THERE is now a steady stream of speculation and conspiracy theories that SARS-CoV-2, the causative agent of Covid-19 was deliberately or accidentally released from a laboratory in Wuhan, China.
Such speculations are not new. There is still a school of thought that says earth is flat, 9/11 was a self-attack, and A(HINI) [ihc-hide-content ihc_mb_type=”show” ihc_mb_who=”2,3,5″ ihc_mb_template=”1″ ]was caused by pharmaceutical companies to create market for their drugs. All these make great ideas for the next blockbuster sci-fi movies.
But science has proven otherwise in many cases. Let us look at SARS-CoV-2, based on a research paper published in Nature Medicine, in March 2020 by scientists in the US, UK and Australia.
https://doi.org/10.1038/s41591-020-0820-9
The virus
SARS-CoV-2 is the 7th coronavirus known to infect humans. Others are viruses that cause SARS, MERS and other milder to moderate respiratory ailments such as HKU1, NL63, OC43 and 229E.
Corona literally means crown or garland in Latin. The virus got its name for the crown-like spikes on their surface (imagine Rambutan). There are four types: alpha, beta, gamma, and delta. SARS-CoV-2 is a beta coronavirus just like SARS-CoV and MERS-CoV.
Coronavirus is an RNA virus which means it lacks one step in making its protein. In DNA viruses, DNA is transcribed into RNA which is then translated into protein. Lacking one step makes coronavirus error prone, causing high levels of mutation to become new coronaviruses.
The findings
The scientists compared alpha and beta coronavirus and found SARS-CoV-2 to have two features:
- This virus binds to ACE2 (angiotensin converting enzyme 2) that is found on surfaces of lungs. This is where the virus will start infecting by latching to the cells.
- A site in its spike that allows human protein (furin) to cleave the virus to allow it to infect the human cells. (Remember, virus does not have any machineries. It uses the host machineries to infect and replicate.)
Here are the reasons why the scientists concluded that SARS-CoV-2 is not a laboratory construct or a purposefully manipulated virus:
1.Although SARS-CoV-2 binds well with ACE2, the interaction between the virus and ACE2 is not ideal. SARS-CoV (the one that causes SARS) does a better job in binding to human cells. This shows that SARS-CoV-2 is not the product of deliberate manipulation. Computational analysis was done to study the binding efficiency.
2. The scientists compared the cleavage sites of SARS-CoV2 with other coronaviruses like HKU1 and SARS-CoV, and those found in pangolin and bats. There is a wide genetic variation in the spike, suggesting it is likely that the same virus or similar strains will be discovered in other species.
3. The scientists compared SARS-CoV-2 to MERS-CoV and bird flu virus. The spikes in MERS-CoV can be very well cleaved by human protein. This allows MERS-CoV that originated from bat to infect human cells. In bird flu, the virus mutates fast where chicken population is high and acquires the effective cleavage site, making the mutated ones to be highly infectious to chickens. The effective cleavage site is acquired after repeated transfer from one animal to another through mutation. This is how SARS-CoV-2 too mutated till it is able to infect humans effectively. This comparison allowed scientists to concluded SARS-CoV-2 as a product of natural mutation.
4. Genetic manipulation cannot be done from scratch. Scientists still need to start from existing organism, in this case a virus. This would involve synthesising a gene based on the trait the scientists want. But when scientists studied the genetic data of SARS-CoV-2, they found that this novel virus is not derived from any previously known virus backbone. SARS-CoV-2 has components that differ from known viruses, so they had to come from an unknown virus or viruses in nature.
5. Scientists proposed two possibilities to explain the origin of SAR-CoV-2.
a.The virus mutated in the animal before it was transferred to humans
b.The virus mutated in humans after transfer from animals
6. Since the earliest case of Covid-19 is reported in Huanan market, it is possible that animal sources were present there. The similarity between SARS-CoV and SARS-CoV-2 suggests bats as the reservoir for this virus. Malayan pangolin illegally imported into Guangdong contain coronaviruses similar to SARS-CoV-2, clearly suggesting the virus is a product of natural mutation.
7. Coronavirus in pangolins have the binding efficiency to ACE2, similar to SARS-CoV-2. The effective cleavage site in SARS-CoV-2 might have been acquired during natural mutation that occurred after infecting humans. It could also been a product of pangolin and bat coronavirus as they swap gene in nature.
8. The virus has too many distinct features that does not make sense. Any scientists engineering a deadly virus will not do that.
9. SARS-CoV-2 has a site for sugar attachment where the sugar from the host protects the virus from host’s immune system. If the virus was made in the lab, tissue culture dishes do not have immune systems for the virus to adapt to have the sugar attachment site.
There are strong scientific reasons to conclude SARS-CoV-2 is not lab-made. These findings are supported by virologists in various other countries including Switzerland. Whatever said, conspiracy theories will stay as they are great fodder for many. pd[/ihc-hide-content]
