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Medicine Science

COVID-19 Virus Does Not Infect Human Brain Cells, Study Suggests (theguardian.com) 65

An anonymous reader quotes a report from The Guardian: The virus that causes Covid-19 does not infect human brain cells, according to a study published in the journal Cell. The findings will raise hopes that the damage caused by Sars-CoV-2 might be more superficial and reversible than previously feared. The study contradicts earlier research that suggested the virus infects neurons in the membrane that lines the upper recesses of the nose. This membrane, called the olfactory mucosa, is where the virus first lands when it is inhaled. Within it are olfactory sensory neurons (OSNs), which are responsible for initiating smell sensations. They are tightly entwined with a kind of support cell called sustentacular cells.

In the new study, Belgian and German researchers claim that the virus infects sustentacular cells but not OSNs. "That is just a critical distinction," said the senior author Peter Mombaerts, who directs the Max Planck Research Unit for Neurogenetics in Frankfurt, Germany. "Once you believe that olfactory neurons can be infected, there is a quick route into the olfactory bulb and then you're in the brain already." The olfactory bulb, at the front of the brain, is where neural input about odors is first processed. If the virus penetrated this structure it could theoretically spread to deeper brain regions where it could do lasting damage -- especially since, unlike OSNs, most neurons are not regenerated once lost. But if the virus only infects the sustentacular cells, then the damage could be less long-lasting. Both pathways could explain the olfactory dysfunction that afflicts an estimated half of all Covid-19 patients. In one in 10 of those, the loss or change of smell is long-term, perhaps permanent. Mombaerts says this could be the result of support for the OSNs breaking down, even if they themselves are not infected. They may function below par, or stop functioning altogether, until the sustentacular cells regenerate.

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COVID-19 Virus Does Not Infect Human Brain Cells, Study Suggests

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  • Whew! Now lets worry about the cells on the other end.

    • Re:Spermy. (Score:5, Informative)

      by Rei ( 128717 ) on Friday November 05, 2021 @04:40AM (#61959337) Homepage

      As usual, the headline doesn't accurately reflect the work. The study showed that yes, both respiratory and olfactory mucosa are infected, and not the nerve cells in the olfactory mucosa, but their supporting supporting sustentacular cells. But they also found the virus abundant in the cranial cavity. It however was not infecting the parenchyma (functional tissue), but the leptomeninges (the tissue that surrounds the brain). Normally the tissue surrounding the brain, when infected, gets inflamed and causes meningitis, but meningitis is relatively uncommon with COVID. They also noticed a lack of negative-sense mRNA in the leptomeninges (note: there were only 11 subjects, 37% of the cohort). They interpret this as the virus not actively replicacting, and think that they may have been looking at whole virions. The question then still becomes, what the heck are they doing in the cranial cavity? The authors have three theories. One, that they traveled up there alongside (but not within) the olfactory nerve; two, that they leaked out of the blood vessels in the meninges en masse; and three, that they're free mRNA. In each case, the authors are concerned about triggering immune or autoimmune reactions within the brain (something a number of studies have shown), and suggest that this may as well - not just attack on sustentacular cells in the olfactory mucosa - impact or be responsible for the anosmia (one of the challenges they had to explain was why other viruses that infect sustentacular cells don't cause anosmia).

      Their overall conclusion, however, was that they found absence of evidence for (but not evidence for absence of) direct neuroinvasion, but rather, side impacts which can affect the nervous system.

  • by angel'o'sphere ( 80593 ) <angelo,schneider&oomentor,de> on Friday November 05, 2021 @12:49AM (#61959137) Journal

    What about my testicles?

  • Then the plan will be complete. Watch out for booster #5.

  • by Antique Geekmeister ( 740220 ) on Friday November 05, 2021 @01:22AM (#61959163)

    While the virus may not directly affect neural tissue, collapsing unattended at home without help or asphyxiating from Covid related lung damage can indeed cause brain damage. Indirect complications from illness should not be ignored.

  • is not like you can die from it... But my brain cells will be preserved!
  • Doesnt effect the taste at all.
  • This is excellent news for people who are worried about the longterm effects of minor COVID cases they have experienced, and for people who are unlikely to suffer a severe case (i.e. kids).

    For others, it is not an indication that there is no neurological risk from contracting COVID, as general inflammation, lack of oxygen (from lungs and heart being attacked), and strokes all can still cause permanent damage, and it's a clinical fact that brain damage has been observed.

  • by Tough Love ( 215404 ) on Friday November 05, 2021 @04:50AM (#61959355)
    • by fazig ( 2909523 ) on Friday November 05, 2021 @05:50AM (#61959415)
      I don't see any major contradictions there.
      Just because a pathogen does not 'infect' a certain type of cell, it doesn't mean that the presence of such a pathogen in your system together with an immune response also can't possibly 'affect' that same type of cell, that it doesn't 'infect'. After all the entire human body is a very complex system of interacting parts. Neurons do not exist in isolation of the rest of the body.

      Scientific terminology can be extremely pedantic, and it does that for a good reason of eliminating ambiguity as far as possible. Without understanding and applying the narrow definitions of scientific terminology, it's not rare that conflicts with colloquial use of those same words arise, which then easily leads to unwilling conflation and also willful equivocation.
      In other words, the devil's in the details, and one of the things that distinguishes the illiterate from the literate is that the latter is willing to bother to look into the details, while the former tends to be satisfied with an equivocation.
      • Fusing neurons together (from inside...) is not "affecting", that is "infecting".

        • by fazig ( 2909523 )
          No. Not really.
          I'd urge you to read both sources again, carefully.

          What you post suggests that the spike protein from the virus can induce fusing interconnected neurons and glial cells.
          Now the question is how does the spike protein get there?

          The researchers independently electroporated two neuronal populations – one with a GFP-expressing plasmid plus a plasmid containing the spike protein, and the other with a mCherry- expressing plasmid plus a plasmid containing the hACE2 receptor. The two neurona

      • Sad that your post got modded up, but I guess that just speaks to the education level of the current slashdotter.

  • The people whining about being injected with microchips for tracking via 5G or think that goat past created to fight parasites will somehow have an effect on a virus haven't been infected? That their comprehension of reality isn't being affected by covid? That they're just naturally delusional?

    Whew! That's good to know.

  • Covid maybe doesn't affect the brain, but the reaction to the disease showcases how damaged some brains already are.

  • Asking for my zombie friend.
  • Study suggests control group has brain cells.

All life evolves by the differential survival of replicating entities. -- Dawkins

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