Coronavirus closely related to the pandemic virus found in Japan and Cambodia

Two lab freezers in Asia have made amazing discoveries.Researcher said Nature They found a coronavirus closely related to the pandemic-causing virus SARS-CoV-2 in the Greater Horseshoe Bat, which is stored in a freezer in Cambodia. Meanwhile, the Japanese team reported the discovery of another closely related coronavirus — also found in frozen bat droppings.

The virus is the first known relative of SARS-CoV-2 found outside of China and is the World Health Organization’s. Search throughout Asia For pandemic animal origin. Strong evidence suggests that SARS-CoV-2 is derived from the Greater Horseshoe Bat, but it remains a mystery whether it is passed directly from the bat to humans or through an intermediate host.

The Cambodian virus was found in two horseshoe bats, Shamel (Rhinolophus shameli) Captured in the northern part of the country in 2010. It is difficult to confirm its full importance to a pandemic, as the viral genome has not yet been fully sequenced and its findings have not been published.

If the virus is very closely associated with the pandemic virus, or even its ancestors, it provides important information about how SARS-CoV-2 was transmitted from bats to humans and is pandemic. It may provide information in the search for origin, says Veasna Duong.A virologist at the Pasteur Institute in Phnom Penh, who led the search for old samples in Cambodia and issued a warning. Nature For their discovery in early November. To provide such insight, the virus must share at least 97% of its genome with SARS-CoV-2. Researchers say this is more than the closest known relatives.

However, the new virus may be more distant. In that case, studying it will help scientists learn more about the diversity of this virus family, says Etienne Simon Loriere, a virologist at the Pasteur Institute in Paris. The virus, then it is publicly shared.

This is the case with another virus called Rc-o319 found in the small Japanese horseshoe bat (Rhinolophus cornutus) Captured in 2013. According to the treatise, the virus shares 81% of its genome with SARS-CoV-2.¹ Published November 2 — too far to provide insight into the origin of the pandemic, says Edward Holmes, a virologist at the University of Sydney, Australia.

Whatever the Cambodian team finds, both findings are exciting because they have confirmed that the virus closely associated with SARS-CoV-2 is relatively common. Rhinolophus Bats, and even bats found outside China, saw part of the Cambodian team’s analysis but were not involved in the study, says Alice Latine, an evolutionary biologist in Vietnam, the Wildlife Conservation Society of Hanoi. I will.

“This is what we were looking for and we found it,” says Duong. “It was exciting and surprising at the same time.”

Origin of the pandemic

The findings also suggest that other undiscovered relatives of SARS-CoV-2 may be stored in the freezer in the laboratory, an infectious disease researcher at Zhejiang University in Hangzhou, China. Says Aaron Irving. Mammals for antibodies to SARS-CoV-2.

“I didn’t expect to find a relative of SARS-CoV-2,” said Murakami, a virologist at the University of Tokyo, who was part of a team that decided to retest virus tests on frozen animal samples as a result of a pandemic. True says.

Only a handful of known coronaviruses are closely associated with SARS-CoV-2, including the closest known relative RaTG13. Found in the Greater Horseshoe Bat in the middle (Rhinolophus affinis) Published in Yunnan, China in 2013² Only at the beginning of this year. There are several other coronaviruses. Rhinolophus With bats Pangolin Captured between 2015 and 2019, scientists have found it to be closely associated with SARS-CoV-2.

“SARS-CoV-2 was probably not a brand new virus that emerged suddenly. This group of viruses existed before they were noticed in 2019,” said the University of California, Davis, which is involved in the Cambodian team. Tracey Goldstein, Deputy Director of the One Health Institute in Cambodia, said.

Latine says the discovery confirms it Rhinolophus Bats are a repository of these viruses.

Cambodian virus

Duong’s team captured Shamel’s Greater Horseshoe Bat in Cambodia as part of a US government-funded PREDICT project. The project has been investigating potential wildlife pandemic viruses around the world for decades and ended earlier this year. In April, the US Agency for International Development granted the program an additional US $ 3 million and a six-month extension to look for evidence of SARS-CoV-2 in animal samples (mainly bats, pangolins, and other animals). I did. Sitting in freezers in Laos, Malaysia, Nepal, Thailand, Vietnam and Cambodia. Full reports of these studies are expected in the coming weeks.

Duong showed that preliminary genomic sequencing of a short fragment of the new bat virus (324 base pair length) resembles the same region of SARS-CoV-2 and RaTG-13, with the three closely linked. Says it suggests that it is related to. The area is highly conserved by the coronavirus and is often used to quickly identify whether the virus is new or known. However, it is not yet clear whether RaTG-13 or the new virus is more closely associated with SARS-CoV-2.

Vibol Hul, a virologist at the Pasteur Institute in Cambodia, who captured the Greater Horseshoe Bat at the entrance to the cave in 2010, says it’s hard to say in such a small piece.About the most well-known coronavirus genome 30,000 base pairs..

In another analysis, the Cambodian team used locally available technology to sequence about 70% of the genome of the new virus, a virologist at the Cambodian Pasteur Institute who helped analyze the bats. Eric Carlson says. Missing from that sequence were instructions for important parts of the virus, such as the gene encoding the spike protein normally used by the coronavirus to enter cells. The sequence in that section shows whether the virus can infect human cells, Duong says.

Irving says the new virus must be at least 99% similar to SARS-CoV-2 in order to be a direct ancestor of the current pandemic virus. The genomic difference between RaTG13 and SARS-CoV-2 is only 4%, but because they share a common ancestor, the difference represents a 40-70 year evolution. Although decades apart, viruses are similar enough to invade cells using the same receptors.Cell research RaTG13 can infect people..

Another close relative

Of the known coronaviruses associated with SARS-CoV-2, the newly discovered Rc-o319 seems to be the most distant, says Duong.

In cell research, the Japanese team discovered that the virus could not bind to the receptors that SARS-CoV-2 uses to invade human cells. This suggests that the virus cannot easily infect humans.

According to Shin, his colleagues will catch more bats in Japan earlier this year and test them for the coronavirus. And in October, Hur returned to a cave in northern Cambodia to catch more bats.

Probably more SARS-CoV-2 related coronaviruses Rhinolophus Holmes says the number of bats that live throughout the region. “Hopefully, one or more of these are so closely associated with SARS-CoV-2 that we can consider it a true ancestor.”