What Makes Us Susceptible to COVID-19?

COVID-19 has been the talk of the town, I mean the world, for the past four months. The deadly respiratory virus originated from Wuhan, China but the number of cases escalated faster than lightning, quivering the entire world. Economies are crashing and countries are on lockdowns leaving people anxious and terrified. The extent of this pandemic has reached, if not surpassed, the level of other dangerous ones such as the Cholera outbreak, Spanish flu, and the Black Death to name a few. Scientists are leaving no stone unturned to develop novel vaccines, while the doctors and nurses are putting their best foot forward to alleviate the health impacts of the virus.

With the rapid spread of the coronavirus globally, it has become important for a deeper understanding of the molecular and genetic interactions of the virus. Coronavirus is reminiscent of the severe respiratory syndrome coronavirus (SARS-CoV) outbreak in 2002-2003; researchers have classified COVID-19 as a new member of the beta coronavirus genus, related to SARS-CoV. According to a study by Wan et al. (2020), bats and palm civets were thought to be natural and intermediate reservoirs for SARS-CoV – ring a bell? Due to such overlapping characteristics, scientists are using previous research on atomic interactions between the SARS-CoV spike protein receptor-binding domain (RBD) and its receptor angiotensin-converting enzyme2 (ACE2). In other words, each virus has specific regions on its surface that enable the virus to attach to host cells in a lock and key type of fashion. Just as keys are specific to locks, ACE2 receptors are specific to each RBD. Researchers provide evidence that COVID-19’s RBDs bind to the ACE2 receptors just like SARS-CoV but with a greater affinity (Wrapp et al. 2020). This is how this chaotic virus gains entry into host cells before initiating the many respiratory symptoms that we’re all too familiar with.

Molecular structure of COVID-19.

Now that we have this information, let’s get to the point – how does this relate to cats?

“The virus binding site on ACE-2 receptors in cats is very similar to those of humans, so it would not be surprising if COVID-19 binds to ACE-2 receptors in cats. However, given the low numbers of dogs and cats reported to be infected with COVID-19, it is impossible to say at this time whether cats are more susceptible to infection or clinical signs of disease.”

Dr. Jane Sykes from the University of California

On the other hand, mice can never get infected by COVID-19. According to Wan et al. (2020), COVID-19 most likely did not use mouse ACE2 receptors for attachment because those receptors possess a small genetic difference – a single building block, histidine, replaces another, lysine; lysine is the preferred one for COVID-19 and is present in humans and cats. So, histidine and lysine are the amino acids that contribute to the difference between ACE2 for mice vs. COVID-19 hosts. It is fascinating how just a single amino acid difference in the host receptor can possibly determine host susceptibility and resistance to COVID-19. This suggests the crucial role of genetic sequences that generate these building blocks.

Do you think these connections hold the key to resistance and vaccine development? Share your thoughts in the comments below.


References

dvm360. (2020, March). Cat tests positive for COVID-19, but there is no cause for panic.dvm360. Retrieved from https://www.dvm360.com/view/cat-tests-positive-for-covid-19,-but-there-is-no-cause-for-panic

Wan Y, Shang J, Graham R, Baric R, Li F. 2020. Receptor Recognition by Novel Coronavirus from Wuhan: an Analysis Based on Decade-Long Structural Studies of SARS Coronavirus. Journal of Virology 94:1–7.

Wrapp D, Wang N, Corbett K, Goldsmith J, Hsieh C-L, Abiona O, Graham B, McLellan Jason. 2020. Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation. American Association for the Advancement of Science :1260–1263.

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