Lead authors Dr. Manali Mukherjee of McMaster University and Professor Chris Carlsten of the University of British Columbia point out that an autoimmune disease develops when the immune system mistakenly attacks healthy parts or organs. of the body, instead of defending the body against disease. This is for example the case in conditions such as rheumatoid arthritis and lupus. Their study provides new clues about the nature of long COVID, and its effects on the immune system, which could lead to improvements in the treatment of these long forms of the disease.
“I am a researcher specializing in respiratory health with a background in the study of the immune system. When I felt the symptoms of long COVID, I started to wonder about the role of the immune system in this condition,” Dr. Manali Mukherjee writes.
The study is conducted among 106 patients diagnosed with COVID-19 between August 2020 and September 2021 as well as among a group of 22 healthy volunteers and a group of 34 patients, free of COVID but having previously experienced a respiratory infection. At 3, 6 and 12 months after recovery from infection, patients reported their symptoms of shortness of breath, cough or fatigue, typical symptoms of long COVID. The researchers also analyzed blood samples for particular antibodies, including those that contribute to autoimmune diseases. The analysis reveals that:
- 80% of COVID-19 patients have 2 or more of these autoantibodies in their blood 3 or 6 months after infection;
41% of COVID-19 patients have 2 or more of these antibodies in their blood, one year after infection;
- most healthy controls do not, with those with non-COVID respiratory infection having extremely low levels of these antibodies;
- 2 specific “auto-antibodies” (U1snRNP and SSb-La), as well as other inflammation-causing cytokines are still detected in approximately 30% of COVID patients, 1 year after infection;
- this finding is even more evident in COVID participants still suffering from fatigue and shortness of breath.
Overall, the study finds that while in the majority of participants showing autoantibodies shortly after infection, this is no longer the case 1 year later, in some patients the autoantibodies persist and these are precisely those patients who are more likely to experience long COVID symptoms.
The researchers therefore call on their colleagues to look for signs of autoimmune disease in patients with symptoms of long COVID. Finally, they note that the detection of these autoantibodies, months after the COVID infection confirms at least the long COVID as a systemic disease.
“We knew that certain infections can, in some cases, trigger longer-term autoimmune diseases like rheumatoid arthritis. This study adds to growing evidence that similar processes may be involved in long COVID.”