Canadian researchers have published the first structural images of a mutation in the B.1.1.7 variant of the Covid-19 virus that may explain why it has proved far more infectious than the previous strain, causing a rapid rise in cases not just in the UK, but possibly also in India and Canada.
The B.1.1.7 variant, first reported by the World Health Organization (WHO) in mid-December last year, has an unusually large number of mutations.
“The pictures, taken at near-atomic resolution, provide critical insight as to why the B.1.1.7 variant – first detected in the UK and now accounting for a growing number of cases across Canada – is more infectious,” University of British Columbia (UBC) said in a statement.
The research team, led by Dr Sriram Subramaniam, professor in UBC faculty of medicine’s department of biochemistry and molecular biology, found of “particular interest” a mutation known as N501Y located on the coronavirus’s spike protein, which is what it uses to attach itself to human cells that it infects.
“The images we captured provide the first structural glimpse of the N501Y mutant and show that the changes resulting from the mutation are localised. In fact, the N501Y mutation is the only mutation in the B.1.1.7 variant that is located on the portion of the spike protein that binds to the human ACE2 receptor, which is the enzyme on the surface of our cells that serves as the entry gate for Sars-CoV-2,” he said.
The coronavirus is 100,000 times smaller than a pinhead and is undetectable using a regular microscope. To “visualise the detailed shapes of viruses and proteins”, the research team used cryo-electron microscopes called cryo-EM that can be up to 12 feet high, and the imaging technology uses beams of electrons to picture the samples at liquid nitrogen temperatures.
“This image from our cryo-EM work that shows the interaction of the mutation introduced Y residue (501Y) with ACE2, which we believe is the cause of increased binding and infectivity of B.1.1.7,” Dr Subramaniam told HT.
The research has some positive news as well, as he noted, “Our analysis revealed that even though the N501Y mutant can bind and enter our cells more readily, it can still be neutralised by antibodies that block the entry of the unmutated version of the virus into cells.”
He said they project to have similar structural images of the B.1.617 variant – that originated in India – by the end of May, while his team is also working on visualising the variants that emerged in Brazil, South Africa as well as in California.
“It’s important to understand the different molecular structures of these emerging variants to determine whether they’ll respond to existing treatments and vaccines and ultimately find ways to control their spread more effectively,” he said.