COVID-19 Autopsies Reveal Multiorgan Tropism, Including Brain

Since starting this blog, a lot of the literature I’ve written about has been circling around the idea that SARS-CoV-2 may infect the brain. We’ve seen neurological symptoms in patients and in vitro assays showing viral invasion of human iPSC-derived neurons, but this week I found a paper published back in May that revealed SARS-CoV-2 does indeed infect the brains of COVID-19 patients. It would have been nice to stumble upon this finding when it first surfaced three months ago, but better late than never!

Writing in the New England Journal of Medicine from the University Medical Center Hamburg-Eppendorf, Puelles et al. analyzed human tissues collected from autopsies of 22 COVID-19 patients. The organs analyzed were the lungs, pharynx, heart, kidneys, liver, blood, and brain (Puelles et al., 2020). The authors found that the organs with the highest number of SARS-CoV-2 RNA copies per cell were the lungs and pharynx, with high numbers also seen in kidneys, liver, and heart. Eight out of 22 patients (36.4%) had high numbers of viral RNA copies in the brain and blood, but others had no viral RNA copies in those areas. It would be interesting to see how RNA copies in the brain correlated with the presence of neurological symptoms in these patients, but such information was not provided.

To summarize what we now know about the neurotropism of SARS-CoV-2, the virus exists in the brains of some COVID-19 patients, it infects and replicates in human iPSC-derived neurons in vitro (see blog post from July 13th, 2020), and it causes neurological symptoms in some COVID-19 patients (see blog post from April 5th, 2020). It would be interesting to now test the hypothesis that brain neurotropism is responsible for neurological symptoms. Building off that, it is unknown which brain regions are at the highest risk of infection and what implications viral infection in those regions might have. A lot of work remains to be done to fully understand how this disease operates within the CNS.