Abstracts

Rationale: Central infection with Theiler’s murine encephalomyelitis virus (TMEV) in C57Bl/6J mice is a valid model of infection-induced acute seizures and epileptogenesis. Diet sterilization alone can modify the severity of acute seizures in mice infected with TMEV (Libbey et al. Nutrition 2016); however, no study has yet defined the extent to which diet influences chronic comorbidities in the TMEV model. Further, no study has yet determined whether gut microbiome dysbiosis is associated with disease modification subsequent to TMEV infection. We thus sought to define the extent to which diet sterilization in the University of Washington (UW) specific pathogen free (SPF) vivarium impacts the onset of acute seizures, chronic behavioral deficits, and the composition and diversity of the gut microbiome. Methods: Baseline fecal samples were collected from male C57BL/6J mice (4-5 weeks-old) immediately upon arrival at the SPF vivarium (Figure 1). Mice were then randomized to either autoclaved (AC) or irradiated (IR) diet used in our prior studies at the University of Utah (Prolab RMH 3000: UU), or IR UW diet (Picolab Rodent 5053; n=13 mice/diet) and maintained on the specific diet throughout. Animals were administered either intracerebral (i.c.) TMEV or PBS three days later. Fecal samples were collected at infection (Day 0) and again on Day 7 post-infection. Behaviors assessed 5 weeks post-infection were anxiety-like behavior, working memory, and seizure threshold. Gut microbiome biodiversity was assessed by 16s rRNA amplicon sequencing of fecal samples from D-3, D0 and D7 (n = 5 mice/diet). Results: Mice infected with TMEV displayed acute handling-induced seizures, regardless of diet: 8/13 (61%) IR UW diet-fed mice, 11/18 (69%) AC RMH diet-fed, and 10/13 (76.9%) IR RMH diet-fed mice. Average seizure burden during the acute period was: 13.0±4.0 in IR UW diet-fed mice; 18.3±4.2 in AC RMH diet-fed, and 18.9±3.9 IR RMH diet-fed mice. Long-term, mice fed IR UW diet demonstrated preserved working memory function compared to mice fed either the AC and IR RMH diet, who exhibited significant impairments in working memory and increased anxiety-like behavior, suggestive of worsened chronic disease severity. The composition of the gut microbiome was also significantly modified in mice fed the AC vs IR RMH diet relative to sham-infected mice fed the same diet. Notably, Akkermansia species were significantly enriched in AC RMH diet-fed TMEV-infected mice relative to PBS-infected, AC RMH diet-fed mice, and relative to IR RMH diet-fed TMEV-infected mice (diet x infection interaction, F(1,16)=25.9, p<0.0001). Conclusions: Dietary modification itself can modify the incidence of animals with seizures and acute seizure burden in the TMEV model of infection-induced epilepsy. Intestinal dysbiosis is also associated with differential acute and chronic disease severity in the TMEV model. Further, our study supports mounting evidence to point to a potential anticonvulsant and/or disease-modifying role of Akkermansia species (Olson et al. Cell 2018) in the context of epilepsy. Funding: This work was supported by the University of Washington Department of Pharmacy and the Institute for Translational Health Sciences Catalyst Award (MBH).