Potential COVID-19 vaccines not affected by dominant ‘G-Strain’
Vaccines currently being developed for Covid-19 should not be affected by recent mutations in the virus, according to a new study involving a University of York virologist.
Most vaccines under development worldwide have been modelled on the original ‘D-strain’ of the virus, which were more common amongst sequences published early in the pandemic.
Since then, the virus has evolved to the globally dominant ‘G-strain’, which now accounts for about 85 per cent of published SARS-CoV-2 genomes.
There had been fears the G-strain, within the main protein on the surface of the virus, would negatively impact on vaccines under development. But the research by Australia’s national science agency the
Commonwealth Scientific and Industrial Research Organisation (CSIRO), found no evidence the change would adversely impact the efficacy of vaccine candidates.
The study tested blood samples from ferrets given a candidate vaccine against virus strains that either possessed or lacked this mutation (known as ‘D614G’).
Professor Seshadri Vasan, who holds an honorary chair in Health Sciences at the University of York, is leading the Dangerous Pathogens Team at CSIRO and is senior author of the paper.
Professor Vasan said: “This is good news for the hundreds of vaccines in development around the world, with the majority targeting the spike protein as this binds to the ACE2 receptors in our lungs and airways, which are the entry point to infect cells.
“Despite this D614G mutation to the spike protein, we confirmed through experiments and modelling that vaccine candidates are still effective.
“We’ve also found the G-strain is unlikely to require frequent ‘vaccine matching’ where new vaccines need to be developed seasonally to combat the virus strains in circulation, as is the case with influenza.”
CSIRO Chief Executive Dr Larry Marshall said the research was critically important in the race to develop a vaccine.
Dr Marshall said: “This brings the world one step closer to a safe and effective vaccine to protect people and save lives.
“Research like this, at speed, is only possible through collaboration with partners in Australia and globally. We are tackling these challenges head on and delivering solutions through world-leading science.”
Vaccines currently being developed for COVID-19 should not be affected by recent mutations in the virus, according to a new study.
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Why are scientists obsessed with the coronavirus G strain?
On Coronacast with Dr Norman Swan
One of the big unknowns with coronavirus to date is how much it’s mutating and how that could hurt the effectiveness of a vaccine.
The worry is that by the time scientists have found a vaccine and tested it, the virus would have already changed rendering the vaccine ineffective.
The dominant coronavirus strain is known as the “G strain”, which has a mutation right where vaccines are targeting.
So what does this mean for the rollout of a coronavirus vaccine?
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* What has the CSIRO found regarding coronavirus’ “G strain”?
* Another study has found that antibodies can disappear after three months. What does this mean for longer term immunity?
* NSW records more COVID cases than Victoria
* An update from the White House. How is President Trump tracking?
Tegan Taylor: Hello, this is Coronacast, a podcast all about the coronavirus. I’m health reporter Tegan Taylor.
Norman Swan: And I’m physician and journalist Dr Norman Swan, it’s Friday, 9 October.
Tegan Taylor: So Norman, one of the things that we get a lot of questions about is whether the coronavirus is mutating, and we know that it is. And one of the big reasons why this is a concern is because all over the world scientists are working on vaccines and treatments against this virus, but if it mutates and the parts of the virus that are mutating are the parts that those treatments are targeting, then they might not work.
So the CSIRO has put out some new research about the G strain of the virus, which is the dominant strain now, and whether the vaccines that are currently in development are still going to work against this dominant strain.
Norman Swan: That’s right, and the reason why this particular strain, if you want to call it a strain of the virus has survived, and the full name of it is the D614G mutation, if that turns you on…
Tegan Taylor: It’s catchy, I like it.
Norman Swan: It’s probably more transmissible and it’s a mutation that has tended to survive around social distancing. So we have socially distanced, the Wuhan version of the virus at the beginning was probably controlled by social distancing which preferentially allowed mutants of the virus which were more transmissible, more contagious, to survive, and this is one of them and it seems to be dominating. It’s certainly dominating in Australia. There is another strain on top of this that’s dominating in Australia as far as I’m aware, which is also probably more transmissible.
Now, the fact is that this mutation is on the spike protein, as you’d expect it to be because the spike protein is the docking mechanism, if you like, for the virus to get into our bodies via the ACE2 receptor, this lock and key mechanism in the body.
Now, if this was in an area which is also targeted by the vaccine, because the vaccines do target the spike proteins, and the spike protein has changed too much, then the vaccines might not be effective against the D614G mutation, and that has been the worry, and particularly with other mutations on top. So as an accident of evolution, could it be that the spike protein becomes resistant to vaccines?
And what they did in this study was a study of ferrets in the CSIRO where they exposed this to a vaccine which has got similar viral background in terms of COVID-19 to the other vaccines around, and they found that in fact neutralising antibodies were generated, and the sort of antibodies that could kill the virus were generated to forms of the virus that did have the D614G mutation. So that’s good news. They also did some modelling on that and they found that from their modelling that supported the fact that the vaccine was going to actually cover this new strain as well. Doesn’t mean to say there won’t be mutations in the future that could mutate around the vaccine, but at the moment we seem to be okay.
Tegan Taylor: One of the things that was kind of comforting for an Australian context at least is that they were looking at Australian isolates, so Australian samples of the virus that are actually currently circulating here, and the research was done here. And so far it still seems like so good in terms of the vaccines that are being developed.
Norman Swan: That’s right, so they exposed the ferrets to viruses with and without the mutation and they also did it in the modelling.
Tegan Taylor: So another thing that has come out research-wise in terms of protection is that they’ve studied Tasmanian healthcare workers who had the virus a few months ago and they found that they don’t have antibodies after about three months. Is this a worry in terms of how long we are immune to the virus if we do catch it?
Norman Swan: That’s a matter of strong debate amongst immunologists and infectious disease experts around the world. The current thinking is no, it doesn’t matter. What matters is has the body’s immune system memorised the virus? And memorising the virus happens in T cells, that’s another form of white blood cell, not the white blood cell that produces antibodies, so you don’t need to have antibodies for the body to have memorised the virus.
So the real question will be is whether or not the fact they’ve got no antibodies protect them against future infection, and we will just have to wait and see on an international basis. And it’s been unclear from the reinfections you’ve seen overseas whether this relates strongly in one way or another to the existence of antibodies over the long term because in some of these reinfection cases they don’t have an accurate assessment of their antibodies.
Tegan Taylor: So the presence or lack of antibodies isn’t a worry in and of itself but it could hint at the fact that immunity isn’t very long lasting.
Norman Swan: So I think that the lack of antibodies, we don’t know what that means and we won’t know what that means until we’ve looked at reinfection rates and the results of vaccine trials and whether or not it really matters whether you’ve got antibodies in your bloodstream or not, it’s really whether or not the T cells have memorised the virus. That will be seen in whether or not the vaccine lasts, and whether or not people who have had COVID-19 disease stay immune to reinfection. So far there haven’t been that many reinfections internationally given that we’ve had tens of millions of cases. But we’ll see.
Tegan Taylor: So we had sort of a dubious milestone in Australia yesterday where New South Wales had more new Covid cases yesterday than Victoria did. We know that Victoria has been the site of a really big and ongoing outbreak. I mean, some of those ones in New South Wales were in a hotel quarantine, so maybe it’s not a fair comparison, but it really says that there is still a fair bit of virus circulating, not just in Victoria but also in New South Wales.
Norman Swan: Well, there’s good news and bad news when you start getting these numbers. So Tegan, let’s just focus on New South Wales. So we noted yesterday I think it was where we had three new cases, didn’t quite know where they were coming from, we said on Coronacast we were recording sooner than we actually knew what was going to happen. They amped up the testing, so the testing was almost tripled in New South Wales overnight, which has been fantastic, and they found more cases.
So they found more cases because they had been targeted, they now know because of contact tracing where a lot of these cases have come from. There’s been a cluster out of Liverpool hospital, their dialysis unit, and there is another cluster that they aren’t quite saying yet. But they also know certain locations around Sydney which you’ve got to watch out for if you’ve been there.
What’s impressive in New South Wales is how quickly they get to these answers. So on the one side, 12 is a bit disturbing, on the other side it’s good that they’ve amped up the testing and they are finding them. And there are not many cases under investigation. I think there is one under investigation in New South Wales. So New South Wales manages to keep these cases, the ones that they are not sure about, to very low numbers, whereas Victoria, it always seems to be a little bit more where they are still not sure. There’s just a degree of precision out of New South Wales which I’m afraid is still a bit lacking in Victoria.
Tegan Taylor: The other thing that everyone has got their eyes on is US president Donald Tromp. We know that people who are likely to have a bad time with Covid, that sometimes doesn’t happen until they’ve had it for a week or two. How is Trump tracking so far?
Norman Swan: I wouldn’t have a clue. I don’t think many people do.
Tegan Taylor: Don’t you have a direct line to the White House, Norman?
Norman Swan: There’s all sorts of mad stuff coming out. Like his doctor the other day said he tested positive for antibodies. Well, of course he’s going to test positive for antibodies, he just had an eight-gram dose of antibodies.
Tegan Taylor: Of course, he’s had the antibody cocktail!
Norman Swan: Duh! as they say. It’s just a joke, a very sad joke for the people in the White House, many of whom are very angry about being exposed to this virus and the wanton ignoring of the rules. So you just do not have a clue.
And people are speculating, yes, he looked breathless, his oxygen saturation dropped last week. They are refusing to release his chest x-ray, as far as I’m aware, and his chest x-ray will tell you where he’s going to go because if he’s got this ground-glass appearance on his chest x-ray, things are not going to necessarily go well for him.
Tegan Taylor: That’s that white sort of shading that you see on a chest x-ray when someone has pneumonia.
Norman Swan: Yes, so they are not saying that. So he is already showing the signs of breathlessness and people are speculating, I think I said this the other day on Coronacast, that his hands are a little bit different colour when he’s got make-up on, but you just can’t tell with video and colouring, that’s just too much speculation. But it’s going to be another couple of days, maybe three or four, before we know.
Tegan Taylor: Yes, we truly don’t wish anyone ill, but a lot hinges on what happens with his case.
Norman Swan: Yes, politically, and even the attitude towards the virus, because the Trump base believes him more than they believe Tony Fauci.
Tegan Taylor: Well, what are the chances that he will come good and that he’s actually fine and that he is past the worst of it already?
Norman Swan: Well, there’s probably, I don’t know, an 80% chance that he won’t go back into hospital, maybe a little bit higher than that.
Tegan Taylor: And he is not a typical case, he’s got the best medical care possibly available to him.
Norman Swan: Well, he hasn’t had the best care. What has to be said is he hasn’t had the best care. He is clearly the patient from hell. And they panicked. They’ve given him unproven therapies and they’ve thrown three therapies at him at a point where they are just not proven, at the same time and they don’t know the interactions.
So they’ve given him remdesivir earlier than it should have been given, they’ve given him dexamethasone earlier than it should have been given where they are not too sure whether it causes more harm than good at this point. And they are giving him this antibody cocktail which has only got anecdotal evidence of benefit, it’s never been properly studied, or not yet reported. They’ve panicked and thrown the book at him to see what happens. That’s not the best care.
Tegan Taylor: But is it so crazy that it might just work?
Norman Swan: If he doesn’t end up in hospital, you will not know whether it was because he would never have ended up in hospital anyway or it was because of the treatment. He will say it was the treatment, but without any treatment at all he had a very high chance of doing quite well. So you’ll never know. That’s why you do randomised controlled trials, so that you know whether the drug works. And you would not have a clue. So just watch this space. If he does get better then he’s going to want emergency approval for the antibody cocktail, just watch and wait.
Tegan Taylor: Well, that’s all we’ve got time for on Coronacast for this week.
Norman Swan: We love your questions, keep them coming in, go to abc.net.au/coronacast and ask your question, and mention Coronacast so we can find it.
Tegan Taylor: And if you want to leave a comment to tell Norman to stop speculating so much about a man who lives on the other side of the ocean from us, you can leave a comment there too, and don’t forget to leave us a review on Apple Podcasts if you can.
Norman Swan: I didn’t say a word about a New Zealander. Anyway, we’ll see you Monday.
Tegan Taylor: See you then.
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One of the big unknowns with coronavirus to date is how much it's mutating and how that could hurt the effectiveness of a vaccine. The worry is that by the time scientists have found a vaccine and tested it, the virus would have already changed rendering the vaccine ineffective. The dominant coronavirus strain is known as the "G strain", which has a mutation right where vaccines are targeting. So what does this mean for the rollout of a coronavirus vaccine? On today's show: * What has the CSIRO found regarding coronavirus' "G strain"? * Another study has found that antibodies can disappear after three months. What does this mean for longer term immunity? * NSW records more COVID cases than Victoria * An update from the White House. How is President Trump tracking?