Chinese scientists have for the first time identified in nature a genetic feature of Sars-CoV-2 that makes it so infectious, but has not been seen before in other coronaviruses.
Before the pandemic, a “furin cleavage site” had not been identified in a bat coronavirus, leading some to suggest that it had been artificially inserted in a laboratory.
Now, scientists working for the Chinese Center for Disease Control have identified two betacoronaviruses, a class of viruses found in bats and rodents with furin cleavage sites and other genetic characteristics similar to Sars-Cov-2.
Genetic sequencing was performed on the stomach contents of 112 bats collected from caves in Hainan province, China, between March 30 and April 1, 2021, according to a study published in Science Direct last week.
Two samples were found to have identical furin cleavage sites resembling the corresponding sites of Sars-CoV-2. Furthermore, one of the CoV CD35 samples had a receptor-binding domain that was “very similar” in structure to that of Sars-CoV-1 and Sars-CoV-2.
“Bat CoV CD35 is so far the closest relative of Sars-CoV-2 with a furin-like polybasic site, strongly suggesting that the cleavage site is naturally occurring,” the authors say.
“In conclusion, this study deepens our understanding of coronavirus diversity and provides clues to the natural origin of the SARS-CoV-2 furin cleavage site.”
The findings do not prove how Covid-19 got from bats to people, and the authors noted that the viruses are “distant relatives” of Sars-Cov-2 that belong to different subgroups of betacoronaviruses.
But Dr Linfa Wang, a professor of emerging infectious diseases at Duke-NUS Medical School in Singapore who played a leading role in identifying bats as the natural host for the Sars virus, said they are important.
“Although the identified sequence is not identical to that of Sars-CoV-2, it is close enough to conclude that such sequences may exist naturally,” said Professor Wang, who was not involved in the research.
The study also noted that the bats that harbor these viruses, the great round-leaf bat and the Himalayan great leaf-nosed bat, are commonly found in southern China, Myanmar, Thailand, Laos, Vietnam and Malaysia. The potential for the virus to spread to humans “remains unknown and needs further investigation,” the researchers added.
Professor Jonathan Ball, professor of virology at the University of Nottingham who was not involved in the study, said: “Possession of a potential furin cleavage site is clearly not unique to Sars-CoV-2, and may be found in other species”. coronavirus, as confirmed by this study.
“Coronaviruses are adept at sharing genetic material through a process we call recombination,” he told the Telegraph. “This is an effective way for the virus to obtain potentially advantageous blocks of genetic material from other coronavirus genetic changes that allow it to acquire new behaviours, for example the potential to infect and transmit in new species.
“It should come as no surprise that Sars-CoV2 probably arose after recombination between one or more circulating ancestral sequences in bats and probably another unknown intermediate host, one of which already possessed the furin cleavage site,” Professor Ball said.
While there is no conclusive evidence to confirm whether the pandemic started with a natural spillover or a laboratory link, the research comes amid a flurry of investigations offering new clues.
Genomic data recently released by a team led by Dr. George Gao, former head of China’s Centers for Disease Control, showed that DNA from suspected wildlife, including raccoon dogs, was mixed with Covid-positive samples. collected at the Huanan wet market soon after. closed in January 2020.
The data is not irrefutable proof, but it does show that animals capable of contracting and spreading SARS-Cov-2 were on the market, something Chinese authorities had originally denied.
A second paper published in March found that 12 percent of people in rural Myanmar have been exposed to Sars-like coronaviruses, including one of the closest known viral relatives of Covid-19, showing just how many unknown pathogens they lurk in bats and wildlife in Southeast Asia. .
It was announced Monday that the EcoHealth Alliance, an organization that is researching the ways zoonotic side events occur, will be re-founded by the US National Institutes of Health.
His research had previously been halted in early 2020 after a dispute over his ties to the Chinese-run high-security lab in Wuhan.