The debilitating neurological symptoms of long COVID are often due to the body's mistaken attack on itself, according to discoveries from two studies that could lead to effective treatments for the condition and changes in blood donation policies.
In both studies, researchers collected so-called autoantibodies in blood from volunteers with long COVID. Normally, the immune system's antibodies defend the body from attack, but autoantibodies – commonly seen after acute viral infections and persisting during long COVID – attack the body by mistake.
When the human autoantibodies were infused into healthy mice, the mice developed neurological features mimicking those of the patients, including fatigue, loss of balance, pain sensitivity, and nerve fiber damage.
In one experiment, the effect was reproduced even when the autoantibodies were collected from patients two years after the initial infection, according to a paper in Cell Reports Medicine.
“This new awareness of the physiology of long COVID will enable us to identify a number of effective treatments for autoimmunity that could significantly improve the symptoms of millions of people with this chronic condition,” Dr. David Putrino from the Icahn School of Medicine at Mount Sinai in New York, coauthor of a separate study published in Cell, said in a statement.
“Before we had no way of predicting who would benefit from (existing) therapies,” he said. “Our study now shows that if you are in a subgroup of long COVID patients who have autoantibodies circulating in your body... you may be a good candidate for these drugs.”
A commentary in Cell said the two studies “provide compelling evidence that autoantibodies directly contribute to symptom generation in a subset of people with long COVID," but neither study provides definitive proof of a single, central mechanism behind the condition.
In addition to their clinical significance, Putrino believes the findings carry an urgent public health warning regarding blood donation.
“In the UK, having long COVID is an exclusion for donating blood, while in the United States these individuals are still allowed to donate,” he said.
“Given the dangers that (autoantibodies in) plasma from people with long COVID can pose for others, this country should be considering fundamental changes to its donation policies.”
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