SARS-CoV-2 genomes obtained from patients in Stockholm belonged to the genetic strains 20C/B.1/G and 20B/B.1.1/GR. Along with B.1/G from Italy, they are the three main strains found in Sweden. B.1/G declined in prevalence by late April in Sweden, while 20C/B.1/G and 20B/B.1.1/GR mutated locally from
B.1/G and they became more prevalent in the country. One of the Swedish strains carries the novel mutation, which affects the attachment of the virion to the cell, thus weakening the spike protein's infectivity. An earlier study by Indian researchers came up with similar results, which found two Swedish mutations, one of which was benign without being specific about the mutations.
A variant was identified that could have destabilizing effects
In one of the genomes, a variant was found at 23463bp that was not found in any other GenBank SARS-CoV-2 genome. The mutation changes an arginine residue to a histidine residue at position 364 in the S1 subunit of the viral spike protein.
The researchers say this variant in the spike protein could have destabilizing effects.
“The variant is located at the surface of the S1 subunit, and could possibly affect the attachment of the virion to the cell, even though it does not change the receptor-binding domain itself,” writes the team.
Three genomes were strains previously thought to have declined in Sweden
On comparing the four SARS-CoV-2 genomes obtained from patients in Stockholm with those detected globally, the researchers found that they belonged to the genetic strains 20C/B.1/G and 20B/B.1.1/GR.
The Public Health Agency of Sweden had previously reported these genetic groups as two of the three main strains found in Sweden.
However, three of the genomes are from group B.1/G, which was also reported by the Public Health Agency of Sweden to have declined in prevalence by late April, say Soratto and team.
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