Why the New Covid-19 Variants Could Be More Infectious
2 min read.Updated: 17 Jan 2021, 12:37 PM ISTThe Wall Street Journal
Mutations in the virus’s appendage have created potentially more infectious versions of the pathogen, including one currently circulating around the world
As viruses replicate, they change, or mutate. Some mutations give these viral variants an edge, such as being better able to latch on to and infect human cells. That’s what scientists think happened with the coronavirus variant that swept through the U.K. recently and which is now showing up in states across the U.S.
Mutations can also make a viral pathogen stealthier, or better at evading the body’s immune system. That’s what some scientists find worrisome about another mutation seen in the variants that emerged recently in South Africa and Brazil.
Key mutations in these variants affect the coronavirus’s spike protein, which studs the surfaces of coronavirus particles. It’s the spike protein that helps the virus enter cells and infect people.
The spike protein is made up of three identical parts known as protomers. In the original version of the coronavirus that originated in China, these protomers usually assumed a closed shape, which is relatively inefficient at binding to human cells. But last spring, a mutation known as D614G made it more likely for the spike protein to have a more open shape, recent data shows. This open conformation enhances the virus’s ability to bind to human cells, according to Jeremy Luban, the University of Massachusetts Medical School virologist who ran the study.
That coronavirus variant soon overtook other existing ones to become the most dominant one in the world, said Vineet Menachery, a coronavirus expert at the University of Texas Medical Branch who has studied the D614G mutation.
He and other experts, including scientists at the Centers for Disease Control and Prevention, think the same could happen in the U.S. and around the world for the variant identified in the U.K. in December.
This new U.K. variant features a mutation known as N501Y, which also seems to affect the virus’s ability to bind to cells. It’s located in a region known as the receptor-binding domain, or RBD. It’s also found in the version of the virus found in South Africa.
The variants that emerged in South Africa and Brazil also have in common another spike protein mutation that affects the RBD.
For this mutation, known as E484K, studies suggest it could help the coronavirus evade the antibodies that the body’s immune system makes following infection with the coronavirus and those given as therapy.
The RBD isn’t the only portion of the spike protein that is affected in the two variants found in the U.K. and South Africa.
These new coronavirus variants also have chunks missing in a region that comes off the side of the protein, shown in blue above. The function of this region, known as the N-terminal domain, is poorly understood, says Jason McLellan, a structural biologist at the University of Texas at Austin who has studied how coronavirus proteins interact with antibodies. But his and other research have shown that antibodies bind to it and help keep the virus at bay. “It’s clear that the virus is trying to escape" from antibodies that target this region, he said.
The N-terminal domain can bear more drastic changes than the receptor-binding domain, where dramatic shifts could compromise the virus’s ability to enter cells, effectively killing the pathogen, he said.
This story has been published from a wire agency feed without modifications to the text