Some Covid-19 patients are attacked by their own immune systems – a new study explains why

  • In a new study, researchers investigated the production of antibodies by the immune system in Covid-19
  • They found that autoantibodies target the tissues of some patients, resulting in severe Covid-19 disease
  • The researchers encourage testing patients post-Covid-19 recovery

Some people are at greater risk of severe Covid-19, the disease caused by SARS-CoV-2. According to a recent study, autoreactive antibody production may explain why this happens.

The study, which was published in preprint server medRxiv, while awaiting peer-review, explains that instead of targeting disease-causing microbes, these immune proteins, called autoantibodies, target the tissues of patients suffering from severe Covid-19.

The researchers explained that their findings have a potential impact on both acute patient care and infection recovery.

Explaining autoantibodies

Harvard Health explains that autoantibodies attack several different parts of the body, resulting in inflammation and tissue damage in the joints, skin, kidney, nervous system (brain and spinal cord), blood, and heart, among others.

More than this, they can also attach themselves to body chemicals and form abnormal molecules (known as “immune complexes”) that trigger additional inflammation when they are deposited in the body’s organs and tissues.

Previous studies during the earlier stages of the pandemic found that abnormal blood clotting in Covid-19 patients is more likely to lead to complications and admissions to the intensive care unit (ICU).

In the recent study, the four researchers highlight that these autoantibodies play a role in dangerous blood clots forming in these Covid-19 patients, and that, more recently, they have also been found to inactivate important components of viral immune defences in a large number of patients with severe Covid-19.

The study authors, from the Lowance Center for Human Immunology at Emory University, Georgia, previously investigated immune responses contributing to autoantibody production in autoimmune disorders such as lupus – which is believed to develop when a person’s body's immune system mistakenly attacks the body's own tissues – and more recently severe Covid-19 cases.

Autoantibodies are usually associated with specific disease types, the lead author, Matthew Woodruff, Instructor at Lowance Center for Human Immunology, Emory University, wrote in an article for The Conversation.

According to Woodruff, patients with lupus, for instance, will often have antibodies that target their own DNA, whereas patients with the autoimmune disorder, rheumatoid arthritis, are less likely to contain those antibodies, but are more likely to show positive tests for rheumatoid factor – antibodies that target other antibodies.

What the researchers did

For their study, the team analysed the medical charts of 52 Covid-19 patients in ICU (none were reported to have a history of autoimmune disorders). However, the patients were tested during infection for autoantibodies found in an array of disorders.

More than half of the 52 patients tested positive for autoantibodies, and in patients with the highest levels of c-reactive protein (a marker of inflammation) in the blood, more than two-thirds were found to have immune systems producing antibodies that were attacking their own tissue.

“Importantly, we believe that the autoreactive responses we have identified here are specific to the SARS-CoV-2 infection – there is no reason to believe that similar results would be expected through vaccination against the virus,” Woodruff wrote.

Digging a bit deeper

Although the study's findings are enlightening, they do note that their data doesn't reveal certain information, such as to what extent these autoantibodies contribute to the most severe symptoms of Covid-19.

What the authors believe is most concerning is the possibility that these responses could self-perpetuate in some patients and result in the emergence of new, permanent autoimmune disorders.

However, they suggest autoreactive testing, as this might help researchers understand whether some cases of “long-hauler” Covid-19 could be related to persisting autoantibodies.

If this is found to be the case, there is positive news: these patients might respond to the same immune-targeted therapies that have been successful in Multisystem Inflammatory Syndrome in Children (MIS-C) where autoantibody production has been reported.

MIS-C, initially named paediatric inflammatory multisystem syndrome (PMS), describes a relatively new health condition seen in children who have been infected with the Covid-19 virus, Health24 previously reported.

“Finally, by testing patients immediately following Covid-19 recovery, we can establish baselines and begin to track the possible emergence of new cases of autoimmunity following this terrible disease, and plan early rheumatological intervention if needed,” Woodruff wrote.

READ | Researchers discover a second 'key' that makes the new coronavirus infectious

READ | PICS: Swab gets stuck inside woman’s lung during coronavirus test

READ | Lockdown: Scientists looked at personality traits to understand why some defy the rules

Image: Pexels/Anna Shvets

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