As the new coronavirus that causes the disease COVID-19 spreads across the globe and the number of cases exceeds 284,000 worldwide, misinformation is spreading almost as quickly.
One myth is that this virus, named SARS-CoV-2, was created by scientists in a laboratory in Wuhan, China, where the outbreak began.
A new analysis of the SARS-CoV-2 coronavirus could finally refute it. A group of researchers compared the genome of the new coronavirus to seven other coronaviruses that infect humans: SARS, MERS and SARS-CoV, which can cause serious illness; along with HKU1, NL63, OC43 and 229E, which usually cause only mild symptoms, the study is published in the journal Nature Medicine.
“Our analysis clearly shows that the coronavirus is not a laboratory construct or a targeted virus,” they write in the article.
Christian Andersen, assistant professor of immunology and microbiology, and his colleagues looked at the genetic template for the spike proteins that reside on the virus envelope.
The coronavirus uses spines to latch onto the outer walls of its host's cells and then enter those cells. They specifically looked at the gene sequences responsible for two key features of these spike proteins: an uptake, called a receptor-binding domain, that clings to cells; and the so-called cleavage location, which allows the virus to open up and enter these cells.
This analysis showed that the 'spine' part evolved to target a receptor in human cells called ACE2, which is involved in the regulation of blood pressure. It is so effective at attaching to human cells that, according to the researchers, the binding proteins were the result of natural selection, not genetic engineering.
Here's why: The SARS-CoV-2 coronavirus is very closely related to the virus that causes Severe Acute Respiratory Syndrome (SARS) that spread around the world almost 20 years ago. Scientists have studied how SARS-CoV differs from SARS-CoV-2 – several key changes in the genetic code.
However, in computer simulations, mutations in SARS-CoV-2 do not seem to be very good at helping the virus to bind to human cells. If scientists had specifically designed this virus, they would not have chosen mutations that computer models suggest would not work.
But it turns out that nature is smarter than scientists, and the new coronavirus has found a way to mutate, becoming better and completely different from anything that scientists could create, the study showed.
Another nail in the 'laboratory leak' theory?
The general molecular structure of this virus differs from known coronaviruses and instead most closely resembles the viruses found in bats and pangolins, which are poorly understood and have never caused harm to humans.
“If someone were looking to create a new virus as a pathogen, they would create it from the base of a virus that is known to cause disease.”
Where did the coronavirus come from?
The research team has proposed two possible scenarios for the origin of SARS-CoV-2 in humans. One scenario follows the origin stories of several other recent coronaviruses that have caused chaos in society. In this scenario, we contracted the virus directly from animals – civets for SARS and camels for Middle East Respiratory Syndrome (MERS). In the case of SARS-CoV-2, researchers speculate that the animal was a bat that transmitted the virus to humans.
In this possible scenario, the genetic traits that make the new coronavirus so effective in infecting human cells (its pathogenic ability) would be in place before moving on to humans.
In another scenario, these pathogenic traits would only evolve after the virus passed from the host animal to the human. Some pangolin-derived coronaviruses have a 'hook structure' (this receptor-binding domain) similar to SARS-CoV-2. Thus, the bat directly or indirectly transmitted its virus to the human host. Then, once inside a human host, the virus could evolve to have another hidden feature – which allows it to easily enter human cells. The researchers said that after developing this ability, the coronavirus will become even more capable of spreading between people.
All of these technical details could help scientists predict the future of this pandemic. If the virus has entered human cells in a pathogenic form, it increases the likelihood of future outbreaks. The virus can still circulate in the animal population and can spread back to humans and cause an outbreak. But the chances of such future outbreaks are lower if the virus must first enter the human population and then develop pathogenic properties, the researchers said.
Sources: Photo: Andriy Onufriyenko / Getty Images
