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Site-specific alteration of murine hepatitis virus type 4 peplomer glycoprotein E2 results in reduced neurovirulence
Abstract:
Strains of the murine coronavirus mouse hepatitis virus type 4 (MHV-4) which contained a mutation in the E2 peplomer glycoprotein were obtained by selection for resistance to neutralization by monoclonal antibodies. Characterization of six variants representing two independent epitopes on E2, E2B and E2C, by in vitro neutralization and antibody-binding assays demonstrated that selection for an alteration in epitope E2B also resulted in changes in epitope E2C and vice versa. We observed a mutation frequency of approximately 10(-4.3) to 10(-4.6), which is consistent with the expected occurrence of single point mutations. The variant virus strains were attenuated with respect to neurovirulence when compared with wild-type MHV-4. Mice normally develop encephalomyelitis and die after wild-type MHV-4 infection. Mice receiving 2- to 3-log-higher doses of the variant strains survived and developed demyelinating disease. As the disease progressed, evidence of remyelination and ongoing demyelination was observed up to 65 days after infection. Virus reisolated 15 days after infection retained the variant phenotype. The data indicate that the E2 glycoprotein plays a central role in determining the cellular tropism and virulence of MHV-4 in the mouse.
Insights
Mutations in the E2 glycoprotein of mouse hepatitis virus type 4 (MHV-4) reduced its neurovirulence, leading to demyelinating disease instead of fatal encephalomyelitis in mice. These E2 variants show altered epitopes and retained their attenuated phenotype.
Area of Science:
- Virology
- Immunology
- Neuroscience
Background:
- Murine coronavirus mouse hepatitis virus type 4 (MHV-4) causes fatal encephalomyelitis in mice.
- The E2 peplomer glycoprotein is crucial for viral entry and pathogenesis.
Purpose of the Study:
- To investigate the role of MHV-4 E2 glycoprotein mutations in viral virulence and tropism.
- To characterize variants resistant to antibody neutralization.
Main Methods:
- Selection of MHV-4 variants resistant to monoclonal antibody neutralization.
- In vitro neutralization and antibody-binding assays.
- Assessment of neurovirulence and demyelinating disease in infected mice.
Main Results:
- Mutations in E2 glycoprotein affected two distinct epitopes (E2B and E2C).
- Variant strains showed reduced neurovirulence, causing demyelinating disease instead of fatal encephalomyelitis.
- Mice infected with variant strains survived higher doses and showed remyelination and demyelination up to 65 days post-infection.
- Reisolated viruses retained the attenuated phenotype.
Conclusions:
- The E2 glycoprotein is a key determinant of MHV-4 cellular tropism and virulence.
- E2 mutations can attenuate MHV-4, altering disease outcome from fatal encephalitis to chronic demyelination.