Does the new Coronavirus Sars-CoV-2 come from a test laboratory, even from the virology laboratory in Wuhan? This rumor has been haunted by the media for several months now, most recently fueled by the US government by references to alleged intelligence reports.
However, no evidence or even conclusive evidence for this speculation is available to date. As early as March, researchers in the journal “Nature” had declared that they had unsuccessfully searched the Sars-CoV-2 genome for traces of artificial changes.
There are now new findings. And they support the theory that natural emergence is more likely than artificial.
“All the things that make Sars-CoV-2 special and that are crucial for how it infects humans, how it is transmitted and spread among us are properties that have come together in a bat virus,” writes evolutionary biologist Andrew Rambaut from the University of Edinburgh on Twitter, who participated in the “Nature” study. “The fact that it is infected and successfully passed on to people is just a coincidence with a large dose of bias bias.”
In other words, it cannot be completely ruled out that coronaviruses were taken from nature, that they developed in laboratory animals such as ferrets in a laboratory like in Wuhan, and that the pandemic was then spread to the world via infected laboratory staff.
The genetic material of a coronavirus, which resulted from such a hypothetical scenario, could not be differentiated from the genetic material of a naturally circulating in bats or pangolins and then spreading to humans.
However, based on everything that researchers now know about Sars-CoV-2 and closely related viruses in bats and pangolines, no laboratory accident or crime story is needed to explain the origin of the novel corona virus.
According to new analyzes, according to Rambaut, all those gene variants that make Sars-CoV-2 so special can be found in the genome of coronaviruses that circulate in bats and pangolines.
If cells of an animal are infected with several such viruses, the genome of one virus can be mixed with genes of the other and the resulting ones acquire a new combination of properties.
There is, for example, the characteristic gene mutation that enables the virus to bind better to human cells. It affects the “spike” protein, a “sting” that docks to a receptor (ACE2) on the surface of human cells.
The receptor binding domain (RBD) of the “spike” protein can be found in a pangolin coronavirus.
Some researchers conclude that Sars-CoV-2 has jumped from pangolines to humans. But the pangolin virus lacks the other equally important and characteristic mutations of Sars-CoV-2. These can be found in bat viruses.
Rambaut believes that it is “much more likely” that the Sars-CoV-2 most similar known bat virus (called RaTG13) once had the RBD mutation, but then lost it or exchanged it with a typical RBD genome.
Mutation mixture in bat cells
The second peculiarity of Sars-CoV-2 is a genetic mutation, which in the first place gives the spike protein the property of smuggling the virus into lung cells: a change in the blueprint of the spike protein. It creates an interface for the enzyme furin, which is sufficiently present in the upper throat area of humans.
If the virus gets into the body and binds to a lung cell with the spikes, the human furin cuts it so that the viruses get into the cell. Other corona viruses need other, less effective enzymes for this. This explains the higher infectivity of Sars-CoV-2.
However, the gene mutation that enables Sars-CoV-2 is not new or even constructed by human hands in the laboratory, but had previously arisen in another corona virus. Researchers discovered these viruses, known as HKU9, in a bat from Guangdong in China.
This is “very convincing evidence,” says Rambaut that this mutation was caught by the virus that later developed Sars-CoV-2 – at a time when it was still circulating in bats.
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