Jan 25, 2021 06:00:00

Immunity of the new corona may 'continue to evolve' rather than decline, is it compatible with mutant strains?

Regarding the validity period of immunity that a person who has recovered from a new coronavirus infection (COVID-19) has, there is a report that

it ' has only a few weeks ', but there is also a treatise that 'it lasts for at least 8 months '. .. Meanwhile, a study published by The Rockefeller University in the United States found that people who recovered from COVID-19 had fairly long-term immunity and that they 'may be able to cope with mutant strains .' It was.

Evolution of antibody immunity to SARS-CoV-2 | Nature
https://www.nature.com/articles/s41586-021-03207-w

The Rockefeller University »The immune system mounts a lasting defense after recovery from COVID-19
https://www.rockefeller.edu/news/30005-sars-cov-2-immune-response-improves-long-term-protection/

When the human body recovers from a viral infection, the immune system produces antibodies to fight off the virus. The new coronavirus (SARS-CoV-2) vaccine ' BNT162b2 ' developed by American pharmaceutical giant Pfizer and Moderna's ' mRNA-1273 ' were also developed for the purpose of obtaining immunity by thismechanism .

Antibodies in the blood remain for weeks to months, but are said to decrease significantly over time. A research group led by Professor Michel C. Nussenzweig, an immunologist at Rockefeller University, analyzed the blood of 87 ex-patients 1.3 and 6.2 months after they were actually infected with SARS-CoV-2. Was confirmed to have dropped to one-fifth.

On the other hand, in contrast to antibodies, we have also found an immune system that hardly decays six months after infection. It is a '

memory B cell ' of immune cells that remembers the pathogen during the first infection and is responsible for producing antibodies quickly during the second and subsequent infections.

When the research group focused on memory B cells that specifically react with the spike protein of SARS-CoV-2, the number of memory B cells in patients 6 months after infection did not decrease. On the contrary, it was even increasing. Regarding this result, Nussenzweig said, 'Antibodies attack the receptor-binding domain (RBD), which is a key point of SARS-CoV-2, but the total number of memory B cells that produce the antibody did not change. This is good news. '

Previous studies have shown that memory B cells remain for a long period of time, but this time, 'memory B cells continue to mutate after recovery from infection and produce stronger antibodies. It turned out that it was. ' When the research group confirmed the function of the antibody produced by memory B cells 6 months after infection in an experiment, it was found that it is not only more effective than normal SARS-CoV-2 but also responds to mutant strains. Was obtained.

'I was surprised that memory B cells continued to evolve, which is common in chronic infections, such as HIV and herpesviruses , where the virus remains in the body,' said Nussenzweig. , SARS-CoV-2 is thought not to remain in the body, so it was totally unexpected. '

To unravel the mystery that memory B cells continue to evolve, the research group worked with doctors at Mount Sinai Hospital to examine the intestinal cells of a former patient who had recovered from COVID-19. As a result, SARS-CoV-2 gene substances and proteins were detected in the intestines of 7 of the 14 people surveyed.

At the time of writing, it is unclear whether the SARS-CoV-2 gene found in the intestine is just a wreckage or remains infectious, but the research group said, 'SARS-CoV-remaining in the small intestine. The trace of 2 may be promoting the evolution of memory B cells. '

In the future, the research group plans to conduct research on more people in order to investigate how SARS-CoV-2 residues affect the progression and immunity of COVID-19. is.