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Pathogenesis of the B variant of encephalomyocarditis virus
R Shafi1, D R Cerutis, D J Giron
1Department of Microbiology and Immunology, Wright State University College of Science and Mathematics and School of Medicine, Dayton, Ohio.
Abstract:
Variants of encephalomyocarditis virus (EMCV) are immunologically indistinguishable by hyperimmune serum, but, with the exception of EMCV-B, each produces a different disease syndrome and infects the central nervous system in mice infected via the intraperitoneal route of inoculation. The B variant is benign in that it does not produce any overt signs of infection at doses as high as 10(6) pfu per animal. The present study was carried out to determine if EMCV-B was pathogenic when administered via the intracranial route and, if so, to delineate the area(s) of the brain infected. The results show that, when given i.c., EMCV-B is similar to other variants of EMCV in that it infects and replicates in the brain, causing encephalitis, neuronal necrosis in Ammon's horn of the hippocampus, and clinical signs of infection. The data indicate that receptor sites for EMCV-B are present on brain cells and suggest that its benign nature when given by the intraperitoneal route reflects an inability to cross the blood-brain barrier.
Insights
Encephalomyocarditis virus (EMCV)-B is not typically harmful when injected into the abdomen. However, when administered directly into the brain, EMCV-B causes encephalitis and brain damage in mice.
Area of Science:
- Virology
- Neuroscience
- Immunology
Background:
- Encephalomyocarditis virus (EMCV) variants are immunologically similar but cause distinct disease syndromes.
- Most EMCV variants infect the central nervous system (CNS) when inoculated intraperitoneally (i.p.) in mice.
- EMCV variant B is considered benign, showing no overt signs of infection even at high doses via i.p. inoculation.
Purpose of the Study:
- To investigate the pathogenicity of EMCV-B when administered intracranially (i.c.) in mice.
- To identify the specific brain regions infected by EMCV-B following i.c. inoculation.
- To understand the factors contributing to EMCV-B's differential pathogenicity via i.p. versus i.c. routes.
Main Methods:
- Intracranial inoculation of EMCV-B in a mouse model.
- Observation and documentation of clinical signs of infection.
- Histopathological examination of brain tissue to identify areas of infection and damage.
- Analysis of viral replication within the CNS.
Main Results:
- Intracranial administration of EMCV-B induced encephalitis and neuronal necrosis in the hippocampus (Ammon's horn) in mice.
- Clinical signs of infection were observed following i.c. inoculation, similar to other EMCV variants.
- EMCV-B replicated within the brain, indicating the presence of susceptible neuronal populations.
- These findings suggest that EMCV-B possesses the capacity to infect brain cells.
Conclusions:
- EMCV-B is pathogenic to the mouse brain when delivered directly via the intracranial route.
- The benign nature of EMCV-B following intraperitoneal inoculation is likely due to its inability to breach the blood-brain barrier.
- The presence of receptor sites for EMCV-B on brain cells facilitates viral entry and replication within the CNS.