A team of researchers led by Washington State University (WSU) has described a coronavirus recently discovered in Russian bats that belongs to the same family as SARS-CoV-2 (sarbecoviruses), and is likely capable of infecting humans. If this virus – named Khosta-2 – were to spill over into human populations, it would be resistant to currently existing vaccines and treatments.
The discovery of the virus stresses the urgent need to develop universal vaccines to protect against sarbecoviruses in general, rather than just against known variants of SARS-CoV-2, in order to avoid future pandemics.
Although hundreds of sarbecoviruses have been discovered in bats in recent years (predominantly in Asia), most of them are incapable of infecting human cells. Initially, scientists believed that the Khosta-1 and Khosta-2 viruses – found in Russian bats in late 2020 – do not pose threats to humans either.
“Genetically, these weird Russian viruses looked like some of the others that had been discovered elsewhere around the world, but because they did not look like SARS-CoV-2, no one thought they were really anything to get too excited about,” said study senior author Michael Letko, a virologist at WSU. “But when we looked at them more, we were really surprised to find they could infect human cells. That changes a little bit of our understanding of these viruses, where they come from, and what regions are concerning.”
While laboratory analyses revealed that Khosta-1 poses a low risk of spilling over to humans, Khosta-2 appeared highly efficient in using its spike protein to infect cells by attaching – just like SARS-CoV-2 – to a receptor protein called angiotensin converting enzyme 2 (ACE2), which is found throughout human cells. Moreover, the researchers found that Khosta-2 is not neutralized by serum derived from human populations vaccinated against Covid-19 or previously infected with the Omicron variant.
These worrisome findings suggest an urgent need to find universal vaccines against this family of viruses. “Right now, there are groups trying to come up with a vaccine that doesn’t just protect against the next variant of SARS-2 but actually protects us against the sarbecoviruses in general,” Letko explained. “Unfortunately, many of our current vaccines are designed to specific viruses we know infect human cells or those that seem to pose the biggest risk to infect us. But that is a list that’s everchanging. We need to broaden the design of these vaccines to protect against all sarbecoviruses.”
Although Khosta-2 appears to lack some of the genes believed to be involved in pathogenesis in humans, there is a significant risk of this virus recombining with other viruses such as SARS-CoV-2 in animal populations and spilling back into humans.
“When you see SARS-2 has this ability to spill back from humans and into wildlife, and then there are other viruses like Khosta-2 waiting in those animals with these properties we really don’t want them to have, it sets up this scenario where you keep rolling the dice until they combine to make a potentially riskier virus,” Letko concluded.
The study is published in the journal PLoS Pathogens.