Popeye had his spinach. Scooby-doo had his Scooby-snacks. And if vaccine researchers have their way, you could soon have your vaccine bananas or raw potatoes.

The charge is on to produce genetically engineered fruits and vegetables that will protect the body from different kinds of disease. These spuds won’t give you the strength of ten men, but they could save your life and the lives of millions of people around the world, especially young children in developing countries.

Sure beats the needles, doesn’t it kids?

"About 15 million kids die every year from preventable diseases." --Charles Arntzen, President, Boyce Thompson Institute for Plant Research, Cornell University

Beyond the most obvious affection that children would have for any food over traditional vaccines--no needles--this edible and unique delivery system offers several advantages over its pointy predecessors. Traditional vaccination is difficult to deliver, and injections need to be kept at cold temperatures to preserve the proteins in the vaccine. Given the right conditions, like your pediatrician’s office, this is managable. But in other parts of the world, those conditions can be more difficult to achieve.

Vaccines must be transported to the people who need them, mostly children in developing countries who will die without them. They can be very costly. And some attenuated, or weakened virus vaccines can pose some threat of infection to a weak or developing immune system. Developing a food vaccine, although extremely difficult, alleviates each of these problems. Once the formidable technological bridges to effective food vaccines have been crossed, scientists are hoping to create new vaccine deliveries for diseases ranging from Traveler’s diarrhea to HIV.

How does a food become a vaccine?

The first results from clinical trials of food vaccines, in the form of raw potatoes, were published in May’s issue of Nature Medicine. Potatoes, the fast-growing "lab rats" of the crop world, were engineered with portions of the genetic blueprint of the disease-causing microorganism E. coli embedded in their own genes. As the potato cells grew and made proteins from their own genetic instructions, they produced pieces of E. coli proteins as well. The volunteers’ immune systems recognized what they thought were bacterial invaders and created an immune response to the bits of E. coli. Potato proteins are recognized as food. Efforts are underway to create food vaccines from bananas, which don’t have to be cooked, and are presumably more appetizing to children than raw potatoes.

But why foods?

Food vaccines are especially useful when the disease it prevents is in the gut. As the potato or banana is broken down by the digestive system, cells along the wall of the intestines are mounting the immune response. Presumably, when they see the E. coli protein again, it will be attached to the harmful bacterium, which will then be dutifully destroyed.

In this sense the vaccine is targeted to specific areas of the body, making edible vaccines especially useful for fighting against enteric diseases like E. coli, cholera, or Norwalk virus, all of which cause diarrhea that can lead to dehydration and death, especially for young children in developing countries.

Researchers are hoping to cram enough vaccine into each potato or banana to make each dose only about a spoonful of fruit, so that the cost per dose of the drug would fall to mere pennies. And because of nature’s unique packaging, refrigeration becomes unnecessary; the vaccine can be grown practically anywhere it is needed--in more than sufficient amounts, and there is no risk of infection.

"The greatest risk is a lack of research." --Charles Arntzen

The second round of clinical trials that is set to begin later this year will expand on the first. They will try to determine how long the antibodies to the bacteria stick around and the timing of their release. Trials with bananas are a little further off. The first crop designed at Boyce Thompson won’t be ready until almost 1999 because bananas are a slow growing fruit that may take up to 18 months to mature (unlike potatoes which only require a few months).

Despite these time constraints researchers are optimistic. Research dollars are going into developing edible vaccines for Hepatitis, Rabies and even HIV.

The outlook for children in developing areas of the world is improving. And closer to home, while your local street vendors won’t be able to boast about any sort of life saving characteristics of the fruits they are selling, in a few years you may be taking your child to the pediatrician for a tablespoon of delicious banana vaccine.

Elsewhere on the Web

NPR’s Talk of the Nation: Science Friday, May 1, 1998: Edible Vaccines

Listen to the Science Friday program in Real Audio!

The National Institute of Allergy and Infectious Diseases

The World Health Organization

The Boyce Thompson Institute for Plant Research