Cholera vaccine in a grain of rice

Jun 12 2007

Japanese scientists have come up with a new strain of rice that carries a vaccine for cholera; they say the breakthrough will provide a cheaper and easier way of distributing the standard injection-based vaccine.

The new discovery was developed by a team of researchers led by Hiroshi Kiyono of the division of mucosal immunology at the University of Tokyo; it is being seen as a revolutionary way to ease delivery of vaccines in developing countries, where storage is difficult due to lack of refrigeration.

Cholera is a disease of the gut that is passed to humans through water or food contaminated with the bacterium Vibrio cholerae; it can kill within a few hours of infection and is prevalent in many of the world's poorest countries. It is one of the most rapidly fatal illnesses known.

The new rice vaccine has to date only been tested in mice, where it causes immune reactions both system wide in the body and in mucosal tissues such as in the mouth, nose and genital tract.

Current vaccines delivered by needle do not cause immune responses in the mucosal areas.

The new vaccine also has an advantage against pathogens that typically infect these membranes, such as cholera, E. coli, human immunodeficiency virus, influenza virus and the SARS virus.

Experts say the new vaccine is very appealing because of the low-cost technology involved.

Many other food vaccine experiments are in the early clinical trials stage before testing whether they are safe to use in people; these include lettuce that produces hepatitis B antigens and spinach that protects against rabies.

Scientists do however caution that getting a good response to orally delivered material is difficult in the harsh environment of the digestive system and more study is needed on ways to protect it from the degradation of the stomach.

They also warn that the use of engineered rice to produce a vaccine reaction does not mean an edible vaccine as the vaccine is delivered in a capsule or pill containing rice powder and should be treated as a drug and not as food.