Publication: Reuters Health
Date: Friday, June 01, 2001

NEW YORK - A potato-based vaccine that protects against several stomach diseases has passed the first round of animal tests, researchers in California report.

For several years, scientists have been trying to develop vaccines that are delivered through foods such as potatoes and tomatoes rather than needles. The hope is that edible vaccines may be more practical for use in developing countries, since the foods do not need to be refrigerated as ordinary vaccines must, and the edible vaccines do not require syringes and other medical equipment.

So far, plant-based vaccines have met with limited success. One problem has been figuring out a way to get edible vaccines into gut tissues without being destroyed by digestive juices.

Drs. Jie Yu and William H. R. Langridge, of Loma Linda University in Loma Linda, California, got past this obstacle by designing a vaccine around the cholera toxin, which can latch onto the lining of the gut without being destroyed by digestive juices. Normally the ability of the toxin to survive in the gut has harmful consequences, leading to cholera, but the researchers were able to use the toxin without causing disease.

Yu and Langridge took bits of the cholera toxin and joined them with proteins, or antigens, from two other infectious pathogens that invade the gastrointestinal tract--rotavirus and a strain of E. coli bacteria. They then developed a genetically modified potato that contained the triple combination.

The approach seems to work, the authors report in the June issue of the journal Nature Biotechnology. Female mice that ate the genetically modified potatoes developed antibodies to all three microbes.

At least some of the vaccine`s benefits seemed to pass on to the next generation of mice, the report indicates. When the offspring of the vaccinated mice were exposed to rotavirus, they were less likely to develop diarrhea than other mice, and the ones that did develop diarrhea had milder cases (diarrhea is a symptom of rotavirus infection, which is a severe problem among infants in developing countries).

``The results suggest that food plants can function as vaccines for simultaneous protection against infectious virus and bacterial diseases,`` Yu and Langridge conclude.

SOURCE: Nature Biotechnology 2001;19:548-552.