According to scientists, similarities between the amino acids present in both organisms reinforce the theory that the virus evolved naturally.
With the advance of the Covid-19 pandemic, researchers around the world are trying to understand where Sars-CoV-2, the coronavirus that causes the disease, originated. Now, a study led by scientists at Shandong University in China, promises to take a new step towards the answer.
According to an article published by the team in the journal Cell Press in early May, some parts of the genome of a virus that infects bats, known as RmYN02, are very similar to that of the new coronavirus. Although it is not a direct evolutionary precursor to Sars-CoV-2, the organism shows that the new coronavirus evolved naturally.
As the researchers explain, what is most striking about the discovery is the presence of amino acids between the S1 and S2 parts of the coronavirus spike protein. “Since the discovery of SARS-CoV-2 there have been a number of unfounded suggestions that the virus has a laboratory origin,” commented Weifeng Shi, the study’s leader, in a statement. “In particular, it has been proposed the S1/S2 insertion is highly unusual and perhaps indicative of laboratory manipulation. Our paper shows very clearly that these events occur naturally in wildlife.”
The closest relative to Sars-CoV-2 is another virus, called RaTG13, which was previously identified in bats in Yunnan province. But RmYN02 is even more like the coronavirus that causes Covid-19: in some parts of the genome, including the longest coding section, called 1ab, the two microorganisms share 97.2% of their RNA.
Still, the two viruses have fundamentally different characteristics – like the insertions between the S1 and S2 parts of the spike protein. According to the experts, these divergences indicate the independent and natural evolution of these microorganisms.
“Our work sheds more light on the evolutionary ancestry of SARS-CoV-2,” said Shi. “Neither RaTG13 nor RmYN02 is the direct ancestor of SARS-CoV-2, because there is still an evolutionary gap between these viruses. But our study strongly suggests that sampling of more wildlife species will reveal viruses that are even more closely related to SARS-CoV-2 and perhaps even its direct ancestors, which will tell us a great deal about how this virus emerged in humans.”