Post-COVID-19 conditions change a person’s immunological response: Study

A recent study from Cedars-Sinai’s Smidt Heart Institute suggests that prolonged COVID-19 may be caused by immune system dysfunction. The study, published in BMC Infectious Diseases, discovered that people with long COVID-19 produced antibodies against the virus that causes COVID-19 for months longer than expected after receiving the COVID-19 vaccine.

When a person is infected, the immune system usually responds by producing antibodies that prevent germs from entering cells. Vaccines mimic an infection so that the body’s immune system knows when it encounters a virus to release specific antibodies. When the suspected infection is gone, the immune system eventually stops producing antibodies in both cases.

“There’s general consensus that some level of aberrant immune response happens in long COVID-19, and this study adds to the evidence to suggest this is true,” said Catherine Le, MD, co-director of the Cedars-Sinai COVID-19 Recovery Program and a senior author of the study.

Long COVID-19 is a condition in which people experience COVID-19-related symptoms three months or more after being infected with the virus that causes COVID-19. It is estimated that 65 million people worldwide suffer from Long COVID-19. Fatigue, shortness of breath, and cognitive dysfunction such as confusion and forgetfulness are common symptoms. Some symptoms can be incapacitating.

Researchers analysed blood samples from 245 people diagnosed with long COVID-19 and 86 people who had COVID-19 and recovered to study the immune response of people with long COVID-19. All participants in the study had either one or two doses of a COVID-19 vaccine regimen.

“We examined one part of the immune system response, the production of antibodies, which is mediated by immune cells called B-cells,” Le explained.

The researchers focused on two types of antibodies that attack the virus that causes COVID-19. One of these is the spike protein antibody, which targets a protein on the virus’s surface. The nucleocapsid antibody, on the other hand, attacks the part of the virus that allows it to replicate.

The researchers discovered that people with long COVID-19 had higher levels of spike protein and nucleocapsid antibodies than people without long COVID-19. Antibody levels in people without long COVID-19 began to decline eight weeks after receiving a dose of the COVID-19 vaccine, as expected. People with long COVID-19, on the other hand, had elevated antibody levels, particularly nucleocapsid antibodies.

“What you would expect after getting a COVID-19 vaccination is a jump in your spike protein antibody levels, but you wouldn’t expect a significant increase in nucleocapsid antibody levels,” said Susan Cheng, MD, MPH, the Erika J. Glazer Chair in Women’s Cardiovascular Health and Population Science, director of the Institute for Research on Healthy Aging in the Department of Cardiology at the Smidt Heart Institute, and a senior author of the study. “You would also expect these levels to eventually decrease and not persist for so long after vaccination.”

According to the study’s authors, while this study shows that long COVID-19 affects the immune system, it is too early to draw firm conclusions from these findings.

“Theoretically, the production of these antibodies could mean that people are more protected from infection,” Le said. “We also need to investigate if the elevated immune response corresponds with severity or number of long COVID-19 symptoms.”

Blood samples from people with long COVID-19 are still being studied by researchers. They hope to find a measurable molecule that can be used to diagnose long COVID-19 and learn more about the biological processes that cause it.