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Monday, March 08, 2021

Biological reason behind slow spread of mutant strain in Asia: NIBMG study

“Under the leadership of Prof Nidhan Biswas, scientists worked hard to find a biological answer,” said Prof Majumder, who also worked on the study.

Written by Anuradha Mascarenhas | Pune |
Updated: February 9, 2021 3:47:59 am
Vaccination drive for Mumbai Police personnel underway at KEM Hospital in Mumbaion Monday. (Express photo by Ganesh Shirsekar)

A team of scientists at the National Institute of Biomedical Genomics (NIBMG) in Kalyani has pointed to a biological reason behind the slower spread of the D614G mutant coronavirus in Asia compared to Europe and the USA.

A lower proportion of Asians, as compared to Europeans and Americans, are deficient in a protein that promotes easier entry of the coronavirus into human cells, scientists said in a study recently published recently in the international journal ‘Infection, Genetics and Evolution’.

Prof Partha Majumder, NIBMG founder and emeritus professor at the Indian Statistical Institute in Kolkata, said several reasons were speculated behind the differential spread of the coronavirus across geographical regions. “The most popular speculation was that the higher temperature in Asia was not congenial to the spread of the coronavirus. However at NIBMG scientists believed the cause had to be biological, rather than physical or social,” he said.

“Under the leadership of Prof Nidhan Biswas, scientists worked hard to find a biological answer,” said Prof Majumder, who also worked on the study.

“The biological explanation for slower spread… in Asia… is related to the additional ‘gate’ of entry into the human cell that the mutation creates. Creation of a ‘gate’ by a mutation does not suffice for actual entry. The gate needs to be opened. The opening is done by a protein of the host, that is, a human protein, called neutrophil elastase,” Prof Majumder said.

This protein is plentifully available in the lungs. When the level of neutrophil elastase is high in an individual, the additional gate created by the mutation in the coronavirus opens up in a larger number of cells, and the virus enters a larger number of human cells enabling it to make many more copies of itself and helps it spread better from one infected individual to another uninfected individual, said Prof Majumder, who is also the National Science Chair, Government of India.

While a high level of neutrophil elastase is not necessarily good, there are helpful functions which include keeping some types of bacteria at bay. The human biological system has evolved to keep the level of neutrophil elastase in check. Humans produce a protein called alpha-1-antitrypsin (AAT) that inhibits the production of neutrophil elastase and keeps its level in check.

However, some naturally-occurring mutations in the AAT-producing gene results in deficiency of the AAT protein. AAT protein deficiency results in higher levels of neutrophil elastase and because of this the coronavirus is then able to enter many more human host cells and spread itself better.

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