They show specific similarities in a key domain of the Spike protein. Viola: «Many viruses are ready to make the leap of species and infect us. It is urgent to carry out structural changes in our healthcare “
Three coronaviruses with a similar genome to Sars-CoV-2 have been identified in bats in Laos, Southeast Asia. Banal-103, Banal-236 and Banal-52, as the viruses have been called, show specific similarities in a key domain of the Spike protein that allows the virus to bind to human cells. The study, of the Institut Pasteur of Paris, National University of Laos and Institut Pasteur of Laos, is published in the journal Nature
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Animal tank
“The discovery of the three viruses supports the theory that Sars-CoV-2 may come from bats that live in the karst plateaus of the Indochinese peninsula, which extends across Laos, Vietnam and China,” said Marc Eloit of the Institut Pasteur in Paris. We still do not know with certainty which is the animal reservoir or the intermediate host of Sars-CoV-2, despite the reports of virus “cousins” in Asian bats and pangolins. The results of the study, the authors write, however indicate that potentially infectious viruses for humans circulate among the Rinolofi (horseshoe bats) in Southeast Asia.
Coronavirus RaTG13
To date, the closest genome to Sars-CoV-2 remains the one identified in a bat Rhinolophus affinis in China in 2013 (the virus was called RaTG13), with 96.1% similarity at the whole genome level. But even in this case the receptor binding domain (RBD, receptor-binding domain) has a limited similarity to that of Sars-CoV-2 and a limited affinity with the human ACE2 receptor (angiotensin-converting enzyme 2). To date, no Sars-CoV-2-like bat viruses have been shown to use ACE2 to effectively enter human cells, and none exhibit the cut site of furin (an enzyme), a feature that appears to be associated with increased pathogenicity in humans.
The closest ancestors to Sars-CoV-2
According to the authors of the new study, viruses with RBD capable of binding to the ACE2 receptor could be precisely those identified in bats living on the Indochinese peninsula. Therefore they could represent a future risk of transmission to humans. Despite the absence of the furin cut site, Laotian coronaviruses are the closest ancestors to Sars-CoV-2 known to date. Only one or two amino acids that interact with ACE2 are modified in these strains with respect to the virus responsible for the pandemic. According to the authors, the results of the work support the hypothesis that Sars-CoV-2 may originally result from a recombination of pre-existing sequences in bats. Rhinolophus which live in the caves of Southeast Asia and South China. However, the epidemiological link between bat viruses and early human cases remains unknown.
Infectious potential
To conclude, the authors state that the bat viruses analyzed appear to have the same potential to infect humans as the early Sars-CoV-2 strains. The members of ascetic religious communities who spend time in the caves, as well as the tourists who visit them, are particularly at risk of becoming infectedscientists say. Further investigation is needed to assess whether these populations have been infected with one of these viruses and whether the infection may confer protection against Sars-CoV-2.
Viruses ready to jump species
“This discovery does not yet answer all the open questions, but it further strengthens the hypothesis of the natural origin of Sars-CoV-2 – commented Antonella Viola, immunologist of the University of Padua -. At the same time, however, she confirms that many other viruses are ready to make the leap of species and infect us. It is therefore necessary not only to monitor the evolution of coronaviruses closely to avoid being caught unprepared, but also to carry out those structural changes in our healthcare that would have allowed us to better manage the emergency. We have to learn the lesson ».
February 19, 2022 (change February 19, 2022 | 17:58)
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