ABSTRACT
SARS-CoV-2, the causative agent of COVID-19, typically manifests as a respiratory illness although extrapulmonary involvement, such as in the gastrointestinal tract and nervous system, are increasingly recognised. Through immunohistochemistry against the SARS-CoV-2 nucleocapsid protein (NP), we aimed to characterise the multisystem viral tropism of SARS-CoV-2. FFPE tissue was obtained from 16 PCR-confirmed post-mortem COVID cases. Of these cases, 10 were full-body, 5 were brain only and 1 was a brain biopsy. Brain regions studied included frontal cortex, medulla, cerebellum, pons and olfactory bulb. Neurological symptoms featured in the cohort included brainstem encephalitis, acute disseminated encephalomyelitis (ADEM) and brain infarction. Immunohistochemistry of digestive system tissues revealed presence of SARS-CoV-2 NP in neurons of the myenteric plexus, a site of high ACE-2 expression, the entry receptor for SARS-CoV-2 and one of the earliest affected cells in Parkinson's disease (PD). Within the brain, staining was widespread in all sampled regions but limited to endothelial cells only (including in the olfactory bulb). Furthermore, in the full-body post-mortem cases, positivity in brain endothelia was restricted to cases exhibiting multiorgan tissue positivity (3/9 cases). The average time from symptom onset to time of death was shorter in positively versus negatively stained postmortem cases (mean = 10.3 days vs mean = 20.3 days, p = 0.0416) suggesting NP detection was confined to the infectious period. Together, our findings provide evidence for enteric nervous system but not brain neuroinvasion of SARS-CoV-2 as well as potential insights into long-term complications of COVID-19 and PD pathogenesis.