Abstracts

Rationale: Temporal lobe epilepsy is the most prevalent form of acquired epilepsy, and it is difficult to treat with current anti-seizure drugs. Thus, the development of new disease-modifying therapies is essential to treat and prevent seizures in high-risk groups. Although the precise mechanism that leads to epilepsy remains unclear, evidence from experimental and clinical work suggests that brain inflammation is a crucial contributor. Inflammation can alter the excitatory/inhibitory balance among neurons and is a significant cause of acute seizures.



The gut microbiota consists of commensal microorganisms that coexist in a symbiotic relationship with the host. An axis between the gut microbiota–central nervous system (CNS) has been proposed, suggesting multifaceted interactions where the gut community impacts immune responses that influence CNS homeostasis and inflammation. Recent studies recognized the involvement of the gut microbiota in several neuroinflammatory diseases. However, the influence of the microbiota in the development of acquired seizure/epilepsy remains unclear.

Mice intra-cranially (IC) infected with Theiler’s murine encephalomyelitis virus (TMEV) develop behavioral seizures 3-8 days post-infection (dpi). Seizures are correlated with innate immune response activation and macrophage infiltration into the CNS. Diet is a modulator of gut composition and diversity, and it can promote the growth or suppression of beneficial or harmful bacteria. The ketogenic diet, an epilepsy treatment, exerts its effect in part by modulating the gut composition. Thus, we hypothesized that the presence of specific gut bacterial population(s) and derived metabolites modulate neuroinflammation and seizure development after CNS viral infection.


Methods: C56BL/6J mice on the 2920X or the 8904 Teklad Rodent diet were infected with TMEV. Handling-induced seizures were determined daily, from 3-7 dpi, and severity was scored based on the Racine scale. At 7dpi, mice were euthanized, brain cells isolated, and their inflammatory states determined by flow cytometry. Fecal samples were collected on days -1 and 7 dpi. 16S rRNAseq was performed in fecal samples. Metabolomics (LC/MS and GC/MS) was conducted on plasma/fecal samples.

Results: Mice fed the 8904 diet showed increased seizure incidence and a significant increase in seizure severity. We also found that diet significantly affected microglia activation and infiltration of macrophages into the CNS. By 16S rRNA-seq, a substantial difference in gut microbiota diversity between mice fed 2920X and 8904 diets was observed. We also found significant distinct metabolite profiles between the two diets and between mice that experienced seizures compared to non-seizing mice.


Conclusions: Our studies indicate a role for the gut microbiota in seizure development after viral encephalitis, and it suggests that manipulating the gut microbiota and derived metabolites may offer promising interventions to prevent and treat the development of acquired epilepsy.

Funding: CURE - Taking Flight Award

NIH-NINDS K22NS123547