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Pathogenicity of glycoprotein C negative mutants of herpes simplex virus type 1 for the mouse central nervous system
J C Sunstrum1, C E Chrisp, M Levine
1Department of Human Genetics, University of Michigan Medical School, Ann Arbor 48109.
Abstract:
A previous study from our laboratory showed that a mutant of herpes simplex virus type 1 (HSV-1), strain KOS-321, carrying a deletion in the structural gene for glycoprotein C (gC) had reduced pathogenicity for the mouse central nervous system when compared to the wild-type virus (Kümel et al., 1985). In this study, eight additional gC negative (gC-) mutants derived from KOS-321 were shown to vary widely in their ability to induce lethal encephalitis in female DBA/2 mice following intracerebral inoculation. This variation in virulence showed no correlation with thymidine kinase activity. One less virulent gC- strain, gC-39, was further studied to determine whether the neurovirulent phenotype could be restored by rescue of the gC gene using standard marker rescue cotransfection procedures. The resulting progeny contained 2% gC+ recombinant virions and was tested for its ability to cause encephalitis. Although this progeny had increased virulence, it was not attributable to the acquisition of the gC gene since passive immunization of mice with a pool of anti-gC monoclonal antibodies had no effect on the development of encephalitis and only gC- viruses were isolated from diseased brain tissues. In agreement with these findings, individual plaque-purified gC positive (gC+) virus recombinants were shown not to have been restored to the wild-type virus level of neurovirulence. It is concluded that gC is not a virulence determinant in this mouse model of HSV-induced encephalitis and that cotransfection procedures can induce additional mutations that affect viral pathogenesis.
Insights
Glycoprotein C (gC) is not a key factor in herpes simplex virus type 1 (HSV-1) neurovirulence in mice. Cotransfection procedures may introduce additional mutations affecting viral pathogenesis.
Area of Science:
- Virology
- Neuroscience
- Immunology
Background:
- Previous research indicated that a herpes simplex virus type 1 (HSV-1) mutant lacking glycoprotein C (gC) exhibited reduced pathogenicity in the mouse central nervous system.
- This study investigates the role of gC in HSV-1 neurovirulence using various gC-negative mutants.
Purpose of the Study:
- To determine if glycoprotein C (gC) is a virulence determinant in a mouse model of HSV-1 encephalitis.
- To investigate whether cotransfection procedures used for gene rescue can introduce additional mutations affecting viral pathogenesis.
Main Methods:
- Generation and characterization of eight gC-negative (gC-) HSV-1 mutants.
- Intracerebral inoculation of female DBA/2 mice to assess lethal encephalitis.
- Marker rescue cotransfection experiments to attempt gC gene restoration.
- Passive immunization with anti-gC monoclonal antibodies.
- Isolation and characterization of viruses from diseased brain tissues.
Main Results:
- gC-negative HSV-1 mutants displayed a wide range of neurovirulence, unrelated to thymidine kinase activity.
- Attempts to restore the gC gene in a less virulent strain (gC-39) did not fully restore wild-type neurovirulence.
- Increased virulence observed in progeny after cotransfection was not due to gC acquisition, as evidenced by antibody neutralization and virus isolation.
- Plaque-purified gC-positive recombinants did not regain wild-type levels of neurovirulence.
Conclusions:
- Glycoprotein C (gC) is not a determinant of virulence in this mouse model of HSV-1-induced encephalitis.
- Cotransfection procedures can inadvertently introduce additional mutations that impact viral pathogenesis, confounding gene function studies.