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According to a new study, the SARS-CoV-2 virus is accumulating genetic mutations, including one called D614G that may have made it more contagious.
Researchers have sequenced the genomes of SARS-CoV-2 strains extracted from 5,085 COVID-19 patients in the Houston, Texas, USA metropolitan area, and have observed that the virus that causes COVID-19 is accumulating various genetic mutations. One of the study’s co-authors, Ilya Finkelstein, associate professor of molecular biosciences at the University of Texas at Austin (UT-Austin), explained that their study shows that “the virus is mutating due to a combination of neutral drift, which simply it means random genetic changes that neither help nor harm the virus, and pressure on our immune system. “
According to the document, during the first wave of COVID-19 cases, 71 percent of the SARS-CoV-2 particles identified in patients in Houston had the D614G mutation. However, in the second wave of the outbreak during the summer, this variant had a prevalence of 99.9 percent. The researchers say this finding reflects a trend seen around the world; A study published in July based on more than 28,000 genome sequences found that variants carrying the D614G mutation became the globally dominant form of SARS-CoV-2 in about a month.
But why has this strain become dominant and the D614G mutation carries an advantage?
The researchers suggest that the mutation may make the strain more contagious, as a study of more than 25,000 UK genome sequences found that viruses with the D614G mutation tended to transmit slightly faster than those without it.
The researchers said that natural selection would favor the strains that are transmitted more easily; however, not all scientists are convinced and some suggest that the D614G mutation might have been more common in the first viruses to reach Europe and North America, essentially giving them an advantage over other strains, what they call ” founding effects “.
The team also reported that the SARS-CoV-2 Spike (S) protein, which the virus uses to infect cells, also continues to accumulate mutations of unknown significance. The team, made up of scientists from Houston Methodist Hospital, UT-Austin, and elsewhere, also showed that one of the mutations allows protein S to bypass neutralizing antibodies produced in response to viral infections. This mutation can also allow SARS-CoV-2 to escape the immune system, which is why the researchers said it is good that the mutation is rare and does not appear to aggravate the disease for infected patients. According to Finkelstein, the group did not identify viruses that have learned to evade first-generation vaccines and therapeutic antibody formulations.
The scientists observed a total of 285 mutations in thousands of infections, although most do not appear to have a significant effect on the severity of the disease. Ongoing studies continue to examine the third wave of COVID-19 patients and characterize how the virus is adapting to neutralizing antibodies that are produced by our immune systems.
The article was published in mBIO.
