In this study, we investigated the roles of the pro-inflammatory cytokines Interferon (IFN) gamma, Interleukin-6 (IL-6) and C-C motif ligand 2 (CCL2) in neuronal hyperexcitability induced by Herpes Simplex Virus-1 (HSV-1) infection.

Herpes simplex virus-1 encephalitis (HSE) involves a high morbidity for patients. Some patients experience acute seizures and status epilepticus which negatively impact the burden of disease, but the pathophysiology behind these events is poorly understood.

Cortical neurons were derived from induced pluripotent stem cells (iPSCs) to provide in vitro samples. Neurons were infected with different multiplicities of infection (MOI) of HSV-1, with some groups cultured in UV treated supernatant of differing MOIs. Invitrogen uncoated Enzyme Linked Immunosorbent Assay (ELISA) studies for human CCL2, IL-6 and IFN gamma were carried out at 72 hours post-infection. Mean hyperexcitability was calculated using data from the multi-electrode array (MEA).

IL-6, IFN gamma and CCL2 were significantly elevated in response to high dose viral infection. The concentration of CCL2 was higher in neurons stimulated with highest dose of infected supernatant than neurons directly infected with the highest dose of virus (mean difference +53.18, p <0.01). IFN gamma was moderately correlated with hyperexcitability (R squared 0.6046, p <0.0001), whereas IL-6 was weakly correlated with hyperexcitability (R squared 0.2077, p <0.05).

Overall, we concluded that direct infection with a high dose of HSV-1 causes significant elevation in pro-inflammatory cytokines IFN gamma, IL-6 and CCL2 with a moderate correlation to hyperexcitability in IFN gamma. Future studies should include blocking cytokines of interest, to assess whether cytokines are produced upstream or downstream of seizure activity and repeating this study with more controls to boost statistical power.