Scientists at the CSIR-Centre for Cellular and Molecular Biology (CCMB), Hyderabad have analysed more than 2,000 SARS-CoV-2 genomes (an organism's complete set of DNA) from India, available in the public domain to understand the various strains in circulation.Earlier in June, the team had revealed the presence of a distinct virus population among Indians.
This was named the clade* I/A3i, and was recognised by the presence of four specific variations in their genetic makeup (genomes).At that time, 41 per cent of all Indian SARS-CoV-2 genomes belonged to this clade.
The current analysis showed that the proportion of the I/A3i clade dropped to 18 per cent."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 [the role of RNA is to convert the information stored in DNA into proteins].
This variant was predicted to be bad for the virus, and if the prediction is indeed correct, we expected A3i clade to slowly disappear with timeThis is exactly what we see now," Dr Divya Tej Sowpati, Scientist at CCMB, who is leading this study said.The 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 increased infectivity.At present 70 per cent of all Indians, 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 in India just like everywhere else.
There is no evidence to state that this mutation is clinically a more difficult one.
The similarity in viral genome globally should be considered positive news because a vaccine or a drug targeting this mutation will work with the same effect all over the world," Dr Rakesh K Mishra, Director, CCMB and a co-author of the study, said.It is, however, important to note that no clade at present has been conclusively shown to be associated with a more severe form of coronavirus, or an increased risk of death.*Clade: A group of organisms believed to comprise all the evolutionary descendants of a common ancestor.