Nature issued an article: Faced with the mutation of the new coronavirus, the human body's immune system is constantly responding to evolution!

So far, the severe acute respiratory syndrome coronavirus has infected more than 98.
8 million people and caused more than 2.
1 million deaths.
In addition, mutant strains of the new coronavirus have also been discovered in the United Kingdom, South Africa and other regions.

In the face of severe epidemics, various countries have successively developed and approved various vaccines against the new coronavirus.

For patients who have been infected with the new coronavirus, neutralizing antibodies produced by the immune system can be produced in their bodies to protect them from infection.

But how long can the antibody activity produced by the immune system against SARS-CoV-2 last? Will the number and quality of B cells decline? Can you identify and respond to the mutated new coronavirus? These are still unknown.

Recently, a research team from Rockefeller University and Icahn School of Medicine at Mount Sinai published a study titled Evolution of antibody immunity to SARS-CoV-2 in "Nature", and found that the patient was infected with SARS-CoV-2 after 6.
2 Within months, although the neutralizing activity of antibodies in body fluids was significantly reduced, memory B cells continued to evolve to produce somatic hypermutations, expressing antibodies with enhanced efficacy and resistance to RBD mutations, and humoral immunity has been continuously developing.

https://doi.
org/10.
1038/s41586-021-03207-w In order to study the long-term antibody immunity in patients infected with SARS-CoV-2, the researchers tested 87 COVID-19 patients after 1.
3 and 6.
2 The level of neutralizing antibodies in the blood and the characteristics of memory B cells at the time of the month were analyzed.

The results of enzyme-linked immunosorbent assay (ELISA) and automated serology found that between 1.
3 and 6.
2 months, the anti-RBD (new coronavirus spike protein receptor binding domain) and anti-N (nucleoprotein) antibodies in the blood decreased significantly.
And the decline of each antibody is inversely proportional to the initial antibody level. Using the HIV-1 pseudovirus containing the SARS-CoV-2 spike protein to measure the plasma neutralizing activity, it was found that the neutralizing antibody titer against the new coronavirus at 6.
2 months was reduced by 5 times compared with 1.
3 months.
It shows that 6 months after SARS-CoV-2 infection, the neutralizing activity of the antibody in the patient's body is significantly reduced, but it is still detectable.

Anti-SARS-CoV-2 plasma antibody dynamics memory B cells are differentiated from B cells in the immune system, and have specific recognition capabilities for antigens.
When the antigen secondarily infects the body, the memory cells can directly proliferate, Differentiation produces plasma cells and produces antibodies that bind to antigens.

Analysis of SARS-CoV-2 memory B cells in patients revealed that the proportion of memory B cells expressing anti-RBD IgG antibodies in the memory B cell population showed a small but significant increase between 1.
3 and 6.
2 months.

Anti-SARS-CoV-2 RBD antibody sequence.
In addition, the researchers also found that memory B cells at 1.
3 and 6.
2 months also showed the renewal of monoclonal antibody types and the evolution of the antibody sequence, which also shows that they are infected.
From 1.
3 to 6.
2 months later, the immune system has been continuously optimizing the antibody immune response to the new coronavirus.

The reactivity of 122 representative antibodies to RBD at these two time points was evaluated, and it was found that 115 of them could bind to RBD, and the EC50 (half maximum effect concentration) of the antibody increased significantly at 6.
2 months.

Anti-SARS-CoV-2 RBD monoclonal antibody reactivity So how resistant are these antibodies to mutant strains of the virus? The researchers measured the binding effect of the wild-type RBD and mutant RBD of SARS-CoV-2 and found that among the antibody clones that appeared at both time points, 83% of the antibody clones were compared with the mutant RBD at 6.
2 months.
The overall binding increase of E484 (mutation positions in Brazil and South Africa), Q493, N439, N440 and R346 these RBD mutant amino acid positions is the most significant increase in binding. Analyzing the neutralization breadth of antibodies that can bind to mutant RBDs, it is found that in addition to having stronger neutralizing power, the antibodies expressed by evolved memory B cells also have a higher neutralizing breadth, and some antibodies can neutralize one Variant of the above virus.

The neutralizing activity of the anti-SARS-CoV-2 RBD monoclonal antibody.
Finally, the researchers analyzed that the continuous evolution of the antibody may be due to the antigen remaining on the surface of follicular dendritic cells in the form of immune complexes for a long time, making the hair growth The B cells produced by the center are caused by somatic hypermutation and continuous selection.
The low-level viral proteins remaining in human tissues may also serve as antigens to further promote the continuous evolution of antibodies.

End Reference: [1]Evolution of antibody immunity to SARS-CoV-2[2]https://