Coronaviruses: Characteristics, Hazards and Cures

Updated: Mar 17, 2020

Opening remarks

It is hardly an understatement to say that the outbreak of the novel Coronavirus of 2019 (nCOV/ SARS-CoV2/COVID19) has become a worldwide problem since its spread around the globe started in late 2019.


There is still a lot that we do not know about COVID19, but with that said, we do have a good grasp about how the family Coronaviridae, works. What is written in this article may not entirely reflect how COVID19 behaves, but it will present how in theory the virus will behave based on observations made so far about the viral family it belongs to.


Structure and function

Coronaviruses are the second most common cause of the cold, with the most common cause being Rhinoviruses (In the family Picornaviridae, same as the Poliovirus). Coronaviruses are given their name by their appearance in an electron microscope, which looks like small suns, surrounded by a halo or a "corona". This is actually their spike proteins embedded in the viral envelope, which is actually just a cell membrane the virus has "stolen" when it buds off from a eukaryotic cell. It is mostly made out of cholesterol and phospholipids. The virus then embeds its own proteins in the envelope to suit its own purposes.


Having an envelope gives the virus certain abilities at the trade-off of losing others:

+ They are more easily spread through fluids (e.g coughing/sneezing)

+Given humid and cold conditions, they are more long lasting as an aerosol when people sneeze or cough.

+ Coronaviruses can survive in the GI tract, thanks to their Spike-glycoproteins on the envelope.


However:

- They are sensitive to drying out e.g by heat or alcohol

- They are sensitive to soap because of their fatty envelope


The virus's genetic material is stored within a protein cover called a capsid, which has different geometrical shapes depending on what types of viruses we talk about. In the case of coronaviruses it has a helical shape (ie, it is basically an empty toilet paper roll). Inside this roll is where the genetic material is stored. For coronaviruses, it is in the form of mRNA. The mRNA strand for coronaviruses is a large one and holds a lot of genetic information.


Infection with Coronaviruses


Different coronaviruses uses different receptors on human cells to enter them. In a recent article in the Lancet, Roth and colleagues discuss comorbidities and infection with COVID19. Other scientists have concluded that both SARS and COVID19 bind to the same receptor, ACE2.


ACE(Angiotensin converting enzyme) is a family of proteins found mostly on blood vessels and epithelial cells. This enzyme family is a common drug target for medication against high blood pressure and kidney disease. Drugs commonly target ACE1, which is mostly involved with regulating blood pressure. ACE2 has a smaller role in blood pressure control. However, Roth and colleagues inquire that patientens using ACE1-inhibitors (drug class), have an increased amount of ACE2 and are therefore more susceptible to COVID19. Other medication can also affect expression of ACE2.


Anyways, all coronaviruses, and not only COVID19, follow a certain structure after infecting a cell.


1. The virus enters the cell and releases it's mRNA, which is readily translated into a viral polymerase by the cells ribosomes (RNA-dependent RNA polymerase/ "L-protein").

2. The viral polymerase produces a new , complementary strand of RNA (negative sense RNA)

3. This strand is then transcribed and translated to form several new types of mRNA for production of viral proteins and more viral genetic material (which is itself just mRNA).

4. The viral constituents are assembled