Where does long covid come from? scientists increasingly see symptoms as signs of autoimmune disease
- The symptoms of long covid increasingly resemble those of an autoimmune disease. Indications that a certain type of antibody causes inflammation in patients with long covid.
- The antibodies attack the body’s own proteins and are a characteristic feature of many autoimmune diseases.
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patients with long covid may soon get the long awaited answer to their question why they still suffer from the consequences of corona infection. The national institutes of health (NHI), an agency of the u.s. department of health and human services, now plans to conduct a $470 million study to investigate the causes of long covid. However, some clues to its possible origins are already emerging: the virus could trigger an autoimmune response – which then causes persistent symptoms such as fatigue, shortness of breath, loss of smell, muscle pain or brain fog.
"we can’t yet say with complete certainty that it’s an autoimmune disease, but it’s starting to look that way," university of arkansas physician john arthur told business insider in an interview. Arthur and his research team have just published a study in the journal plos one.
the researchers’ suspicion, which was confirmed in the study: some patients with long covid develop so-called auto-antibodies during infection. These attack the body’s own proteins, which in turn can lead to harmful inflammation. Such a reaction is typical for autoimmune diseases – and could also be the trigger for long covid, according to the research team. "so far, everything kind of fits together. We’re just not quite there yet in terms of understanding what’s going on behind the scenes," says Arthur.
If the theory of the researchers around john arthur is confirmed, this would have implications for how long covid patients are treated. Certain antihypertensive drugs could then be used, for example, to stop the harmful inflammatory response. In addition, some study results suggest that the corona vaccines may also help alleviate the long covid symptoms. This may be due to the regulation of antibodies by the vaccines, the research team suggests.
In many long covid patients, the immune system seems to fight their own antibodies
At least one-third of all corona patients have at least one persistent symptom of covid-19 over twelve weeks or longer. This is the result of a recent study that has yet to be verified by independent experts. Scientists have been looking at what the reasons for long covid might be for more than a year.
"i see a lot of younger patients with chronic covid symptoms. Many of them, however, had no health problems before the corona infection, especially no lung disease," says dixie harris, for example. She is a pulmonologist at intermountain healthcare in utah, u.s. "they were totally active beforehand, running marathons and playing sports. Now they rely on external oxygen."
researchers know that the bodies of sick people develop antibodies to neutralize the coronavirus. However, in many long covid patients, the immune system seems to mistake these antibodies for a foreign threat. The body then forms auto-antibodies to fight its own supposedly harmful antibodies.
arthur’s team analyzed blood samples from 32 long covid patients who had donated plasma at the university of arkansas. Another 15 who had been treated at the local hospital were also included in the study. The analysis shows that about 81 percent of the plasma donors and 93 percent of the hospitalized patients had developed a certain type of auto-antibody. These inhibited the so-called ACE2 enzymes, which serve as an "entry port" for the coronavirus to enter the cells. But at the same time, these enzymes are essential for calming down the immune system. If there are not enough enzymes of this type, the immune system can cause too much inflammation. "inhibition of the ACE2 enzyme basically clogs up the whole system," explains arthur. "it’s like having a clump of hair down the drain pipe. The water can no longer drain away and starts to accumulate on top."
However, further research is needed to provide a clear explanation. It is not yet possible to say with certainty whether these ACE2 antibodies actually cause long covid, the researchers say. For example, it is not yet certain whether severe infections produce more auto-antibodies than mild illnesses. Results of a study published in may in "nature" had pointed to this possibility. John arthur emphasizes, however, that long covid is also found in people with mild disease progression.
Scientists consider antihypertensive drugs as possible treatment
However, the results of the study by arthur’s team suggest that there are potentially other treatment options for long covid patients than those that have been used so far – such as the previously mentioned drugs that are normally used to treat hypertension.
The reason: ACE2 enzymes normally contribute to the regulation of blood pressure. They convert a substance that increases blood pressure into one that improves blood flow. Long covid could prevent this conversion process so that the substance, which increases blood pressure, could cause harmful levels of inflammation, it is thought. Possibly drugs against high blood pressure could therefore attenuate this inflammatory reaction.
At the same time, the study conducted by arthur suggests that corona vaccines may balance the levels of covid antibodies and auto-antibodies in patients with long covid. a british study published in march found that symptoms improved in 57 percent of those affected by long covid after vaccination. However, the study and its results still have to be verified by independent experts. arthur’s team also wants to do research for this. "this is one of the issues we will be looking at in the next phase," he says. "we want to gain insight into how vaccination status affects the frequency of ACE2 antibodies."