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Persistent in vitro infection with mouse hepatitis virus 3
Abstract:
Mouse hepatitis virus 3 (MHV3) infection in mice displays various types of sensitivity according to mouse strains: resistance, full susceptibility and semisusceptibility . MHV3 infections were carried out in primary cultures of embryonic fibroblasts originating from various mouse strains and in mouse lymphoid cell lines. Persistent infection was induced in 2 out of 3 primary embryonic fibroblast cultures. A high production of virus was obtained, as tested by viral titers and cell membrane antigen detection. Cytopathic effects characterized by cell lysis were related to in vivo phenotypes. Persistent MHV3 infection established in vitro in YAC mouse lymphoid cell line was characterized by virus production, occurrence of cellular viral antigens and cell lysis. Cell cloning and antibody treatment experiments indicated that the type of viral transmission was horizontal and not vertical. These data indicate that persistent infection induced by MHV3 in lymphoid cell lines is characterized by a viral "carrier state" where production of infectious viral particles remains in equilibrium with cell permissiveness. Biological and biochemical properties of MHV3 variants derived from persistently infected YAC lymphoid cells were characterized. Similar heterogeneous thermosensitive properties were observed when YAC-derived cloned substrains (YAC-MHV3) were compared to parental-derived cloned viruses, indicating that no selection of temperature-sensitive mutants was induced in persistently infected YAC cells. The capacity, however, of YAC-MHV3 to induce a lethal acute disease when injected into susceptible mice was lost very rapidly and seemed to be regulated by host factors.
Insights
Mouse hepatitis virus 3 (MHV3) establishes persistent infections in mouse cell cultures, leading to viral carrier states. These persistent infections alter the virus, reducing its ability to cause acute disease in mice.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Mouse hepatitis virus 3 (MHV3) exhibits varied pathogenicity across different mouse strains.
- Understanding MHV3 infection dynamics in vitro is crucial for correlating with in vivo observations.
Purpose of the Study:
- To investigate persistent MHV3 infection in mouse embryonic fibroblasts and lymphoid cell lines.
- To characterize the biological properties of MHV3 variants emerging from persistent infections.
Main Methods:
- Infection of primary mouse embryonic fibroblasts and mouse lymphoid cell lines (YAC).
- Viral titration, cell membrane antigen detection, and assessment of cytopathic effects (cell lysis).
- Cell cloning, antibody treatment, and characterization of MHV3 variants (thermosensitivity, pathogenicity).
Main Results:
- Persistent MHV3 infection was established in vitro, characterized by high virus production and cell lysis.
- Viral transmission was confirmed as horizontal, not vertical.
- MHV3 variants from persistent infections lost their capacity to induce lethal acute disease in susceptible mice, suggesting host factor regulation.
Conclusions:
- Persistent MHV3 infection in lymphoid cells creates a viral "carrier state" with equilibrium between virus production and cell permissiveness.
- MHV3 variants derived from persistent infections exhibit altered pathogenicity, with reduced virulence regulated by host factors.