October 23, 2021

Biology Reporter

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Mild travel via COVID-19 ensures long-lasting immunity to the virus

Mild travel via COVID-19 ensures long-lasting immunity to the virus

A study published in Nature Weekly shows that immune cells that produce antibodies from people with mildly Covid-19 disease may provide long-term protection against the coronavirus.

Therefore, recurrence of COVID-19 should be somewhat rare, rate the study authors (https://www.nature.com/articles/s41586-021-03647-4).

Last fall, there were reports that the antibodies (against SARS-CoV-2 – PAP) are rapidly disappearing after being infected with the virus that causes COVID-19, and well-known media have interpreted this as evidence that immunity against the coronavirus is not long-term. Permanent, ”commented study co-author Dr. Ali Al-Bedi of Washington University School of Medicine in St. Lewis (USA).

In his opinion, this is a wrong interpretation of the data. “It is normal for antibody levels to drop after an acute infection; however, it does not drop to zero, but it stabilizes. In our study we found the presence of antibody-producing cells 11 months after the first symptoms appear. These cells will live and produce antibodies for the rest of their lives. This is strong evidence of long-lasting immunity, ”Dr. Ellebedy evaluates.

During a viral infection, immune cells that produce antibodies to the virus divide and circulate in the blood rapidly. This causes the level of antibodies to rise sharply. As the infection clears, most of these cells die and antibody levels decrease. However, a small group of antibody-producing cells – so-called long-lived plasma cells – migrate to the bone marrow and settle there and consistently produce a small amount of antibodies. This is to protect you in the event that you next encounter the virus.

Dr. Ellebedy and colleagues screened 77 people after contracting COVID-19. Most of them had a mild history of COVID-19, with only six requiring hospitalization. Blood samples were taken from them at regular intervals, and from 18 patients, 7-8 months after infection, bone marrow samples were also taken. After another four months, another sample of bone marrow was collected from five of them. For comparison, the researchers also obtained bone marrow samples from 11 people who had never had COVID-19.

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As expected, the antibody levels in the blood of patients with a history of COVID-19 decreased rapidly in the first four months after infection, and then stabilized in most cases over the following seven months. Antibodies were detected 11 months after infection.

It was also found that in the bone marrow samples of patients 7-8 months after infection with COVID-19, cells that produced antibodies that specifically identified the coronavirus causing COVID-19 were present. These cells were still present in five patients who donated another sample of bone marrow 11 months after infection. However, it was not found in any of the 11 people who did not have COVID-19.

“These cells do not divide. They are asleep, they just sit in the bone marrow and produce antibodies” – comments Dr. Ellipidi. In his opinion, these cells are part of a long-term immunity against the Coronavirus that can last a lifetime. Moreover, the researchers also demonstrated the presence of circulating memory B cells that recognize the coronavirus S protein.

As they speculate, people with SARS-CoV-2 infection may also develop long-term immunity to the virus.

The researchers also plan to check whether patients with a history of moderate or severe COVID-19 develop long-term immunity. This is completely uncertain, as co-author of the work Dr Jackson Turner explains, because the increased inflammation, which plays a major role in the acute course of COVID-19, may weaken the immune system’s response. (PAP)

Author: Joanna Morga

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