It is important to note that no strain of coronavirus or clade at present has been conclusively shown to be associated with a more severe form of COVID-19 or an increased risk of death, affirmed scientists at the CSIR-Centre for Cellular and Molecular Biology (CCMB) on Sunday.
Scientists have analysed more than 2,000 SARS-CoV-2 genomes from India available in the public domain to understand the various strains in circulation. Earlier in June, the scientists’ team had revealed the presence of a distinct virus population among Indians named ‘clade I/A3i’, and is recognised by the presence of four specific variations in their genetic makeup (genomes).
At that time, 41% of all Indian SARS-CoV-2 genomes belonged to this clade. Current analysis showed that the proportion of the ‘A3i’ clade has dropped to 18%. “One of the four distinct variations that define the A3i clade is present in a key viral enzyme called RDRP, involved in making new copies of the viral RNA. This variant was predicted to be deleterious or bad for the virus, and if the prediction is indeed correct, we expected A3i clade to slowly disappear with time, and other clades without this variation will prevail. This is exactly what we see now,” says CCMB scientist team leader Divya Tej.
Decrease in the proportion of ‘A3i’ clade is accompanied by an increase of the ‘A2a’ clade, also referred to as the ‘G’ clade or the ‘20A/B’/C clades in other nomenclatures. Viruses of the ‘A2a’ or the ‘G’ clade carry the ‘D614G’ mutation in their spike protein which is shown to be associated with an increased infectivity.
“At present 70% of all Indian as well as global SARS-CoV-2 genomes fall into this clade. As expected for a strain which is more infectious, A2a clade quickly became the dominant clade everywhere. There is no evidence to state that this mutation is clinically a more difficult one. The similarity in viral genome globally should be considered a positive news, because a vaccine or a drug targeting this mutation will work with the same effectiveness all over the world,” said CCMB Director Rakesh K. Mishra, also the co-author of the study.
The findings of the study conducted with scientists from CSIR-Institute of Genomics & Integrative Biology (IIGB) as collaborators, are now peer-reviewed and published in the journal Open Forum Infectious Diseases published by the Oxford University Press. – MB Bureau