The discovery of the Russian bat virus could be bad news for humans

According to research, a relative of the SARS-CoV-2 virus, which was originally found in Russian bats, may be capable of infecting human cells.

Authors of an article that appeared in the journal PLOS PathogensThey also showed that the virus is resistant to the antibodies of people vaccinated against SARS-CoV-2 – which causes COVID-19 – in laboratory tests.

The researchers said the study’s results show that sarbecoviruses in wild animals outside of Asia pose a “threat to global health” as well as to ongoing COVID-19 vaccination campaigns. Sarbekoviruses are a group of coronaviruses that include SARS-CoV-2, SARS-CoV-1 (the cause of SARS, or acute respiratory distress syndrome) and several hundred genetically similar viruses found mainly in bats.

As part of the study, scientists examined two sarbecoviruses – known as Khosta-1 and -2 – that were discovered by Russian scientists in 2020 in southwestern Europe.

“Initially, sarbecoviruses – in the early 2000s – were thought to only circulate in a certain type of bats in southern China, but over the past 20 years, scientists have discovered a lot more in a variety of species and geographic locations.” – Michael Letko, author of the study who he’s from Washington State University, he said Newsweek.

To date, sarbecoviruses have been identified as circulating in wild animals – such as bats, pangolins, raccoon dogs, and palm civets – in China, Laos, Japan, Russia, Great Britain, Africa, and Bulgaria.

It is almost certain that scientists will discover more of these viruses in the future, Letko said.

While hundreds of sarbecoviruses have been identified – many of them in attempts to determine the origin of SARS-CoV-1 and -2 – most of them are not capable of infecting human cells. However, several of these viruses remain unexplored and therefore their ability to spread to humans is unknown. Now the authors of a new study have shown that Khosta-2 – one of the newly discovered Russian sarbecoviruses – can use the same entry mechanisms to infect human cells that SARS-CoV-2 uses.

These findings have potential public health implications, given that the “spread” of sarbecoviruses from animals to humans caused the original SARS outbreak and is believed to have been the cause of the ongoing coronavirus pandemic. (A minority of experts say that in the latter case, the virus may have come from a laboratory leak.)

In the latest study, researchers used a platform previously developed by Letko to safely assess whether coronaviruses could infect humans. In January 2020, Letko used this platform to characterize the receptor for SARS-CoV-2.

The platform is completely in vitro, meaning that the experiments are performed in a laboratory outside their normal biological context – in this case using cell cultures and non-infectious virus-like particles.

“I’d like to emphasize that there is no real virus in our study – just molecular surrogates that cannot replicate and have no other coronavirus genes other than the spike protein” that pathogens use to bind to and enter cells, Letko said.

“I have now started a laboratory expanding this research, so naturally when two new coronaviruses were discovered in Russia, I was very interested in trying them out on my laboratory’s platform,” he said.

Among the key findings PLOS The study is that Russian Khosta viruses use the same receptor as SARS-CoV-2 – known as ACE2 – to infect human cells.

“Although genetically related to SARS-CoV-2 only distant, the Russian viruses are most genetically similar to other sarbecoviruses found in Africa and other parts of Europe,” Letko said. “For the most part, the specific group of sarbecoviruses, to which Khosta viruses belong, cannot bind to human ACE2 or infect human cells. At least we thought so.

He continued: “The receptor used by any virus dictates what tissues the virus infects, which in turn is related to the types of disease symptoms the virus causes and how it is transmitted between hosts. Since Khosta-2 uses the same human cell receptor as SARS-CoV-2 – and SARS-CoV-1, as well as some other seasonal coronaviruses – it may be able to infect the same cell types in humans. “

The photo shows the lesser horseshoe bat. The Khosta-2 virus has been identified in this species by Russian scientists.
iStock

Second, researchers found that the blood serum of people vaccinated against COVID-19 did not neutralize the Khosta-2 virus under laboratory conditions, according to Letko. This was not necessarily surprising.

“One of the standard ways that scientists measure vaccine effectiveness is with a” neutralization test, “Letko said. “In this experiment, we combine viruses – or in our case, virus-like particles – with the sera of people who have received Moderna or Pfizer vaccines and then add them to cells in test tubes. If the antibodies in the serum from the vaccinated person can bind to the virus, then the virus cannot infect the cells. We can measure this.

“When SARS-CoV-2 gains even a handful of new mutations, we call it a new variant and it is generally more resistant to vaccines. Since Khosta-2 is so different from SARS-CoV-2, it is not too surprising that the vaccine we use for SARS-CoV-2 cannot effectively stop Khosta-2 from infecting cells, “Letko said.

Third, the team found that infection with an Omicron variant of the coronavirus may not protect against Khosta-2. Serum from people who recovered from Omicron did not fully neutralize the virus. Again, because Khosta-2 is different enough, the vaccine is not effective.

Letko said it is important to remember that for the second and third discoveries, it cannot be said with certainty that these reactions really mimic an infection in a real person, given that the results come from cell culture experiments.

“It is possible that the immune response in a real person would be more varied and effective than this simplified experimental system that we are using,” he said.

According to Letko, at this stage it is difficult to say whether the Khosta-2 could cause an epidemic or even a pandemic.

“Just because a virus can infect human cells doesn’t mean it will cause a pandemic or even spread to one person,” he said. “There are a number of factors that determine whether a virus will transmit and spread from person to person with the high levels needed for a pandemic.”

Letko continued: “At this point, we do not know the prevalence or probable true distribution of this virus in nature. As the original scientists who discovered Khosta viruses in their research noted, [they] are missing genes in pathogenic human sarbecoviruses that are likely responsible for immunity avoidance and disease ‘.

What is perhaps more interesting for scientists is the possibility of a process known as “recombination” occurring.

“We know pretty well from the last 40 years of coronavirus research that if two coronaviruses are genetically similar and are in the same cell, they can recombine,” Letko said. “Parts of one genome can replace similar fragments in the other genome, resulting in a hybrid genome of both viruses.”

Since SARS-CoV-2 and Khosta-2 are genetically similar enough to be called sarbecoviruses and can infect the same cell types using the same mechanisms, it is possible that they could recombine in a way that SARS-CoV- would produce 2 resistance to the vaccine from Khosta-2, while maintaining other virulence characteristics of SARS-CoV-2.

“The chances that SARS-CoV-2 will ever” meet Khosta-2 in nature are certainly very small, but there have been an increasing number of reports describing SARS-CoV-2 spreading back into the wild – like a white-tailed deer. to the East Coast of the United States, “Letko said. “This is all a worst-case scenario, but it’s just one of the things we think about in my lab as we try to prevent another pandemic from happening again.”

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