ASC- and caspase-1-deficient C57BL/6 mice do not develop demyelinating disease after infection with Theiler's murine
Dandan Li1, Melanie Bühler1, Sandra Runft1
1Department of Pathology, University of Veterinary Medicine Hannover, Foundation, Bünteweg 17, 30559, Hannover, Germany.
Abstract:
Theiler's murine encephalomyelitis virus (TMEV) induces an acute polioencephalomyelitis and a chronic demyelinating leukomyelitis in SJL mice. C57BL/6 (B6) mice generally do not develop TMEV-induced demyelinating disease (TMEV-IDD) due to virus elimination. However, TMEV can persist in specific immunodeficient B6 mice such as IFNβ-/- mice and induce a demyelinating process. The proinflammatory cytokines IL-1β and IL-18 are activated by the inflammasome pathway, which consists of a pattern recognition receptor molecule sensing microbial pathogens, the adaptor molecule Apoptosis-associated speck-like protein containing a CARD (ASC), and the executioner caspase-1. To analyze the contribution of the inflammasome pathway to the resistance of B6 mice to TMEV-IDD, ASC- and caspase-1-deficient mice and wild type littermates were infected with TMEV and investigated using histology, immunohistochemistry, RT-qPCR, and Western Blot. Despite the antiviral activity of the inflammasome pathway, ASC- and caspase-1-deficient mice eliminated the virus and did not develop TMEV-IDD. Moreover, a similar IFNβ and cytokine gene expression was found in the brain of immunodeficient mice and their wild type littermates. Most importantly, Western Blot showed cleavage of IL-1β and IL-18 in all investigated mice. Consequently, inflammasome-dependent activation of IL-1β and IL-18 does not play a major role in the resistance of B6 mice to TMEV-IDD.
Insights
The inflammasome pathway, involving Apoptosis-associated speck-like protein containing a CARD (ASC) and caspase-1, does not determine resistance to Theiler's murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD) in C57BL/6 mice. These mice efficiently clear the virus regardless of inflammasome function.
Area of Science:
- Neuroimmunology
- Virology
- Infectious Diseases
Background:
- Theiler's murine encephalomyelitis virus (TMEV) causes demyelinating disease in susceptible mice, but C57BL/6 (B6) mice are typically resistant due to efficient viral clearance.
- The inflammasome pathway, crucial for innate immunity, activates proinflammatory cytokines like IL-1β and IL-18.
- Understanding resistance mechanisms to TMEV-induced demyelinating disease (TMEV-IDD) is vital for developing therapeutic strategies.
Purpose of the Study:
- To investigate the role of the inflammasome pathway, specifically Apoptosis-associated speck-like protein containing a CARD (ASC) and caspase-1, in the resistance of C57BL/6 (B6) mice to TMEV-IDD.
- To determine if inflammasome-mediated cytokine activation contributes to viral clearance and resistance in B6 mice.
Main Methods:
- Infection of wild type, ASC-deficient, and caspase-1-deficient B6 mice with TMEV.
- Histological and immunohistochemical analysis of brain tissue.
- Gene expression analysis using RT-qPCR.
- Protein analysis using Western Blot to detect cytokine cleavage.
Main Results:
- ASC- and caspase-1-deficient B6 mice successfully eliminated TMEV and did not develop TMEV-IDD, similar to wild type littermates.
- No significant differences in IFNβ and cytokine gene expression were observed in the brains of deficient and wild type mice.
- Western Blot analysis confirmed the cleavage of IL-1β and IL-18 in all infected mice, indicating inflammasome activation was not essential for resistance.
Conclusions:
- Inflammasome-dependent activation of IL-1β and IL-18 is not a major factor in the resistance of C57BL/6 mice to TMEV-induced demyelinating disease.
- Viral clearance and resistance in B6 mice against TMEV are likely mediated by inflammasome-independent mechanisms.
