Gut Dysbiosis and Carbamazepine Differentially Impact Hippocampal Glial Response and Neurodegeneration in a Viral Infection-Induced Seizure Model

Abstract Objective Brain infection is an underrecognized global cause of epilepsy due to the ensuing neuroinflammation and neurological damage. Immune system response, including underlying neuroinflammation, is dynamically shaped by the intestinal microbiome. In experimental rodent epilepsy models, seizure burden and antiseizure medication (ASM) activity can be dramatically influenced by gut dysbiosis, including in the Theiler’s murine encephalomyelitis virus (TMEV) infection model of acute symptomatic seizures and long-term epilepsy. We previously demonstrated that experimentally induced gut dysbiosis via repeated antibiotic administration alters seizure burden and carbamazepine (CBZ) anticonvulsant activity in this model (1). However, whether dysbiosis and CBZ differentially shape neuropathological damage and neuroinflammation following TMEV infection was not reported. Methods Here, we extended our earlier study to quantify the extent to which antibiotic-induced gut dysbiosis and repeated CBZ administration during TMEV infection altered the severity of acute neuropathology. Hippocampal tissue was analyzed 7 days post-infection using quantitative immunofluorescence to assess neuronal death, microglial and astroglial reactivity, and neuronal proliferation across CA1, CA3, and dentate gyrus (DG) subregions. Results Dysbiosis markedly exacerbated hippocampal neurodegeneration and gliosis, accompanied by increased glial proliferation, whereas CBZ administration reversed these effects in a hippocampal region-dependent manner. Collectively, these findings demonstrate that the gut microbiome primes hippocampal neuroimmune responses to viral infection-induced acute seizures and modifies associated neuropathology in a hippocampal region-specific manner. Significance This work identifies the gut-brain axis as a critical determinant of neuroinflammatory damage after infection-induced symptomatic seizures, highlighting the gut microbiome as a potential therapeutic target to alleviate the worldwide epilepsy burden. Highlights Experimentally-evoked gut dysbiosis exacerbates hippocampal neurodegeneration after brain viral infection. Experimentally-evoked gut dysbiosis increases microgliosis and glial proliferation after brain viral infection. Carbamazepine reversed dysbiosis-induced neuroinflammation and neurodegeneration. Experimentally-evoked gut dysbiosis differentially modulates glial response in the dentate gyrus.