Eating genetically modified plants could one day be used to 'immunise' sufferers against asthma, according Australian scientists who have engineered a new type of lupin.

Dr Simon Hogan, a molecular scientist at the Australian National University in Canberra and colleagues report their research in the current issue of the Journal of Immunology.

Hogan and team have developed a genetically-modified (GM) lupin plant that they report protects against asthma in laboratory mice. The asthma protection is based on the principle that very low doses of an allergen can be used to induce a protective immune response in the body.

This 'tolerance' ensures that when the body is exposed to a fuller dose of the allergen, it is not triggered into an overactive immune response that can lead to inflamed airways and ultimately asthma attack. The same principle underlies vaccination by injection.

So far, experiments with plant-based vaccines - using plants such as bananas, potatoes and tomatoes - have been for treatment of infectious diseases, and this is the first time that a plant-based vaccine has been used to protect allergy, Hogan told ABC Science Online.

"We wondered if you ate a GM plant expressing an allergen whether the tolerance induced in the body would be protective in the lungs," said Hogan.

In conjunction with the CSIRO Plant Industry, a specialist division of Australia's Australia's Commonwealth Scientific & Industrial Research Organisation, the team genetically modified a lupin plant to produce an asthma allergen called sunflower albumin.

They fed the GM lupin to a group of mice which were not allergic to sunflower albumin, but were able to have asthma experimentally induced in them. Another group of the same mice were fed non-GM lupin.

The researchers then exposed both groups of mice to large amounts of sunflower albumin in the air they breathed, and tried to induce asthma in them. The mice fed the GM lupin were protected against asthma whereas the control mice fed normal lupin - and as such had no opportunity to develop tolerance - did develop asthma.

"So the mice fed the transgenic plant were actually protected," said Hogan. "This means that from an experimental point of view you can induce a protective effect in the gut which protects other organs like the lungs from an allergic response."

"The next step is to work out the exact mechanism of the protective immune response.
Once we fully understand this we will be able to focus on that as a therapeutic approach."

Hogan said the GM plant asthma vaccine potentially provided a more long term approach to asthma treatment: "Most treatment at the moment is based on suppressing the immune response. The plant based vaccine modifies the immune response to have an ongoing protective effect."

He added that human trials would be at least 10 or 15 years away and that there were other hurdles to clear as well. "There are concerns with the ecological and health effects of GM plants that need to be further investigated," he said.

Funding for this research has come from Australia's National Health & Medical Research Council and the university's John Curtin School of Medical Research. Hogan has also set up a company, PlantImmunex Diagnostics, which is currently looking for funding to develop GM plants for treatment of disease.

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