Mild COVID-19 induces ‘antibody immune response’ that could last lifetime: US scientists

Mild cases of COVID-19 leave those infected with “lasting antibodies response” that can provide protection from the repeated bouts of illness for the lifetime, researchers at Washington University in St. Louis, US, have found. According to the new study published on May 25 in Nature journal, the antibody-producing immune cells rapidly multiply and circulate in the blood, driving antibody levels to the maximum during the fight against the COVID-19 infection. But once the infection is cured, most such cells die off, and blood antibody levels drop. 

Scientists, however, have discovered a small population of antibody-producing cells, termed the long-lived plasma cells, that were found migrating to the bone marrow and settling for a longer period of time. This is where these immune cells continually secreted low levels of antibodies into the bloodstream that reduced the risk of another encounter with the COVID-19 infection. there were reports that antibodies wane quickly after infection with the virus that causes COVID-19, and mainstream media interpreted that to mean that immunity was not long-lived," said senior author Ali Ellebedy, Ph.D., an associate professor of pathology & immunology, of medicine and of molecular microbiology. "But that's a misinterpretation of the data, she goes on to add. 

Furthermore, Ellebedy explained that while it was normal for the antibodies to reduce after acute COVID-19 infection, they did not down to zero. “They plateau,” she said. Scientists found the antibody-producing cells present in the bodies of COVID-19 recovered patients at least 11 months after the first symptoms. “ These cells will live and produce antibodies for the rest of people's lives. That's strong evidence for long-lasting immunity,” they said in the groundbreaking study. According to Ellebedy, the key to figuring out whether COVID-19 leads to long-lasting antibody protection lies in the bone marrow. 

Long-lived plasma cells

Ellebedy explained, that those patients who recovered from mild cases of COVID-19 host long-lived plasma cells that produce antibodies that “specifically target” SARS-CoV-2. The findings were established from 77 enrolled participants whose blood samples were collected at three-month intervals starting a month after the initial COVID-19 infection. While most volunteers had mild coronavirus infection, as many as six were hospitalized. Scientists also obtained bone marrow from 18 of the participants seven or eight months after their initial infections.