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Closest known relatives of virus behind COVID-19 found in Laos

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Rhinolophus bats roosting in a cave in Thailand. Credit: Getty

Scientists have found three viruses in bats in Laos which might be extra just like SARS-CoV-2 than any known viruses. Researchers say that elements of their genetic code bolster claims that the virus behind COVID-19 has a pure origin — however their discovery additionally raises fears that there are quite a few coronaviruses with the potential to contaminate individuals.

David Robertson, a virologist on the University of Glasgow, UK, calls the discover “fascinating, and quite terrifying”.

The outcomes, which aren’t peer reviewed, have been posted on the preprint server Research Square1. Particularly regarding is that the brand new viruses comprise receptor binding domains which might be nearly similar to that of SARS-CoV-2, and might due to this fact infect human cells. The receptor binding area permits SARS-CoV-2 to connect to a receptor referred to as ACE2 on the floor of human cells to enter them.

To make the invention, Marc Eloit, a virologist on the Pasteur Institute in Paris and his colleagues in France and Laos, took saliva, faeces and urine samples from 645 bats in caves in northern Laos. In three horseshoe (Rhinolophus) bat species, they found viruses which might be every greater than 95% similar to SARS-CoV-2, which they named BANAL-52, BANAL-103 and BANAL-236.

Natural origin

“When SARS-CoV-2 was first sequenced, the receptor binding domain didn’t really look like anything we’d seen before,” says Edward Holmes, a virologist on the University of Sydney in Australia. This triggered some individuals to invest that the virus had been created in a laboratory. But the Laos coronaviruses verify these elements of SARS-CoV-2 exist in nature, he says.

“I am more convinced than ever that SARS-CoV-2 has a natural origin,” agrees Linfa Wang, a virologist at Duke–NUS Medical School in Singapore.

Together with relatives of SARS-CoV-2 found in Thailand2, Cambodia3 and Yunnan in southern China4, the research demonstrates that southeast Asia is a “hotspot of diversity for SARS-CoV-2 related viruses”, says Alice Latinne, an evolutionary biologist on the Wildlife Conservation Society Vietnam in Hanoi.

In an additional step in their research, Eloit and his crew confirmed in the laboratory that the receptor binding domains of these viruses may connect to the ACE2 receptor on human cells as effectively as some early variants of SARS-CoV-2. The researchers additionally cultured BANAL-236 in cells, which Eloit says they’ll now use to review how pathogenic the virus is in animal fashions.

Last yr, researchers described one other shut relative of SARS-CoV-2, referred to as RaTG13, which was found in bats in Yunnan5. It is 96.1% similar to SARS-CoV-2 general and the 2 viruses most likely shared a typical ancestor 40–70 years in the past6. BANAL-52 is 96.8% similar to SARS-CoV-2, says Eloit — and all three newly found viruses have particular person sections which might be extra just like sections of SARS CoV-2 than seen in every other viruses.

Viruses swap chunks of RNA with each other by way of a course of referred to as recombination, and one part in BANAL-103 and BANAL-52 may have shared an ancestor with sections of SARS-CoV-2 lower than a decade in the past, says Spyros Lytras, an evolutionary virologist on the University of Glasgow. “These viruses recombine so much that different bits of the genome have different evolutionary histories,” he says.

Missing hyperlinks

The Laos research provides perception into the origins of the pandemic, however there are nonetheless lacking hyperlinks, say researchers. For instance, the Laos viruses don’t comprise the so-called furin cleavage web site on the spike protein that additional aids the entry of SARS-CoV-2 and different coronaviruses into human cells.

The research additionally doesn’t make clear how a progenitor of the virus may have travelled to Wuhan, in central China, the place the primary known instances of COVID-19 have been recognized — or whether or not the virus hitched a trip on an intermediate animal.

Answers would possibly come from sampling extra bats and different wildlife in southeast Asia, which many teams are doing.

Another preprint, additionally posted on Research Square and never but peer reviewed, sheds mild on the work beneath approach in China7. For that research researchers sampled some 13,000 bats between 2016 and 2021 throughout China. But they didn’t discover any shut relatives of SARS-CoV-2, and conclude that these are “extremely rare in bats in China”.

But different researchers query this declare. “I strongly disagree with the suggestion that relatives of SARS-CoV-2 may not be circulating in Chinese bats, as such viruses have already been described in Yunnan,” says Holmes.

The corresponding writer of the research declined to answer Nature’s questions concerning the findings, as a result of the paper continues to be beneath overview.

Wang says that each research spotlight the significance of ramping up sampling in areas outdoors China to assist uncover the origins of the pandemic.