Ketogenic diet fails to mitigate seizures and neuroinflammatory responses in a mouse model of virus‐induced epilepsy

Abstract Objective The ketogenic diet (KD) is a high‐fat, low‐carbohydrate intervention widely used to treat drug‐resistant epilepsy, thought to reduce seizures through a combination of metabolic, neuronal, and microbiota‐dependent mechanisms. Additionally, recent studies suggest that the anticonvulsant effects of KD require the gut microbiota, with taxa such as Akkermansia and Parabacteroides contributing to seizure protection by modulating host neurotransmitter balance and neural excitability. Whereas KD has been shown to be effective in reducing seizure burden across different epilepsies, its antiseizure effect on infection‐induced seizures, which are often driven by acute neuroinflammation, has not been determined. Here, we evaluated the effects of KD on seizure burden, neuroimmune responses, and gut microbiota composition in the Theiler's murine encephalomyelitis virus (TMEV) model of virus‐induced epilepsy. Methods Mice were maintained on either a KD or a normal diet prior to intracerebral TMEV infection. Seizures were induced by handling and scored twice daily from day 3 to 7 postinfection. Neuroimmune responses were assessed by flow cytometry, and fecal microbial composition was analyzed using 16S rRNA gene sequencing. Results Despite achieving ketosis, KD did not reduce seizure incidence, seizure burden, or seizure severity during acute TMEV infection. KD also did not significantly alter overall immune cell infiltration into the central nervous system, indicating limited effects on global neuroinflammation. However, KD significantly reshaped the gut microbiota, reducing alpha diversity (richness, Shannon diversity, and evenness) and strongly altering community structure, with clear separation between diet groups, including enrichment of taxa such as Akkermansia , Acetatifactor , Dorea, and Flintibacter and depletion of fiber‐associated taxa such as Bifidobacterium and Roseburia . However, these microbial shifts were not associated with protection against inflammation‐driven seizures. Significance These results demonstrate that KD's antiseizure efficacy is highly context‐dependent, and that KD‐driven changes in microbiota‐ and metabolite‐mediated mechanisms may be ineffective against infection‐associated epilepsy, suggesting that inflammation‐driven seizures require distinct therapeutic approaches.