A research team at Tokyo's Keio University has found that the TOKYO nerve symptoms experienced by some COVID 19 patients may be caused by the infection of immune system cells that clean up the brain.
People with long-term effects of a coronaviruses or so-called long COVID sometimes exhibit symptoms associated with central nervous system damage, such as convulsions, cognitive impairment, and brain fog, a catchall term that includes low concentration, forgetfulness, confusion, and slowed thinking.
The coronaviruses can enter the brain but it is difficult for it to invade nerve cells, and the mechanism for how the brain was infected had remained a mystery. What was known was that COVID 19 patients had a buildup of inflammatory substances in their brains.
A Keio University research team, led by neurology professor Hideyuki Okano, used induced pluripotent stem iPS cells to produce cells including neurons and microglia, a type of immune cell that cleans unwanted substances out of the brain. They infected these cells with imitation pseudoviruses that are similar to the original coronaviruses and subsequent strains, including the omicron variant.
Of all the cell types in the experiment, the team found that only the microglia were infected at a high rate by all the pseudovirus strains. The researchers believe that infected microglia start to behave abnormally or die, leading to the boost in inflammatory substances found in the brains of COVID 19 patients and subsequently neural tissue damage.
The results raise the possibility that the coronaviruses are not completely eliminated from the brain due to a decline in microglia and other immune functions, resulting in continued microglia infection and prolonged aftereffects.
Research team member Yoshitaka Kase, a specially appointed professor of neuroscience at Keio University, said anti-inflammatory drugs and drugs that suppress the function of substances released by microglia could be a treatment for COVID 19's aftereffects.
The results of the study were published in the journal Experimental Neurology.