Safe Sex, Sexually Transmitted Diseases and Cervical Cancer Vaccines

28 November 2004
Presented by Chris Smith, Helen Scales.

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In the run up to World AIDS week consultant GU medicine physician Dr Sarah Edwards joins us to talk about the present epidemic of sexually transmitted infections including chlamydia, HIV, herpes, syphilis and gonorrhoea, and Prof. Margaret Stanley, from the Department of Pathology at the University of Cambridge, discusses how she has developed a vaccine against human papilloma virus (HPV), the agent which causes cervical cancer. Also joining us on the show is Dr. Helen McShane, from Oxford University, to talk about a new vaccine she has developed to combat the huge global problem of tuberculosis (TB).

In this episode

Mobiles That Can Iron Out Background Noise

Imagine you're in a crowded pub, or out with someone you ought not to be, and your boss calls your mobile. The noise in the background would instantly belie your true whereabouts, and make it difficult to the other person to hear what you were saying over the din. But that could all be about to change thanks to a new phone design from American inventor Jaime Siegel. The new gadget uses 2 microphones - one placed on the side of the phone closest to your face, and the other on the opposite side facing the noisy room or street. The mic closest to your face picks up what you say, plus the background noise, whilst the mic facing the room picks up mostly background noise. Now subtract one signal from the other…and you eliminate a lot of the background noise.

A Sound Way To Sort Out The Unopened Pistachios

A bag of pistachio nuts always contains a few unopened specimens, largely because the process used to sort the open from closed nuts is far from perfect. But now a Kansas-based inventor, Tom Pearson, has come up with a sound way to separate the two - by creating a machine that can tell the difference between the noises made when opened and closed nuts clatter onto a steel tray. Unopened nuts make a shorter ringing sound when they drop onto the tray, compared with their open counterparts, and these unwanted specimens are blown away with a puff of compressed air. Capable of sorting 25 nuts a second, the new machine is slower than the existing technique, which relies on opened nuts being caught by a series of needles as they are spun in drum, but the new technique is 97% accurate, compared with 90% for the needle method. This could save companies up to half a million pounds a year, and a lot of frustrated customers !

Tank Accessory Must Have

How do you like the idea of having a real gold-fish. Not just an orange one, but one that really glows gold in the dark ? Because that's exactly what a Taiwan-based company have developed by genetically manipulating normal fish so that they carry a fluorescent gene from jellyfish. Last year they produced a popular brand of neon-glowing fish, but now they have taken things a step further and produced a fish that genuinely glows gold. Whilst it may sound impressive, environmentalists remain sceptic that there may be dangers surrounding these genetically modified fish, especially if they were to escape and begin interbreeding with wild-type fish stocks. However, the company claim that they have made the fish sterile, so they wouldn't be able to breed even if they were to survive in the wild, which they say is unlikely. Nonetheless, it is still worrying that there are no controls in Taiwan to regulate the release of genetically modified organisms - and even though it is thought to be safe, we really don't know enough about the technology to be sure. If wild fish began to glow gold though, it's unlikely they'd last very long ! It would be like wearing a fluorescent jacket on a battlefield and waving a banner saying shoot me !

- Virtual Hunting on The Internet

The world's first website that lets you hunt and shoot real animals...

Virtual Hunting on The Internet

An American man with a penchant for shooting things has come up with the world's first website that lets you hunt and shoot real animals on his Texas-based ranch, but without having to leave the comfort of your home computer keyboard. Visitors can log in to the site and control a gun mounted on a platform overlooking the 330-acre ranch. Kills are retrieved by an attendant and sent off to the butcher or taxidermist. John Underwood, the brain behind the site, got the idea after looking at another website in which cameras posted in the wild enable you to snap photos of animals, "then a lightbulb went off in my head," he said. Texas officials are currently looking into the legality of such a venture "current state statutes don't cover this sort of thing", said Mike Berger, director of the Texas Parks and Wildlife Department.

- A Vaccine For Cervical Cancer

The Naked Scientists spoke to Professor Margaret Stanley.

A Vaccine For Cervical Cancer
with Professor Margaret Stanley.

Margaret - It has always been realised that cervical cancer is a sexually transmitted disease because celibate people don't get it! However, it was only in the 1970s that people discovered that cervical cancer is caused by a virus from a common family called papilloma (the same virus that causes warts). At this time, there were two ways to make virus vaccines: one was to deactivate the virus; the other was to grow it up in the laboratory over a period of time to change it so it was no longer dangerous, or pathogenic; you could then inject it into people to give them immunity. But neither of these methods worked with papilloma. In the 1980s, two scientists in Australia came up with an answer. They found a way to construct the protein 'shell' of the virus in the laboratory without having to grow it in tissue culture. Injecting this protein 'shell' into the body should cause the body to mount a defence against the shell (thinking it was real papilloma virus), making that person immune. This made the possibility of vaccine development highly probable, but no-one was sure it would work. Extensive trials over the last five years have shown that it does.

Chris - Does having sex more often mean a woman is more likely to get it?

Margaret - Yes and no. What really matters here is knowing what your partner has been doing! When people have sex, they exchange a whole zoo of microbes. Most of these are perfectly harmless, but some are ones you want to stay clear of. If you have sex with lots of people, you acquire a very exotic zoo that is more likely to contain some disease-causing microbes. Therefore, someone who has had sex with very few people can contract the virus just because their partner has had many partners beforehand. Individuals particularly at risk are those who have lots of sex and/or unprotected sex, so you have to be sensible about it.

Chris - What about age as a factor?

Margaret - If you have sex at an early age, the cervix is very sensitive to the virus and is more likely to be affected. By around 20 years old, the cervix has started to settle down, and the risk of contracting the virus is lower. However, anyone who has sex is at risk, so in that sense, there is no age when you are completely safe.

Chris - Cervical cancer is the leading cause of cancer death in women worldwide, and kills 3500 women in Britain each year. Do you think this may soon be a thing of the past?

Margaret - You must never say that we can get rid of something completely, but we can certainly reduce it substantially. The vaccine that is likely to be first used, if given in the most optimal way, is likely to get rid of 70-80% of cervical cancers without any other intervention. However, it must be given before girls have sex, which in 2004 is realistically to 10 year olds !

Chris - How long will the protection last?

Margaret - That is a critical point, but the answer is that we don't know. We have only been having controlled trials for the past four years, which isn't really long enough to know how long protection will last. However, the results coming through are showing that there is protection up to four years, which is a long time for this type of vaccine. We need further tests to see if the vaccine will also work in men.

The Epidemic of Sexually Transmitted Infections
with Sarah Edwards

Chris - There has been a huge surge in HIV recently, with 7000 new cases this year. What do you think are the reasons for this?

Sarah - There have been a lot of changes in sexual behaviour, including a decrease in the age at which people are first having sex and a longer period between people first having sex and settling down. This means that people have more time to fit in a greater number of sexual partners. A further problem is that many young people think that AIDS is easily treatable. Although there are drugs to help, some people have bad side effects and it is very difficult to remember to take the right drugs at the right time with the right food restrictions. Complacency is a big problem.

Chris - What are the other big players among STIs?

Sarah - Chlamydia is the biggest player as it has long term implications for women such as infertility and ectopic pregnancy. As infection is frequently latent, people can pass it onto each other without knowing. Condoms are the best way to prevent this but we must first make condoms more fashionable and user friendly. Even those with good intentions can find that after a few drinks they end up putting condoms aside and placing themselves at risk.

Mycobacterium Tuberculosis Culture

- A New TB Vaccine

A new TB vaccine can improve the effectiveness of the existing BCG...

A New TB Vaccine
with Helen McShane, University of Oxford

Scientists from Oxford University have formulated a new vaccine which can improve the effectiveness of the existing BCG. The new approach, which has been developed by Helen McShane and her colleagues, involves using a strain of vaccinia virus (cow pox) to which has been added a gene from TB. When the virus is administered to an individual, the cells which become infected also express the TB gene, provoking the immune system to respond by simultaneously developing an anti-TB response. As a result the vaccinee becomes immune to TB and smallpox ! Helen McShane joins us to describe why TB is a huge global problem, and how the new vaccine works :

Helen - TB is a bacterium that causes two million deaths each year and is widespread in the developing world. Those with HIV are even more susceptible, making TB a big problem. The reason tuberculosis is so common is that it is highly infectious. Some people with the disease develop abscesses in their lungs, meaning that every time they cough, they also cough up the bacterium. Treatment usually lasts about 6 months, but many people stop taking the drugs after one month when they start to feel better. This often results in the disease coming back or drug resistant strains of the disease emerging. Other people, especially in the developing world, do not take all the necessary drugs because they are too expensive. This further prevents TB from being eradicated.

Chris - So how do we currently protect ourselves from TB?

Helen - In Britain, children are given a BCG injection at the age of thirteen or fourteen. Studies have shown that this has been successful in reducing the incidence of tuberculosis in this country. In the developing world, BCG is administered at birth. This offers some protection against disseminated TB (TB spread outside of the lungs) in the first ten years of life, but doesn't offer any great protection from lung disease in early adulthood. A second BCG injection later in life makes no difference to a person's level of immunity. In fact, BCG in the developing world offers more protection against leprosy than TB!

Chris - I've spent some time working in London around TB patients. Does this mean that I have some TB bacterium in me that my immune system has managed to keep under control?

Helen - Yes, it's possible. Only one in ten people exposed to TB will go on to develop the disease. The rest will either get rid of the bacterium or have what is known as latent infection. This is when a person carries a disease but does not show any symptoms. However, the disease can be reactivated if you become immuno-suppressed, such as by taking drugs, becoming old, or contracting HIV. A third of the world are infected with TB in this way (about 2 billion people), although in Britain, latent infection is much lower. The levels of TB are higher in London, which is mostly to do with a higher and denser population.

Chris - So now we understand the problems with TB, what have you done to try and sort them out?

Helen - We have developed a vaccine which boosts the immune response to TB as well as improving the efficacy of BGC. As BCG already provides protection in the first ten years of life, it seemed unethical to replace it, so we have tried to improve it instead. The vaccine is based on the smallpox vaccine and also contains one protein from TB. Trials have not only shown the vaccine to be very safe, but if a person has already had a BCG injection, it stimulates a stronger immune response that lasts longer. This is very encouraging but is the first step on along path.

Chris - How are you measuring the effectiveness of the vaccine?

Helen - At the moment, we are measuring the immune response induced by the vaccine. TB lives inside cells and so we need a particular type of cellular immunity involving T-cells rather than antibodies. Our vaccine is a very strong stimulator of T-cells. Ultimately, we need to test it in the field, and we hope to do this in South Africa in two or three years time, after further preliminary studies. The experiment would involve giving half of the people in the study both the BCG and the new vaccine, whilst the other half would receive only the BCG. We would then follow these people for three years to see how many contract TB. An added benefit of the new vaccine is, of course, that those who receive it will also become immune to smallpox!

- How does breathable waterproof clothing work?

How does breathable waterproof clothing work?

How does breathable waterproof clothing work?

Breathable waterproofs rely on the fact that water is very sticky. Water has an oxygen atom stuck onto two hydrogens, and looks like a tiny boomerang. The oxygen atom is quite negative and pulls electrons towards it. This means that there are plus and minus bits on the molecules which attract plusses and minuses on other molecules, making the molecules stick together. This attraction is known as hydrogen bonding and is the reason why water has a surface tension. When water forms into drops, they are very large and don't easily break into smaller ones. The fabric in breathable Gore-tex raincoats is called Teflon; the same material used on non-stick frying pans. The holes in the fabric are so tiny that 9 billion can fit into one square inch of the raincoat! When water leaves your body as water vapour, the molecules are small and can fit through the holes. When it reaches the outside of the raincoat, it condenses into big sticky raindrops that can't get back through. But your raincoat will only stay breathable if you keep it well waterproofed. Waterproofing creates a gradient between the inside and outside of the coat: the inside has lots of water vapour while the outside has no water because it has formed drops and run off the fabric. This gradient ensures water is pulled away from your skin and stops you getting sweaty inside your raincoat!

- Do fish ever get thirsty, and do they sweat?

Do fish ever get thirsty, and do they sweat?

Do fish ever get thirsty, and do they sweat?

Bony fish that live in the sea have blood that is less concentrated (in terms of salt) than the water they live in. By a process called osmosis, these fish will lose lots of water into the sea. To stop them from dehydrating, bony fish drink lots of water. Although drinking salt water is never a good idea if you're a thirsty human, fish have special mechanism on their gills that enables them to excrete the excess salt they are drinking. By pumping the salts back out again, they are able to drink water without become even more dehydrated. In contrast, sharks make their bodies as concentrated as the water around them. They do this by building up levels of urea in their blood. This is why dead sharks smell like urine. Having highly concentrated blood also means that sharks won't do very well if put into freshwater - water will rush into the shark by osmosis and it might even explode! Sweating is a process designed to help organisms cool down. On land, sweat on the skin evaporates and takes heat away from the body, making you feel cooler. In the sea, water can't evaporate off the fish because they are already in water! So no, fish don't sweat.

- After syphilis, why can I not give blood?

I had syphilis about 40 years ago. Why can I not give blood, and why am I now allergic to penicillin?

After syphilis, why can I not give blood?

Just as if you have a cut and get a scar, having syphilis will also leave a scar in your blood. This scar will be in the form of antibodies that won't disappear, so your blood screenings will always come up positive. If you are keen to give blood, you should probably go along to your local health clinic and ask for a test for syphilis. If you actually had another disease (such as gonnhorea) that leaves no trace, you will be able to give blood, But you are unlikely to be able to give blood if syphilis antibodies are present. As to your penicillin allergy, some people don't know they are allergic to something until they get exposed to it. If you were slightly allergic to penicillin before, receiving it for syphilis will have made your body expert at reacting to it with the result that any time you now take penicillin, your immune system will go into overdrive and give you an allergic reaction.

- What was the shadow I saw pass across the moon?

I was looking at the moon and saw what looked like a huge great rock float past it. What was it?

What was the shadow I saw pass across the moon?

To block out the moon it would have to have been a huge chunk of rock a long way off, or a smaller piece much closer to the Earth. But in either case we would have known about it because of the obvious risk to satellites and to the Earth itself. Also, it probably would have gone on to burn up in the atmosphere, producing a bright light which we would have seen. But it seems very unlikely that what you saw was actually in space. As it appeared so large, it could well have been an aeroplane, or possibly a helium weather balloon...or perhaps a stealth aeroplane or even a UFO !?

- Why does Indian tonic water stop restless legs?

Why does Indian tonic water stop restless legs?

Why does Indian tonic water stop restless legs?

I'm not sure whether it can affect genuine restless leg syndrome, but tonic water can certainly help leg cramps because it contains quinine which is added to give it is bitter taste. Doctors sometimes prescribe quinine to people who complain of night time leg cramps. Perhaps your legs are restless because of cramps and the quinine in the tonic water you drink settles them down?

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