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The PI capsid region of Theiler's virus controls replication in mouse glial cell cultures
Abstract:
The GDVII strain of Theiler's virus is virulent. The DA strain is avirulent and can persist and initiate lesions of inflammatory demyelination in the CNS of susceptible strains of mice. Other, resistant strains of mice clear the infection. Replication of the GDVII and DA strains of Theiler's virus and their genetic recombinants R2, R3 and R4 were compared in mixed glial cell cultures derived from the mouse CNS. Differences were observed in the early rate of viral production. These mapped to the P1 capsid region of the viral genome. Viruses with GDVII P1 sequences produced virus and spread more rapidly than viruses with DA P1 sequences. GDVII virus infected greater numbers of cells than DA virus. Both strains of virus rapidly replicated at least to the level of translation in astrocytes (GFAP+), macrophage/microglial cells (F4/80+), oligodendrocytes (O4+) and bipotential precursor (A2B5+) cells. Early in infection many A2B5+ and GFAP+ cells were infected and destroyed. In contrast, O4+ cells were relatively resistant to cell-death. The cultures survived and produced virus over 14 days of study, at which time all 4 cell-type were present in the culture but < 1% of all the cells, the majority of which were O4+, expressed viral protein. Most of these infected O4+ cells retained a healthy morphology with extensive sheets of cytoplasm, suggesting that Theiler's virus infection of mature oligodendrocytes was non-destructive.
Insights
Theiler
Area of Science:
- Neurovirology
- Immunology
Background:
- Theiler's virus causes inflammatory demyelination in the central nervous system (CNS).
- GDVII strain is virulent, while DA strain is avirulent.
- Susceptible mice develop disease, resistant mice clear infection.
Purpose of the Study:
- To investigate the replication and cell tropism of GDVII and DA strains of Theiler's virus in mixed glial cultures.
- To identify genetic determinants of viral replication differences.
Main Methods:
- Comparison of GDVII and DA strains, and their recombinants (R2, R3, R4), in mixed mouse CNS glial cultures.
- Assessment of viral production rates and cell infection/destruction.
- Mapping of replication differences to the P1 capsid region.
Main Results:
- GDVII virus showed a higher early replication rate and faster spread than DA virus.
- Differences in replication mapped to the P1 capsid region.
- GDVII infected more cells, particularly astrocytes and precursor cells, leading to their destruction. Oligodendrocytes were relatively resistant to cell death and maintained healthy morphology.
- Mature oligodendrocytes showed non-destructive infection by Theiler's virus.
Conclusions:
- The P1 capsid region of Theiler's virus influences early replication rate and spread.
- GDVII and DA strains exhibit differential tropism and pathogenicity in CNS glial cells.
- Mature oligodendrocytes are relatively resistant to Theiler's virus-induced cell death, suggesting a non-destructive infection mechanism.