Coronavirus Mutates To Escape Immune System

Live Science

The virus often mutates by simply deleting small pieces of its genetic code. The mutations "disguise" the virus from antibodies.

Transcript

00:00The novel coronavirus has recently developed a number of worrisome mutations, resulting

00:05in multiple new variants popping up around the world.

00:08A new study sheds light on how the virus mutates so easily, and why these mutations help it

00:14escape the body's immune system.

00:16The beauty of this story is it's quite complex, but it's really rather simple.

00:27The study researchers found that SARS-CoV-2, the virus that causes COVID-19, often mutates

00:33by simply deleting small pieces of its genetic code.

00:37Although the virus has its own proofreading mechanism that fixes errors as it replicates,

00:43the deletions get around this.

00:45So what deletions do is not only alter one site, but they can alter a string of sequential

00:50letters in a row.

00:51And so you can't proofread against that, and you can alter a number of amino acids that

00:57build up that protein.

00:59And so it does represent a way that the virus can quickly adapt.

01:02Oh, it's devilishly clever.

01:05For their study, the researchers used a database to analyze nearly 150,000 genetic sequences of

01:12SARS-CoV-2.

01:13They found that these deletions frequently show up in similar spots on the genome.

01:18And these deletions started to line up to very distinct sites, and so that's why we've

01:23called them recurrent deletion regions, because we kept seeing them over and over and over

01:26again from viruses from different places at different times in genetically distinct

01:32viruses.

01:33Possibly these deletions were leading to the escape or the evolution away from antibodies

01:38that are binding it.

01:39This would be a way to get around that, because the antibodies won't be able to recognize.

01:43Yeah, because remember, the key thing in biology is shape, and precise little changes in shape,

01:50even in a big molecule, can have really, really big effects, right?

01:56So perfectly attuned to recognize shape, small movement, and this thing doesn't see this

02:02anymore.

02:03I mean, one missing building block out of about 1,200 can knock out the binding of antibodies

02:09that are potently neutralizing.

02:10So you're looking at, you know, less than a 1%, you know, change there.

02:15Small changes in biology can have massive effects.

02:19And that's why we have to think about antibiotic resistance and antiviral drug resistance, and

02:26da-da-da-da-da-da.

02:27That's where it's really hard whenever you're trying to describe this, because it's hard to

02:32show something which is gone, right?

02:34Absence is hard to show, but these tiny little absences have a big, big effect.

02:42Does it seem like the main goal from the evolution perspective is to sort of escape the immune

02:49system, and this transmissibility might be like a secondary factor, or we don't, like

02:54a beneficial side effect, but we don't really...

02:56The virus has evolved to replicate efficiently, and it'll evolve around anything that gets in

03:01its way, or go extinct.

03:03Evolution finds these sweet spots, and this is a pretty good virus, right?

03:08What it's doing is, every single time it's replicated, think of the millions of people

03:12that the virus is replicating in the world each day, right?

03:15Because anything that we can do to dampen the number of times it replicates, just like

03:20Kevin said, will buy us a little bit of time.

03:25Coming up with the tools now that we know that they're important, and that they can alter

03:28the immunogenicity of the molecule the way that some antibodies bind it, and understand

03:34if there's clinical changes that are associated with that.

03:37And that's, in some ways, what happened with the discovery of the variants from South Africa,

03:42and from the United Kingdom, both of which have deletions.

03:45Will we see something happen like we do with flu vaccines, that these need to be reformulated

03:51frequently?

03:52You know, it's not going to be an all or nothing where one day, you know, the virus can be blocked

03:57by a vaccine, and the next day it's gone.

04:00It's a continuum.

04:01But you still have something that's 90 or 85% efficacious, which I think, at the start

04:06of this pandemic, we'd all sign up for.

04:08It's not just going to be this virus.

04:09It'll be the next virus, and the next virus, and the next virus, and the next virus.

04:13They will continue to emerge.

04:15They will continue to evolve.

04:17And we continually have to play cat and mouse and stay one step ahead of them.

04:23Their results underscore the importance of closely monitoring the virus's evolution

04:28by tracking these deletions and other mutations.

04:31The findings also show why it's important to wear a mask and implement other measures

04:36to prevent the virus from spreading.

04:38The more people it infects, the more chances it has to replicate and potentially mutate.

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