Abstracts

Rationale:
Refractory seizures, including status epilepticus, is a manifestation of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. The etiology of autoimmune seizures in encephalitis is unclear but two possible hypotheses include the direct effects of autoantibodies leading to hyperexcitability of the neuronal network, or the development of neuroinflammation that may facilitate seizures. We previously showed that intraventricular administration of CSF from patients with anti-NMDAR encephalitis to mice precipitates seizures, thereby confirming that antibodies are directly pathogenic for seizures. To establish the role of the innate immune system in seizures and determine if interleukin (IL) proteins are fundamentally involved in epileptogenesis in autoimmune seizures, we asked if blocking the effects of IL-1 by anakinra, a selective IL-1 receptor antagonist, blunts the antibody-induced seizures.
Method:
Naïve male C57BL/6 mice were implanted with two subdural EEG electrodes, an EEG head mount, and a guide cannula targeted to the lateral ventricle. Seven days later purified serum IgG from patients with anti-NMDAR encephalitis or monoclonal anti-NMDAR IgG derived from a plasma cell lineage of an affected patient were infused into the lateral ventricle by subcutaneous osmotic minipumps, and mice were connected to EEG. Following a 6-day assessment of their baseline seizure counts, mice were treated with anakinra (25 mg/kg s.c., twice daily) or vehicle (days 13-17). The EEG was discontinued (day 21) and behavioral tests were performed to assess motor function, anxiety and memory. Upon the completion of the experiments, immunohistochemistry was carried out to assess astrocytic (GFAP) and microglial (Iba-1) activation in hippocampus.
Results:
Of 31 mice infused with purified patient NMDAR-IgG (n=17) or monoclonal NMDAR-IgG (n=14), 25 mice (87%) developed seizures. The median baseline daily seizure counts during the exposure to antibodies was 3.8. (25-75% Interquartile range, IQR 3.7-4.1) and the majority of seizures were electrographic only. The administration of anakinra attenuated daily seizure frequency by 60% (p=0.02, p=0.04: two-way ANOVA). The median duration of seizures during the baseline was 62.5 sec (IQR 47-114). Anakinra attenuated the duration of seizures; however, the effect was delayed and was not apparent until after the cessation of treatment (p = 0.009, p = 0.02: two-way ANOVA). Anakinra improved the novel object recognition in mice with antibody-induced seizures (p = 0.03, paired t tests); however, it had no effects on locomotor function or anxiety scores (p=0.76 and p=0.48, respectively, t-tests).
Conclusion:
Our evidence, together with previous reports of therapeutic effects of anakinra in other severe autoimmune and inflammatory seizure syndromes, suggests that IL-1 plays a role in the pathogenesis of seizures in anti-NMDAR encephalitis. Targeting inflammation via blocking IL-1 receptor mediated-signaling may be promising for the development of novel treatments for refractory autoimmune seizures.
Funding:
:O. Taraschenko received grant support from the American Epilepsy Society Junior Investigator Research Award. Anakinra was a gift from Swedish Orphan Biovitrum (Stockholm, Sweden).