EGR1 influences neuropathology in mice following infection with Venezuelan equine encephalitis virus (VEEV) in a sex - dependent manner

VEEV is a New World alphavirus that causes encephalitis in humans and equines. No FDA-approved medical countermeasures exist for humans and 4-14% of survivors experience debilitating neurological sequelae. Traditional approaches of studying VEEV pathogenesis in mice have utilized lethal doses. However, this is not recapitulative of human VEEV cases where <1% of infections result in death and does not incorporate the neurological sequelae observed. To understand the molecular drivers inducing neurological damage, we leveraged transcriptomic, proteomic, and histopathological analyses of brains from uninfected or VEEV infected mice on days 4, 7, and 28 post-infection (DXpi). Principle component analysis revealed distinct clustering of VEEV infected mice at D4, 7, and 28pi. Top canonical pathways at D4 and 7pi included Pathogen Induced Cytokine Storm Signaling Pathway and Role of Pattern Recognition Receptors in Recognition of Bacteria and Viruses whereas at D28pi Mitochondrial Translation and RHO GTPase Cycle signaling pathways were most altered. Notable DEGs upregulated on D4, 7, and 28pi from the Pathogen Induced Cytokine Storm Signaling Pathway included CXCL10, GZMB, ZBP1, PRF1, and IRF7, all of which play a role in apoptosis, a hallmark of VEEV infection. D28pi brain homogenates showed increased expression of IL-9, IL-10, IP-10, and MIG. Mild pathology was observed on D4pi and severe pathology was observed on D7 and 28pi, including perivascular cuffing, meningitis, infiltrating neutrophils, neuronal necrosis, and gliosis. Interestingly, D28pi mice had recovered from acute infection and appeared normal, yet had severe neuropathological damage, suggesting sustained inflammation following resolution of the acute phase of disease likely contributes to the development of neurological sequelae. Collectively, these results provide insight into the cellular mechanisms, signaling pathways, and molecular markers that contribute to VEEV-induced neuroinflammation and neuropathology and will aid in countermeasure development against VEEV.