Will potatoes help prevent hepatitis E?

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Will potatoes help prevent hepatitis E?
May 31, 2005
By Anna Groner
Checkbiotech
ITHACA / TOKYO / TEMPE - Researchers in the U.S. and Japan are trying to develop an oral vaccine to prevent hepatitis E ? with a little hard work, it may come in the form of a potato.

Hepatitis E is a disease of the liver that results in an acute inflammation of this essential organ. The hepatitis E virus (HEV), which causes hepatitis E, spreads via the stool and subsequently through water. Therefore HEV is found mainly in developing countries with low standards of hygiene.
Like hepatitis E, hepatitis A also spreads via the stool. In addition, hepatitis A and E cause only acute infections, whereas hepatitis B,C and D can result in a chronic display of disease symptoms. Yet in contrast to hepatitis A, there is no existing vaccine preventing the onset of hepatitis E.
Therefore, Hugh Mason from the Biodesign Institute at Arizona State University (ASU) and his collaborators at the Boyce Thompson Institute for Plant Research in Ithaca, NY and at the National Institute of Infectious Diseases in Tokyo, Japan want to develop a special vaccine against HEV. The aforementioned scientists recently published their current work in the journal Vaccine, in an article titled: ?Challenges in creating a vaccine to prevent hepatitis E?.
The major aim of their work is to engineer plants which synthesize a HEV vaccine. After appropriate treatment this vaccine then can be orally delivered to patients. According to Hugh Mason, an associate professor at the Biodesign Institute at ASU, ?We believe that plants offer an economy of scale that will allow production of massive quantities at lower cost?.
Moreover, Mason stated that the delivery of oral vaccines offers distinct advantages over the injection of vaccines. Some of the reasons include: lower costs, easier preparation of the vaccine and more efficient protection against specific infective agents, such as HEV.
Since vaccines need to maintain their correct structure to be active, they need to be resistant to digestion. Mason explained, ?The proteins that cover viruses, or bacteria, and cause diarrhea have evolved to be resistant against digestion.?
For this reason virus-like particles (VLPs) which normally cover HEV, are resistant to digestion, which makes them a perfect target for an oral vaccine. In studies where monkeys were administered an oral VLP vaccine, it was able to trigger complete protection against HEV in the monkeys. In order to obtain a plant derived HEV vaccine, the researchers engineered potato plants which synthesized VLPs.
After appropriate preparation, the potatoes containing VLPs could be orally administred to patients. However, when the transgenic VLP expressing potatoes were fed to mice, no HEV protection developed. The researchers think that this occurred because of low levels of VLPs in potatoes.
When asked about the next steps in the HEV vaccine development, Mason replied, ?We will continue to use model systems as potato for research because they are convenient.? Moreover, the scientists will try to optimize and increase the amount of VLPs in potato.
Mason added, ?The plant-derived vaccines must be processed and formulated by means that readily identify them as pharmaceutical products and distinguish them from food. Use of fresh material is not practical, because it has a short shelf-life [?]. Thus we envision a drying process, such as freeze-drying and air-drying of whole plant organs, or spray-drying of crude extracts.?
Moreover, Mason pointed out that the success of this approach also involved ?regulatory issues, such as containment of the foreign genes in the environment, as well as the need to rigorously control the production to ensure that vaccine-containing plant material will not contaminate food supplies.?
Concerning future plans of the Biodesign Institute, Mason told Checkbiotech, ?We are building a lab at ASU-East that will incorporate processing equipment for production of [plant] material to be used in clinical trials. At present we are focusing on the use of tomato and corn, but other plants could be contemplated.?
On the topic of collaboration with scientists from diverse fields, Mason stated confidently, ?Interdisciplinary research is very important for this technology, because it requires the participation of experts from diverse fields of study. We plant biotechnologists are beginning to develop some expertise in vaccinology, and microbiology, but we still greatly value our collaborations with the experts in these fields.?
Mason hesitates to answer the question concerning when he will have a working oral HEV vaccine using plants. ?It would likely be at least 10 years for a human vaccine, but animal vaccines could be available much sooner.?
Anna Groner is a Science Journalist for Checkbiotech and has finished her diploma degree in Molecular Biology at the University of Basel, Switzerland. Her major area of interest include results and outlooks in biomedical research. Contact her at Anna.Groner@stud.unibas.ch.
Challenges in creating a vaccine to prevent hepatitis E