Protein deficiency, not age or weather, reason for spread of Covid in Europe, US
The variant of the virus that spread rapidly across the world had acquired a mutation since it left Wuhan that allowed it to use another human protein called neutrophil elastase to also cleave the S1-S2 junction
It was not the age profile or weather conditions, but the deficiency of a particular protein that led to the rapid spread of coronavirus disease (Covid-19) among Europeans and North Americans, according to a study by researchers from National Institute of Biomedical Genomics-Kalyani.
The study was recently published in the journal Infections, Genetics and Evolution.
The entry of the Sars-CoV-2 virus in the human body is a two-step procedure. First, the spike protein of the virus attaches to the ACE 2 (Angiotensin-Converting Enzyme 2) protein found on the surface of certain human cells in the lungs, intestine, and other tissues and organs. Second, another human protein TMPRSS2 (type II transmembrane serine protease) breaks the S1-S2 junction in the spike protein to allow the genetic material of the virus to enter the human cell.
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However, the variant of the virus that spread rapidly across the world had acquired a mutation since it left Wuhan that allowed it to use another human protein called neutrophil elastase to also cleave the S1-S2 junction.
“Now the neutrophil elastase is used by the human body usually to kill the organism attacking the lungs. However, it also damages the lung tissue in the process. Hence, a protein called Alpha-anti-trypsin (AAT) is needed to balance its action. Our research shows that the deficiency of this AAT protein among the people in Europe and North America led to the rapid spread of the infection in these populations,” said Nidhan Biswas, the co-author of the article.
The paper shows a co-relation between the level of AAT in populations and the spread of the infection, he said.
“So far, we had seen that these regions were reporting higher number of cases but we did not know why. Some thought it was because of the elderly population or the cold weather. But, if you look at Japan it has a considerable old population but the disease was not as widespread. Conversely, the population of Brazil is younger and yet the disease was widespread. Now, we have shown that the reason for higher spread is the deficiency of AAT protein,” said Biswas.
He said, “Even among the European population, the AAT deficiency is highest among those in Spain and Italy. And, Italy saw one of the biggest outbreaks initially.”
The study has found a co-relation between the levels of AAT and the disease spread. However, the researchers have not found any link between the level of the protein and the severity of the disease.
“This is the first time a co-relation has been established between this protein and the spread of Covid-19. However, this will have to be validated in appropriate cell lines and animal models. However, this gives us important information about the mechanism used by the virus to enter the human cells and the knowledge may be used to develop molecules in the future that can prevent the entry of the virus into the human body,” said Dr Soumitra Das, director, NIBMG.