Coronavirus evolution in bats may have resulted in highly efficient human pathogens

Researchers in the United Kingdom, the United States, and Belgium have said that although there have been major changes in the evolutionary history of the SARS-CoV-2 virus, these changes may have occurred when the virus was found primarily in bats. I found myself to be a “relatively generalist”. “A virus that could infect humans without the need for intermediate species.

To Study published on Friday PLOS BiologyResearchers have pointed out that changes in the viral host are usually associated with new adaptations of the virus itself that allow microorganisms to better utilize cells of new host species. However, SARS-CoV-2 seems to have required little or no significant adaptation to humans from the beginning of the COVID-19 pandemic until October 2020.

Researchers evaluated the types of natural selection taking place in Salvecovirus In Himekikugamo, we compared them to the early human SARS-CoV-2 evolution. They found some evidence that the positive selection diversifies in human SARS-CoV-2, but it is moderate, limited to the early stages of the pandemic, and the purification selection is SARS- more than the associated bat. It was much weaker with CoV-2. Salvecovirus.. In contrast, they found a significant positive transient diversification choice that acts on the basis of the bat strain in which SARS-CoV-2 emerged and is associated with the action of antiviral mechanisms in these ancestral bats. Hosts with an adaptive depletion of presumed CpG composition.

Therefore, researchers suggest that intermediate species may have promoted bat-to-human transmission of SARS-CoV-2, but their data show that SARS-CoV-2 progenitor cells are efficient in humans. He said it suggests that humans can be infected. As a result of its adaptive evolutionary history in bats.

Using the 133,741 genomic sequences of the GISAID database as of October 12, 2020, the researchers first analyzed the selections that act on the SARS-CoV-2 encoding amino acids. This represents a sample of mutants that circulate in humans during the first 11 months of the pandemic. .. Most of the mutations observed in these samples occurred very infrequently, with 79% of the mutations observed in less than 10 of the 133,741 SARS-CoV-2 genomic sequences.

“Our findings show that changes have occurred in SARS-CoV-2, but most of these mutations are not evolutionarily important, and as with all viruses, what It accumulates by “surfing” along with millions of communication events, “said lead author and University of Glasgow researcher Oscar McLean in a statement. “The slow evolution is that the human population is very sensitive to this new pathogen, the pressure from the population’s immunity is limited, and lack of containment can lead to exponential growth. There is sex. “

In contrast, however, the researcher’s analysis Salvecovirus The clade in which SARS-CoV-2 appeared, coupled with the adaptive shift in CpG composition in this strain, provided evidence of positive selection in the deeper branches of the clade. Changes in CpG suppression at the base of the new coronavirus clade may indicate an indication for antigenic escape by evading the immune system of mammals that target known CpG, such as ZAP, they said. ..

Importantly, researchers have shown signs of increased selective pressure associated with faster spread and a higher number of non-synonymous substitutions in some recent strains of the virus since the end of 2020. Of note — variants of the United Kingdom (B.1.1.7) and South Africa (B.1.351). These strains appear to have evolved in humans in relation to human immunity, probably due to previous exposure and / or chronic infection of immunocompromised individuals, and are associated with acute SARS-CoV-2 infection and infection. Not because of the slow evolution. They said they were pandemic and dominant until October 2020.

More urgently, senior author and Glasgow bioinformatics researcher David Robertson has evolved in a statement from the January 2020 variant used in all current vaccines. It states.

“Current vaccines continue to work for circulating mutants, but the longer the elapsed time and the greater the difference between the number of vaccinated and unvaccinated people, the greater the chance of evacuating the vaccine. “I will,” he said. “The reason the SARS-CoV-2 gear has shifted in terms of increased evolutionary rate at the end of 2020 is related to more highly mutated strains and has changed the immunological profile of the population. The first race. It was to develop a vaccine. The competition now is to get people around the world to get the vaccine as soon as possible. “

In their study, the authors are also highly diverse and generalist in nature. Salvecovirus, Future spillover from bats may be linked to recombination events with SARS-CoV-2. Such events can lead to the emergence of the SARS-CoV-3 virus, which in itself can be sufficiently divergent to evade either innate or adaptive immunity.

“Therefore, surveillance needs to be dramatically enhanced. Salvecovirus The human-animal interface carefully monitors the emergence of future SARS-CoV in human populations, “they conclude.

This story was first published in our sister publication, Genomeweb..