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Influenza A Virus Studies in a Mouse Model of Infection
Published on: September 7, 2017
Age-dependent and strain-related differences of virulence of Semliki Forest virus in mice
Abstract:
Factors that influence the virulence of Semliki Forest virus for mice have been studied. In vivo experiments showed that maximum brain infectivities following i.p. inoculation of adult mice with a virus strain of low virulence were less than those found in mice showing clinical signs in virulent infections. The virulent strains generally caused death before antibody could be detected in brain tissue; the less virulent strain caused an infection that was neuroinvasive, but infectivity increased less rapidly in the brain and allowed antibody to intervene before clinical signs were apparent. IgG3 antibody was first detected in brain tissue coincident with the beginning of the decline of brain infectivities in avirulent infections; other sub-classes of IgG antibody were not detected until later. In vitro experiments showed differences in abilities of SFV strains to replicate in tissue culture and adult mouse brain tissue, and differences in susceptibility to infection of brain tissue from mice of various ages. These in vitro results could provide a basis for differences of virulence.
Insights
Semliki Forest virus (SFV) virulence in mice depends on viral strain and host factors. Antibody response, particularly IgG3, influences neuroinvasion and disease outcome, with less virulent strains allowing intervention before severe illness.
Area of Science:
- Virology
- Immunology
- Neuroscience
Background:
- Semliki Forest virus (SFV) is an alphavirus known for its variable virulence in mice.
- Understanding factors influencing SFV virulence is crucial for predicting disease progression and developing interventions.
Purpose of the Study:
- To investigate the factors affecting Semliki Forest virus (SFV) virulence in mice.
- To correlate in vivo observations with in vitro findings regarding viral replication and host susceptibility.
Main Methods:
- In vivo studies involved intraperitoneal inoculation of adult mice with SFV strains of varying virulence.
- In vitro experiments assessed viral replication in tissue culture and mouse brain tissue, as well as age-dependent susceptibility of brain tissue.
- Antibody responses, including IgG subclasses, were monitored in brain tissue.
Main Results:
- Virulent SFV strains caused rapid mortality, preceding detectable antibody responses in brain tissue.
- Less virulent SFV strains resulted in neuroinvasive infections where infectivity increased slower, allowing antibody intervention before clinical signs.
- IgG3 antibody was detected in brain tissue coinciding with reduced viral infectivity in less virulent infections.
Conclusions:
- SFV virulence is influenced by the interplay between viral replication kinetics and the host's immune response, specifically early IgG3 production.
- Differences in viral replication and host cell susceptibility observed in vitro may explain the observed in vivo virulence variations.
- The timing and effectiveness of the antibody response are critical determinants of SFV neuroinvasion and disease severity.
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