Rice remedy to combat cholera
19 June 2007
For the first time, Japanese scientists have engineered a strain of rice to contain a vaccine for cholera. The new plants could lead to easier, cheaper and safer ways to immunise large numbers of people against this often fatal disease.
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Image: stock.xchng
Cholera kills thousands of people every year, especially in developing countries where water supplies and sanitation are poor. The disease is caused by infectious bacteria found in contaminated food and water. These bugs make a toxin which damages people's intestines, resulting in severe diarrhoea and life-threatening dehydration.
Existing vaccines aren't 100% effective, and they're simply not practical in an emergency situation or when there is a large cholera outbreak. Organising an immunisation programme is often difficult, time-consuming, and expensive.
Contaminated water is a common source of infection.
Image: CDC
Scientists inserted the gene for cholera toxin into the DNA of these rice plants.
Image: Hiroshi Kiyono
But now scientists think they have a better way to tackle cholera. Reporting in the journal Proceedings of the National Academy of Sciences, they say they have genetically modified rice so that it contains a harmless part of the toxin in its seeds. The idea is to harvest the rice, and turn it into easy-to-swallow tablets. |
Since the rice only contains part of the toxin it doesn't make people ill. But it's enough to kick start an immune response so that when the body encounters cholera for real it knows what to do.
These bacteria, Vibrio cholerae, make a toxin that causes cholera.
Image: CDC
Usually vaccines are injected into the bloodstream because they are digested in the stomach if swallowed. But the new vaccine gets round this potential problem.
Hiroshi Kiyono and his team's vaccine reaches the small intestine unharmed, thanks to proteins in the rice grain that protect it from being digested. Once there, it's taken up by the cells of the intestine's lining and the immune response begins.
'This method should have many advantages,' says Hiroshi Kiyono. 'The vaccine can be administered painlessly without a needle and syringe, stored for one and a half years, and does not have to be kept refrigerated, as current vaccines do. It will also avoid the risks of infection from left-over needles and syringes.'
Taking the vaccine directly to the site of infection should provide a much stronger level of protection too.
The next step will be to do more tests on animals, before conducting clinical trials on humans. But eventually, Kiyono and his team hope the new technique could be used to tackle infectious diseases and bioterrorism on a global scale by developing vaccines for influenza, HIV, botulinus, and anthrax.
Hiroshi Kiyono
Image: Hiroshi Kiyono
'This is a great development that solves many of the problems associated with existing vaccines,' says Julian Ma from St George's, University of London. 'It gives the chance for developing countries, where infectious diseases are most prevalent, to establish their own vaccine industries, since the cost of investment is relatively low.
'There is potential to produce the vaccines on a large scale, and they will be simple and safe to deliver.'
Julian Ma, St George's, University of London
Image: Julian Ma