Happy Tuesday, friends!
Recently, JdM shared a link to a story on NPR that discusses the effects of COVID on blood vessels. I couldn’t have said it better, so I’m sharing the story in its entirety.
In other news, there’s been a lot of interest (and a lot written) on various COVID-19 treatments – but what is the science behind how they work?
But first – a little background. Back in May, I discussed how viruses enter cells.
For COVID – the surface of the novel coronavirus is studded with a Spike protein (the little red spikes in the diagram above, which happens to be a good fit for the ACE2 receptor, which is found all through our respiratory system. The spike protein effectively unzips, exposing two chains of amino acids in order to fuse to the cell. When the spike protein of the virus fits (or docks) into the ACE2 receptor, the cell thinks a friendly neighbor (or food) has come to visit, so it invites the virus in by a process called endocytosis, which means the cell membrane fuses with and surrounds the virus and takes it inside the cell. Once inside the enzymes in the cell helpfully disintegrate the virus’ coat, releasing the viral genetic material. From there, the virus uses the cell’s machinery to make more of the virus, and then the virus is packaged and exits the cells in a similar way to how it entered.
Knowing a little bit about how the virus operates, helps us understand better how some of the main treatment strategies work. So – what are these strategies?
- One strategy is to prevent the virus from infecting our cells. This is obviously the first line of defense as anyone would tell you.
Vaccines use this strategy. There are currently no approved vaccines, but in the case of most COVID vaccines that are under development right now, the vaccine introduces into our body a piece of the coronavirus (like the spike protein I mentioned above). Because it is just an isolated piece of the virus, it can’t infect us, but what is does do is signal our immune system to get to work. When vaccinated, our bodies will produce antibodies (large, Y-shaped proteins produced mainly by plasma cells that are used by your body’s immune system to fight off infections.) These antibodies will then recognize the virus if you are exposed to it and help fight off the virus before it can enter cells.
Other scientists have investigated other treatments that will keep the virus from entering cells. One was described recently in the New York Times. It has only been tested in a small number of animals, so of course is a long way from being tested for humans and approved by the Food and Drug Administration (FDA), but the Times article explains the concept well. The treatment (tested in a small number of ferrets) is a nasal spray that contains a small protein sequence that matches the virus’ spike protein. When the spike protein tries to unzip and fuse to the cell wall, this peptide in the nasal spray inserts itself and latched on tightly to the spike protein, thus preventing the virus from attaching to the cell.
- Vaccines are still under development, so another option is to prevent the virus from spreading once someone is infected.
This is how anti-viral medications like Remdesivir work. As you probably have heard, the FDA gave an emergency use authorization for this drug in May.
Remdesivir (chemical structure shown above) was developed by Gilead pharmaceuticals and is a broad-spectrum antiviral medication (meaning it works to varying degrees against a wide range of viruses). In its active form, Remdesivir it looks like one of the building blocks of RNA (ribonucleic acid), which is the type of genetic material found in coronaviruses. As I mentioned above, when the virus enters the cells, it uses the cell to make more copies of itself, including its genetic material. Remdesivir looks enough like a building block of RNA to be taken up into this copying machinery, but it actually causes the replication of the virus’ genetic material to stop and thus prevents the virus from multiplying.
Several companies also have antibody treatments that are currently in clinical trial. Instead of having the body produce antibodies, these treatments consist of doses of antibodies against COVID that have been developed in the laboratory. These antibodies also work to help fight off COVID much like ones produced by your body. Regeneron’s treatment, called REGN-COV2, consists of two antibodies against the coronavirus spike protein. Early results from a clinical trial that Regeneron released in September showed that these antibodies may help treat coronavirus patients outside of the hospital by reducing virus levels and symptoms.