Tanscript May 2007
Gareth Mitchell: From Europe's leading science university this is the official podcast of Imperial College London.
And I'm Gareth Mitchell, presenter of the BBC's Digital Planet and in a parallel universe kind of way I'm also a lecturer here at Imperial in the Science Communication Group. Welcome to the podcast that takes you to the heart of the world's ninth best university. And some of the treats in store for you this month include news of a promising new vaccine for banishing polio once and for all.
Nick Grassly: For the government of India and for the World Health Organisation this is the first proof that this vaccine is working effectively in the field.
GM: That's in just a few moments. And in a few more moments, the stardust that fell to Earth and ended up here at Imperial giving researchers some fascinating new insights into how the Solar System formed.
Phil Bland: A lot of the minerals are actually very high temperature, I mean, or they were formed at very high temperatures like, you know, 2,000 or 3,000 degree centigrade is the conditions at which they're stable. And we can only do those sort of temperatures really deep in the inner Solar System. So we have to get those particles from, in some cases, close to the Sun all the way out to beyond the orbit of Pluto where this thing formed, which is bonkers.
GM: And as if that wasn't quite enough we'll also throw in some quick news headlines from around the College. All that and more right here on the official podcast of Imperial College London.
Nick Grassly on a new polio vaccine
Right, well first let's get the latest on one of the big stories at the moment from Imperial. The polio vaccine that's three times as effective as the standard type. Well, for more on this I've come to our St Mary's campus in Paddington and I'm with Dr Nicholas Grassly in the Department of Infectious Disease Epidemiology. So, Nick, can you first of all start by telling us a bit about polio? We know it's debilitating. It causes paralysis in children, basically?
NG: That's right. Polio is a highly infectious disease of childhood. In countries with poor sanitation you can expect most children to be infected before the age of five years old. There are three different types of polio virus and each time you get infected with one of those types there's a small chance, about 1 in 200, that you will become paralysed in the limbs.
GM: I suppose as we'd expect from viruses, quite often if a child has been exposed to the virus in some way and they've been fortunate enough not to become symptomatic then they have natural protection against that virus, is it?
NG: That's right. So once a child has become infected with poliovirus and they clear that infection then they become immune to that infection. And it's thought that that immunity lasts a lifetime.
GM: And you've been studying this as part of a fellowship with the Royal Society and you're interested in a numbers of issues about the Global Polio Eradication Program Programme then? You've been focusing in India specifically?
NG: That's right. At the end of 2005 there were four remaining endemic countries in the world. So those were countries that never interrupted poliovirus transmission and they included India, Nigeria, Pakistan and Afghanistan. So the Polio Eradication Programme has achieved some great successes. Back in 1988, when it was rolled out, around about 1,000 children were being paralysed everyday by polio and it was endemic in many countries. At the end of 2006 the average number of children being paralysed each day was just five, and it was endemic in these remaining four countries. Now, when we began this work a couple of years ago transmission in India was a real puzzle because the Indian government and the World Health Organisation and Rotary International, US Centres for Disease Control and UNICEF had all invested a lot of time and a lot of finance into controlling polio. And in fact children in India had on average received 12 doses of vaccine at the end of 2005 and yet polio transmission was still ongoing. And so that was a puzzle that we sought to explain where we published some results at the end of last year in Science which showed that in fact it appears that in these difficult conditions, the poor sanitation, very high population density, not only do those conditions favour the spread of wild poliovirus but they also favour the spread of other infections and diarrhoea which interfere with this live oral poliovirus vaccine. And in fact the efficacy of this standard trivalent vaccine in this setting was extremely low, just 10 per cent.
GM: Right, and to set up some of the terminology here then a trivalent vaccine, an oral vaccine, this would be, as the name trivalent suggests, to vaccinate against the three strains of polio? It's like a three-in-one vaccine then?
NG: That's right. So, as I mentioned, there are three strains of wild poliovirus and the standard trivalent vaccine includes attenuated vaccine strains against those three types. So it contains live vaccine, vaccine that was passed through kidney cells and through monkey kidneys back in the 50s by Sabin, a pioneer of vaccine development. And these attenuated forms infect a child and that child then becomes immune but without any of the symptoms of polio. The problem with this trivalent vaccine is that those three strains can interfere with one another. And in fact this trivalent vaccine, particularly in a developing country setting, seems to result in preferential infection with the type-2 vaccine strain to the detriment of infection with the other two types. And so this vaccine works quite effectively against type-2 poliovirus but less effectively against type-1 and type-3. And that perhaps explains why we've succeeded in eradicating wild poliovirus type-2. The last case globally was reported in Uttar Pradesh in northern India in 1999.
GM: And in the introduction I mentioned this new vaccine that's three times as effective as the standard one you've been talking about there, the standard one being the trivalent. This newer one is monovalent, in other words it goes for one strain of polio?
NG: That's right. The observation that in India type-1 wild polio virus was the dominant strain by far led to the thought of introducing a monovalent vaccine. Now, the monovalent vaccine, because it excludes the other two vaccine types, has a greater efficacy against the type against which it's targeted. It still suffers the problem of interference from other infections and diarrhoea in children so in this setting it still has a lower efficacy than we might see in a developed country but the efficacy is significantly higher than the standard trivalent vaccine. Although it's not as high as we would like it to be, in this kind of setting a threefold greater efficacy has great potential for eradicating poliovirus. If we think about the trivalent vaccine, which again has this problem with interference in this setting and has quite low efficacy, because that vaccine works slightly better against type-2 we seem to have succeeded in eradicating type-2. So we would hope with a more effective vaccine now against type-1 the same can be done against type-1 poliovirus.
GM: This mo novalent vaccine called mOPV1 is an oral vaccine, that's w hat the ‘O' stands for, yet in this country we have, and have had for a few years now, injectable vaccines, IPVs. Why not bring these in, in India?
NG:The reason that the injectable vaccine was introduced in the UK just over two years ago was because with the live attenuated oral polio vaccine (OPV) there's a very small chance that a child who receives that vaccine becomes paralysed by the vaccine strain of the virus. That's about a one in a million chance per dose given, or for the first dose given. In the UK, because we haven't seen any polio cases, we've controlled polio, then that risk, even though it's very small, is no longer really justifiable and so we switched to an injectable polio vaccine that doesn't have that problem. Now, in a setting where there's continued transmission of poliovirus, preventing those many thousands of cases of paralysis justifies the use of a vaccine that has this very small risk when given to children. The reason that we can't really use the injectable polio vaccine in some of these more difficult settings, for the time being at least, are several fold. The first is that this kind of vaccine, although it protects a child against paralysis, it doesn't provide good protection against infection. So a child who has this vaccine is unlikely to be paralysed but they can transmit infection. So you don't see the kind of herd immunity effects that you see for the oral polio vaccine where you can eradicate poliovirus with less than 100 per cent coverage. But with the injectable poliovirus vaccine it's not clear that it will have this kind of herd immunity in a developing country setting. Then there are also issues that because it's an injectable vaccine it's very hard to scale up this kind of vaccine. If we look at routine coverage with injectable vaccines in the northern parts of India then on average only around 30 per cent of kids are receiving three does of routine immunisation of injectable vaccines. And also there's an issue of cost. Although I think if IPV was scaled up the costs would come down.
GM: And so, Nick, the important thing about the study that you've just done is this mOPV1 vaccine, the monovalent, does it just give people like the World Health Organisation and the authorities in India a better handle on the most effective way of dealing with polio in their region?
NG: Yeah. For the government of India and for the World Health Organisation this is the first proof that this vaccine is working effectively in the field. So there have been studies, serial conversion studies, that are ongoing to look at whether a child who receives the vaccine develops an antibody response. But this is the only study showing that this new vaccine is actually working effectively in the field.
Headlines from around the College
GM: In a few moments I get up close and personal with some bits of comet but ahead of that here are some stories from around Imperial that have been making the headlines recently.
GM: Human beings and many of the world's mammals can thank the mass extinction that killed off the dinosaurs, for banishing them, and leaving our ancestors alone. Or perhaps not. The idea that we were one of many species biding our time before the mass extinction destroyed the dinosaurs may be misplaced. That's according to a tree of life that's just been completed by Imperial researchers with collaborators at the Zoological Society of London. Over the last decade the scientists have formed part of a multi-national team going through fossil records and applying the latest in molecular analysis to trace the origins of the world's creatures. The results suggest that the ancestors of many modern mammals were indeed around 85 million years ago doing their best to survive amongst the dinosaurs and actually did manage to hang on during that mass extinction event. But they didn't proliferate straightaway. They continued to be held back by many other species that had survived with them. These others eventually fell by the wayside when the planet warmed significantly 10 to 15 million years after the dinosaurs had gone finally giving our ancestors the opportunity to achieve world domination.
GM: And from fauna to flora. And we now know what triggers plants to flower when the days get longer. So say researchers in Imperial's Division of Biology working with colleagues at the Max Planck Institute for Plant Breeding Research in Cologne. They've discovered how a protein travels the long distance from a plant's leaf to its shoot tip to trigger the tip to flower. The protein, called the Flowering Locus T or simply FT protein, is produced by the similarly named FT gene that's switched on when the length of the day changes. The scientists have demonstrated the FT protein's journey from the leaf to the buds by tracking it with a fluorescent protein from jellyfish. The findings could be useful commercially. It should now be possible to control when certain plants flower. And if we can crack that it could help extend the growing season for many of the world's crops.
GM: And finally in this news roundup, could hydrogen be the answer to the world's energy crisis? Well, we don't know for sure but if anyone can help us find out and then find some ways of making it happen it'll be the scientists and engineers about to set up shop at Imperial's new £4.2 million Energy Futures Lab. There's much excitement over hydrogen because when you put it into a fuel cell out comes electricity produced at high efficiency and the only omission is water. Well, we like the lack of greenhouse gases but the big drawback is that producing the hydrogen in the first place gives off environmentally unfriendly by-products that undo much of the good from using the gas. One of the big projects on the Energy Future Lab's to-do list is in developing a solar driven process for producing hydrogen. It'll work a bit like photosynthesis in plants using green algae in water. In this eco-friendly process the Sun's bountiful energy will produce oxygen and hydrogen which can be separated with the hydrogen stored to power the fuel cells of the future.
GM: And you can get more breaking news from the College before it even gets into the newspapers. Just visit our Press Office website at imperial.ac.uk/news.
Phil Bland on comet dust
Right then, well let's go back to last month's edition of the podcast where we gave you the inside story on some extraterrestrial treasure that's been causing some great excitement here on campus.
Recording: All stations we have touchdown.
PB: Watching it come in was incredibly exciting. I rang up a friend of mine in Berkeley. Potentially they could have actually seen the fireball of the capsule coming through and they did try and get to it but there was a pile-up on the freeway or something so they couldn't actually get out. So I rang her and she was just going mad as well, you know, waiting for it to come through. And then watching it land was just terrific.
Recording: Three, two, one, rapid brightening.
Descent sees it.
Near spec is required.
We see it.
Oh, that's cool.
Quite a trail.
Near spec has a great view.
HDTV, you've got a strong wake, go get it.
GM: Sounds there of NASA's Stardust Mission returning to Earth with a capsule of dust recovered from a comet in the depths of the Solar System, as heard on last month's podcast from reporter Daniela de Angel. You heard there Dr Phil Bland who's of the Earth Science and Engineering Department here at Imperial and he was speaking to Daniela about this time last year having just got his hands on some of that precious cargo for analysis. Well, 12 months on he and his coll eagues here in the Royal School of Mines have had a pretty good look at the samples, I hope anyway, and I'm with Phil now to find out. So first, before we hear about what you've found so far, Phil, what was it like to go back to last year and hear that clip again from the Podcast?
PB: It was really interesting actually. I remember how exciting it was. I'd not thought about it but I remember how exciting it was to get that box of samples in the post. So it was actually really interesting to hear that.
GM: And this is science on a grand scale, you know, you send a spacecraft up to intercept a comet. It crashes down to Earth. The samples then have to be distributed amongst labs around the world including here at Imperial College. First of all, why study a comet? What's so interesting about comets in learning about the Solar System?
PB: I guess to take that one first is when we look at comets they've obviously got a lot of ice and very volatile materials associated with them, and that's why you get a big tail behind it when it comes in the inner Solar System. And what that's really telling us is that they've not been heated up much. You don't get a lot of ice remaining on objects that have seen high temperatures. It boils off. And so it means that comets preserve a record of essentially what conditions were like. That hasn't been changed, you know, that record hasn't been changed much since the beginning of the Solar System. So that makes them priceless samples really.
GM: As indeed we heard last year from your colleague, Matthew Genge. He told us why this mission was so important.
Matthew Genge: This mission is the first time that we can collect dust from a known source, so from a known comet. We really do have no idea what comets are made out of. Astronomers will tell you that, well, there's lots of ice and there's plenty of dust embedded in the ice. And we can make a guess at what minerals are in there from observations from the ground of comets and from spacecraft observations of comets but we can't tell you what size the dust grains are. We can't tell you what composition the carbonaceous material is. What compounds it contains. And questions like this are very important because we believe that it was comets that delivered the ice to the Earth that formed the Earth's oceans. And also possibly comets delivered the carbonaceous material, the organic materials, that got life started.
GM: Matthew Genge there. So you have some of the particles with you. I gather that some of actually recently been delivered in this here envelope?
PB: Well it did, yeah. These are actually some that we did some of the first analyses on. So these were some of the ones that we got out of that first box.
GM: So you're drawing some material out of a plain old Jiffy bag there. Very scientific.
PB: NASA spend a bit more money. It didn't come in a Jiffy bag but we're spending it back to them in a Jiffy bag. There's a little particle in here that's embedded in a small chunk of resin. And this was actually the first one that we looked at and that we got really excited about when we first saw it in the lab.
GM: It's amazing. So you're actually holding a piece of comet here. I love that. It's about, what, half a centimetre maybe a centimetre across. I'll tell you what it looks like actually. It's like a match head. If you strike a match and it's gone out, that's what it looks like.
PB: Yeah. And basically embedded right in the end of that little blob is about a micron size particle of comet dust. So a micron, about a thousandth of a millimetre. That's about the size of this little bit of dust, which is obviously pretty small.
GM: And obviously to have a proper look at it we'd need to put it under an electron microscope. And that's what you've been doing over the last year. As we heard Matthew describing there, you're interested in gauging the size and the composition of these particles. So what have you found?
PB: One of the really interesting things that's come out of analyses that has been done not just here but all over the world is that what we were expecting in a way is to find minerals that kind of fit with ideas about a comet. There's loads of ices in there so you'd expect fairly low temperature minerals. In fact a lot of the minerals are actually very high temperature, or they were formed at very high temperatures like, you know, 2,000 or 3,000 degree centigrade is the conditions at which they're stable. And we can only do those sort of temperatures really deep in the inner Solar System. So we have to get those particles, in some cases, close to the Sun all the way out to beyond the orbit of Pluto where this thing formed, which is bonkers. So it's a really interesting problem, you know, how do we do that? And there's a lot of ideas, some interesting ideas, and we're still knocking that around. But that was a big surprise.
GM: And that's something that you could only have found after analysing these samples from Stardust. You couldn't have known that before?
PB: No, absolutely not. Really one of the first ideas that people had when they started looking at any rocks from space, meteorites or anything, was that all of these rocks seemed to be different in composition from one another so there can't be much mixing. So the inner Solar System, there couldn't have been much mixing otherwise you smear out difference. So one of the first, in a way, model's constraints on how our Solar System formed has now hit the bin because of these samples.
GM: And can you give a sense of how profound that is in science? Is there some pretty serious head scratching and re-writing of text books going on because of these samples?
PB: There will be, absolutely. It's basically the equivalent of, you know, somehow we've got evidence here that there was large scale mixing but we still have to get discreet compositions. The planets have different compositions. Different meteorites have different compositions out the other end. So it's kind of like putting a whole bunch of different fruit in a blender, zizzing it up and not just having one flavour smoothie come out the other end. Somehow we get different flavour smoothies coming out the other end, and we still don't really know how to do that. We've got hints. And that's what's exciting is that I think my hunch is that in the next five years we'll crack it. And along with it we'll get much closer to the general problem of how you make planets, which is really the big question.
GM: And so the ingredients that have led to the planets and the other bodies in the Solar System, it's a kind of richer mix of ingredients than we originally thought?
PB: Absolutely. A richer mix and richer in terms of how we can move things around and probably how things changed over time. The Solar System obviously changed massively in composition over time but it also changed hugely spatially, you know, depending where you were. It's fascinating, yeah. It's going to take us a little while but certain of these grains, the Stardust grains, take us a lot further to a solution.
GM: And as we heard there from Matthew Genge a minute ago, last year he was interested in whether there was any carbonaceous material in these samples. Have you found any?
PB: We have. That's not our forte here but a lot of labs have tucked into that and they have found a lot of stuff. The problem there is that the spacecraft flew through the tail of the comet at 6 kilometres a second. So although the designers did everything they could to capture material as gently as they could, fundamentally if you get hit at 6 kilometres a second by something it's going to mess you up a little bit. At the moment it's a bit tricky to tease out those kind of capture effects from the real composition. But th ey're getting there. It might take a little while longer to get confirmed results out of that.
GM: Well, let's hear a bit more from last year and from what Matthew Genge was telling us because he was really in no doubt about how far the mission could take our understanding of the formation of the Solar System.
MG: The wonderful thing about this mission is it's probably going to provide us more information than the last 100 years of observation of comets. And just in the 10,000 or so dust particles that we actually recover somewhere in there may be the answer to the formation of our Solar System or the origins of life.
GM: Matthew Genge there. So pretty fundamental. Telling us about the formation of the Solar System, origins of life. But, Phil, it sounds as if there really are hints of carbon related materials in these samples then maybe we can get insights as to how life got started in the Solar System. Can we? Or maybe not yet?
PB: On the early Earth the seas, oceans, would have been getting hit by rocks from space that contained some interesting compounds. Not life but quite complex organic materials. So really anything else, that helps us. So that's part of the story of how life kicked off.
GM: So what about the broader findings then? I mean you spent, I'm sure, many hours pouring through your electron microscopes at these samples. What kinds of things have you found? Any surprises?
PB: An interesting one is that in primitive meteorites, in meteorites that haven't seen too much action, we actually find grains that are from somewhere other than the Solar System. They were around before the Solar System formed. If we could analyse their ages they'd be the oldest things that we have. So these things were actually formed in the atmospheres of other stars that existed before the Sun switched on. What's kind of weird is that there's far fewer of these in the Stardust samples than we were expecting. Stardust is called Stardust because we were expecting to get a lot of this stuff, a lot of stardust, and there's a lot less. There's one or two but there's fewer than even in some regular meteorites. And that's a real surprise. We still don't really understand why that is. Is that something to do with this particular comet? Or is it something to do with how the material was collected? Who knows. So that's a wacky one.
GM: Looking ahead over the next year or so what else do you expect or hope to find from Stardust?
PB: One that we're going to try and get at is the chemical composition of the material at as good a resolution as we can. So that'll help us an awful lot with this whole issue of how stuff was moved around because the chemistry is just as distinctive as the actual type of mineral. And so that's something that we're going to do. Technically it's quite a challenge but it'll be fun to have a go at that. So we're going to try and get a much better idea of chemistry both of individual grains and of the whole comet as a whole if we can.
GM: Dr Phil Bland there still enthusing over his dust from the stars. Well, that's it for this month's edition. But you must pop back in and see us next month where we'll be meeting up with the Imperial researchers looking at reintroducing wolves to the wild.
John Dennis: So this is the alpha female European wolf. This is Lataya.
Alison Kirby: She's lovely.
JD: She is. She's lovely.
GM: And of course there'll be plenty more from around the College.
This podcast is co-produced by the Science Communication Group and the Imperial College Press Office in the kind of collaboration that so many dream of and so few achieve. Ozgur Buldum is the man who wrote this very music. It's called Layla and it's our theme tune. Hear more of Oscar's work at ozgurbuldum.com
The official podcast of Imperial College, London is available on the first working day of each month, which means we'd better get cracking on the June edition for you. Until then though from me Gareth Mitchell and producer Helena Rant, thanks very much for listening and goodbye.