01-24 – In vitro modelling of seizure genesis during HSV-1 encephalitis

The high rate of acute seizures and status epilepticus (SE) contributes to the severity and adverse clinical outcome of herpes simplex virus-1 encephalitis (HSE). However, little is known about what specific mechanisms influence the development of seziures and SE in patients. Neuronal hyperexcitability is a hallmark of seizures and is known to be induced by pro-inflammatory cytokines, of which astrocytes are a major source during infection. We have developed an in vitro model of seizures provoked by HSV-1 infection using human iPSC-derived cortical neurons to identify mechanisms by which neuronal network hyperexcitability may be provoked by HSV-1 infection through neurotropism or indirectly through pro-inflammatory cytokine secretion. We established a model comprising functional hiPSC-derived cortical neurons on a multi-electrode array which measures neuronal electrophysiological activity and viability in real time. hiPSC-derived cortical neurons were exposed to live HSV-1 infection at an MOI of 0.1 as well as UV-inactivated HSV-1. Neuronal spike frequency, burst frequency and network burst frequency were non-invasively quantified at regular intervals before and after exposure using a multi-electrode array (Axion Biosystems). Our in vitro model shows spontaneous and evoked firing with burst activity that can be modulated with small molecules and infectious agents. At 20 hours post-infection, neurons showed significantly increased spike and burst frequency, as well as significantly increased network burst frequency and synchrony, despite no significant change in culture viability. We conclude that acute HSV-1 infection triggers neuronal hyperexcitability and network hypersynchrony prior to significant neuronal death.