mRNA Vaccine for COVID-19
Figure 1 Ribosome Molecular Motor (credit sciencemag.org)
It is December 2020. The long-awaited vaccines to end the COVID-19 global pandemic are arriving and are currently being distributed to hospitals and long-term care facilities across the nation. By Spring 2021 most Americans in the high-risk category (over 65 and/or having co-morbidity conditions) will have received a COVID shot. But is it safe? I will address that in this blog, along with some images that will hopefully give you a clearer understanding of how this all works. To begin, let’s take a closer look at our enemy, the SARS-CoV-2 virus that produces the COVID-19 infection (Figure 2).
Figure 2 COVID-19 Virus Structure (credit Unite for Sight)
A virus is not a living organism; it is a parasite that can only reproduce by entering a typical living cell (see Figure 4). Viruses come in many shapes and sizes; COVID-19 belongs to a group known as coronavirus, characterized by a spherical shape covered with spikes – reminiscent of a WWII explosive harbor mine. Inside the virus is a bunch of messenger RNA (mRNA), short for ribonucleic acid; it is very similar to double helix DNA, which contains the code for all living things – plant and animal. Most important are the spikes, also called neuraminidase, which are special COVID proteins configured to attach to a normal human cell receptor – like a hand into a glove. Once the virus attaches to a cell, it can transfer its mRNA codes into the cell with instructions to make millions more duplicates to spread to other cells.
Figure 3 DNA and RNA (credit Shutterstock)
Figure 3 gives us an abbreviated picture of DNA and RNA. Both DNA and RNA are ribbon-like helix structures; RNA is one half of a DNA double-helix molecule. The four color-coded interior rods are nitrogenous bases. Notice that DNA and RNA share three bases in common (Cytosine, Guanine, and Adenine), but the fourth base is different – Uracil (RNA) vs Thymine (DNA). Inside DNA various base pairs are joined. A virus genome contains ~ 13,000 base-pairs which code for up to 14 different proteins; by comparison, a single strand of a human DNA molecule contains an astounding three billion base-pairs, the code or blueprint for everything human! And each nucleus of every human cell contains the same pattern of DNA. Enough for the microbiology lesson.
Figure 4 Eukaryote Cell (credit BioNinja)
By definition, the least common denominator of life is the cell; it is self-sustaining and can reproduce. Figure 4 is an oversimplified schematic of a human eukaryotic cell. Inside our cells, the DNA sequences that hold the instructions for each of the roughly 20,000 protein-coding genes in the human genome are safely sequestered inside a cell’s nucleus for protection; DNA never leaves the nucleus. Messenger RNA is produced inside the nucleus through a process called transcription. The nucleus is filled with enzyme proteins, which are microscopic molecular motors called RNA polymerase. When it is time to transcribe some mRNA, these enzymes attach to the DNA template. The newly formed strands of mRNA are released into the main body of the cell (cytoplasm), where they encounter floating protein molecular motors called the ribosomes. Figure 1 shows an mRNA strand (blue) entering the ribosome (grey), which decodes RNA instructions to manufacture a new protein (black) for a specific task. Once the protein is made, the mRNA is quickly destroyed by enzymes in the cytoplasm.
Figure 5 COVID mRNA Vaccine Inside a Cell (credit Chemical Abstracts Service)
When a virus enters a human host, it wants to multiply itself. The way to do that is to find some cells and “infect” them. The virus must depend on the host cell to reproduce itself. Here’s how. The spike, one of the 14 proteins associated with the coronavirus, is designed to attach to a receptor on the cell. When it does, it injects some mRNA into the cell, which makes its way to the various ribosome molecular motors. The ribosomes then make more virus cells which multiply, cause the cell to burst, and distribute the virus throughout the body. The cells do all the slave-work on behalf of the virus.
The human immune system then kicks in, recognizing the invading live virus, and forming an army of antibodies (T cells) to fight it.
Figure 6 How mRNA Vaccines Work (credit Bloomberg research)
So how do the Pfizer and Moderna mRNA vaccines work, and why are they safe? Genetic scientists first had to break the entire code for the SARS-CoV-2 genome. Then they focused on the “spike protein” to make some “fake” mRNA of a fragment of that protein. Since only part of the protein is made, it does not do any harm to the person vaccinated. But that protein-piece is antigenic, meaning it is able to cause the immune system to begin producing antibodies and activating T-cells to fight what it thinks is an infection. Figure 6 tells how the mRNA vaccine works. Figure 5 depicts a more detailed picture. Here, the lipid-coated mRNA vaccine containing fragments of the spike protein is welcomed into the cell, where it quickly finds its way to the nearest ribosome. The ribosomes translate the mRNA into spike proteins, which ultimately follow pathways to activate the immune system in the forms of CD8 T-cells (cell-mediated immunity) and CD4 T-cells (antibody-mediated immunity). After the piece of spike is made, the cell breaks down the mRNA strand and disposes of them using enzymes in the cell. The mRNA never enters the cell’s nucleus or affects genetic material.
All would agree that the COVID-19 pandemic has caused terrible suffering throughout the world. We look to God for answers but are often unsatisfied. Is it possible to uncover blessing in the wake of this global catastrophe? Messenger RNA vaccines are emerging from the horizon with promise to mitigate or cure a host of human diseases – viruses, rabies, and even cancer. Project “warp speed”, through government-private agreements, has paved the way to develop and bring new vaccines to the market faster than anyone could have imagined. Humanity around the world is the beneficiary. Judgement or blessing – only God knows?
