 MHV isolates were obtained from 19 infected mouse colonies.
- Nucleoprotein (N) gene sequencing confirmed genetic variation among isolates.
- Experimental inoculation of infant mice was performed to determine tissue tropism (intestine, liver, spleen, brain).
Main Results:
- All 15 isolates represented independent genetic variants.
- Nine isolates showed exclusive intestinal tropism.
- Four isolates infected intestine and liver; one infected intestine, liver, and brain; and one infected liver.
- The enterotropic biotype was confirmed as predominant.
Conclusions:
- The enterotropic biotype of Mouse hepatitis virus (MHV) is the most common in contemporary laboratory mouse populations.
- Recognizing the specific biotype of MHV is essential for effective management and control of infections in research settings.