April 26, 1996. Copyright, 1996, Graphic News. All rights reserved

PLANT VACCINES SHOW PROMISE
By Laura Spinney, Science Editor

LONDON, April 26, Graphic News Ð Tests of a new plant-derived vaccine are showing ÔpromisingÕ results, according to scientists at a British biotechnology company. Although the data from the tests is not yet available, this could be the first step in the development of a new breed of vaccines.

The prototype vaccine being tested by Cambridge-based Axis Genetics is based on a technique that modifies plant virus particles. The technique, which has been developed in collaboration with scientists at the John Innes Centre in Norwich, involves inserting a fragment of a virus that causes disease in animals into another virus that infects only plants. When the modified plant virus particles are rubbed into the leaves of a plant Ð in this case the black-eyed bean plant Ð the cells of the inoculated plant recognise the genetic material of the inserted fragment and produce millions of copies of it. Within two to three weeks the plant grows more leaves, all of which contain the modified virus particles. The leaves are then harvested, ground up and the particles extracted.

Tests have already shown that the animal virus fragments mass-produced in this way are enough to stimulate the immune system of mice to produce antibodies against those viruses. But the question that scientists are now asking is whether they can offer real protection against disease in the form of a vaccine. The researchers have been experimenting with the canine parvovirus which infects dogs, and which is closely related to other viruses that infect cats and mink. Although they have been concentrating on vaccines for veterinary use, they are also working on human vaccines for AIDS and hepatitis B.

The advantage of this system is that the black-eyed bean plant is used as cattle fodder in many developing countries, so that if it is shown to be effective, livestock could be inoculated simply by being fed the modified plants. ÔWhat excites me about it is that you can forget all the high-faluting immunology,Õ says Dr Bill Hamilton, director of research at Axis Genetics. ÔIf it can actually protect an animal from challenge with a disease, this is a very pragmatic approach.Õ

And whereas the prospect of an edible plant vaccine for humans would have been Ôpie in the skyÕ five years ago, says Hamilton, the technology could soon be available to produce the virus particles in fruits and vegetables. Instead of involving a painful injection, inoculation could mean nothing more unpleasant than swallowing a banana.

Sources: Axis Genetics