A recently US study uncovered another deadly animal virus, found in Russian bats and capable of infecting humans, and which is resistant to all COVID vaccines.
The study tested how well the spike proteins from these bat viruses (called Khosta-2) infect human cells under different conditions.
“We found that the spike from the Khosta-2 virus could infect cells similar to human pathogens using the same entry mechanisms but was resistant to neutralisation by serum from individuals who had been vaccinated for SARS-CoV-2,” the researchers said.
More worryingly is that current medicines cannot neutralise the new respiratory virus, reports Health-e News. This is because antibodies developed from the Omicron variant weren’t effective against the bat virus, even though both pathogens belong to the same acute respiratory coronaviruses, known as arboviruses.
Urgent need for vaccine development
“Critically, our findings highlight the urgent need to continue the development of new and broader-protecting arbovirus vaccines,” said the study authors. “These findings suggest that some coronaviruses may infect human cells through a presently unknown receptor. Sarbecoviruses have been shown to co-circulate in bats, so this variation in receptor usage among closely related viruses may even represent an evolutionary strategy for viral persistence within the reservoir host population.”
The study also found that, in the lab, when the receptor binding domains (RBD) on a SARS-CoV virus were replaced with Khosta-2 RBD, serum from vaccinated individuals was less effective at neutralising the pseudovirus.
“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 anything to get too excited about,” said Michael Letko, one of the authors from Washington State University.
“When we looked at them more, we were surprised to find they could infect human cells. That changes our understanding of these viruses, where they come from and what regions are concerning.”
It is not yet clear if the virus that infects these bats can spill over to humans in the real world, but initial findings in the lab suggest it’s certainly possible.
Not yet out of the woods
WHO Director-General Dr Tedros Adhanom Ghebreyesus has previously indicated that the world has never been in a better position to end the COVID-19 pandemic as a global health emergency. But last week, he warned that vaccination gaps, low rates of testing and sequencing, and lack of access to antivirals in some countries put this at risk.
“After two and a half years, we are just beginning to glimpse the light at the end. But we are not at the end yet. We are still in the tunnel, and many obstacles can trip us up if we don’t tread carefully. We continue to urge all member states to prioritise the vaccination of all health workers and all older people. This will help achieve the target of 70% coverage in all countries,” said Ghebreyesus.
Study details
An ACE2-dependent Sarbecovirus in Russian bats is resistant to SARS-CoV-2 vaccines
Stephanie Seifert, Shuangyi Bai, Stephen Fawcett, Elizabeth Norton, Kevin Zwezdaryk, James Robinson, Bronwyn Gunn, Michael Letko.
Published in PLOS BIOLOGY on 22 September 2022
Abstract
Spillover of sarbecoviruses from animals to humans has resulted in outbreaks of severe acute respiratory syndrome SARS-CoVs and the ongoing COVID-19 pandemic. Efforts to identify the origins of SARS-CoV-1 and -2 has resulted in the discovery of numerous animal sarbecoviruses–the majority of which are only distantly related to known human pathogens and do not infect human cells. The receptor binding domain (RBD) on sarbecoviruses engages receptor molecules on the host cell and mediates cell invasion. Here, we tested the receptor tropism and serological cross reactivity for RBDs from two sarbecoviruses found in Russian horseshoe bats. While these two viruses are in a viral lineage distinct from SARS-CoV-1 and -2, the RBD from one virus, Khosta 2, was capable of using human ACE2 to facilitate cell entry. Viral pseudotypes with a recombinant, SARS-CoV-2 spike encoding for the Khosta 2 RBD were resistant to both SARS-CoV-2 monoclonal antibodies and serum from individuals vaccinated for SARS-CoV-2. Our findings further demonstrate that sarbecoviruses circulating in wildlife outside of Asia also pose a threat to global health and ongoing vaccine campaigns against SARS-CoV-2
Heath-e News article – Concern as new vaccine-resistant virus emerges (Open access)
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