Theiler’s Murine Encephalomyelitis Virus Model (mouse)

Viral infections of the CNS increase risk of seizures and status epilepticus, and the inflammatory cascade triggered by the infection contribute to the development of seizures and epilepsy (Misra et al., 2008; Vezzani et al., 2016). Human patients with viral infection-induced encephalitis who present with seizures during the acute infection period are up to 22 times more likely to develop spontaneous, unprovoked seizures than the general population (Misra et al., 2008). Thus, treatments that can attenuate such acute seizures may provide significant benefit to prevent subsequent long-term epileptogenesis. A novel model of infection-induced epilepsy was developed with Theiler’s murine encephalomyelitis virus (TMEV) infection specifically in the C57BL/6J mouse wherein the majority of TMEV-infected animals develop handling-induced seizures after the initial infection (days 3-7) and show significant elevations in inflammatory cytokines (Libby et al., 2008; Stewart et al., 2010). Animals survive the initial infection and some then subsequently develop spontaneous, recurrent seizures weeks later. This model is currently being used to evaluate if test agents can attenuate the development of handling-induced seizures during the acute infection period (days 3-7) in TMEV-infected animals (Barker-Haliski et al., 2015).

On day 0, 5-6 weeks old male C57BL/6J mice from the Jackson Laboratory (n = 20 in vehicle and test drug group) are briefly anesthetized using 2-5% isoflurane and injected with 20 µl of the Daniels strain of TMEV (3 x 105 plaque-forming units) intracortically to a depth of 2.5 mm in the parietal region of the right hemisphere (posterior and medial to the right eye). Starting post infection day 1 and continuing through day 7 handling sessions are performed consisting of cage shaking and individual handling of mice. The onset of handling-induced seizures begins on post infection day 3 and continues through post infection day 7. Experimental compounds are administered once or twice daily and seizure monitoring is performed at the previously determined time-of-peak effect (TPE). Injection and observation times vary depending on the TPE of individual compounds. Dose and TPE is determined based on the available information (activity in other mouse seizure models and pharmacokinetic data – if available). Seizure monitoring includes cage agitation and handling of the tail and rotation of the mouse 3-5 times followed by observation for seizure behaviors. The intensity of seizure activity is assessed using the Racine scale (Racine, 1972): stage 1 (mouth and facial movements), stage 2 (head nodding), stage 3 (forelimb clonus), stage 4 (rearing), and stage 5 (rearing and falling). During the experiment, the person handling the mice is blinded to the treatment.