Researchers at Washington State University (USA) have discovered a virus discovered in a Russian bat that is similar to SARS-CoV-2, the Covid-19 virus, which appears to be capable of infecting humans and, if it were to spread, it would be resistant to current vaccines. Khosta-2, as the virus is called, belongs to the same coronavirus subcategory as SARS-CoV-2, the sarbecoviruses.
The researchers found that the spike proteins of the bat virus, called Khosta-2, can infect human cells and are resistant to both monoclonal antibodies and serum from people vaccinated against SARS. CoV-2.
“Our research further demonstrates that sarbecoviruses circulating in wildlife outside of Asia, including in places like western Russia where the Khosta-2 virus was found, also pose a threat to global health and vaccination campaigns against the virus. SARS-CoV-2”, warns virologist Michael. Letko, corresponding author of the study published in the journal “PLoS Pathogens.”
Letko said the discovery of Khosta-2 highlights the need to develop universal vaccines to protect against sarbecoviruses in general, rather than just known variants of SARS-CoV-2.
“Right now, there are groups trying to find a vaccine that not only protects against the next variant of SARS-2, but actually protects 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 seem to pose the greatest risk of infecting us. But that is a list that is constantly changing. We need to scale up the design of these vaccines to protect against all sarbecoviruses.”
Although hundreds of sarbecoviruses have been discovered in recent years, predominantly in bats in Asia, most are not capable of infecting human cells. The Khosta-1 and Khosta-2 viruses were identified in Russian bats in late 2020 and initially did not appear to be a threat to humans.
“Genetically, these strange Russian viruses resembled some of the others that had been discovered in other parts of the world, but because they didn’t resemble SARS-CoV-2, no one really thought they were anything to get too excited about. But when we analyzed them we were very surprised to discover that they could infect human cells. That changes our understanding of these viruses a bit, where they come from and which regions are of concern.”
As explained in the study, Khosta-1 poses a low risk to humans, but Khosta-2 showed some worrying features.
Like SARS-CoV-2, Khosta-2 can use its spike protein to infect cells by binding to a receptor protein, called angiotensin 2 converting enzyme (ACE2), which is found in all human cells.
Furthermore, by using serum derived from human populations vaccinated against Covid-19, the team found that Khosta-2 was not neutralized by current vaccines. They also tested serum from people who were infected with the omicron variant, but the antibodies were also ineffective.
Fortunately, Letko acknowledges that the new virus lacks some of the genes thought to be involved in pathogenesis in humans. However, there is a risk that Khosta-2 will recombine with a second virus such as SARS-CoV-2.