Recently, some medical experts said: the body of patients after recovery contains a large number of comprehensive antibodies, which can fight against the virus. The novel coronavirus pneumonia can be prevented and controlled by the research and application of these antibodies. Is there any antibody that can resist the virus? Can the epidemic be effectively suppressed? Things are not as simple as you think.
On the evening of February 13, Sinopharm group announced that it had completed the collection of plasma from some convalescent patients and carried out the preparation of new coronavirus special plasma products and special immunoglobulin.
The novel coronavirus pneumonia is China's biological product. It is a plasma containing highly effective new crown virus specific antibodies donated by rehabilitative patients. It is treated by virus inactivation and neutralizing antibodies against new crown virus and detected by multiple pathogenic microorganisms. It is used for the treatment of critically ill patients with new crown pneumonia.
Seeing this, some people may think: as long as we have antibodies in our body, we can resist the new coronavirus?
Huang Bo, deputy director of the Institute of basic medicine of the Chinese Academy of Medical Sciences and the Department of immunology of Peking Union Medical College, said the facts were not so simple.
Not any antibody can resist virus
According to Huang Bo, antibody is a kind of protein molecule, which presents Y-shaped structure like a tree branch. The tree branch part can recognize and bind antigens, which are usually alien proteins.
"There are all kinds of alien proteins in nature, and antibodies are used to identify their branches, which are also correspondingly various." Huang Bo said.
Let's talk about novel coronavirus. The nucleic acid genetic material of the virus lies in the core and is surrounded by nucleocapsid protein. And then there's a membrane, which has a membrane protein, a membrane protein, and a nail protein - a protein that magnifies to look like a nail.
In addition to the proteins that form the structure of the virus, the nucleic acid genetic material of the virus can also guide the generation of other viral proteins that do not participate in the structure of the virus. However, these viral proteins do not exist in the virus, but in the infected cells.
"All these virus proteins belong to alien proteins. For any alien protein, the body may produce antibodies specifically for it. Therefore, novel coronavirus infected people can produce various antibodies against viruses. Huang Bo said.
In this case, is every antibody able to play an antiviral role? Not necessarily.
"Antibody should play the role of antiviral, the precondition is that antibody should recognize and combine with virus. And only the antibodies that recognize the proteins on the surface of the virus can have antiviral effect. " Huang Bo said.
In this way, some viral proteins do not exist in the virus, and antibodies against such viral proteins have no antiviral effect. In addition, the virus protein in the virus envelope cannot be contacted by the antibody, and this part of the antibody has no antiviral effect.
Neutralizing antibody is the main force of antiviral
So, how does an antibody that can play an antiviral role work?
Huang Bo introduced that the novel coronavirus makes people sick, by combining the nail protein on the surface of the virus with the protein called ACE2 on the surface of the lung epithelial cells.
Subsequently, the shape and structure of ACE2 changed, and the virus took the opportunity to enter the cell. They use molecules in human cells to synthesize new viruses through chemical reactions. These new viruses are released out of the cells and will be repeated to infect the surrounding normal cells.
But the human body doesn't get caught. The antibodies produced in the human body against the nail protein can bind to the nail protein on the surface of the virus and block their binding with ACE2, thus blocking the virus from entering the cell.
"This antibody against nail protein is called neutralizing antibody. Neutralizing antibodies are produced by preventing viruses from invading cells
The protective effect of volatilization is the main strength of antiviral effect of antibody Huang Bo said.
Once the neutralizing antibody against the virus is produced, it can effectively block the virus from entering the cell. If the virus can't enter the cell, it can't reproduce and expand, and the virus outside the cell will gradually decompose.
Don't forget that in addition to nail protein, there are also envelope protein and membrane protein on the surface of coronavirus. Huang Bo introduced that the latter two proteins may not mediate the virus into the cell, so the antibody combined with them may not affect the virus into the cell. However, the non neutralizing antibodies combined with them can mediate the phagocytosis of virus particles by immune cells.
To fully understand the complexity of antibody
Generally speaking, there are two ways for antibody to play a role: the combination of neutralizing surface antibody and virus can prevent the virus from entering the cell and keep the enemy out of the country; the combination of non neutralizing surface antibody and virus can mediate immune cells to phagocytize, clear the virus and kill the enemy in the country.
Huang added that non neutralizing antibodies mainly mediate the virus into macrophages and play an antiviral role in the early stage, but may cause lung immune damage in the middle and late stage.
"In the novel coronavirus pneumonia, the antibody is too much hope. But antibodies are not as simple as they are generally understood. We need to know enough about the complexity of antibodies and even the aggravating side of the disease. " Huang Bo said.
Huang Bo believes that recognizing this is also important for vaccine research and development. Because the purpose of vaccination is to make the body produce neutralizing antibodies against virus surface proteins. It is easy to produce antibodies, but it is difficult to produce neutralizing antibodies, which is one of the great challenges in vaccine research and development. We should be cautious and carry out intensive work.
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