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Medicine and Health

"Vaccine -plants": a European première

   
 
Picture
Vigna unguiculata. A common and easy to grow fodder crop, whose properties could revolutionise methods of vaccination.
In a world first, European biologists working together on a Community project have made an important breakthrough in research into producing vaccines from plants. The results of animal vaccine trials are very promising, and may well herald some interesting developments for the human race. The large-scale engineering of inexpensive "edible vaccines" in plant hosts would usher in a genuine pharmaceutical revolution.

 

It all started with a modest fodder crop, the cowpea (Vigna unguiculata) - also known in the English-speaking world as the blackeye bean. Basing their work on a virus that commonly affects the cowpea, European researchers taking part in a FAIR programme project found a way of combating three viral diseases that mainly attack animals: canine parvovirus, mink enteritis and the feline panleukopenia virus.

The virus that infects the cowpea has a feature that makes it eminently attractive from the researchers' viewpoint: its surface is composed of sixty copies of two proteins, one of which has a sort of molecular loop projecting outward. The scientists proceeded in two stages. First, they isolated a peptide - a short string of amino acids - common to the proteins of the three viruses in question. Then, they managed to insert the peptide into the multiple loops of the plant virus.

From plant to animal
Consequently, when the plant virus - now carrying sixty copies of the peptide - infects the cowpea and multiplies there, the latter becomes a very abundant source of an important element of the disease-causing virus which can stimulate the animals' immune systems. Once it has been administered to the animals, the modified plant virus will act as an antigen, setting off the production of antibodies just like a vaccination.

All that remains to be done is to harvest the leaves of the infected plant, crush them, and isolate the modified plant virus for use. The system could hardly be better: not only are production volumes relatively very high (1 to 2 grams per kilo of undried material), but the plant, having lost some leaves, carries on growing, thereby ensuring sustained production.

Once purified, as controlled tests have confirmed, the modified plant virus becomes a powerful vaccine when administered in appropriate doses (from 100 micrograms to one milligram per animal treated). Since a single kilo of plant material may yield 2 000 doses of vaccine, one of the main advantages of the process is clear: its low cost.

The need for an international strategy
"Such research would have been impossible to carry out in a single laboratory given the range of scientific expertise required - from plant physiology to product development, not to mention animal and plant virology, immunology, molecular biology and process development," explains Paul Rodgers, development director at Axis Genetics and coordinator of the project. "To continue along this path, an international research strategy was needed. Today, this openness policy brings with it a second advantage - access to the largest markets. In this respect, the European Union can assist by setting up laboratory consortia that can be called on to focus on specific applications for the technology we have developed."

In time, researchers believe it will be possible to administer vaccines simply by oral ingestion of the active agent. "A practical method which would help enormously in epidemiological prevention campaigns," comments Paul Rodgers. For, it goes without saying, that if so far the project has been limited to testing the process for producing animal vaccines, the potential benefits for humankind are just around the corner. Certain auto-immune diseases may be preventable, even if not treatable, thanks to the somewhat artificially induced, but renewable attributes of a simple fodder plant. Could we be on the threshold of 21st century phytotherapy?

 

 

Project Title:  
The plant as a factory for the production of oral vaccines and diagnostics

Programmes:
FAIR

Contract Reference: FAIR CT 95720

CORDIS databaseFor more information on this project,
go to the Cordis database Record

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