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PRI's Environmental News Magazine

Low Cost Edible Vaccines

Air Date: Week of February 14, 1997

Steve Curwood talks with Dr. Charles Arntzen about his emerging innovative low cost oral vaccines. Pharmaceutical bananas are being developed to prevent some diarrhea, and questions are raised about what other uses may come from bio-engineered food vaccines.


CURWOOD: Last year for want of vaccinations, millions of children died from such diseases as diarrhea, hepatitis, and cholera. But developing countries often can't afford conventional vaccines and all the refrigeration and sterilization needed to deliver them. Researchers have been working on cheaper and easier ways to immunize people. One of the most promising efforts so far involves moving the production of vaccines into the fields of developing nations, where costs are lower and delivery problems are reduced. But this plan doesn't call for the building of conventional pharmaceutical facilities. Instead it calls for the use of genetically altered plants to produce vaccines which can then be taken orally. One of the pioneers in this field of so-called edible vaccines is Dr. Charles Arntzen. He's a molecular biologist who says he came up with this notion during a trip to Southeast Asia.

ARNTZEN: I was on assignment to look at biotechnology in Thailand and happened to be at the floating market outside Bangkok. Was watching a mother carrying an infant. She went down to the floating market, bought a bunch of bananas, and walked over to a park bench not far away. And as she was peeling one of these bananas her infant started squalling, just really crying intensely. And it was fascinating, because I watched this mother who had just peeled a banana, took a little portion of a banana on the end of her finger and stuck it in the child's mouth. And it just -- it seemed very intuitive, again, to me, saying now if we could put a special product like a vaccine in that banana, this could really be powerful. So I went back home and recruited a couple of colleagues and we set out to find ways to put genes in the bananas and are now well on our way to produce vaccine-containing bananas.

CURWOOD: Now, how do you expect to actually deliver these vaccines? Are there simply going to be bananas that have the vaccine in it? How will you know if somebody's getting an overdose or not?

ARNTZEN: First of all, I'm not sure that the diseases we're talking about that you would ever have an overdose of the vaccine. But we do anticipate this is going to be a pharmaceutical product, and it would be produced and delivered under health care standards that would be established by the country. So I would imagine that it would take a relatively small amount of acreage to grow the banana crop, harvest it, and then perhaps put it in something like a baby food jar for delivery by health care workers to the parents or to the children themselves in the country.

CURWOOD: Now, you've tested this concept with animals so far, right?

ARNTZEN: We've used 2 specific vaccines -- or we call them candidate vaccines because they're still under evaluation. One is for a viral form of diarrhea; it's called Norwalk Disease. We've also worked with a gene from a bacterium called intero-toxic e-coli, or ITEC. This also causes a very common form of bacteria, so if you go to many developing countries and come back with what's called Traveler's Disease or Traveler's Diarrhea, probably about 90% chance that you've picked up ITEC.

CURWOOD: And so you've made a vaccine that works against this.

ARNTZEN: What we've done is put the gene into potatoes, and we feed our raw potatoes to mice, and they develop antibodies both in their bloodstream and secreted into their gut against the active protein from these 2 infectious agents. And we know that if antibodies are produced, there is a high likelihood that it's going to be an effective vaccine. But again, the ultimate test is to go to primates, animal models closer to humans, or to humans. And we are in the process now of accumulating all the data that's necessary to put together a request to the Food and Drug Administration for human clinical trials.

CURWOOD: If we put vaccines in plants, other organisms aside from humans are going to come in contact with them. The birds might eat them, or even the microbes in the soil in which they're grown might be exposed to them. Has there been adequate research into the potential effects on non-target species.

ARNTZEN: If we produced a plant which had relatively modest amounts of this particular protein and we produced relatively modest amounts of the plant material, only the amount needed for vaccines, I think you would find that the amount of protein we're producing is dwarfed by the natural abundance of that protein which is already widely distributed in the environment. For instance, ITEC, this form of intero-toxic e-coli. It is found in soil and contaminated water throughout the world, but especially in developing countries where hygiene levels are not the same as they would be in the developed world with good sewer systems etc. So I really can't quite envision how we would have a danger from this particular approach.

CURWOOD: You're starting with anti-diarrheal vaccines. Is there any limitations to the kind of vaccines that could go into food? I mean, if there's a vaccine some day for HIV, could we put that in bananas? How about hepatitis or polio or the flu for that matter?

ARNTZEN: Let me start with hepatitis, which you mentioned. We have spent a fair amount of our research, my colleagues and I, studying hepatitis-B vaccines produced in plants. We have shown that plants will produce a hepatitis-B vaccine that in all respects is identical to the commercial vaccine now available on the market. Our big technical challenge right now is cause the plants to produce more of this particular protein so that it becomes a cost effective production system. So, we have technical hurdles left in front of us in that particular case. You asked about other vaccines such as HIV. To date there is no good HIV vaccine that's available. I'm sure with all the current research interests that are going on, that will come some time in the next 5 years. If we were to ever consider or contemplate a worldwide immunization program for something like HIV, we're going to have to find an inexpensive delivery system that could be used in every country in the world, especially in developing countries in Southeast Asia and Africa etc. I believe that our plant delivery system and production system would be a very appropriate technology. As to whether or not it would work, there is no theoretical limitation at the present time, but as with everything in science we need to test it before we can say yes, this is the approach you should take.

CURWOOD: Well, I want to thank you for taking this time with us. Dr. Charles Arntzen is a plant biologist and president of the Voice Thompson Institute for Plant Research at Cornell University. Thank you, sir.

ARNTZEN: Thank you, Steve.



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