When SARS-CoV-2 – the virus behind COVID-19 – surfaced in China and quickly brought the entire world to a standstill, then-President Donald Trump liked to refer to it as “the Chinese virus”.
Fast forward two and a half years, and US scientists are warning that a recently discovered virus harboured by Russian horseshoe bats is also capable of infecting humans and evading COVID-19 antibodies and vaccines.
The bat virus, named Khosta-2, is known as a sarbecovirus – the same sub-category of coronaviruses as SARS-CoV-2 – and it displays “troubling traits,” according to a new study published in the journal PLoS Pathogens.
A team led by researchers at the Paul G. Allen School for Global Health at Washington State University (WSU) found that Khosta-2 can use its spike proteins to infect human cells very much like SARS-CoV-2 does.
“Our research further demonstrates that sarbecoviruses circulating in wildlife outside of Asia – even in places like western Russia where the Khosta-2 virus was found – also pose a threat to global health and ongoing vaccine campaigns against SARS-CoV-2,” Michael Letko, a virologist at WSU and corresponding author of the study, said in a statement.
He said this discovery highlights the need to develop new vaccines that don’t only target known variants of SARS-CoV-2, such as Omicron, but that protect against all sarbecoviruses.
‘Weird Russian viruses’
Among the hundreds of sarbecoviruses discovered in recent years, most have been found in Asian bats and are not capable of infecting human cells.
The Khosta-1 and Khosta-2 viruses were discovered in bats near Russia’s Sochi National Park in 2020, and it initially appeared they were not a threat to humans, according to the study’s authors.
“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,” Letko said.
“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”.
Letko and his colleagues determined that Khosta-1 posed a low risk to humans, but Khosta-2 was more concerning.
In particular, like SARS-CoV-2, Khosta-2 can use its spike protein to infect cells by attaching to a receptor protein, called angiotensin-converting enzyme 2 (ACE2), which is found throughout human cells.
The scientists next wanted to find out whether the virus could evade the immunity offered either by previous coronavirus infections or COVID-19 vaccines.
Using serum derived from people vaccinated against COVID-19, the team discovered Khosta-2 was not neutralised by current vaccines.
They also tested serum from people who were infected with the Omicron variant, but there again, the antibodies were ineffective.
Fortunately, the authors write that the new virus lacks some of the genetic features thought to “antagonise” the immune system and contribute to disease in humans – but there is a risk that Khosta-2 could wreak havoc by recombining with a second virus such as SARS-CoV-2.
“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 said.