Slight reduction in transmissibility observed in most coronavirus variants

Like any other virus, the coronavirus SARS-CoV-2 responsible for COVID-19 pandemic we are experiencing changes constantly. It is a natural process related to mutations random that are generated replication after replication in hosts. Sometimes genetic changes emerge that can provide an advantage to the virus, other times a disadvantage. But in the vast majority of cases, as experts explain, the mutations are completely harmless e meaningless. Those of particular interest to scientists are located on the proteina S O Spike of the coronavirus, the glycoprotein that constitues the outer shell of the pathogen (the pericapsid or peplos) used as a “biological pick” to unhinge the cell wall, introduce theViral RNA and create replication, the mechanism responsible for disease. These mutations, in fact, can for example guarantee a greater coronavirus transmissibility or perhaps an ability to resist neutralizing antibodies, both due to precedents natural infections that ai vaccines.

By analyzing the variations in the genomic heritage of the different variants that have emerged to date, an international research team has determined that the coronavirus has certainly become more transmissible than at the beginning of the pandemic, however, due to the accumulation of recurrent and deleterious mutations precisely in relation to protein S, a slight decline in the ability to infect has begun to be observed in various lineages. Describing this phenomenon was a team led by researchers from University College London, who collaborated closely with colleagues from the Department of Zoology of the University of Oxford and the Department of Ecology and Evolution of the Australian National University (ANU). of Canberra. The scientists, coordinated by Professor François Balloux, a Genetics expert at the UCL Genetics Institute of the University of London, came to their conclusions after thoroughly analyzing the genomic data (phylogeny) of SARS-CoV-2 from the databases GISAID. The data was updated as of April 15, 2021, when the survey was conducted.

Professor Balloux and colleagues found that many mutations and deletions are often repeated in the so-called variants of concern (VoC), such as the South African variant (B.1.351 or 501Y.V2), la English variant (B.1.1.7 the Variant of Concern 202012/01 – VOC-202012/01) and there Brazilian variant (P.1 or Variant of Concern 202101/02 and 20J / 501Y.V3). A mutation detected in different strains is for example the E484K, an “immune leak” mutation that would make the pathogen able to resist antibodies. While noting an increase in transmissibility, the authors of the study identified a trend in the various lineages for the substitution of citidina with the thymidine (C-> T), a mutation associated with “a reduction in estimated transmissibility”, reads the study abstract. By evaluating transmissibility as a whole through genomic data, the researchers determined that the English variant appears to be the most transmissible in circulation today; Not surprisingly, a recent study determined that it is up to 90 percent more transmissible than the original Wuhan strain. However, a slight but significant reduction in transmissibility is being observed in most strains.

“This model is consistent with the expectation of a decay of transmissibility in mainly non-recombinant lines caused by the accumulation of weakly deleterious mutations,” Balloux and colleagues write in the abstract of the study. “SARS-CoV-2 remains a highly transmissible pathogen, although such a trend could plausibly play a role in the turnover of the different global viral clades observed so far during the pandemic,” the experts conclude. The details of the research “A phylogeny-based metric for estimating changes in transmissibility from recurrent mutations in SARS-CoV-2” have been uploaded to the BiorXiv online database pending publication in a scientific journal.

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