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  • - [Reporter] This is a spike protein.

  • It's what gives the coronavirus its unmistakable look

  • and scientists think it may be the key to why new variants

  • of the virus are becoming more transmissible.

  • - A new study by the CDC is raising the alarm

  • on the coronavirus variant spreading across the country.

  • - The fast-spreading COVID-19 variant

  • first found in the UK is now evolving in a way

  • that could make existing vaccines less effective.

  • - [Reporter] New research shows

  • that the more transmissible variant from the UK,

  • called B117, will likely become the most common version

  • of the virus in the US.

  • - The big concern is that, with more transmissible variant,

  • you have more cases and you have more chance

  • for superspreading events and epidemic surges

  • which overwhelm our healthcare systems.

  • - [Reporter] Here's the science

  • behind why these new variants are spreading faster

  • and what this could mean for vaccines.

  • (soft music)

  • Like other viruses, when the coronavirus replicates,

  • small genetic mistakes, or mutations, can occur.

  • - You can be almost certain

  • that as long as there's a lot of virus

  • circulating in the community, there will be the evolution

  • of mutants because that's what viruses do.

  • - Many of those do nothing.

  • Some of those actually confer a survival benefit

  • for the virus to transmit more effectively, for instance.

  • - [Reporter] Abraar Karan is a global health physician

  • who has been studying the coronavirus pandemic.

  • - And so, as it does that,

  • it has a better chance of spreading to new hosts

  • and continuing to replicate in those hosts.

  • - [Reporter] Karan says this is likely what is happening

  • with the new, more transmissible variants

  • appearing around the world.

  • Recent research has shown that a number

  • of these new versions of the virus have mutations

  • that affect the spike protein.

  • Take a look at this model of the coronavirus.

  • You can see each spike protein

  • is made up of three identical parts known as protomers.

  • These protomers have the ability to change their position

  • from closed to open, affecting how easily

  • they can bind to and infect human cells.

  • - You can visualize it like a flower.

  • So you've got petals on the outside,

  • the really obvious thing that you see.

  • There are three of them.

  • The three of them have to bind to the receptors.

  • - [Reporter] Jeremy Luban is a virologist

  • who studies the coronavirus.

  • He explains that when the protomers are down,

  • infection is more difficult.

  • But when these parts are up and open, it's much easier.

  • In the first version of the coronavirus

  • that originated in China in 2019,

  • these protomers usually had a closed shape,

  • which may have made it less transmissible

  • than some more recent versions of the virus.

  • This is another view of a spike protein

  • that helps to show where these mutations occur.

  • In the winter of 2020,

  • one mutation, known as D614G, emerged.

  • It appears in this region of the spike protein.

  • This mutation made it more likely for the spike

  • to have an open shape, increasing the virus' ability

  • to infect human cells.

  • Soon after the mutation emerged,

  • variants that had it took over.

  • - So by June, pretty much all the viruses around the planet

  • had this change, this mutation.

  • Our belief is that it supplanted the original virus

  • because it was more transmissible.

  • - [Reporter] Luban thinks this is what is happening

  • with some of the new variants

  • that are emerging around the world as well.

  • - In the United Kingdom,

  • that variant really expanded very rapidly.

  • It was first seen in September

  • and now it's the dominant version of the virus

  • circulating in the United Kingdom.

  • Does indeed appear as if the same thing happened

  • in South Africa.

  • - [Reporter] Another element

  • that affects the spike protein is antibodies.

  • These are proteins that defend the body

  • against the coronavirus by blocking the ability

  • of the spike protein to attach to cells,

  • which prevents the virus from infecting.

  • Antibodies are produced by the immune system

  • in response to infection or vaccines,

  • and so far, the new coronavirus variants

  • scientists are worried about all have mutations

  • that affect the spike protein.

  • Here are some that scientists are focusing on.

  • The first is called N501Y, which was first detected

  • in the variants from the UK and South Africa

  • in the second half of 2020.

  • This mutation is located in a region of the spike protein

  • known as the receptor binding domain, or the RBD.

  • This is the main location

  • where the virus attaches to human cells and infects them.

  • The N501Y mutation seems to be helping the virus bind,

  • which could help explain the higher transmissibility.

  • The second mutation

  • that scientists are focusing on is called E484K.

  • It's found in variants

  • from South Africa and Brazil and reduces the ability

  • of certain antibodies to bind to the RBD,

  • which helps the virus' chances of infecting cells.

  • - What the antibody recognizes is the shape.

  • If you're playing with blocks and you have triangles

  • and circles and you have to fit them

  • into the appropriate holes,

  • you can't fit a circle into a triangular hole.

  • It's analogous to that.

  • If the virus then changes

  • so that it's no longer a triangular hole

  • but it's a circular hole,

  • then the antibody will no longer fit.

  • - [Reporter] Scientists have also found

  • that some of the new coronavirus variants have parts missing

  • in a region that comes off the side of the spike protein.

  • This is known as the N-terminal domain.

  • - Some of those mutations

  • are removing surfaces of the protein

  • that other antibodies bind to.

  • If the virus mutates that surface or deletes it,

  • those antibodies are no longer going to work

  • to block the virus.

  • - [Reporter] Scientists say this may help explain

  • why current vaccines may be becoming less effective

  • against some new variants.

  • This is why experts are urging caution.

  • - Variants are gonna continue emerging

  • and we need a public health strategy that addresses it.

  • We have to focus on getting better ventilation.

  • We have to get people better personal protection;

  • better, higher-grade masks that can filter better;

  • we have to test; we have to trace;

  • we have to isolate the fundamentals of epidemic control.

  • - [Reporter] And Karan says that while vaccines

  • should still be effective in preventing severe illness,

  • a booster variant shot may be needed later in the year.

  • - They work extremely well right now,

  • right, With Moderna and Pfizer 95% vaccine efficacy.

  • They will start to work less well

  • against some variants into the future,

  • but that is to be expected

  • and that is why vaccines will be a major part

  • of COVID control for the foreseeable future.

  • - [Reporter] Experts continue to emphasize

  • the importance of getting vaccinated

  • along with other strategies to keep transmission low

  • and stop the spread.

  • (soft music)

- [Reporter] This is a spike protein.

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为什么新的 Covid 变种传播速度更快的背后科学(The Science Behind Why New Covid Variants Are Spreading Faster | WSJ)

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    joey joey 發佈於 2021 年 05 月 30 日
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