SARS-CoV-2 shows stable evolution: Study

As the world awaits the coronavirus vaccine, researchers seem to be worried about another constraint — the changes in the genetic sequence of the SARS-CoV-2.

According to a new study published in the journal bioRxiv server, there are seven different clades into which the virus has diversified. Now, the researchers are exploring the important haplotypes (the set of genetic determinants in a chromosome).

The study noted that the clades circulating most widely at the start of the pandemic were L, O, S, and V and these have been called as the ‘founding clades’. However, during the course of the pandemic, the D614G mutation emerged in the ‘G clade’, in the spike protein, and soon attained a high prevalence.

Later, ‘GR clade’ emerged, which soon became dominant in every region where it was introduced. The GH reached its highest frequency at 30 per cent in May 2020 but has subsequently decreased. The researchers suggested that these three clades have higher transmissibility, though have not caused a more severe disease.

For the analysis, the researchers examined 2,100 sequences that represented all seven clades of the virus. The study was carried out to identify the patterns in which their genes had changed and the rate of change of the nucleotides at the genomic region of the spike.

The scientists found that the various patterns of gene variants that are inherited together, called ‘haplotypes’. They found almost 480 haplotypes in these clades.

According to the scientists, the primary reason for this higher evolutionary rate is because the genome contains many regions that are highly conserved, but the ‘S’ region, on the other hand, is among the sequences that are changing most rapidly.

The authors pointed out: “The present evolutionary analysis is relevant since the spike protein of SARS-CoV-2 is the target for most therapeutic candidates; besides, changes in this protein could have consequences on viral transmission, response to antivirals and efficacy of vaccines.”

The researchers intend to explore the characteristics of the other clades of the virus in order to figure out whether they are capable of reinfecting people or not.