The COVID-19 pandemic has taught humanity several painful lessons. One such learning was that under the right conditions, viruses like SARS-CoV-2 can spill over to human beings and wreak havoc globally. Now, scientists have found that a COVID-like virus discovered in Russian bats, has the potential to infect human beings, and is resistant to existing COVID-19 vaccines.
According to a new multi-institutional study, Khosta-2, a virus that was identified in 2020 among bats in Russia, can infect human cells. It was also learnt that the virus is resistant to both SARS-CoV-2 monoclonal antibodies and serum from individuals vaccinated against COVID-19. These findings are of significance as both SARS-CoV-2 and Khosta-2 are sarbecoviruses, a sub-category of coronaviruses.
"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," said Dr. Michael Letko, corresponding author of the study, in a statement. The findings were published in the journal PLoS Pathogens.
Potential to Infect Cells
Sarbecoviruses are coronaviruses that can cause respiratory infections. In recent years, numerous bat-dwelling sarbecoviruses have been discovered in Asia. Thankfully, most of them lack the ability to infect human cells. The viruses investigated in the current study—Khosta-1 and Khosta-2—were identified in samples collected from Rhinolophus bats near Sochi National Park, Russia, between March-October 2020.
At the time of their unearthing, no threat of human infection was attributed to them. This was because they were genetically distinct from the lineage of pathogenic viruses such as SARS-CoV-2. In order to study the virus closely, scientists from Washington State University's Paul G. Allen School for Global Health and Tulane University School of Medicine teamed up. Their analysis revealed that the risk posed by Khosta-1 to humans was low.
On the other hand, Khosta-2 exhibited concerning characteristics. It was observed that Khosta-2 can infect cells employing the exact mechanism as SARS-CoV-2: using its spike protein to latch on ACE2 (angiotensin-converting enzyme 2), an enzyme found on the surface of several human cell types such as the lungs, kidney, and heart, among others.
Resistant to COVID-19 Vaccines
Next, the authors tried to ascertain whether COVID-19 vaccines could provide any cross-reactive protection against Khosta-2. For this, the team utilised serum derived from individuals vaccinated against COVID-19. However, it was gleaned that the current vaccines were unable to neutralise Khosta-2. When serum derived from people who had contracted the Omicron variant was tested against the new virus, the antibodies in them were also found to be ineffective in neutralising the sarbecovirus.
Highlighting the need for vaccines offering broader protection against viruses, Dr. Letko noted, "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."
According to Dr. Letko, Khosta-2 lacks certain genes that are associated with pathogenesis in humans. However, he added that the risk of it recombining with a second virus such as SARS-CoV-2 exists. "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," concluded Dr. Letko.