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Updated: Feb 18, 2026
A Model for Epilepsy of Infectious Etiology using Theiler's Murine Encephalomyelitis Virus
Published on: June 23, 2022
Investigating the Role of Cortical Microglia in a Mouse Model of Viral Infection-Induced Seizures
Lakshmini Balachandar1, Lauren Buxton1, Ireland Kearns1
1Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, Utah 84112.
Abstract:
Microglia, resident immune sentinels in the brain, are crucial in responding to tissue damage, infection, damage signals like purines (ATP/ADP), and clearing cellular debris. It is currently unknown how microglial reactivity progresses and contributes to seizure development following Theiler's murine encephalomyelitis virus (TMEV) infection. Previously, it has been demonstrated that purinergic signaling in microglia is disrupted in the hippocampus of TMEV-infected mice. However, whether reactive cortical microglia also exhibit changes in purinergic signaling, cytokine levels, and purinergic receptors is unknown. Thus, we seek to evaluate region-based differences in microglial reactivity in the TMEV model. We employed a custom triple transgenic mouse line expressing tdTomato and GCaMP6f under a CX3CR1 Cre promoter and exogenously applied ATP/ADP to acute brain slice preparations from TMEV-infected mice and controls of either sex. Interestingly and in contrast to what is observed in the hippocampus, we found that despite microglial reactivity in the cortex, microglia can respond to purinergic damage signals and engage calcium signaling pathways, comparable to PBS controls. Using a cytokine panel, we also found that proinflammatory cytokine levels (TNF-α, IL-1α, and IFN-γ) are brain region dependent in mice infected with TMEV. Using RNAscope FISH, we observed increases in expression of purinergic receptors responsible for microglial motility (P2Y12R) and inflammation (P2X7R) in the cortex. Collectively our results suggest that following TMEV infection, microglial response to novel damage signals, as well as the production of proinflammatory cytokines, varies as a function of the brain region.
Insights
Cortical microglia in TMEV-infected mice remain responsive to damage signals and show altered purinergic signaling and cytokine expression, varying by brain region. This suggests region-specific roles for reactive microglia in viral-induced epilepsy.
Area of Science:
- Neuroimmunology
- Neurovirology
- Epilepsy Research
Background:
- Microglia, the brain's resident immune cells, are vital for responding to damage, infection, and clearing debris.
- Theiler's Murine Encephalomyelitis Virus (TMEV) infection can lead to seizures, with purinergic signaling disruptions noted in the hippocampus.
- The specific changes in reactive cortical microglia following TMEV infection, including purinergic signaling and cytokine profiles, remain largely unknown.
Purpose of the Study:
- To investigate region-based differences in microglial reactivity in the TMEV mouse model of epilepsy.
- To assess the responsiveness of cortical microglia to purinergic damage signals and their calcium signaling capacity.
- To analyze changes in cytokine levels and purinergic receptor expression in reactive cortical microglia.
Main Methods:
- Utilized a custom triple transgenic mouse line (CX3CR1 Cre-driven tdTomato and GCaMP6f) in a TMEV infection model.
- Applied exogenous ATP/ADP to acute brain slices from TMEV-infected and control mice.
- Analyzed cytokine panels and used RNAScope-FISH to examine purinergic receptor expression (P2Y12R, P2X7R).
Main Results:
- Despite reactivity, cortical microglia in TMEV-infected mice responded to purinergic damage signals and engaged calcium signaling, similar to controls.
- Pro-inflammatory cytokine levels (TNF-α, IL-1α, IFN-γ) exhibited brain-region-dependent variations in TMEV-infected mice.
- Increased expression of P2Y12R (motility) and P2X7R (inflammation) purinergic receptors was observed in cortical microglia.
Conclusions:
- Microglial responses to damage signals and pro-inflammatory cytokine production are brain-region specific following TMEV infection.
- Cortical microglia retain functional purinergic signaling capabilities despite reactivity, suggesting a complex role in seizure development.
- Findings highlight regional differences in reactive microglia that may influence seizure generation and progression in viral-induced epilepsy.
