SARS-CoV-2 is the seventh known member of the human infectious disease of the Coronaviridae family of RNA viruses. Genomic analysis efforts have identified a subgenus of coronaviruses, called sarbecoviruses, that has been circulating in bat species in China.
Unlike other RNA viruses, sarbecoviruses can easily undergo mutations, such as specific receptor-binding ground layers and the inserted furin acting site, after they have evolved into new host species for reproduction and proliferation. -effective. In particular, SARS-CoV-2 takes advantage of the general properties from obtained modifications to increase angiotensin-converting enzyme 2 (ACE2) binding and to induce the infectivity of nonbat species, including into people.
Mutation characters can be useful in understanding the effect of genetic modification action. Motions under positive selection are more likely to reflect functional changes; however, frequency data associated with these mutations can be misleading, as growing populations tend to increase in average virus susceptibility. Viruses also undergo genetic transmission, with destructive mutations “surfing” propagation waves.
In the present study, an international team of researchers from the UK, USA and Belgium examined the evolutionary history of bat sarbecoviruses that shaped the emergence and rapid spread of SARS-CoV-2 by making comparison of positively selected mutations in the virus that has been circulating in humans since then. the uprising to signatures of historical selection began to work on associated bat viruses.
In total, the researchers analyzed 133,741 SARS-CoV-2 genomes sampled from December 2019 to October 2020 and compared them to 69 sarbecovirus genomes separated into phylogenetically based sympathetic regions. recurrence patterns found. The open source analytical framework, Hypothesis Testing using Phylogenies (HyPhy), originally developed by study author Sergi Pond, PhD, professor of biology at Temple University, was instrumental in finding media names -growth rooted in the genomes of the virus.
Record of evolutionary history suggested by the researchers about the new coronavirus cover and intelligence events that led to SARS-CoV-2. Image courtesy of Oscar MacLean et al. Allowed under CC-BY.
“What’s been surprising is just how portable SARS-CoV-2 has been from the beginning,” Pond noted. “Viruses that jump to a new host species usually take some time to get changes to become as viable as SARS-CoV-2 at release, and most never. passing that level, resulting in a deadlock or a local breach. “
Significant changes occurred to SARS-CoV-2, but before humans
Analysis of SARS-CoV-2 genomes across the pandemic of the pandemic from December 2019 to October 2020 reveals a lack of proliferative selection taking place during the circulation of the virus in humans. However, there is evidence of continued positive selection associated with minor improvements in the human population.
However, most of the mutations produced by the SARS-CoV-2 virus occurred before its appearance in the human population.
“This does not mean that no changes have taken place, meaningless evolutionary mutations accumulate and surf across millions of transmission events, as they do in all viruses,” explained the author Oscar MacLean, PhD, bioinformatician at the University of Glasgow.
The data suggest that the progenitor SARS-CoV-2 is from a viral line with a relatively generic nature. Virus specialization is driven by rates of change and the opportunities for their transmission, but at a general price and the ability to reproduce in multiple species.
“This stasis [neutral evolutionary changes] due to the highly susceptible nature of the human population to this new pathogen, with limited pressure from population immunity, and lack of restriction, it can lead to abstract growth making almost all viruses a winner, ” MacLean explained.
According to the authors, the ability of SARS-CoV-2 to easily transfer to other animals, such as pangolins and cats, is evidence of the common property of the virus, which was developed in bats. The lack of evidence on the proliferation of a selection of immediately preceding versions of SARS-CoV-2 before humans has emerged in which the changes in bats that allow it to be a capable general in humans and many mammals appear to have occurred. capture another and not in an intermediate host. .
“Interestingly, one of the most intimate bat viruses, RmYN02, has an interesting genome structure made up of both SARS-CoV-2-like and bat-bat-like species,” said Spyros Lytras, author and candidate at the University of Glasgow Center for Virus Research “Its genetic material carries the two distinct signatures (related to host antiviral immune function), supporting this change of evolutionary rate in bats. no need for a medium animal breed. “
What about new versions from October 2020?
The authors noted that there are signs of increased selective stress in recent versions of SARS-CoV-2 (such as variants B.1.1.7 and B.1.351) that are associated with greater distribution. faster and higher than usual number of unnamed agents.
“[This] this is because the immunological profile of the human population has changed, “explained David Robertson, PhD, a professor at the University of Glasgow ‘s Virus Research Center.
As the virus communicates with existing host immunity, changes that are possible to select host responses are increasingly selected. Coupled with immunosuppression in long-term infections in breast cancer (e.g., in vaccinated patients), these new selective strains increase the number of significant virus mutants.
Due to the high prevalence and general nature of sarbecoviruses, it is possible to overdose in the future, which may be accompanied by a relapse event with SARS-CoV-2, according to the researchers. The appearance of “SARS-CoV-3” may be a natural immunity or vaccine. Therefore, the authors advocate for increased sensitivity to sarbecoviruses at the human-animal interface and carefully monitor for future SARS-CoV exposure in human populations.
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