According to a study, a SARS-CoV-2 virus relative that was originally found in Russian bats may be able to infect human cells.
The author of the letter, which was published in the journal PLOS pathogenalso showed that the virus is resistant to antibodies from people vaccinated against SARS-CoV-2 – which causes COVID-19 – in laboratory tests.
Researchers said the study’s findings suggest that sarbecovirus in wildlife outside Asia poses a “threat to global health” as well as to ongoing COVID-19 vaccination campaigns. Sarbecoviruses are a group of coronaviruses that includes SARS-CoV-2, SARS-CoV-1 (the cause of SARS, or severe acute respiratory syndrome) and several hundred genetically identical viruses found mostly in Bat,
In the study, researchers examined two sarbecoviruses—known as Khosta-1 and -2—that were discovered by Russian scientists in the European southwest of the country in 2020.
“Cerbecoviruses were originally thought – in the early 2000s – to circulate in southern China only in one specific type of bat, but over the past 20 years scientists have discovered many more in diverse species and different geographic locations, Michael Letko, an author of the study with Washington State University, told newsweek,
To date, cerbecoviruses have been identified as circulating in wildlife in China, Laos, Japan, Russia, the United Kingdom, Africa and Bulgaria – such as bats, pangolins, raccoon dogs and palm civets.
Letko said it is almost certain that researchers will uncover more of these viruses in the future.
While hundreds of sarbecoviruses have been identified—many during efforts to determine the origin of SARS-CoV-1 and -2—most have not been able to infect human cells. But many of these viruses have not been tested, and so their ability to transmit to humans is unknown. Now, the authors of the new study have shown that Khosta-2—one of the newly discovered Russian sarbecoviruses—can use the same entry mechanism to infect human cells that SARS-CoV-2 uses.
These findings have potential public health implications, given that “spillover“The original SARS outbreak of sarbecoviruses from animals to humans is believed to be the cause of the ongoing coronavirus pandemic. (A minority of experts have argued that, in the latter case, the virus may have originated from a) lab leak,
In the latest study, researchers used a platform that Letco had previously developed to safely assess whether coronaviruses have the potential to 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 experiments are conducted in a laboratory outside of their normal biological context – in this case, using cell cultures and non-infectious viral-like particles.
“I would like to emphasize that there are no real viruses in our study – only molecular surrogates that cannot replicate and have no other coronavirus genes other than the spike protein,” which are responsible for binding to pathogens and entering cells. for use, Letko said.
“I’ve now started a lab expanding on this research, so naturally when two new coronaviruses were discovered in Russia, I was very interested in trying them out on my lab’s platform,” he said.
Among the major findings of Other than this The study is that Russian Khosta viruses use the same receptor employed by SARS-CoV-2—known as ACE2, to infect human cells.
“While genetically only distantly related to SARS-CoV-2, Russian viruses are genetically similar to other sarbecoviruses that have been found elsewhere in Africa and Europe,” Letko said. “For the most part, the specific sarbecovirus group that Khosta virus belongs to, cannot bind to human ACE2 or infect human cells. Or so we thought.”
He continued: “The receptor used by any virus determines which tissues the virus infects, which in turn is related to what type of disease symptoms the virus causes and how it is transmitted between hosts. Because 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 similar types of cells in humans Huh.”
Secondly, researchers found that the blood serum of individuals vaccinated against COVID-19 did not neutralize Khosta-2 virus in laboratory conditions, according to Letco. This was not necessarily surprising.
“One of the standard ways scientists measure the efficacy of a vaccine is with a ‘neutralization assay,'” Letko said. “In this experiment, we mix viruses—or in our case, virus-like particles—with the serum of people who have received modulations or pfizer vaccine and then add it to the cells in the test tube. If antibodies in the vaccinated person’s serum can bind to the virus, the virus cannot infect cells. We can measure it.
“When SARS-CoV-2 also has some new mutations, we call it a new variant and are generally more vaccine resistant. Because Khosta-2 is very different from SARS-CoV-2, it is very Not surprisingly, the vaccines we use for SARS-CoV-2 cannot effectively prevent Khosta-2 from infecting cells,” Letko said.
Third, the team found that infection with the Omicron variant of the coronavirus could not protect against Khosta-2. The serum of people who were cured of Omicron did not completely neutralize the virus. Again, because Khosta-2 is quite different, the vaccine is not effective.
Letko said it’s important to note that in the case of the second and third findings, it’s not possible to say with certainty that these reactions actually mimic an infection in a real person, given that the results come from cell culture experiments. Huh.
“It may be possible that the immune response in a real person will be more diverse and effective than this simplified experimental system we have used,” he said.
According to Letco, it is difficult to say at this stage whether Khosta-2 has the potential to cause an epidemic or even an epidemic.
“Just because the virus can infect human cells doesn’t mean it will cause an epidemic or even transmit to a person,” he said. “Many factors control whether a virus will transmit and if it will spread among individuals with the high efficiency required for an epidemic.”
Letko continued: “At this point, we do not know the prevalence or possible distribution of this virus in nature. As the original scientists who discovered Khosta virus, noted in their study, [they] Found in pathogenic human sarbecoviruses are missing genes potentially responsible for immune evasion and disease.”
Researchers are perhaps more concerned about which process known as “recombination” is likely to occur.
“We know very well from the past 40 years of coronavirus research that if two coronaviruses are genetically identical and are in the same cell, they can recombine,” Letko said. “Bits from one genome can replace similar bits in another genome, resulting in hybrid genomes of both viruses.”
Because SARS-CoV-2 and Khosta-2 are genetically similar, called sarbecoviruses and can infect the same types of cells using similar mechanisms, it may be possible that they can recombine in this way. This allows for vaccine resistance to SARS-CoV-2 from Khosta-2 while still retaining other virulence characteristics from SARS-CoV-2.
“The likelihood of SARS-CoV-2 meeting ‘Khosta-2’ in nature is certainly very low, but there are an increasing number of reports describing SARS-CoV-2 spreading back to wildlife – such as white-tailed deer. East Coast of the United States,” Letko said. “It’s all a worst-case scenario, but those are the things we think about in our lab when trying to prevent the next pandemic from happening again.”