COVID-19 invades the brain, new evidence
Recently, I wrote a piece about the new evidence showing that there is biological disturbance in long-haulers (see article here).
Now instead, we have got something looking not so good. It seems that the virus SARS-CoV-2 is capable of crossing the blood-brain-barrier. I will be using the term COVID-19 across this article to refer to both the disease and the virus (SARS-CoV).
The cerebrospinal fluid (CSF) is a colorless fluid present in both the brain and spinalcord. This liquid is usually tested when doctors suspect you might have an illness that could be affecting your nervous system, like a virus.
It is true that we had previous evidence of infection of the cerebrospinal fluid in COVID-19 patients. However, those were a handful of cases and the levels of COVID-19 found in the CSF were really low, which lead some scientist to propose blood contamination rather than direct COVID-19 infection (Lucchese, 2020).
Then, another study (currently under review), a group of scientist from France proposed that viral persistence might be causing the long-term anosmia (loss of smell). They showed (in hamsters) that as long as the virus was infecting the olfactory epithelium and the olfactory bulb, the anosmia persisted. This could be extended to several months. They argued that they proved that COVID-19 can infect the central nervous system (CNS). However, they also discussed at the end of their article that COVID-19 infecting the central nervous system is highly debatable (De Melo et al, 2020).
Anyway, the point of this post was to highlight another article published in the prestigious journal Nature Neuroscience (Rhea et al, 2020). They injected a spike of the virus (S1) into mice and discovered that it was capable of crossing the blood-brain barrier (BBB). The BBB is a super selective border that prevents things in the blood from crossing into the nervous system. In addition, the spike was capable of traveling to other organs (lungs, spleen, liver and kidneys).
Many people think the brain has no defenses, but this is untrue. There is such a thing called Neuroimmune system. William Banks, one of the authors, highlighted that when these proteins detach from the virus, it can cause an apocalypsis in the brain, as the brain releases cytokines to defend itself. This can lead to inflammation, which can lead to neuronal damage. Finally, the researchers found that once in the brain, the spike was degraded there rather than sent somewhere else to be degraded. Interestingly enough, the researchers also were able to find that inflammation made the brain take higher quantities of the spike.
Follow me on Twitter (@tschmauck), I will be posting posts in English regarding COVID-19 from now on.
