The TMEV-induced animal model of epilepsy, as described above, has opened new horizons to understand the pathobiological mechanisms involved in the induction of epilepsy and ultimately new avenues for studies on disease prevention (anti-epileptogenesis) and disease modification (anti-seizures) (Stewart et al., 2010a) in infection induced epilepsies. The presence of early seizures during the early phase (0-7dpi) of infection, was observed visually and confirmed with 24/7 video EEG (vEEG) recording (Stewart et al., 2010a). However, the frequency of behavioural seizures per week during the chronic disease phase (2-7 months pi) was very low and continuously decreased over time. This renders seizure frequency, generally used as measure of disease progression and therapeutic efficacy in various animal models of epilepsy (Twele et al., 2016), a non-suitable biomarker to evaluate the effects of drug treatments in this model. However, all the infected animals showed epileptiform activity (IEDs) in terms of spikes (Stewart et al., 2010a), providing a window of opportunity to characterize and quantify these as a potential biomarker for epilepsy development and later therapeutic disease modification (Engel et al., 2013).
Hypothesis:
Interictal spiking activity can be used as a potential biomarker to differentiate between epileptic and non-epileptic mice
Most of the studies conducted by the University of Utah group are on early seizure development, focusing on underlying mechanisms and the role of the immune system, with a relatively short period of visual observations for seizure occurrence (2 hours per day at same time every day) or vEEG recordings. Thus there was a need for extensive long term (up to 90 days post infection) simultaneous 24/7 video EEG recordings to answer the following questions, (1) What are the general characteristics of EEG recorded in TMEV model of epilepsy? (2) Is it possible to develop an algorithm to characterize and analyze EEG in-silico?
(3) What is the length of latent period, if any? (4) How seizure pattern evolve over time? (5) What is the frequency and intensity of early and chronic seizures (6) Is it possible to find out a potential EEG biomarker such as spikes and spike clusters in EEG recordings for distinguishing between epileptic / non-epileptic mice? (7) Can we use observed spikes and spike clusters as a quantifiable biomarker for therapeutic targeting?
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2 Brain inflammation, neurodegeneration and seizure development following
picornavirus infection markedly differ among virus and mouse strains and substrains
Sonja Bröer a, Christopher Käufer a,b, Verena Haist c,1, Lin Li b,c, Ingo Gerhauser c, Muneeb Anjum a,b, Marion Bankstahl a,b, Wolfgang Baumgärtner b,c, Wolfgang Löscher a,b,⁎
a Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany
b Center for Systems Neuroscience, Hanover, Germany
c Department of Pathology, University of Veterinary Medicine, Germany
Published in: Exp Neurol. 2016 May; 279:57-74. doi: 10.1016/j.expneurol.2016.02.011.
Epub 2016 Feb 15.
Personal contributions
SB designed the study and performed the experiments, analyzed the data and wrote the manuscript. CK performed the experiments, analyzed the data and wrote the manuscript.
VH designed the study and performed the experiments. LL performed the experiments.
IG analyzed the data and wrote the manuscript, MA learned the model, performed the experiments, analyzed EEGs, MB helped in analysing the data. WB supervised and analyzed the data and wrote the manuscript. WL supervised and analyzed the data and wrote the manuscript. All authors revised the manuscript.
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Abstract
Infections, particularly those caused by viruses, are among the main causes of acquired epilepsy, but the mechanisms causing epileptogenesis are only poorly understood. As a consequence, no treatment exists for preventing epilepsy in patients at risk. Animal models are useful to study epileptogenesis after virus-induced encephalitis and how to interfere with this process, but most viruses that cause encephalitis in rodents are associated with high mortality, so that the processes leading to epilepsy cannot be investigated. Recently, intracerebral infection with Theiler's murine encephalomyelitis virus (TMEV) in C57BL/6 (B6) mice was reported to induce early seizures and epilepsy and it was proposed that the TMEV mouse model represents the first virus infection-driven animal model of epilepsy. In the present study, we characterized this model in two B6 substrains and seizure resistant SJL/J mice by using three TMEV (sub) strains (BeAn-1, BeAn-2, DA). The idea behind this approach was to study what is and what is not necessary for development of acute and late seizures after brain infection in mice. Receiver operating characteristic (ROC) curve analysis was used to determine which virus-induced brain alterations are associated with seizure development. In B6 mice infected with different TMEV virus (sub)strains, the severity of hippocampal neurodegeneration, amount of MAC3-positive microglia/macrophages, and expression of the interferon-inducible antiviral effector ISG15 were almost perfect at discriminating seizing from non-seizing B6 mice, whereas T-lymphocyte brain infiltration was not found to be a crucial factor. However, intense microglia/macrophage activation and some hippocampal damage were also observed in SJL/J mice. Overall, the TMEV model provides a unique platform to study virus and host factors in ictogenesis and epileptogenesis.
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3
Automated quantification of EEG spikes and spike clusters as a new read out in Theiler’s virus mouse model of encephalitis-induced epilepsy
Syed Muhammad Muneeb Anjum1,2*, Christopher Käufer1, Rüdiger Hopfengärtner3, Inken Waltl1,2, Sonja Bröer1*, and Wolfgang Löscher1,2
1Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany
2Center for Systems Neuroscience, Hannover, Germany
3Epilepsy Center, Department of Neurology, University Hospital Erlangen, Germany
*On leave from the Institute of Pharmaceutical Sciences, University of Veterinary & Animal Sciences, Lahore, Pakistan
** Present address: Neurona Therapeutics, South San Francisco, CA, USA
Published in Epilepsy & Behavior, 2018 October; 88: 189-204. doi:
https://doi.org/10.1016/j.yebeh.2018.09.016
Personal contributions
SMMA Designed and performed the experiments, conceived, designed, executed and wrote algorithm, analyzed the data and wrote manuscript. CK performed experiment, edited manuscript, RH analyzed algorithm technically, wrote manuscript, IW performed experiments, SB designed and performed experiments, and WL supervised and analyzed the data and wrote the manuscript.
32 Abstract
Intracerebral infection of C57BL/6 mice with Theiler's murine encephalomyelitis virus (TMEV) replicates many features of viral encephalitis-induced epilepsy in humans, including neuroinflammation, early (insult-associated) and late (spontaneous) seizures, neurodegeneration in the hippocampus, and cognitive and behavioral alterations. Thus, this model may be ideally suited to study mechanisms involved in encephalitis-induced epilepsy as potential targets for epilepsy prevention. However, spontaneous recurrent seizures (SRS) occur too infrequently to be useful as a biomarker of epilepsy, e.g., for drug studies. This prompted us to evaluate whether epileptiform spikes or spike clusters in the cortical electroencephalogram (EEG) may be a useful surrogate of epilepsy in this model. For this purpose, we developed an algorithm that allows efficient and large-scale EEG analysis of early and late seizures, spikes, and spike clusters in the EEG. While 77% of the infected mice exhibited early seizures, late seizures were only observed in 33% of the animals. The clinical characteristics of early and late seizures did not differ except that late generalized convulsive (stage 5) seizures were significantly longer than early stage 5 seizures. Furthermore, the frequency of SRS was much lower than the frequency of early seizures. Continuous (24/7) video-EEG monitoring over several months following infection indicated that the latent period to onset of SRS was 61 (range 16–91) days. Spike and spike clusters were significantly more frequent in infected mice with late seizures than in infected mice without seizures or in mock-infected sham controls. Based on the results of this study, increases in EEG spikes and spike clusters in groups of infected mice may be used as a new readout for studies on antiepileptogenic or disease-modifying drug effects in this model, because the significant increase in average spike counts in mice with late seizures obviously indicates a proepileptogenic alteration.
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