US, WASHINGTON (ORDO NEWS) — There are many different theories about the origin of the SARS-CoV-2 virus, which caused a pandemic worldwide. In particular, there is a version that it is artificial and originated in the laboratory. However, an article published in the edition of Nature Medicine, shows that this virus – the product of natural evolution.
An international team of scientists conducted a comparative analysis of the sequences of the SARS-CoV-2 genome and its related viruses. Researchers have not found any evidence that the dangerous pathogen may be of synthetic origin.
“We can firmly establish that SARS-CoV-2 came about as a result of natural processes,” says Christian Andersen, a contributor to the Scripps Research Institute in California, one of the authors of the article.
In the course of their work, scientists analyzed the RNA regions in the genes of the spike-like proteins of the viral envelope. These are the main surface proteins of the virus, which are necessary for binding to the cell and penetration into it.
Researchers were primarily interested in nucleic acid sequences encoding the receptor-binding domain of spike proteins (RBD), as well as sequences corresponding to cleavage sites – “molecular canning knives”, by which the virus destroys the cell membrane.
It turned out that the RBD domain of viral proteins evolved in such a way as to interact most effectively with ACE2 receptors on the surface of the host cells. Evidence of natural evolution was obtained from the overall molecular structure of SARS-CoV-2. If hypothetical “bioterrorists” tried to construct a killer virus, they would create it on the basis of an already known pathogen with proven virulence.
But scientists claim that the “molecular backbone” of SARS-CoV-2 is markedly different from most similar known human viruses. It mainly resembles related viruses found in bats and reptiles. “These virus features preclude laboratory manipulation as a potential origin of SARS-CoV-2,” says Andersen.
The most likely origin of the virus fits into one of two possible scenarios. According to the first, the virus gradually changed in the body of the previous host (most likely, bats), acquiring high pathogenicity, after which it “turned over” to the person. So the previous major outbreaks of coronaviruses arose: for example, people received SARS-CoV (SARS) from civet, and MERS-CoV from camels.
In another scenario, the virus entered the human population in a non-pathogenic state and evolved in it already.
Scientists found confirmation of this hypothesis in pangolins: the RBD domains of some coronaviruses circulating among these animals resemble similar sites in SARS-CoV-2 proteins. It is possible that the virus went from the pangolins to humans through an intermediate host, and its spike-like protein restriction sites mutated later.
If SARS-CoV-2 has already entered the human body in its current pathogenic form, this increases the likelihood of future outbreaks, as the virus-causing strain of the virus can still circulate in animal reservoirs.
The likelihood that a non-pathogenic coronavirus entered the human population and then acquired properties similar to SARS-CoV-2 is noticeably lower. But while the researchers are not ready to say which scenario took place.
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