Scientists in China have reported that they have identified a new coronavirus—HKU5-CoV-2—in bats, capable of infecting human cells through a mechanism similar to SARS-CoV-2 that triggered the Covid-19 pandemic five years ago.
The discovery, reported in the journal Cell last week, has since triggered worries across the world.
The latest findings have been reported by a team of virologists at the Center for Emerging Infectious Diseases at the Wuhan Institute of Virology, led by Shi Zhengli, who came into prominence as “batwoman” during the pandemic for her work with bat coronaviruses and also faced allegations for her facility’s central role in the emergence of SARS-CoV-2.
HKU5-CoV-2, like SARS-CoV-2, belongs to a family beta coronavirus, one of the four broad types of coronaviruses, named so for crown-like protrusion on their surfaces, and can cause respiratory infection in animals and humans.
The newly-identified virus is closely linked with HKU1, first detected in a 71-year-old man in 2004 in Hong Kong who was hospitalised with acute respiratory distress and severe pneumonia, and is one of the seven types of coronaviruses known for infecting humans.
The scientists at the Wuhan Institute have now warned that just like SARS-CoV-2, the bat virus HKU5-CoV-2 contains a feature known as the furin cleavage site that helps it enter human cells via the ACE2 receptor—a protein on the surface of many cells.
As part of the scientific project, the researcher collected the HKU5-CoV-2 strain from a small subset of hundreds of Pipistrellus bats from various Chinese provinces and analysed them for their affinity to human cells.
Their experiment revealed that the virus belongs to a distinct lineage of coronaviruses that includes the one causing Middle East Respiratory Syndrome (MERS) and is distantly related to SARS-CoV-2.
What really triggered the concern was the finding that the HKU5-CoV-2 strain can enter human cells by binding to the ACE2 receptor, mirroring the mechanism used by SARS-CoV-2 to infect cells, replicate, and transmit.
Structural and functional analyses indicate that HKU5-CoV-2 has a better adaptation to human ACE2 than lineage 1 HKU5-CoV. Authentic HKU5-CoV-2 infected human ACE2, expressing cell lines and human respiratory and enteric organoids, researchers noted.
“This study reveals a distinct lineage of HKU5-CoVs in bats that efficiently use human ACE2 and underscores their potential zoonotic risk,” they have cautioned.
Scientists in India said that while the latest discovery should not raise an alarm immediately, there may be a need to maintain surveillance for highly pathogenic zoonotic viruses.
“HKU5-CoV2 is a specific strain of HKU5 needing surveillance as of now with no human-to-human transmission but can bind to ACE 2 receptors,” said a scientist with the epidemiology division at the Indian Council of Medical Research (ICMR).
‘Face to the faceless threat’
Senior immunologist Dr Dipyaman Ganguly, who is associated with Ashoka University, told ThePrint that the major concern over HKU5-CoV2 comes from the fact that the discovery has demonstrated potential for the receptor binding domain (RBD) of this virus to engage receptors on human cells and thus infect them.
Findings from the lab experiments suggest that HKU5-CoV-2 may also infect a broad variety of mammals, underscoring its potential for cross-species transmission.
While the results indicate that the pathogen has the potential for animal-to-human transmission, it has also been noted that HKU5-CoV-2 has a lower binding affinity to human ACE2 than SARS-CoV-2, and its ability to infect humans on a large scale remains uncertain.
More research is needed to determine if it poses a serious health threat, the scientists have suggested.
“The results confirm existing knowledge that there are zoonotic viruses out there capable of human jump. Also, it gives a face to otherwise faceless threats,” said biologist Dr Anurag Agarwal, who is also dean of the Trivedi School of Biosciences with Ashoka University.
Dr Agarwal, however, reassured that as of now, there is no cause for any new concern beyond a general readiness.
Dr Ganguly pointed out that due to the Covid pandemic, a majority of the human population have neutralising antibodies that can interfere with ACE2 binding by SARS-CoV-2 RBD.