Unique coronavirus mutation in Bengal, experts say too early to know its impact
After Kerala and Gujarat, West Bengal has sequenced the SARS-CoV-2 genome and identified one unique mutation in the S2 domain of the spike protein of the virus in all samples sequenced from the state when compared to those sequenced in the other two states and Wuhan in China. There is one more mutation in S1 domain of the spike protein, which is similar to what Gujarat has found.
S1 attaches the virus to the cell membrane by interacting with host receptor while S2 mediates fusion between the virus and cell membrane , according to Uniprot which provides resources on protein sequence.
But it is too early to say how these mutations will affect us, said independent experts. The paper, led by CSIR Institute of Chemical Biology, Kolkata, and the Academy of Scientific and Innovative Research (AcSIR) in Ghaziabad, said that five sequences from West Bengal have been deposited on the Global Initiative on Sharing All Influenza Data (GISAID) on April 27. Scientists compared the sequences from West Bengal with other sequences reported in India and with isolates of Wuhan origin.
Authors explain in their paper which is yet to be peer reviewed published in Medrxiv, a pre-print server for health research that when a virus tries to adapt to a new environment and population it would change its genetic makeup to utilise the host’s body in favour of virus’s survival and propagation. Broad mutation profile of this protein from extensive genome sequencing from different geographical areas is key to designing effective antiviral therapy or vaccine.
While the sequences from West Bengal do tell us they are different from those in Gujarat and Kerala, the knowledge is inadequate in understanding how that can impact virulence or disease.
“There appears to be a new mutation in West Bengal, which hasn’t been described previously. Some mutations are important while some are not. It’s too premature to say anything. The spike protein is a hotspot for mutation. We need some real-life studies of how these mutations change the virus. Some of these mutations may affect the way the virus enters the body,” said Dr Shobha Broor, former head of the AIIMS department of virology, who has read the study. “There will be mutations. For example, the Kerala sequence was very similar to the one from Wuhan, the rest were similar to those from Italy. Mutations are critical, depending on where they are happening. For example, the receptor binding area of the RNA is important,” she added.
There can be better understanding only though large scale global sequencing studies but for now it doesn’t seem like SARS-CoV-2 is mutating very rapidly or significantly. “The question is whether one vaccine will hit all viruses globally. It might or might not. That is to be studied by several groups globally. There are umpteen examples in case of measles, polio, Japanese Encephalitis where one vaccine managed to hit all mutated viruses globally. In HIV, there was an antigenic shift which is why one vaccine didn’t help. In Influenza, we see antigenic drift, so one vaccine cannot be of help but this paper doesn’t address these questions. The mutations in SARS-CoV-2 are unlikely to affect the critical part of the spike glycoprotein. As of now, one vaccine is expected to protect all,” said Dr T Jacob John, professor emeritus and former head of virology at Christian Medical College, Vellore.