Rice vaccine to fight cholera18th June 2007
Japanese researchers have developed a strain of rice which could carry protection against cholera for those who take it - but unfortunately not in its fragrant, steamed form.
A team led by immunologist Hiroshi Kiyono of the University of Tokyo inserted some of the genetic material from the bacteria that cause cholera - vibrio cholerae - into a rice plant, whose genome has recently been sequenced.
The bacterium gives rise to around 200,000 cases annually in Africa, India and Russia. It is carried in water and on washed food, and can live there for up to a week.
Currently available vaccines need refrigeration from the moment they are produced, while the rice-based vaccine can be stored at room temperature for up to 18 months.
Kiyono said his team was considering rice as a new vaccine production and storage system, and natural vaccine delivery vehicle.
"The vaccine expressed in rice, or rice-based vaccine, will become a new form of vaccine production and delivery to [the] digestive tract for the initiation of antigen-specific mucosal and systemic immune responses," he said.
Rice offers several advantages over traditional vaccines: it does not require needles, purification or refrigeration. In fact, the rice proved just as potent after 18 months of storage at room temperature and the vaccine did not dissolve when exposed to stomach acids, the researchers report in Proceedings of the National Academy of Sciences USA.
But Kiyono said oral boosters might be necessary for the induction of antigen-specific immune response. A pill, in other words, would be needed to ensure people received the correct dosage, and to compensate for the variations in amounts from rice grain to rice grain.
So the vaccine was unlikely to be delivered using rice as a vehicle in its cooked state, as food, he added.
"A powder form of rice-based vaccine will be given in a tablet or capsule form," he said.
Rice plants do not scatter pollen as widely as some genetically-modified crops, so would be unlikely to contaminate other strains.
Indeed, they may be a better candidate for a vaccine delivery vehicle than some GM crops already used for the purpose, like corn, wheat and tomatoes, Kiyono said.
The same technique could be used to deliver immunity to influenza, botulism or anthrax.
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