Mode of action of mRNA
How does the vaccine COMIRNATY® work?
- The BioNTech vaccine contains synthetic mRNA, which is an artificially-produced copy of a section of the SARS-CoV-2 genome.
- The vaccine does not contain any biologically active virus or infectious viral components and cannot cause an infection.
- The vaccine only contains a copy of the instructions for producing a non-infectious viral spike protein. These instructions are called mRNA (messenger ribonucleic acid), and they are also not infectious. The body uses these instructions to produce the non-infectious spike protein itself. This protein is then used by the body to generate an immune response to SARS-CoV-2 that includes antibodies and memory cells.
The role of mRNA in the human body
mRNA is a natural component of our cells that plays a very specific role in the human body.
To put it simply, each natural mRNA in our bodies is a blueprint of a certain section of our genome. They are used as a mobile copy of the instructions for building proteins and transport these blueprints from the nucleus of each cell to the protein factories (ribosomes) of the cell.
The process in detail:
Most of the cells in our body have a nucleus where our deoxyribonucleic acid (DNA) is located. DNA contains all the information needed for the structure and function of our body, including the instructions for building proteins. However, in order for proteins to be produced, the information in the DNA needs to be converted into a mobile version of the instructions, which is called mRNA. Proteins play many roles in the body. One of their functions is to help produce new cells. Muscles, bones, and hair are mostly made of protein.
Our body use the following steps to produce proteins:
A cell contains a nucleus, ribosomes (protein factories), cytoplasm (the watery space outside the nucleus), a cell membrane, and other components.
An mRNA contains a copy of information from the DNA that can be read by a ribosome. The ribosome then uses these instructions to build proteins.
DNA is located in the nucleus of the cell.
In order for the body to build proteins, it first needs instructions on how to do so. This information is found in the DNA located in the nucleus of the cell.
The section of the strand of DNA that contains this information is first copied.
In this process, the information in the DNA on how to build a protein is copied onto an RNA molecule called mRNA: the “m” stands for “messenger”, and so “mRNA” stands for “messenger ribonucleic acid”.
The information about the protein to be produced is transported from the nucleus into the cytoplasm - the main body of the cell - in the form of mRNA.
In other words, the mRNA migrates from the site where it is produced (the nucleus) to the site where proteins are produced (the ribosomes).
The ribosome recognizes the information on the mRNA (i.e. the copy of the instructions) and translates this information into the proper protein chains.
This is the process the body uses to produce proteins.
After this process is finished, the mRNA is broken down and destroyed.
The body can then use the individual building blocks of the previous mRNA again to produce new mRNA.
The role of mRNA from the vaccine
The mRNA vaccine provides the body with a blueprint for creating a specific non-infectious viral protein.
This protein is located on the surface of the novel coronavirus and is called the spike protein due to its appearance.
In other words, the vaccine does not contain the protein itself. Instead, the protein is produced by the body’s own cells after vaccination. This process triggers the immune system to develop an immune response. The immune system produces memory cells and antibodies against the viral protein, and thus against SARS-CoV-2 itself.
The viral protein produced by the body is not infectious. However, the protein is a characteristic feature of SARS-CoV-2. Therefore, the presence of just this fragment of the viral surface is enough for the vaccine to activate the immune system and establish protection against COVID-19.
After vaccination, the mRNA crosses into cells. Once inside a cell, it goes directly to the protein factories called ribosomes which are located in the cytoplasm. The mRNA does not enter the nucleus of the cell.
The mRNA arrives at the ribosomes, the protein factories.
There, it is read by the ribosomes and translated into protein chains.
These protein chains are then rearranged to form the finished spike protein. The spike proteins are located on the surface of the novel coronavirus and get their name from their spike-like appearance. In the next step, the spike proteins are transported out of the cell.
Once this happens, the immune system reacts to the foreign spike proteins by mounting an immune response to the novel coronavirus. This response consists of specific antibodies and memory cells. Antibodies are protein molecules that are produced by immune cells to target specific infectious diseases, while memory cells are used to store the memory of the initial contact with an infectious disease within the immune system. This allows the immune system of a vaccinated person to generally react more quickly to an infection with the novel coronavirus and to prevent this infection.
This explains how vaccination can help protect against COVID-19.
Vaccination thus provides effective protection from COVID-19 for the majority of people.
mRNA in brief
Natural and synthetic mRNA are produced at different locations. However, both forms of mRNA are used to provide the information needed to build a certain protein.
| Natural mRNA | Vaccine mRNA | |
|---|---|---|
| Production | Created naturally from the DNA in the nucleus | Created synthetically in the lab by copying a DNA template |
| Transport | From the nucleus into the cytoplasm of the cell | Crosses from outside the cell into the cytoplasm after vaccination without entering the nucleus |
| Function | Protein blueprint that is read by ribosomes | Protein blueprint that is read by ribosomes |
Purpose | Helping the ribosome build the protein according to the blueprint, followed by destruction of the mRNA | Helping the ribosome build the protein according to the blueprint, followed by destruction of the mRNA |
Two vaccinations are required:
The vaccination is carried out as a series of 2 doses. It is recommended that the second dose is given 3 weeks after the first dose. The best possible vaccine-mediated protection is expected from day 7 post second dose.
