Scientists Report “Rogue Antibodies” Behind Severe Clotting With COVID-19

Illustration of antibodies (y-shaped) responding to an infection with the new coronavirus SARS-CoV-2. The virus emerged in Wuhan, China, in December 2019, and causes a mild respiratory illness (covid-19) that can develop into pneumonia and be fatal in some cases. The coronaviruses take their name from their crown (corona) of surface proteins, which are used to attach and penetrate their host cells. Once inside the cells, the particles use the cells’ machinery to make more copies of the virus. Antibodies bind to specific antigens, for instance viral proteins, marking them for destruction by other immune cells, such as the macrophage white blood cell behind the virus.
"Rogue antibodies" that seem to trigger severe blood clotting and illness in COVID-19 patients have been identified by scientists.

HealthDay News — “Rogue antibodies” that seem to trigger severe blood clotting and illness in COVID-19 patients have been identified by scientists. The report was published online Feb. 17 in Arthritis & Rheumatology.

Their analysis of blood samples from 244 patients hospitalized for COVID-19 revealed circulating antiphospholipid antibodies. These autoantibodies are more common in people with autoimmune disorders, such as lupus, but can be activated in response to viral infections and also activate other immune responses, according to the study authors.

Specifically, the investigators found that blood samples from the COVID-19 patients had higher levels of the antibody immunoglobulin (Ig)G than blood samples from people without COVID-19. Higher levels of IgG were associated with greater COVID-19 disease severity, such as requiring breathing assistance.

When the researchers removed IgG from the COVID-19 patients’ blood samples, there was a decline in molecular indicators of “blood vessel stickiness.” When IgG antibodies were added to blood samples from people without COVID-19, there was an increase in the blood vessel inflammatory response that can lead to clotting.

Because all organs have blood vessels in them, higher levels of IgG that can increase the “stickiness” of blood vessels in COVID-19 patients may help explain why the virus can damage so many organs, including the heart, lungs, and brain, study co-corresponding author Yogen Kanthi, M.D., a cardiologist who leads the Laboratory of Vascular Thrombosis and Inflammation at the U.S. National Heart, Lung, and Blood Institute, said in a U.S. National Institutes of Health news release. The researchers observed similar patterns after analyzing blood samples from 100 patients hospitalized for sepsis, which can leave the body in inflammatory shock following a bacterial or viral infection.

The study authors suggested that future research assess the potential benefits of screening COVID-19 patients for antiphospholipids and other autoantibodies and do so at earlier stages of infection. This may help identify patients at risk for severe blood clotting, vascular inflammation, and respiratory failure. Other studies could assess the potential benefits of giving these patients treatments to protect their blood vessels or fine-tune their immune system, Kanthi and colleagues noted.

Abstract/Full Text (subscription or payment may be required)