How does RNA vaccine work?

  You may already know DNA. DNA exists in the nucleus of every biological cell and is protected by the nuclear membrane. Our full set of genetic code is “written” in the “code book” of DNA in the form of a pair of four-base “letters”. The 4 bases are A, C, G, and T. Genes are fragments of DNA, or paragraphs or chapters in this “code book”. The instructions they contain “draw” the blueprint of your body, making you the unique you.
Daily work of mRNA

  However, genetic instructions must be transmitted to the ribosome, a “protein factory” in the cytoplasm, in order to assemble the protein. Speaking of protein, you might immediately think of muscle. So, is it to give us muscles? not completely. Because the role of protein is much broader than you think. Cells need to rely on proteins to complete many processes required by the body’s operations. For example, many metabolic reactions (that is, the reaction that converts food into energy) require the catalysis of enzymes, and enzymes are a kind of protein.
  DNA itself does not go out of the nucleus. It also does not call the ribosome directly. So, how to tell its instructions to the ribosome? By the way, this needs to be delivered through messenger RNA (mRNA for short).
  Messenger RNA, when you hear its name, you know that it functions as a messenger. That’s right. DNA transcribes some “chapter” information to mRNA, and mRNA sends the information to the “protein factory”. Once the mRNA reaches its destination, the cell can produce specific proteins based on these instructions. This is the daily work of mRNA.

Ribosomes are protein processing factories
Comparison of RNA vaccines and traditional vaccines

The difference between RNA and DNA

  Every cell in an organism has the same DNA. There is only one type of DNA, but there are many types of RNA, which are classified according to their functions: such as transfer RNA (tRNA) that transports amino acids to the ribosome and ribosomal RNA (rRNA) that composes the ribosome. Messenger RNA (mRNA) is just one of the most common. DNA is not found in all organisms, but RNA is found in all organisms. Like many viruses, including the new coronavirus, the genetic material inside is only RNA, not DNA. Some scientists speculate that RNA may be older than DNA, and that the earliest life may only consist of RNA, not DNA.
  Every cell in an organism, from lung cells to muscle cells, nerve cells, etc., has the same DNA. It can be said that DNA is a stable and universal existence. Even if the organism dies, DNA can be preserved for tens of thousands of years under the right environment. But mRNA is only produced on demand. It is a dynamic existence: when and where the body needs what protein, then, at that time, that place produces mRNA that carries the instructions to make that protein.
  In this way, mRNA provides a way for cells to control protein production. mRNA is like an order for a “protein factory”. It determines when to start, when to stop, what kind of product to produce, and how much. Because there is no need to have every cell produce all the proteins in your entire genome instructions at once.
  Unlike DNA, which can be stored for tens of thousands of years, mRNA is like a short message that is deleted as soon as it is read. It will be automatically destroyed at regular intervals, ranging from a few minutes to a few hours in length. Some features in the mRNA structure—base U and single-stranded form—ensure that it has only a short lifespan. Once the mRNA instruction is destroyed, the “protein factory” will be shut down until a new instruction is received. In our cells, because multiple RNAs exist at the same time, in order to distinguish, a small letter is usually added in front. But in the virus body, there is only one kind of RNA, which plays the role of DNA and mRNA in our cells. Therefore, when we talk about virus RNA in the following article, it means mRNA.
RNA vaccines and traditional vaccines

  In spy war films, the enemy often pretends to be his own and enters our team and issues wrong instructions, causing us damage. Good luck is really amazing, and this scene is also being staged in a small cell. The mRNA of the enemy (mainly virus) can also pretend to be “self” and issue false instructions to the “protein factory” to make foreign proteins for it.
  However, the magic is one foot high, and the road is one foot high. There is a kind of ribonuclease in the cell, which can recognize the foreign RNA that has been secretly inserted in the mRNA and remove it to protect the cell from the influence of wrong instructions. In this process, ribonuclease recognizes and remembers these foreign invaders.
  But this set of security mechanisms is not invulnerable, otherwise there will be no viruses. Viruses can avoid being identified through various methods.
  In any case, this contest between identification and removal has aroused great interest among vaccine developers. The goal of vaccination is to make your immune system react and remember the pathogen or a certain part of the pathogen, so that when the real pathogen invades, your immune system can recognize it in time and enter the battle quickly.
  There are currently two approaches for vaccine development, one is traditional attenuated or inactivated vaccines, and the other is RNA vaccines.
  The strategy used in traditional attenuated or inactivated vaccines is to familiarize our immune system with the entire pathogen. For this purpose, researchers first culture the virus in vitro through multiple generations, then pick out the virus whose toxicity has been reduced (attenuated) or lost the ability to reproduce (inactivated), and then inject it into the human body to let our body produce the virus. antibody.
  The RNA vaccine adopts another strategy, that is, only let our immune system be familiar with a certain part of the pathogen-the key and the part that is not prone to mutation. Take the new coronavirus as an example. In order for the new coronavirus to invade human cells, it needs to anchor and land on human cells, just as pirates want to invade a country and need to find a port to drop anchor. The “anchor” of the new coronavirus is the spinous protein on its surface. As long as our immune system can recognize the spike protein on the surface of the new coronavirus and attack it, the virus will have no way to gain a foothold.
  Make an analogy. In order to teach new born lambs how to recognize wolves, the traditional vaccine method is that the mother sheep leads the lamb to a sick or dead wolf and says, “My child, wolves look like this. I will meet them like this in the future. The child’s animal must be avoided.” The RNA vaccine method is that the mother sheep shows the toe of the dead wolf’s paw to the lamb, and said: “My child, you must avoid any animal with this paw in the future.”
Advantages of RNA vaccines

  In order to allow our immune system to “recognize” the spike protein in advance, the researchers first produced mRNA for the synthesis of spike protein in vitro, and injected it into the human body through vaccination. The mRNA of the spike protein was cleverly camouflaged to reach the cell’s “protein”. Factory” and activate the cellular machinery to produce spinous protein for it. However, as a foreign protein, the spike protein will be recognized by our immune system, eliminated and remembered. In the future, when the virus with this spike protein really strikes, it will be recognized in time.
  Because the RNA vaccine that scientists choose to develop is aimed at the “everything invariable” part of the virus, no matter how the virus mutates, it will not escape the eye, so the effectiveness of the RNA vaccine is relatively high.
  As for some people’s concerns, will the RNA in the vaccine enter the nucleus and damage the DNA. This worry is completely unnecessary. Our nucleus is not a rookie, and foreign objects basically cannot pass the nuclear membrane.
  Although the concept of RNA vaccine has been proposed for many years, it was only developed and put into use during this epidemic. Compared with traditional vaccines, it has other advantages (see “Comparison of Traditional Vaccines and RNA Vaccines”). Its outstanding performance in this epidemic indicates that it has broader application prospects in the future. Scientists from various countries are currently developing RNA vaccines against influenza, Zika, rabies and other viral infectious diseases.

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