COVID patients face risk of self-attacking antibodies

A patient is brought into a Brooklyn hospital that has seen a high number of COVID-19 patients on January 27, 2021 in New York City. (Credit: Spencer Platt/Getty Images)

A new study shows that at least 1 in 5 hospitalized COVID-19 patients develops antibodies that attack their own tissue within a week of admission.

Autoantibodies are antibodies directed at their own tissues or at substances immune cells secrete into the blood. Autoantibodies can be early harbingers of full-blown autoimmune disease.

“If you get sick enough from COVID-19 to end up in the hospital, you may not be out of the woods even after you recover,” says PJ Utz, professor of immunology and rheumatology at Stanford Medicine.

As reported in Nature Communications, researchers looked for autoantibodies in blood samples drawn during March and April of 2020 from 147 COVID-19 patients at three university-affiliated hospitals: Philipps University Marburg in Germany, the University of Pennsylvania, and Stanford, and from a cohort of 48 patients at Kaiser Permanente in California. They used blood samples drawn from other donors prior to the COVID-19 pandemic as controls.

The researchers identified and measured levels of antibodies targeting the virus; autoantibodies; and antibodies directed against cytokines, proteins that immune cells secrete to communicate with one another and coordinate their overall strategy.

Upward of 60% of all hospitalized COVID-19 patients, compared with about 15% of healthy controls, carried anti-cytokine antibodies, the researchers found. This could be the result of immune-system overdrive triggered by a virulent, lingering infection. In the fog of war, the abundance of cytokines may trip off the erroneous production of antibodies targeting them, Utz says.

If any of these antibodies block a cytokine’s ability to bind to its appropriate receptor, the intended recipient immune cell may not get activated. That, in turn, might buy the virus more time to replicate and lead to a much worse outcome.

On the hunt for autoantibodies

For about 50 patients, blood samples drawn on different days, including the day they were first admitted, were available. This allowed the researchers to track the development of the autoantibodies.

“Within a week after checking in at the hospital, about 20% of these patients had developed new antibodies to their own tissues that weren’t there the day they were admitted,” Utz says. “In many cases, these autoantibody levels were similar to what you’d see in a diagnosed autoimmune disease.”

In some cases, the presence of those newly detected autoantibodies may reflect an increase, driven by the immune response, of antibodies that had been flying under the radar at low levels, Utz says. It could be that inflammatory shock to the systems of patients with severe COVID-19 caused a jump in previously undetectable, and perhaps harmless, levels of autoantibodies these individuals may have been carrying prior to infection.

In other cases, autoantibody generation could result from exposure to viral materials that resemble our own proteins, Utz says.

“It’s possible that, in the course of a poorly controlled SARS-CoV-2 infection—in which the virus hangs around for too long while an intensifying immune response continues to break viral particles into pieces—the immune system sees bits and pieces of the virus that it hadn’t previously seen,” he says. “If any of these viral pieces too closely resemble one of our own proteins, this could trigger autoantibody production.”

Another reason to get the vaccine

The finding bolsters the argument for vaccination, he adds. Vaccines for COVID-19 contain only a single protein—SARS-CoV-2’s so-called spike protein—or the genetic instructions for producing it. With vaccination, the immune system is never exposed to—and potentially confused by—the numerous other novel viral proteins generated during infection.

In addition, vaccination is less intensely inflammatory than an actual infection, Utz says, so there’s less likelihood that the immune system would be confused into generating antibodies to its own signaling proteins or to the body’s own tissues.

“Patients who, in response to vaccination, quickly mount appropriate antibody responses to the viral spike protein should be less likely to develop autoantibodies,” he says.

Indeed, a recent study in Nature to which Utz contributed showed that, unlike SARS-CoV-2 infection, the Pfizer COVID-19 vaccine doesn’t trigger any detectable generation of autoantibodies among recipients.

“If you haven’t been vaccinated and are telling yourself, ‘Most people who get COVID get over it and are OK,’ remember that you can’t know in advance that when you get COVID-19 it will be a mild case,” Utz says.

“If you do get a bad case, you could be setting yourself up for a lifetime of trouble because the virus may trip off autoimmunity. We can’t say yet that you’ll definitely get an autoimmune disease—we haven’t studied any patients long enough to know whether these autoantibodies are still there a year or two later, although we hope to study this—but you certainly might. I wouldn’t want to take that chance.”

Utz intends to study blood samples from SARS-CoV-2-infected people who are asymptomatic or who’ve had mild COVID-19 symptoms. That could help determine whether the massive hyperactivation of the immune system, which doesn’t occur in mildly symptomatic or asymptomatic people, is what causes trouble, or whether the mere molecular resemblance of SARS-CoV-2 proteins is enough to trigger autoantibody generation.

Additional coauthors are from the University of Pennsylvania, Philipps Marburg University, the University of Tennessee, Oklahoma Medical Research Foundation, Kaiser Permanente Northern California, and Stanford.

Funding for the study came from the National Institutes of Health, the Henry Gustav Floren Trust, the Parker Institute for Cancer Immunotherapy, the Sean N. Parker Center, the Frank Quattrone and Denise Foderaro Family Research Fund, the Chan Zuckerberg Biohub, the Allen Institute for Immunology, the CEND COVID Catalyst Fund, the Chen Family Research Fund, the Carreras Foundation, the Foundation for Pathobiochemistry and Molecular Diagnostics, Universities Giessen and Marburg Lung Center, the German Center for Lung Research, the Deutsche Forschungsgemeinschaft, and Stanford Medicine.

Source: Stanford University