Studies suggest that mild COVID infection induces sustained antibody protection

ST. Louisouri, Missouri — Even months after recovering from a mild COVID-19 case, researchers say that there are still immune cells in the body that shed antibodies to the virus that causes COVID. on the other hand.

A study from Washington University in St. Louis Medical School was published in the journal on Monday. NatureMild cases of COVID remain infected with persistent antibody protection, suggesting that repeated attacks of the disease are likely to be rare.

“Last fall, there were reports of antibody decline shortly after being infected with the virus that causes COVID-19, which the mainstream media interpreted as meaning immunity was short-lived,” said senior author Dr. Ali Elbedi. I did. Pathology and immunology, medicine and molecular microbiology. “But that’s a misunderstanding of the data. It’s normal for antibody levels to drop after an acute infection, but not to zero. They’re plateaus. Here, to people 11 months after the first symptoms. Antibody-producing cells have been found. These cells live and produce antibodies for the lives of the rest of us. This is strong evidence of long-lasting immunity. “

During viral infection, antibody-producing immune cells proliferate rapidly and circulate in the blood, pushing antibody levels high in the air. When the infection is cleared, most of these cells die and blood antibody levels drop. A small population of antibody-producing cells, called long-lived plasma cells, migrate to the bone marrow and settle there, where they continuously secrete low-level antibodies into the bloodstream to prevent another encounter with the virus.

Ellebedy recognizes that the key to understanding whether COVID-19 leads to long-term antibody protection lies in the bone marrow. Ellebedy collaborates with other professors to determine whether people who have recovered from mild cases of the virus have long-lived plasma cells that produce antibodies that specifically target SARS-CoV-2. Followed antibody levels in blood samples from COVID survivors.

The team had already enrolled 77 participants who were providing blood samples at 3-month intervals approximately one month after the initial infection. Most participants were mild cases and only 6 were hospitalized.

Ellebedy et al. Obtained bone marrow from these 18 participants. COVID occurred 7-8 months after the first infection, and 5 of them returned to provide a second sample 4 months later. For comparison, scientists also obtained bone marrow from 11 people who never had COVID.

As expected, blood antibody levels in COVID-19 participants dropped rapidly in the first few months after infection and then almost leveled off, with some antibodies detectable even 11 months after infection. In addition, 15 of the bone marrow samples of people infected with COVID-19 contained antibody-producing cells. Such cells were still found in 5 people who returned to provide a second bone marrow sample after 4 months. None of the 11 people who had never experienced COVID-19 had such antibody-producing cells in their bone marrow.

“People with mild cases of COVID-19 get rid of the virus from their bodies 2-3 weeks after infection, so no virus causes a vigorous immune response 7-11 months after infection,” Ellebedy said. Says. “These cells are not dividing. They are stationary, they just sit in the bone marrow and secrete antibodies. They have been doing that ever since the infection was resolved, and they I will continue it indefinitely. “

Researchers speculate that immunity may last longer in people who are infected and asymptomatic. However, it has not yet been investigated whether people who have tolerated more severe infections will be protected from future bouts of the disease, they said.

“It can go in either direction,” said author Dr. Jackson Turner, a pathology and immunology instructor. “Inflammation plays a major role in severe COVID-19, and too much inflammation can lead to a defective immune response. But on the other hand, the reason people really get sick is often in the body. This is because there are many viruses in and around them, which can lead to a good immune response. Therefore, it is not clear. Reproduce the study in people with moderate to severe infections. You need to understand if you are likely to be protected from reinfection. “

Ellebedy and colleagues are currently investigating whether vaccination also induces long-lived antibody-producing cells.

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