Prior to the pandemic, the fastest vaccine to be developed was the 1967 mumps vaccine, taking a grand total of four years. Flashforward to November 2020 — BioNTech and Pfizer shattered records with their announcement of the first vaccine against the SARS-CoV-2 virus(14), developed in less than a year. Shortly after, Moderna announced their development of the vaccine. The speed at which these biotechnology companies developed their vaccines can be traced to the use of novel cutting-edge mRNA technology.
The mRNA vaccine takes use of one specific part of the SARS-CoV-2 virus: the spike protein, allowing the virus to enter the cells of the host organism. When injected into the body on its own, the spike protein is harmless. However, the organism’s host cells will recognize the spike protein as a foreign threat and immediately launch an immune response, teaching the body how to fight the virus as a whole.
Within the spike protein, the vaccine uses the genetic information encoded in its mRNA, delivered through a lipid nanoparticle. The lipid nanoparticle is a phospholipid bilayer(1) that wraps around the mRNA to act as a vehicle or transport mechanism for the virus into the host cell. Acting as a vesicle, the lipid nanoparticle fuses with the cell of the host organism, pushing the mRNA into the host cell. The mRNA uses the host cell’s ribosomes(2), located on the rough endoplasmic reticulum(3), to help assemble proteins through the process of translation. The newly produced proteins then express themselves upon the cell membrane as either the MHC-I protein(4) or the MHC-II(5) protein. The MHC-I protein is found on all nucleated cells of the body, however, the MHC-II protein is solely found on antigen-presenting cells: the B-cells(11), macrophages, and dendritic cells. When expressed on the host cell, the proteins attract immune cells such as the TH Cell (T-Helper Cell)(6), which has a membrane protein that interacts with TCR(7), a viral antigen, and the CD4 protein(6), which interacts with the MHC-II Complex. Once the interactions occur, the T-Cell becomes activated and it starts to release cytokines such as IL-2, IL-4, and IL-5(8). These interleukins (IL) signal the B-cell to proliferate and differentiate into plasma cells which develop and change due to released cytokines. The plasma cells then start to make antibodies that are directed against the spike protein on the SARS-CoV-2 virus. Once the antibody binds to the spike protein of the virus, the virus is either neutralized, or its destruction is enhanced. In addition, interactions between the MHC-I complex, the T-C Cell (Cytotoxic Cell)(9), and the CD-8 protein(10) release cytokines that destroy host cells if infected with the SARS-CoV-2 virus in the future, while releasing cytokines that amplify the immune response of the B-cell’s(11) proliferation(12) to plasma cells(13).
Finding a vaccine was a turning point for the pandemic, but the pandemic might also be a turning point for vaccines. The vaccines developed by Pfizer-BioNTech and Moderna employ groundbreaking methods to elicit an immune response. While these vaccines will make a large impact on the battle against COVID-19, their real impact is only just beginning. A vaccine that employs mRNA technology to send specific instructions to host cells opens up a whole new world of vaccine technologies and disease treatments. In the future, scientists and researchers alike hope to develop this technology to use against maladies such as cancer and HIV.
1 phospholipid bilayer: a continuous two layer barrier that surrounds all cells. It acts as a gate that allows certain molecules to enter into a cell, while barring others.
2 ribosomes: the protein-producing organelle of the cell, found either in the cell’s cytoplasm or rough endoplasmic reticulum.
3 rough endoplasmic reticulum: located near the cell’s nucleus, houses the ribosomes which produce proteins.
4 MHC-I protein: one of two classes of major histocompatibility complex (MHC) molecules and are found on the cell surface of all nucleated cells in the bodies of vertebrates.
5 MHC-II protein: one of two classes of major histocompatibility complex (MHC) molecules and are found on the cell surface of all antigen-presenting cells; important in initiating immune responses.
6 TH-Cell (T-Helper Cell): also known as CD4+ cells, are a type of T-cell that play an important role in the immune system, particularly in the adaptive immune system as they are required for almost all adaptive immune responses.
7 TCR (T-Cell Receptor): a protein complex found on the surface of T cells that are responsible for recognizing antigens bound to MHC molecules.
8 IL-2 (Interleukin-2), IL-4 (Interleukin-4), IL-5 (Interleukin-5): types of cytokine signaling molecules in the immune system.
9 T-C Cell (Cytotoxic Cell): a type of white blood cell (lymphocyte) that kills damaged cells — cancer cells, cells infected with viruses, etc.
10CD-8 protein: protein (binded to a carbohydrate) that is a co-repector for the T-Cell Receptor (TCR); plays a role in T-cell signaling and aiding with cytotoxic T-cell-antigen interactions.
11 B-Cell: a type of white blood cell that secretes antibodies useful for initiating immune responses.
12 proliferation: to increase in number rapidly.
13 plasma cells: white blood cells that originate in the bone marrow and secrete antibodies useful for initiating immune responses.
14 SARS-CoV-2 virus: also known as Coronavirus or COVID-19