Rice-based edible vaccine developed

A strain of rice containing edible vaccine has been developed that could be used for large-scale and cost-efficient immunisation programmes.

Researchers said 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.

Developing countries, many of which have rice as a staple food, were likely to benefit most.

The Japanese scientists carried out their experiments with a cholera vaccine because it was so well understood and studied.

The aim was to develop an edible vaccine that targeted the immune system's first line of defence, the "mucosal" sites of the nose, mouth, lungs or genito-urinary tract where many microbes and viruses typically enter the body.

Most existing vaccines are injected into the bloodstream and trigger immune responses against pathogens that have already broken through the mucosal barrier.

It is widely recognised 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 immunisation in the developing world is the cost of storage. Traditional vaccines cannot be stored at room temperature, and the world-wide cost of refrigerating them is put at between £101 million and £152 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.

source:www.channel4.com