First identified in late 2020, a virus hosted in a Russian bat species capable of infecting human cells, according to a Washington State University study published in the journal Plos Pathogens. In laboratory tests, scientists found that the so-called Khosta-2, which belongs to the same subcategory of coronavirus as Sars-CoV-2, is resistant to current vaccines. The animal where the pathogen lodges is not present in Brazil and there are no indications that the microorganism will be able to jump from the flying mammal to humans, despite its potential.
As Khosta-2 shares the sarbecovirus subcategory with the one that causes COVID-19, scientists thought that vaccines developed for Sars-CoV-2 or serum from convalescent patients could neutralize the microorganism. Like the “kin”, the pathogen detected in Russia uses the spike protein to bind to the ACE2 receptor on human cells.
However, using serum derived from populations vaccinated for COVID-19, the team found that Khosta-2 was not neutralized by these substances. The scientists also tested serum from people infected with the micron variant, but the antibodies were also ineffective. Corresponding author of the study, Michael Letko, a virologist at Washington State University, says this finding reinforces the need to develop universal vaccines for sarbecoviruses, not just variants of Sars-CoV-2.
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“Right now, there are groups trying to create a vaccine that not only protects against the next variant of Sars-CoV-2, but also against sarbecoviruses in general,” says Letko. “Unfortunately, many of our current vaccines are designed for specific viruses that we know to infect human cells or those that appear to pose the greatest risk of infecting us. But this is an ever-changing list. sarbecovirus.”
In the last 10 years, hundreds of sarbecoviruses have been discovered, predominantly in bats in Asia, most of which are not able to infect human cells. Khosta-1 and Khosta-2 viruses were identified in Russian bats in late 2020, and initially it appeared that they were not a threat to humans.
Genetically, the strange Russian viruses resembled some others already discovered in other parts of the world. However, as they did not appear to be similar to Sars-CoV-2, the scientists felt there was no cause for concern. “But when we looked at them further, we were really surprised to find that they can infect human cells. It changes our understanding of these viruses a little bit, where they come from and which regions are of concern.”
Letko, viral ecologist Stephanie Seifert, and viral immunologist Bonnie Gunn, also at Washington State University, studied the two newly discovered viruses. They found that Khosta-1 posed a low risk to humans, but 2 showed some worrying features. The virologist points out, however, that the microorganism seems to lack genes that make it host in humans. The risk is that Khosta-2 will recombine with another pathogen, such as the one causing the coronavirus. “This combination could create a potentially riskier virus.”
“That’s why we need to develop more broadly protective vaccines against sarbecoviruses to prevent further outbreaks of zoonotic coronaviruses,” says virologist Arinjay Banerjee of the University of Saskatchewan in Canada, who was not involved in the research. “This study highlights the importance of surveillance research in the field. We can’t fight an enemy we don’t know exists. By identifying microbial threats, we can develop countermeasures to prevent further outbreaks,” he says.
Three questions for…
Michael Letko, a virologist at Washington State University
Is it possible to predict how the virus would be transmitted to humans?
It is not easy to predict how Khosta-2 could be transmitted to humans because we scientists are not sure of all the interactions that bats that carry the Khosta virus have with other species. In other words, it is difficult to predict all the ways humans might come into indirect contact with these bats.
Are there clues about the potential for transmissibility?
Transmissibility is also difficult to predict from the limited data we have. All we can really conclude is that these viruses may have the ability to infect humans. How well these viruses would transmit between humans – if at all – is not something we can predict with our experimental approach to this study.
Should health surveillance authorities in non-endemic places such as Brazil be concerned?
Public health authorities should not necessarily be concerned about this particular virus. However, the intent of this study was to show that there are Sars-related viruses with zoonotic potential circulating in wildlife outside of Asia. A second intent of our study was to show that some of the other viruses only remotely related to Sars-CoV-2 should also be considered by researchers designing vaccines to prevent future pandemics.