March 24, 2021 12:34:48 am
Just like the imported UK, Brazil and South African variants of SARS-CoV2 virus, the local ones are equally important in terms of genomic surveillance, according to experts. While Maharashtra had reported mutations, it is still unclear whether it is linked to the surge in the state, they said.
Maharashtra, Punjab, Gujarat, Chhattisgarh, Karnataka and Tamil Nadu have reported a rise in daily new cases of coronavirus infection, accounting for 81 per cent of daily new cases (40,175) on March 22.
Maharashtra has some unique Indian lineages of SARS-CoV2 virus that are not seen as frequently in other parts of the world. One sixth of the 6000 genome sequences are in B.1.1.306, which is the dominant lineage in Maharashtra. There are some 138 lineages in the country.
“Even if there are 100 different lineages of SARS-CoV2 virus in the country, the top five cover a large fraction of the total lineages and vary from state to state. Hence, it is important to understand locally what has happened in different states and whether some are associated with higher transmission, immune escape… assess what are the mutations that need to be studied to understand biological implications.” Dr P Chitra, from the National Institute for Mental Health and Neurosciences, Bengaluru, told The Indian Express.
Mutations can occur throughout the genome of SARS-CoV virus but what is important is the changes to the spike protein of the virus. Globally there are 88 mutations which may lead to immune escape/reinfection/ drop in vaccine efficacy. What is of concern is that mutations can be acquired and apart from continuous genomic surveillance, the crucial aspect is to break the chain of transmission, said experts.
As many as 86 of the 120 genetic variants associated with immune escape were detected in genomes circulating worldwide, of which 19 were found circulating in India, according to studies.
Mutations such as E484 Q and L452 R were recently found in samples from Maharashtra. Efforts are underway to ensure whether or not it is correlated with the peak in the state, state health officials said. “We have to rule out reasons like was there a local super-spreader event in the community and can it be associated then to a particular variant that is allowing higher transmission,” said an expert.
For instance, of the 74 samples from Nagpur, 39 had shown some of the escape variants like L452R and E484Q. However, National Institute of Virology scientists made it clear to the state officials that these were not new variants and had been reported in other countries earlier.
Dr A Raghunathan, NCL scientist who helps the Pune Knowledge Cluster towards understanding Covid-19, told The Indian Express that genomic surveillance of SARS-CoV-2 variants is critical to monitor mutations in the spike glycoprotein, which mediates attachment to cells and is a major target of neutralizing antibodies. Any new emergent variants need to be tracked across time and states in the country.
The major problem of a variant with multiple mutations in spikes that increase transmissibility, as seen world-wide, is that it can cause a surge, lead to increased hospitalisations and overwhelm the health system, said experts.
Current vaccines stimulate an immune response to the entire spike protein, thus they may continue to provide protection despite sequence variation at antigenic sites in the new variant. However, defining these dynamics, and their potential influence on vaccine effectiveness, will require large-scale monitoring of SARS-CoV-2 evolution and host immunity.
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