A dramatic “friendly fire” from the immune system could trigger a severe Covid-19 illness and leave patients with a “long covid” – when medical problems persist for a significant period of time after being infected with the virus, scientists say.
Yale University researchers found that Covid-19 patients had high levels of abnormal antibodies in their blood that targeted organs, tissues, and the immune system rather than fighting the invading virus.
Scientists compared immune responses in patients and non-infected individuals and found a variety of different antibodies to the former. These block the antiviral defenses, destroying useful immune cells and attacking the body at many points, from the brain, blood vessels and liver to connective tissue. And gastrointestinal tract.
Further tests revealed that patients had high levels of “autoantibodies” in their blood, making their disease worse. Covit-19 patients had higher levels of antibodies than those with lupus, an autoimmune disease caused by similar leading antibodies.
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“Covit-19 patients develop autoantibodies that actually interfere with the immune response to the virus,” said Aaron Ring, Yale’s immune biologist and senior author of the study. Many other autoimmune diseases attack certain parts of the body that are known to be damaged in infected people.
“We are confident that these autoantibodies will be harmful to Govit-19 patients,” Ring said, adding that the harmful effects may continue once the infection has subsided, thus leaving patients with long-term medical problems. “Since the antibodies last a long time, it is conceivable that they may contribute to the development of chronic goiter diseases,” he said.
The ring teamed up with Akil Iwazaki, a professor of immunology at Yale, to screen 194 patients and hospital staff with the severity of Kovid infection for autoantibodies targeting nearly 3,000 human proteins. Antibodies inactivate viruses by binding to proteins on the surface of the virus, but autoantibodies form incorrectly and bind to proteins released or released by human cells.
Scientists describe a “dramatic increase in autoantibody reactions” in Kovit patients compared to 30 healthy hospital staff who are virus-free. Some patients had autoimmune bodies prior to Govit-19 infection, while others appeared and increased as the disease progressed.
More than 5% of hospitalized patients had autoantibodies, which weakened a key arm of the immune system, which is regulated by proteins called interferons. These patients could not control the level of the virus in their body and therefore developed a very serious disease.
In two particularly severe examples of friendly fire, other patients had autoantibodies that target B cells, cellular plants that trigger antibodies to fight the virus, while a patient had autoimmune bodies that appeared to destroy many of their protective D-cells.
Rather than blaming one type of autoantibody, scientists believe that Covit-19 worsens when different guiding antibodies arise in the same patient. Experiments in mice with certain autoantibodies confirmed that they were more susceptible to infection and increased the risk of dying from the disease.
“The total amount of these multiple responses may explain a significant portion of clinical variability in patients,” the authors write.
Scientists have long known that conditions such as rheumatism, lupus and multiple sclerosis are triggered by dysfunction of the immune system and attacking the body. But little is known about the potential for triggering viral infections and autoimmune reactions. Work is now underway to determine whether autoantibodies cause chronic symptoms in patients with diseases such as Ebola and chikungunya, and after immunotherapy.
The ring said that if covid-19 autoantibodies are carried in the body they may play a role in the long covid. “Post-goiter symptoms can be caused by autoimmune bodies for a long time and will get better even after the virus is removed from the body,” he said. “As such, there are immunosuppressive therapies used for rheumatism that can be effective.” Longcovite is estimated to affect 10% of people aged 18 to 49, rising to one in five over the age of 70.
Danny Aldman, a professor of immunology at Imperial College London, who was not involved in the study, said autoimmune bodies can well explain various goiter symptoms and chronic diseases that some patients experience.
“I think this is very likely, especially when compared to Ebola and Chikungunya. Immunity seems to be a big part of the response. A large part of our laboratory direction for the coming months is trying to associate long-term symptoms with autoimmune profiles,” he said.