SARS-CoV-2 infection is associated with hypothalamic orexin suppression and persistent cortical NeuN attenuation

Long COVID frequently presents with persistent neurological symptoms, including cognitive impairment, fatigue, and sleep disturbances; however, its underlying mechanisms remain unclear. Here, we show that SARS-CoV-2 infection induces lasting cortical neuronal injury and hypothalamic orexin (hypocretin) dysfunction in vivo. In K18-hACE2 and wild-type BALB/c mice, viral RNA persisted in the brain and coincided with focal loss of Neuronal Nuclei (NeuN)-positive cortical neurons beyond acute infection. SARS-CoV-2, but not the influenza A virus, triggered rapid and sustained suppression of hypothalamic orexin expression, defining a virus-specific neuropathological signature. Considering the downregulation of orexin and focal cortical NeuN attenuation, we found that exogenous orexin-A/B supplementation increased NeuN abundance in vitro and in vivo under the tested conditions. Overall, these findings identify the orexin system as a candidate neural vulnerability to SARS-CoV-2 and suggest that orexinergic dysfunction may contribute to the neurological manifestations of Long COVID.