Japanese scientists have created a vaccine for cholera that can be well, eaten.
Immunologist Hiroshi Kiyono of the University of Tokyo and his colleagues inserted the genetic material from the microbe responsible for producing cholera toxin, into a rice plant, whose genome has recently been mapped. The plants produced the toxin and when the rice grains were fed to mice they provoked immunity from the diarrhea-causing bacterium.
The bacteria that cause cholera infect the gut and causes bloody stools. Nearly 200,000 cases of cholera occur each year in Africa, India and Russia, among other places.
The causal organism- Vibrio cholerae, travels from host to host in water as well as on washed food. Here, it can persist for almost a week.
Vaccines do exist, yet they are short-lived protection, as some require refrigeration from when they are brewed in an industrial vat to the moment they are injected into a patient. Now, the researchers say this strain of rice acting as a vaccine, can last for more than a year and a half at room temperature.
The benefits of such a vaccine have far-reaching effects. It could be used for large-scale and cost-efficient immunization programs.
Developing countries, many of which have rice as a staple food, are likely to benefit most.
Says Kiyono: "We are 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 adds.
It is widely recognized that an effective mucosal vaccine would probably offer the best protection against infections such as cholera, Escherichia coli, HIV, influenza and SARS.
One of the big hurdles in the way of developing easy to administer edible vaccines is that they tend to be destroyed by digestive enzymes.
Another obstacle to large-scale immunization in the developing world is the cost of storage. Traditional vaccines cannot be stored at room temperature, and the worldwide cost of refrigerating them is put at between Ģ101 million and Ģ152 million a year.
The new vaccine is said to solve both problems. In tests it was resistant to the digestive enzyme pepsin, and it remained stable at room temperature for more than 18 months.
The Japanese researchers say that the cholera vaccine bound within the rice can be stored at room temperature over long periods and is immune to digestion. They believe such rice vaccines could in future protect large populations against a wide range of infectious diseases.