ABSTRACT
Background: Neurological manifestations are a major complication of sudden acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and likely contribute to symptoms of "long COVID". Elucidating the mechanisms that underlie neuropathogenesis in infection is critical for identifying or developing viable therapeutic strategies. While neurological injury in infection is varied, cerebrovascular disease is seen at a high frequency among patients over 50 years of age. Additionally, microhemorrhages and hypoxic-ischemic injury are often described in brain autopsy series of human subjects who died from COVID-19. Here, we report neuropathology in aged SARS-CoV-2 infected non-human primates (NHPs) is consistent with that observed in aged human subjects and provide insight into the underlying cause. Methods: Four adult Rhesus macaques and four African green monkeys were inoculated with the 2019-nCoV/USA-WA1/2020strain of SARS-CoV-2 via a multi-route mucosal or aerosol challenge. Two of each species were included as age-matched controls. Frontal, parietal, occipital, and temporal lobes, basal ganglia, cerebellum, and brainstem were interrogated through histopathological and immunohistochemical techniques to identify and characterize the observed pathology. Results: Like humans, pathology was variable but included wide-spread inflammation with nodular lesions, neuronal injury, and microhemorrhages. Neuronal degeneration and apoptosis were confirmed with FluoroJade C and cleaved caspase 3 IHC, which showed foci of positivity, particularly among cerebellar Purkinje cells. This was seen even among infected animals that did not develop severe respiratory disease but was not seen in age-matched controls. Significant upregulation of the alpha subunit of hypoxia inducible factor 1 (HIF1-α), indicative of tissue hypoxia, was observed in brain of all infected animals, regardless of disease severity. Sparse virus was detected in brain endothelial cells but did not associate with the severity of CNS injury. Conclusion: SARS-CoV-2 infected NHPs are a viable animal model for advancing our current understanding of infection-associated neuropathogenesis. Upregulation of HIF1-α in brain of infected animals suggests cerebral hypoxia may underlie or contribute to neuroinflammation and neuronal injury/death and may provide some insight into neurological manifestations observed among asymptomatic patients or those only suffering mild disease.