The COVID-19 Vaccine

The COVID-19 Vaccine

The COVID-19 global pandemic has caused 2020 to be the worst year of some people's lives. Scientists have been working non-stop to create a safe and effective vaccine to combat this virus, and have crafted a few viable options in record time. These options include the Moderna vaccine, the Pfizer/Biontech vaccine, and the Astrazeneca/Oxford vaccine. Firstly, however, how do our bodies fight infection?

Antibodies

The main purpose of vaccines is to either prevent contraction of an illness or infection, or prevent harmful and dangerous symptoms of an illness. This can be achieved because vaccines prompt the natural biological function of creating antibodies to fight unwanted cells and infections. The first thing to know about our immune system are B-cells.

B-cells are a kind of white blood cells that are always present in your body, but not always active. These cells become activated when they bind to a foreign substance, which signals activation and cell division in a process called clonal expansion. The activation of B-Cells can also be a response in a signal transduction pathway (caused by some sort of chemical signal or secondary messenger). The cloned cells differentiate into something called a plasma cell, which is what creates antibodies, which are the Y shaped proteins that bind to foreign molecules and render it harmless. T-cells are another type of white blood cells that act similarly to B-Cells. If both a B-Cell and T-Cell recognize a molecule as an invader, an immune response will be triggered, most likely with the use of chemical signals and various signal transduction pathways.

The Moderna and Pfizer/Biontech Vaccine

The Moderna and Pfizer/Biontech vaccine uses mRNA technology and is considered an mRNA vaccine. No mRNA vaccine has been widely available to the public before, but the processes behind these vaccines are fascinating. Basically, scientists worked backwards to isolate the mRNA that codes for the spike protein on the COVID-19 molecule. Generally, when the COVID-19 enters the body, its spike protein latches onto membrane receptors (ACE2 receptor) from cells in the respiratory tract. This signal triggered a response chain where the virus fuses into human cells and inserts its own genetic material, RNA into the host cell.

In march, the University of Tokyo released their findings that Nafamostat mesylate, a drug used to treat acute pancreatitis, could be effective at inhibiting these processes by preventing the absorption of the COVID-19 particle into the host cell. That RNA then utilizes the cells natural processes to create new virus particles. Scientists take the mRNA that codes for the s protein that attaches to the membrane receptors, for it does not contain harmful virus material and is the starting signal for the virus takeover. They place that mRNA in a lipid nanoparticle, which is just a lipid bilayer protecting it before it enters the body. It then gets injected into the body, and the membranes fuse, allowing the mRNA to enter the target cell, which is communication via direct cell contact, where membrane modifications, such as gap junctions, allow the mRNA into the cell.

The mRNA then utilizes the ribosomes already in the endoplasmic reticulum to create proteins in the process of translation. The shape of these proteins are then expressed on the cell membrane on the MHC II proteins (only for antigen presenting cells), and the MHC I proteins (found on all cells with nucleus). The presence of these proteins act as a signal on the cell membrane, attracting immune system cells, such as the T helper cell. The T Helper cell communicates with the vaccine host cell through contact between the T helper receptor protein and the signal protein on the membrane of the host cell, which triggers activation of the T cell and a signal transduction pathway, which includes the release of cytokines. These cytokines, through the signal transduction pathway, tell B-cells to multiply and differentiate into plasma cells (along with other immune system cells), which create antibodies, like described in the above paragraph. The other protein complex, MHC I, will do a similar process when it expresses the crafted protein, but will have apoptosis as one result of its signal transduction pathway (which will only result in cell death should the cell be infected in the future), with another result being the aid of the other immune cell signal transduction pathway.

The Astrazeneca/Oxford Vaccine

The Astrazeneca/Oxford vaccine works a little differently and is considered a vector vaccine. This vaccine uses something called a chimpanzee adenovirus, which houses a nucleic acid.

This type of vaccine has been widely studied and effectively and safely used many times before. It is basically a weak live virus (different from the COVID-19 virus particles) that contains genetic material from the COVID-19 virus particles. We use a chimp adenovirus because our bodies will not generate an immune response to it. The DNA molecule inside of the adenovirus, however, expresses a specific protein, in this case one that is very similar to the s protein in the COVID-19 molecule.

The main difference in this virus is that it is a DNA molecule, versus an mRNA molecule. The DNA within the adenovirus gets released directly into the host cell. This cell to cell communication does not require a receptor on the membrane of the host cell, for the DNA enters directly into the cytoplasm, where it then migrates to the nucleus of the cell. It does not get integrated into the DNA, however, just utilizes the enzymes in the nucleus to translate it into mRNA to get released back into the cytoplasm. From there, the resulting processes are the same as the Moderna and Pfizer/Biontech vaccine.

The Protein Subunit Vaccine

The last type of vaccine is called a protein subunit vaccine, which inserts pieces of protein from the COVID-19 virus, which would then trigger all the communication and pathways described above, just without the need for the protein to be synthesized first.

Ultimately, most of the vaccines we currently have use different methods of signaling the same type of signal transduction pathways to heed the same result: antibodies and immunity. Although some are still in phase 3 clinical trials and all of them require multiple doses, they are proving effective at fighting the COVID-19 virus.

Bibliography

“Adaptive Immunity.” Khan Academy, Khan Academy, 2021, https://www.khanacademy.org/science/in-in-class-12-biology-india/xc09ed98f7a9e671b:in-in-human-health-and-disease/xc09ed98f7a9e671b:in-in-types-of-immunity-and-the-immune-system/a/adaptive-immunity. Accessed 6 January 2021.

Ghose, Tia. “What are antibodies?” Live Science, Future US, Inc., 17 July 2020, https://www.livescience.com/antibodies.html. Accessed 3 January 2021.

“How does the novel coronavirus infect a cell?” Scripps Research, The Scripps Research Institute, 13 July 2020, https://www.scripps.edu/covid-19/science-simplified/how-the-novel-coronavirus-infects-a-cell/index.html. Accessed 3 January 2021.

The Institute of Medical Science, The University of Tokyo. “Nafamostat is expected to prevent the transmission of new coronavirus infection (COVID-19).” EurekAlert!, American Association for the Advancement of Science (AAAS), 30 March 2020, https://www.eurekalert.org/pub_releases/2020-03/tiom-nie032420.php. Accessed 3 January 2021.

Ninja Nerd Lectures. “COVID-19 Vaccines: MODERNA | PFIZER/BIONTECH | ASTRAZENECA.” YouTube, 7 December 2020, https://www.youtube.com/watch?v=35Idb_lCU4o. Accessed 3 January 2021.

“Understanding How Covid-19 Vaccines Work.” Centers for Disease Control and Prevention, 18 December 2020, https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/how-they-work.html. Accessed 3 January 2021.