SARS-CoV-2 is an RNA virus that causes COVID-19. Among the many questions regarding the new SARS-CoV-2 vaccine, one of the most pressing ones is “how does it work?” A fundamental understanding in biology is that DeoxyriboNucleic Acid (DNA*) contains all the genetic information within our cells as a sequence of nucleotides (A, T, G, and C). That genetic code is transcribed into RiboNucleicAcid or RNA**, a sequence of ribonucleotides (A, U, G, and C – where the T beforehand is interchanged to a U). RNA is a messenger that delivers the sequence to be translated into proteins. Those proteins are the major functional units that carry out cellular processes.
RNA differs slightly from DNA because of its structure: there is an added hydroxide (OH-) group on the RNA backbone. Because of the extra hydroxyl group, RNA has less stability than DNA. At room temperature, the genetic code stored as DNA is stable for long periods of time, while the code stored as RNA breaks down quickly. Therefore, RNA cannot store information the same way that DNA can. Even though RNA is considered unstable, the advantage is that it allows the rapid amplification of protein production, so cells can respond more quickly to their environment. The dynamic of information storage (DNA), information transfer (messenger RNA), and information translation for structure and function (protein) can explain how a cell works. The current understanding of this mechanism allows the scientific community to modify cells for medical purposes. For example, it is possible to induce the production of important proteins, like insulin for diabetic patients [1]. You can read this post for more information.
Researchers are using this knowledge to enhance our techniques to fight infectious diseases. Most vaccines use dead or weakened pathogens*** (or their proteins****) as outlined in this post. Unlike them, the COVID-19 vaccine contains mRNA (messenger RNA).
The mRNA sequence in the vaccine has the code for the rapid production of the spike protein. The spike is a protein that covers the surface of SARS-CoV-2, so it is a good target to identify and fight the virus [2]. Our immune system, which constantly monitors our body for any sign of foreign and dangerous signals, will mark the spike as foreign. This marking initiates the creation of antibodies***** and triggers other immune responses. One of the advantages of our immune system is that it has a “memory.” Thus, our body will “remember” past encounters with this spike and respond much more effectively next time. Then, after vaccination, our body will be more prepared to fight a future infection of SARS-CoV-2 [3].
During natural infection, the SARS-COV-2 virus contains many additional proteins besides the spike. Those additional viral proteins and enzymes are absent in vaccines. Moreover, the vaccine mRNA does not enter the nucleus and cannot be incorporated into the human DNA. The mRNA vaccine only induces the production of the S protein and, afterward, the unstable mRNA gets broken down by other cellular processes [4].
Although mRNA vaccines came into the spotlight with the COVID-19 pandemic, they have been studied for many years. Scientists have already worked to analyze mRNA vaccines for influenza, rabies, zika, and even cancer! [5] The trials so far have found that vaccination helps prevent serious symptoms of COVID-19 and increases our immune response against SARS-CoV-2 [6], marking a success in the battle against COVID-19! The Moderna and the Pfizer-BioNTech COVID-19 vaccine require taking two shots. They have similar efficacy with mild or moderate side effects (it is rare to have severe side effects). The CDC offers up-to-date information about vaccination [7]. If you have had previous allergic reactions to vaccines, it is important to speak with your physician beforehand. The doctor will determine if it is safe for you.
*DNA - deoxyribonucleic acid, one of the nucleic acids found in living cells. DNA is formed by 4 nucleotides, which can be organized in different sequences and different lengths like letters are organized to form a text. In this case, the “text” formed by the sequence contains the instructions to form a whole organism. DNA is normally found as a paired double strand, in a double helix shape.
**RNA - Ribonucleic acid, one of the nucleic acids found in cells. It is transcribed from DNA. There are many types of RNAs, some of which can have a specific function controlling or regulating some processes in cells while others (known as messenger RNAs, or mRNAs) carry the genetic information that can be translated into proteins by ribosomes.
***Pathogens - any microorganism that can cause infection and disease.
****Protein - a molecule that forms the structure and gives function to organisms at the most basic level. Proteins consist of amino acids, which can be combined in different sequences to form different protein structures with different functions in cells.
****Antibody - a molecule produced by immune cells that recognizes and binds to another molecule that is foreign to the organism, the antigen. By binding to the antigen, the antibody can tag the foreign molecule for destruction or directly neutralizes it.
————————————
Written by: Nicole
Edited by: Adrian and Natasha
BioDecoded is a volunteer group committed to sharing accurate scientific information. We cannot offer any specific health advice. If you have any doubts about getting vaccinated due to previous health conditions, please speak with your healthcare professional or family physician. Your doctor can revise your medical history and advise you on the best path to follow. If you have any questions about this topic, please comment or send them to our email.
References:
Baeshen, N. A. et al. Cell factories for insulin production. Microb. Cell Fact. 13, 141 (2014). Available at: https://microbialcellfactories.biomedcentral.com/articles/10.1186/s12934-014-0141-0
Huang, Y., Yang, C., Xu, X., Xu, W. & Liu, S. Structural and functional properties of SARS-CoV-2 spike protein: potential antivirus drug development for COVID-19. Acta Pharmacol. Sin. 41, 1141–1149 (2020). Available at: https://pubmed.ncbi.nlm.nih.gov/32747721/
Izda, V., Jeffries, M. A. & Sawalha, A. H. COVID-19: A review of therapeutic strategies and vaccine candidates. Clin. Immunol. 222, 108634 (2021). Available at: https://pubmed.ncbi.nlm.nih.gov/33217545/
Lee, H.-H., Wang, Y.-N. & Hung, M.C. Functional roles of the human ribonuclease A superfamily in RNA metabolism and membrane receptor biology. Mol. Aspects Med. 70, 106–116 (2019). Available at: https://pubmed.ncbi.nlm.nih.gov/30902663/
Pardi, N., Hogan, M. J., Porter, F. W. & Weissman, D. mRNA vaccines — a new era in vaccinology. Nat. Rev. Drug Discov. 17, 261–279 (2018). Available at: https://www.nature.com/articles/nrd.2017.243
Chu, L. et al. A preliminary report of a randomized controlled phase 2 trial of the safety and immunogenicity of mRNA-1273 SARS-CoV-2 vaccine. Vaccine (2021). Available at: https://pubmed.ncbi.nlm.nih.gov/33707061/
National Centre for immunization and Respiratory Disease, D. of V. D. Understanding mRNA COVID-19 Vaccines | CDC. Available at: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/mrna.html. (Accessed: 19th April 2021)
Comentários