A study from Washington University School of Medicine has shown people carry immune cells in their bodies that produce antibodies to fight against the SARS-CoV-2 virus long after recovering from mild COVID19 infection. Experts who have been involved in the study have said that such immune cells can remain in the body for a lifetime. The authors of the new study have said that people who have caught mild COVID19 infection in the past might be found with lasting antibody protection. They have said that reinfection of COVID19 is highly unlikely among these people. In the last fall season, there have been several reports that have shown that natural immunity acquired from prior infection with the SARS-CoV-2 virus might wane away quickly. Earlier, experts have thought natural protection from the virus that is acquired after COVID19 infection is quite short-lived. The senior author of the new study, Ali Ellebedy who works as a professor of pathology and immunology of medicine and molecular microbiology has said that experts have misconstrued the process of antibody. He has said that the levels of antibodies go down after an acute infection, which is a natural phenomenon. However, they never reduce to zero rather they keep floating around. The authors of the new report have said that around 11 people have been identified with antibody-producing immune cells 11 months after they have started showing symptoms of the disease for the first time. Health experts have said that these antibody-making cells will remain in the bodies of these people for their lifetime. The results of the report have been released in the journal known as Nature.
The new study has been able to find strong evidence of lasting immunity acquired from prior infection. When a person is diagnosed with a viral infection, immediately antibody-making cells multiply and start circulating in the bloodstream. This process shoots up the levels of antibodies in the blood. Once the patient is recovered and infection is reduced, most of these immune cells die off and the level of antibodies in the blood as well reduces. Experts have said that small amounts of these cells that are known as long-lived plasma cells are transferred to the bone marrow. In the bone marrow, these cells keep secreting low levels of antibodies in the bloodstream to help the immune system to prevent the virus. The study has clearly mentioned that the key to finding out whether prior infection with COVID19 can lead to long last antibody immunity lies in the bone marrow. A team of experts has enrolled around 77 people who have tested positive for COVID19 in the past. They have been giving their blood samples at intervals of three months. They have started giving their blood samples one month after the initial infection. Most of these participants have been dealing with mild COVID19 infection, said the experts. Around six of them have been hospitalized. Scientists have taken samples of bone marrow from 18 participants seven to eight months after their early infections. Around five of them have provided the second samples of their bone marrow after four months. Experts have taken samples of bone marrow from other 11 people who have never been infected with the virus as well for assessment.
Experts have said that as expected the levels of antibodies in the bloodstream of COVID19 participants have reduced quite rapidly in the first couple of months after the initial infection. However, some antibodies have been detectable 11 months after the initial infection. The study has found around 15 out of 19 bone marrow samples of the people who have been infected with the virus have been found to have antibody-producing immune cells. These cells as well have been detected in the people who have provided the second bone marrow samples after four months. The senior author, Ali Ellebedy has said that people, who are diagnosed with mild COVID19 infection, are usually recovered within two to three weeks after infection, therefore, there will be no virus in the body to trigger an active immune response seven or 11 months after infection. He has said these immune cells are not dividing rather they are dormant. They stay in the bone marrow and keep producing antibodies. The authors of the study have said that these cells have been doing this ever since the infection has been resolved.
They will keep doing this for a lifetime, said the experts. Health experts hope that people who have been infected with the virus and have never shown symptoms might as well have this long-lasting protection from the virus. However, it needs to be investigated further whether or not people who have been severely ill with COVID19 are protected from a future encounter with the virus. An instructor in pathology and immunology, Dr. Jackson Turner has said that inflammation has a crucial role to play in severe COVID19 disease and high levels of inflammation can result in defective immune responses. However, on the other hand, severe COVID19 disease takes place due to high viral load in the body and high viral load might lead to a good immune response as well. Well, this is yet not clear; experts need to repeat this study among people who have been down with moderate to severe form of COVID19. At present, experts from the Washington University are studying whether or not vaccines can trigger long-lasting antibody-producing cells in the body.