Scientists in the French lab couldn’t mutate the bat virus to make it look like SARS-CoV-2.Important reason

New Delhi: In a study that provided potentially important clues about the origin of the Covid-19 pandemic, scientists at the Pasteur Institute in France conducted experiments with a bat virus similar to SARS-CoV-2 and tested it in humans. Adapt to cells.

The virus, named BANAL-236, was able to bind to human cells in the Petri dish, but was unable to develop important functions related to infectivity. According to scientists, this indicates that this feature of SARS-CoV-2 is likely to have evolved in bats rather than in the process of “silent circulation” between humans.

For their research, scientists isolated a strain of coronavirus similar to SARS-CoV-2 from bats in a cave in Laos in mid-2020. After that, various experiments were conducted.

and February treatise Was announced in NatureResearchers have reported that the virus can infect human cells by tightly binding to the same protein that SARS-CoV-2 uses for invasion. However, it lacked the furin cleavage site, which is a characteristic that infects SARS-CoV-2 very easily.

Furin is an enzyme found in human cells. The SARS-CoV-2 virus has a unique amino acid orientation in the spike protein, and when it comes into contact with an enzyme, it is cleaved in two at that site. Flynn cleavage sites are uniquely suitable for infecting human cells with the virus and are thought to be more contagious than their relatives.

After that, the scientists report In a June research paper (not yet peer-reviewed), BANAL-236 had a very mild effect on laboratory animals. They found that while SARS-CoV-2 replicates rapidly in the lungs of mice, BANAL-236 cannot replicate to the same extent as it does in humans. Similarly, when two macaques were exposed to BANAL-236 via nasal spray, the effect was even milder and the virus replicated in the intestine rather than in the lungs.

Evolutionary experiments with viruses may provide important scientific insights into pandemics, but raise questions about safety and ethics.

Last year, experts discussed the possibility of a Covid-19 pandemic after a lab leak.It was suggested that the Wuhan Institute of Vessels often carried out Function acquisition experimentFrom where the virus may have been accidentally leaked.

“Gain of function” is a field of study focused on increasing the generation of microorganisms under conditions that cause mutations in the virus. Such experiments allow scientists to more accurately predict emerging infectious diseases and develop vaccines and treatments.

Gain-of-function research may use genetic engineering or continuous passage. Genetic engineering involves “editing” the genetic code to modify the virus in a pre-determined way by scientists. On the other hand, in continuous passage, the pathogen is propagated in various situations and changes are observed. This is what the French team did.

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What the findings suggest about Covid-19

The Pasteur Institute team wanted to investigate the possibility that SARS-CoV-2 invaded the human population as a strain like BANAL-236. It does not cause serious illness and is not highly infectious.

Scientists hypothesize that before the first clinical Covid-19 cases were detected at the end of 2019, the virus was circulating among humans and mutated to the point of developing a furin cleavage site and becoming fatal. Did.

Taking advantage of the fact that BANAL-236 is not fatal and causes only mild illness, the team conducted a series of passage experiments.

The team removed lung tissue from mice infected with BANAL-236 and used the tissue to infect healthy animals. They then repeated this cycle to transfer the virus from mouse to mouse.

In another experiment, they infected a dish of human enterocytes with BANAL-236 and then used a new virus produced by the cells to infect the dish.

In both experiments, the team limited such transfers to six. To avoid the risk of creating a virus that may adapt to humans.

The team was unable to introduce the furin cleavage site of the BANAL-236 virus in either experiment. The virus acquired new mutations, but did not improve infections in mouse lungs or human cells.

The team suggests that their experiments show that the SARS-CoV-2 strain acquired the bat wind chime site prior to “spillover” to humans.

Researchers argue that the appearance of wind chime locations during the human “circulation of silence” is “unlikely”. I got it: “Based on our study, the most likely hypothesis about the natural origin of the virus is the presence of bat virus, which contains wind chimes that may have infected humans directly or through other animal species. It seems that.”

The research team is currently conducting further research in caves in China and its neighboring countries to understand the origin of furin cleavage sites.

However, researchers acknowledged the alternative hypothesis that “human infections may have occurred during the course of virus isolation in the laboratory.”

Impact on Wuhan’s “Laborique” theory

Experts say that if BANAL-236 researchers are unable to evolve the furin site into the virus during continuous passage experiments, Wuhan Institute of Veterinary Science scientists will do so with SARS-CoV-2. It suggests that it is highly possible that it could not be done. The “Laborique” theory suggests.

“This is another nail in the casket of Labreak theory and should have been tightly sealed in the basement so far,” said Edward Holmes, a virologist at the University of Sydney. Quote As saying by New York Times..

However, other experts believe that the experiment in question is too small to reach a drastic conclusion.

(Edited by Asavari Singh)

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