But the study added another possible route: they also discovered activated immune cells in the brain and olfactory mucosa; that is, RNA virus in the upper part of the nose, suggesting that the infection followed this route, giving it a direct line to the brain.
The leftover genetic material was small, but this could be because the autopsy was performed, on average, one month after the death of the person affected with COVID-19.
According to the study, the same proteins found on the outside of SARS-CoV-2 were also found in the cells of some subjects that the researchers identified as neurons. Again, evidence that the virus is finding some way to cross the blood-brain barrier and into the brain through the long, threadlike projections of the olfactory nerves.
“These data support the idea that SARS-CoV-2 can use the olfactory mucosa as a port of entry to the brain. Once inside the olfactory mucosa, the virus seems to use neuroanatomical connections, such as the olfactory nerve, to reach the brain ”, clarifies Frank Heppner, author of the study and director of the Department of Neuropathology at the Charité-Universitätsmedizin in Berlin.
How the virus moves from nerve cells is unclear.
“Our data suggest that the virus moves from one nerve cell to another to reach the brain,” adds Helena Radbruch, co-author of the work. “However, it is likely that the virus is also transported through the blood vessels, as evidence of the virus was also found in the blood vessel walls of the brain.”.