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Mousepox in inbred mice innately resistant or susceptible to lethal infection with ectromelia virus. II. Pathogenesis
Abstract:
The pathogenesis of mousepox due to infection with ectromelia virus strain NIH-79 was characterized in genetically susceptible (BALB/cAnNCr) and genetically resistant (C57BL/6NCr) mice. BALB/c mice inoculated subcutaneous (s.c.) or intranasally (i.n.) had high mortality. Most mice died within 7 days from severe necrosis of the spleen and liver. Necrotic foci in livers of BALB/c mice that survived beyond 7 days often were accompanied by mononuclear cell infiltrates and by hyperplasia of lymphoid tissues. C57BL/6 mice inoculated by either route remained asymptomatic and necrotic lesions were mild or absent, whereas focal non-suppurative hepatitis and lymphoid hyperplasia were prominent. Infectious virus and viral antigen were distributed widely in tissues of BALB/c mice, but had limited distribution in C57BL/6 mice. Both mouse strains had infection of the respiratory tract, genital tract, oral tissues and bone marrow, and BALB/c mice also had infection of the intestines. Both strains also developed serum antibody to vaccinia virus antigen after infection. The results show that ectromelia virus occurs in tissues conducive to mouse to mouse transmission and that the severity and character of mousepox lesions correlate directly with resistance and susceptibility to infection. They also support the concept that cellular immunity contributes to survival from infection.
Insights
Mousepox pathogenesis differs between resistant and susceptible mice. Susceptible mice exhibit high mortality and severe organ necrosis, while resistant mice show milder lesions, indicating genetic control of ectromelia virus infection severity.
Area of Science:
- Virology
- Immunology
- Pathogenesis
Background:
- Mousepox, caused by ectromelia virus, is a significant disease in laboratory mice.
- Understanding the genetic basis of susceptibility and resistance is crucial for disease management.
Purpose of the Study:
- To characterize the pathogenesis of mousepox in genetically susceptible (BALB/c) and resistant (C57BL/6) mouse strains.
- To investigate the correlation between host genetics and ectromelia virus disease severity.
Main Methods:
- Inoculation of BALB/c and C57BL/6 mice with ectromelia virus strain NIH-79 via subcutaneous and intranasal routes.
- Assessment of mortality, clinical signs, gross and microscopic lesions, and viral distribution.
- Evaluation of host immune responses, including antibody production.
Main Results:
- BALB/c mice exhibited high mortality with severe splenic and hepatic necrosis, widespread viral dissemination, and intestinal involvement.
- C57BL/6 mice showed mild or absent lesions, limited viral distribution, and prominent non-suppurative hepatitis and lymphoid hyperplasia.
- Both strains developed antibodies to vaccinia virus antigen, suggesting cross-reactivity.
Conclusions:
- Ectromelia virus infection leads to distinct pathological outcomes based on host genetic background.
- Disease severity and lesion character correlate with mouse strain susceptibility.
- Cellular immunity likely plays a role in host survival during ectromelia virus infection.