[Science] The truth about the source of SARS-CoV-2 is revealed?

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Author: Daisy Guide: On September 29, the researchers targeted the close relatives of SARS-CoV-2 discovered by scientists in Lao bats in "Science"-they are better than any other relatives.
Known viruses are more similar to SARS-CoV-2, with a closeness of 96.
8%.
Discussing this clue may help determine the origin of SARS-CoV-2
.

Among the bat coronaviruses isolated by scientists in Laos, none of the spike proteins contained a furin cleavage site, a symbolic component of the pandemic virus
.

It may be due to insufficient sampling of bats, or the cleavage site obtained in the transmission chain of the intermediate animal host, or it may be in the population
.

In short, the newly discovered viruses are the closest coronaviruses to the ancestors of the new coronavirus.
They may essentially pose the risk of direct transmission of the coronavirus to humans in the future.
Anything related to the origin of this virus will be carefully studied
.

When SARS-CoV-2 was discovered in early 2020, some researchers initially suspected that it might have been designed in the laboratory and escaped accidentally, partly because a region of the virus surface protein is tightly connected to human cell receptors.
, Has an incredible fit
.

"It looks a little strange, right?" said Edward Holmes, an evolutionary biologist at the University of Sydney.
"People say that maybe it was selected in the laboratory
.

" However, Holmes said, from the people living in the limestone caves in Laos.
Three coronaviruses have been found in bats, which greatly increases the weight of the existing evidence that the virus is not genetically modified
.

These three viruses were reported in a preprint on Research Square on September 17.
They are the closest viruses to SARS-CoV-2 found so far, and they are also the first almost identical viruses discovered in this key area
.

Wang Linfa, a bat coronavirus researcher at Duke National College of Medicine in Singapore, said: “The core function of SARS-CoV-2 is partly of natural origin
.

This has been proven
.

” Some scientists said that this discovery did not explain the so-called “laboratory”.
The “leakage” situation, the so-called “laboratory leak” scenario, refers to a natural, unaltered virus that first infects people who work in the field or in the laboratory
.

Gilles Demaneuf, a data scientist and member of an Internet organization called DRASTIC, said that the Laos findings have not changed anything at all
.

The organization defended the laboratory origin hypothesis and believed that these attacks were unreasonable
.

In the process of evolution, for decades, scientists have isolated these bat viruses and called them BANAL viruses.
Because researchers have found these viruses in SARS-CoV-2 bat anal swabs, new viruses are impossible.
Cause a pandemic
.

But this research further expands the pedigree of SARS-CoV-2 and raises new questions about how it came about
.

Wang Linfa reminded: “These BANAL viruses are likely to pose a threat to humans
.

This virus may be SARS-CoV-3
.

” In this study, a group of researchers from Laos National University and Pakistan from Laos Institute Colleagues from the Steward Institute collaborated and collected 645 bats from four different locations
.

In the karst zone of Fuang District, they found three different types of horseshoe-shaped bats.
They were infected with a virus with the same gene sequence as SARS-CoV-2, up to 96.
8%, and named them BANAL-52 and BANAL-103.
And BANAL-236
.

On September 29th, the researchers published an article titled "Close cousins ​​of SARS-CoV-2 found in a cave in Laos yield new clues about pandemic's origins" in "Science", studying in a cave in Laos The discovered close relatives of SARS-CoV-2 provide new clues to the origin of the pandemic
.

doi: 10.
1126/science.
acx9257 The most recent previous isolate RaTG13 is from another bat species, R.
sinicus, which lives in a cave in Mojiang, Yunnan Province, China
.

Its similarity with SARS-CoV-2 is 96.
2%, which is only slightly lower than BANAL virus, but its number masks the profound difference between the new isolate and RaTG13
.

SARS-CoV-2 uses its surface spike protein to dock with human cell receptors called angiotensin-converting enzyme 2 (ACE2) and cause infection
.

The small part at the top of the spike is called the receptor binding domain (RBD) and plays a leading role in this process
.

Compared with the RBD on RaTG13, the RBD sequence of BANAL is closer to the RBD sequence on SARS-CoV-2
.

More importantly, the crystallography of BANAL-236 (an isolate grown in a culture medium), a difficult laboratory feat showed that its structure is the same as the RBD of SARS-CoV-2
.

In test-tube studies, BANAL-236 can easily infect cells with human ACE2 receptors
.

Marc Eloit, the lead researcher of the project and a virologist at the Pasteur Institute, said: "It is very exciting when we see that RBD is very close to SARS-CoV-2
.

" These BANAL isolates have joined SARS.
-The ranks of CoV-2 related bat coronaviruses, which have also been found in Cambodia, Thailand and Japan
.

All are rhinos or horseshoe bats, they do not migrate very far, but usually infect other commensal species
.

Eloit and other researchers believe that this allows the coronavirus to jump around in Southeast Asian countries and China
.

Holmes said: "This tells us.
.
.
they are very common in rhinos in southern China and Southeast Asia
.

" Like all close relatives of SARS-CoV-2, these BANAL isolates lack a pandemic called furin cleavage site.
Iconic component of the virus
.

The furin cleavage site was found in bat coronaviruses far away from the SARS-CoV-2 family tree
.

But coronaviruses do not require furin cleavage sites to make animals sick
.

Eloit's team plans to implant BANAL-236 in "humanized" mice and monkeys to see if it can cause disease, which will provide clues as to whether it poses a threat to humans
.

Eloit pointed out that this research will be conducted by vaccinated researchers under strict biosafety rules
.

This study may also show that the isolate of BANAL is not pathogenic.
In this case, considering the similarity of SARS-CoV-2, this new virus may even protect people from SARS-CoV-2 infection.

.

Eloit said: "This is either like SARS-CoV-3 or a free live vaccine
.

" However, in BANAL-236 and other SARS-CoV-2 close relatives, the lack of furin cleavage sites raises a problem, namely How and when the ancestors of the pandemic virus discovered its locus
.

Wang Linfa and many other researchers believe that this may have already happened when it exchanges genetic material with other more distant coronaviruses, and these coronaviruses do have a furin cleavage site
.

Recombination occurs very frequently in bats
.

Others believe that it is more likely that the recombination occurred in some other animal species that were simultaneously infected with bat coronavirus and another virus with a furin cleavage site.
This may include from canines and rodents.
Any animal from animal to feline
.

Holmes said: "I doubt whether it spread directly from bats to humans, because this rarely happens
.

" Eloit said: "It may also happen to humans
.
The
other four coronaviruses spread in the human body, and they all cause mild.
Some diseases have furin cleavage sites
.

"furin cleavage sites may also appear without recombination
.

Eloit said: "This virus replicates very fast in humans, especially when they don't have any previous immunity, and they have accumulated a large number of mutations, which may produce a furin site
.

"When the virus accumulation of these mutations, it may be between people" silent communication ", let it have time to move from rural areas to China, Wuhan, and Wuhan pandemic broke out in early 2020
.

He said:" I I am very interested in finding any serological screening data in Wuhan before the outbreak
.

"The harvest in Laos is even more strange.
There were also reports this month that a similar but much larger-scale relative search operation for SARS-CoV-2 in neighboring China resulted in nothing
.

Chinese Academy of Medical Sciences and Peking Union Medical College.
Wu Zhiqiang and colleagues in the September 20 issue of the study, between 2016 to 2021 found no SARS-CoV-2-associated virus in China 703 13 064 bats collected in place
.

the researchers concluded that, SARS -CoV-2-associated virus "may not be active in China in the spread of bat"
.

size and geographic scope of this study to scientists left a deep impression, in fact, during a pandemic, there is little bat coronavirus research From China
.

Wang Linfa said: "I think this is positive because they tell you what they are doing
.

"But he suspects that sampling bias can explain why the researchers did not find any SARS-CoV-2 related viruses
.

A visit to a location usually does not produce any interesting isolates
.

If you go to a cave 10 times, you will be lucky.
Get one
.

Holmes is "very skeptical" about this study, especially because his own research team and others have reported that SARS-CoV-2 (including RaTG13)-related viruses have been found in some of the locations sampled by the new study
.

"It is difficult to know what happened in China.
Anything related to the origin of this virus will be scrutinized carefully
.

It is not clear what we can see
.

" Reference: https:// /close-cousins-sars-cov-2-found-cave-laos-yield-new-clues-about-pandemic-s-origins Note: This article aims to introduce medical research progress and cannot be used as a reference for treatment options
.

If you need health guidance, please go to a regular hospital
.

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