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Discovery an alternative to inconvenient injections in developing world,
researchers say, February 2005.

Researchers have found a way to grow potatoes that carry a vaccine for
hepatitis B, providing doctors in the developing world with an easily
produced, non-refrigerated means of supplying protection against the virus.

While child vaccination campaigns have reduced the threat of hepatitis B in
the United States, the virus remains a worldwide health problem. Experts
estimate that over 350 million people now carry hepatitis B worldwide, and
in many places vaccination has not been viable because some countries cannot
afford to buy or refrigerate injectable vaccines.

Hepatitis B is a serious illness caused by a virus that attacks the liver.
The virus can cause lifelong infection, cirrhosis of the liver, liver
cancer, liver failure and death. In the U.S., children usually receive the
vaccine in infancy, followed by booster shots as they grow.

Using genetically modified plants, lead researcher Charles J. Arntzen,
co-director of the Center for Infectious Diseases and Vaccinology at Arizona
State University's Biodesign Institute, said he and his colleagues hope to
increase hepatitis B immunization rates around the world.

"We have been able to produce a form of the hepatitis B vaccine that can be
delivered orally, that triggers a robust and lasting response in humans,"
Arntzen said.

In their experiment, Arntzen's team genetically modified ordinary potatoes
to carry the gene for hepatitis B surface antigen. These potatoes were then
cloned and cultivated. The researchers then tested the vaccine on 42
volunteers. Of these, about 60 percent had signs of immunity against
hepatitis B after eating bite-sized pieces of the modified raw potato.

The report appears in this week's issue of the Proceedings of the National
Academy of Sciences.

The problem with the current hepatitis B vaccine is that only 40 percent of
the children around the world receive it, Arntzen said. "The other 60
percent don't get vaccinated due to a combination of factors," he added.

These barriers include cost, problems with delivery and a lack of
professional health-care workers. "Our focus is to devise a system [so] that
we can bio-manufacture the hepatitis B vaccine, but deliver it not by
needles, but rather orally," Arntzen said.

Arntzen's next step is to convert the plant material, either potato or other
vegetable, such as tomatoes, into something that looks like a traditional
pill. "We use food processing to freeze dry the plant material and grind it
into a powder. Then we pack the dry powder into gelatin capsules so we can
measure accurate doses," he explained.

He believes that by using accurate doses, doctors in the field will achieve
more than a 60 percent response.

The process is still being tested in animals, but Arntzen hopes to begin
human trials in the foreseeable future. He hopes this method can be used for
both primary and booster vaccinations.

According to the Arizona researcher, plant-based delivery might also work
with other vaccines, such as those for measles and cholera.

In addition, when vaccines are eventually developed for diseases such as
dengue fever, river blindness and malaria, this process will make oral
vaccines more widely available. "In the next decade, we will make these
vaccines," Arntzen said. "Our challenge is how to get them out to the people
who need them."

"Producing oral vaccines that don't require refrigeration would vastly
simplify the distribution of vaccines for global immunization," Arntzen
said. "Our strategy is to work on vaccines that are not getting around the
world as they should."

"The authors envision a day when most, perhaps nearly all, important
vaccines will be mass-produced in some genetically modified plant, and
delivered by ingestion," said Dr. David L. Katz, director of the Prevention
Research Center at Yale University School of Medicine. "Such a system would
overcome many of the factors that limit global immunization today, among
them cost, availability, vaccine stability and the logistical demands of
administration by injection."

But Katz is cautious. "There are miles to go before science can keep such
promises," he said. "While the glass of plant-derived, ingestible vaccines
may not be more than half full at present, it was, until recently, empty.
The progress is clearly a cause for optimism, provided it is coupled with
patience."

[abcnews.go.com]

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