SARS-CoV-2: The Video Explainer
The coronavirus, also known as SARS-CoV-2, has drastically altered the way we live our day to day lives. Including social distancing, entering a quarantine that affected much of the nation last spring, and the hazards to our health, the uncertainty of this virus has been the source of much stress and anxiety.
Hopefully by sharing a bit of knowledge we gained in our biochem studies we, students at Middlebury College, can begin to demystify the science behind the virus and how it might be overcome with a vaccine. But first, let us explain what COVID is and how the coronavirus infects our bodies.
COVID-19 is a severe respiratory illness caused by the coronavirus, which attacks cellular tissue in our lungs, among other organs. We can think of coronavirus particles as small spheres covered in little spikes made of protein. These spheres can enter our bodies through our mucus membranes, which include our eyes, ears, mouth, and nose.
Contact between the virus and these parts of our body provides an entryway for the virus as it makes its journey through the body to the lungs. Once in the lungs, the spike proteins reach out and attach to proteins on our lung cells named ACE2 receptors. The interaction between the spike proteins and the ACE2 receptors initiates the fusion of the viral particle with our cells.
Once joined together, the virus uses its chemical machinery to hijack our cells. The virus inserts its genome — the set of instructions used to make copies of itself — into our cell. This replication of the virus causes the infected cells to stop performing its normal functions. The cells devote their machinery to making new viral particles, which then bud from the cells. These new viral particles can move on to infect other cells. The sustained infection of these cells results in inflammation of lung tissue, which causes the severe pneumonia symptoms that an infected person would experience.
Now that these viral particles have replicated and made their way to other parts of the body, they can become a part of your saliva. When an infected person coughs or sneezes or even just breathes, these particles are released into the air in the form of little droplets, which can cause someone nearby to become infected with the virus through the process just discussed.
When faced with foreign pathogens, our bodies have a natural defense system to protect our cells from these pathogenic attacks. The first line of defense is our mucus membranes, which help block viruses and bacteria from entering our bodies.
The second line of defense is the immune system, which is the coordinated effort of many types of cells which help fight off infections. Among those cells are macrophages, B-cells, and T-cells, which are all types of white blood cells. Macrophages engulf and digest unrecognized particles in our bodies such as viruses. After destroying these particles, they leave traces of the virus, which are called antigens. These antigens are then recognized by B-cells, which make antibodies that bind to the antigens. This antibody production helps our body distinguish between our own cells and harmful pathogens. The antibodies can bind to antigens expressed on a pathogen’s surface, making it difficult for the pathogen to infect cells.
Other than the macrophages and B-cells, we have T-cells. One type of T-cell is called the cytotoxic T-cell, which targets infected cells in the body so that the infected cells can be destroyed before they can make new virus particles. Through direct attack on infected cells and prevention of cell infection, the immune system works to fight the viral attack.
So how do vaccines work? When the body first encounters a virus, it can take a long time for the body to recognize and mount an immune response. Vaccines help us decrease the amount of time required to develop all of the tools necessary to fight infection.
Vaccines are essentially a “practice round” for our immune systems. When we get a vaccine, we are injected with a small sample of live, weakened virus, or fragments of viral material. Without causing any illness, these particles or fragments cause our bodies to create antibodies. The B- and T-cells that can efficiently produce this response are stored as memory-B-cells and memory-T-cells, which have the ability to recognize a viral infection and begin an immune response much more quickly. This fast response allows our body to better contain the infection, which will result in a less severe case of a virus.
To put this into the context of coronavirus, most vaccines being developed for COVID cause production of antibodies for the spike protein, the protein on the coronavirus surface that allows it to infect cells.
One thing to know is that not everyone’s immune system works in the same way. For individuals who have immune deficiency, the immune system doesn’t respond as well to infections. In regards to COVID-19, the virus is able to infect more and more cells causing more harm to the body. Immune deficiency is commonly hereditary, but also is more common amongst individuals who are of old age. In order to protect individuals with weakened immunity, it is imperative to follow the COVID prevention rules: Wear a mask, give others as least six feet of social distance, and wash your hands.
Additionally, vaccines are very important because they increase the likelihood of herd immunity. Herd immunity occurs when a large proportion of the population becomes immune to a disease, therefore making it harder for the virus to spread. The virus cannot make lots of copies of itself in an immune host so there’s ultimately less virus around. Herd immunity can also happen naturally, the downside is that a large proportion of the population would have to be infected, which puts those who are immune deficient at great risk.
Therefore, as vaccines help to prime the recipient’s immune system, they also protect the overall population. While we wait for the wide distribution of a vaccine, there are some crucial steps that we can all take to protect ourselves and those around us including washing your hands, maintaining 6 feet of social distancing, and wearing a mask.
The video was written by Middlebury College students Matt Brockley, Jenny Pushner, and Carter Lombardi. It was illustrated by Matt Brockley. They noted their thanks to Professor Lindsay Repka for all she did to help with this video, and they acknowledged students in Middlebury College’s Fall 2020 Biochemistry course for their efforts to make the coronavirus a more accessible topic to Addison County residents.
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