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Of: TT
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Photograph: Matt Slocum / AP / TT
Penny Cracas is preparing vaccination with Moderna vaccine by staff at, among other things, emergency care in Chester, Pennsylvania.
The covid-19 vaccines that have been approved so far in the US, Britain and the EU are based on a genetic method that has not been used on a large scale before.
This is how the vaccine works.
Vaccination involves showing a harmless form of the disease to the body’s immune system. In this way, the immune system can calmly train its ability to detect and attack this type of attack in the future.
The classic way to make a vaccine against viral diseases is to first neutralize the virus and then inject it into the body to trigger a reaction from the immune system. It is also possible to produce certain typical virus proteins by artificial means.
But the vaccines developed by Pfizer / Biontech, Moderna and Astra Zeneca are based on a different method. They contain a small piece of genetic code from the sars-cov-2 virus, which causes covid-19.
When the genetic code enters the cells of the body, it is picked up by machinery that is normally dedicated to reading similar codes to produce the types of proteins that the body needs.
Club shaped peaks
But now, instead, the body produces a small, harmless piece of the corona virus – that is, parts of the club-shaped spikes (nail protein) that the virus has on its surface to enter the cells of the body. They are considered a good target for training the immune system, because they are critical to the function of the coronavirus.
Since the viral protein does not belong to the body, the body’s immune system is activated, which, among other things, begins to develop personalized antibodies against virus spikes. This creates an immune memory, which allows the body to react quickly to real covid viruses in the future.
The genetic code used in the vaccine acts as a “temporary manual” and is broken down in the body when used. Therefore, there are no changes in the genetic material of the organism itself.
The advantage of these genetic vaccines is that it is much faster to produce a genetic code that is translated into protein in the body than it is to produce finished protein in the laboratory. However, genetic vaccines have not been used on a large scale before. This is partly due to the fact that it has long been difficult to produce sufficiently durable gene sections. Companies have now solved this problem in various ways.
Sensitive molecule
Both Pfizer / Biontech and Moderna use a type of genetic code called messenger RNA (mRNA). It can be compared to a kind of functional copy of genes stored in the form of DNA within the cell nucleus.
The advantage of RNA molecules is that they do not have to reach the cell nucleus for them to take effect. It is enough that they enter the outer space to the cell nucleus, the cytoplasm, where the cellular machinery for the production of proteins is located.
Both Moderna and Pfizer / Biontech have solved this problem by encapsulating RNA molecules in tiny envelopes of fat, which are captured by the cells of the body and introduced into the cytoplasm.
However, RNA is a very sensitive molecule. That is why vaccines must be stored very cold. The Pfizer / Biontech vaccine requires minus 70 degrees Celsius. Modern has found a slightly more robust design, where minus 20 degrees is sufficient. Besides this difference, the two vaccines are very similar.
In the vaccine that Astra Zeneca has developed, in collaboration with the University of Oxford, the genetic code consists of DNA. It is a more durable molecule, which means that the vaccine can be stored at normal refrigerator temperature. On the other hand, the DNA fragment must be transported to the cell nucleus for it to function.
Smuggled virus glass
This is done with the help of a cold virus, which specializes in smuggling genetic material into the nucleus of our cells. In this case, the researchers started from a chimpanzee adenovirus, which has been depleted of its own genetic material. What is left is a small shell, which is filled with the DNA clip from the vaccine and then travels to the cell nucleus.
Once in place in the cell nucleus, the DNA fragment is handled as a temporary gene. It is first translated into a piece of mRNA, which is then released into the cytoplasm. There, it is captured by the protein machinery, which then begins to produce the viral protein that will activate the immune system, much like Moderna and Pfizer / Biontech’s mRNA vaccines.
Because the DNA fragment ends up loose within the cell nucleus, it never becomes part of the body’s own genome. Instead, it breaks down after a while. Also, the cell itself will be attacked by the immune system. This has been shown in several studies. Therefore, there is no risk that the gene will continue to live inside the body after vaccination.
A disadvantage of this type of DNA vaccine is that the body can develop immunity to the transport virus used to smuggle the DNA fragment into the cell nucleus. This reduces efficiency.
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