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Rice

Engineered to Carry Cholera Vaccine

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Jun 11, 7:15 PM (ET)

By RANDOLPH

E. SCHMID

WASHINGTON

(AP) - A team of Japanese researchers has developed a type of rice that can

carry a vaccine for cholera, a step that could one day ease delivery of

vaccines in developing countries.

While it's only the latest of several plants

being tested as potential means of producing vaccines, the development is

potentially important in medically underserved countries that lack

refrigeration to store regular vaccines.

But the work is preliminary, having been

tested only in mice.

The team, led by Hiroshi Kiyono of the

division of mucosal immunology at the University of Tokyo,

reports the development of the new vaccine in Tuesday's issue of Proceedings of

the National Academy of Sciences.

A major advantage of this approach, they said,

it that it causes immune reactions both systemwide in the body and in mucosal

tissues such as in the mouth, nose and genital tract.

Standard vaccines delivered by needle do not

spur immune responses in the mucosal areas.

That means the new vaccine could have an

advantage against pathogens that typically infect these membranes, such as

cholera, E. coli, human immunodeficiency virus, influenza virus and the SARS

virus.

Attempts to alter plants to produce proteins

that induce an immune reaction to various diseases

have been under way for years, but none has reached the state where it could be

used in humans.

" This has not progressed to the degree

that we had hoped it would by this time, " said Hugh S. Mason, a researcher

at Arizona State University

who has worked on several lines of plant vaccine study.

Mason cautioned that getting a good response

to orally delivered material can be tricky in the harsh environment

of the digestive system.

" We're going to have to work on ways to

protect it from degradation of the stomach and then release it lower down in

the gut so it can be taken up, " he said.

In 1998 he published a paper on modifying

potatoes to produce a vaccine for Norwalk

virus. But he said in a telephone interview last week that " was a

relatively preliminary study. "

Most recently, Mason said, he has been working

with nicotiana Benthamiana, a relative of tobacco, but which is smaller and has

fewer alkaloids than tobacco.

Many researchers are moving away from food

plants because of public concern about altered items getting into the food

chain, Mason said.

W. Pascual, a molecular biologist at Montana State

University in Bozeman, said the Japanese researchers were

able to generate a protective immune response in the mice while avoiding any allergic

reaction to the rice itself.

In addition, the transgenic rice can be stored

at room temperature and doesn't have the risks of infection from an injection.

Pascual, who was not part of the research

team, noted that several other plants have been developed to carry vaccines.

Potatoes and tomatoes have been tested for

vaccine against Norwalk

virus, he said, potatoes, corn and soybeans against enterotoxin, potatoes for

cholera vaccine, and soybeans for E. coli.

One reason for the slow progress in the field

has been lack of interest and funding from major pharmaceutical companies,

Mason said.

The only plant-based vaccine in use counters Newcastle disease

in chickens, and that reached development only after Dow Agroscience became

interested, he said.

The Japanese research was funded by several

agencies of the Japanese government.

The use of rice engineered to produce a vaccine

reaction doesn't mean it's an edible vaccine, Kiyono stressed.

" We do not wish to create the condition

that public is thinking of eating steamed rice for vaccination, " he said

via e-mail.

Instead, the vaccine is delivered in a capsule

or pill containing rice powder and should be treated as a drug, not food, he

said.

With the first work done in mice, Kiyono said

more basic studies are needed and he hopes to test the vaccine in a primate

" in the near future. "

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On the Net:

PNAS: http://www.pnas.org