Washington, July 9 (IANS) The lowly tomato can also act as a vehicle for an oral vaccine against Alzheimer's, according to scientists.

HyunSoon Kim of Korea Research Institute of Bioscience and Biotechnology (KRIBB) and colleagues from Digital Biotech Inc.

and Wonkwang University are examining the possibility.

Although the research is still in infancy, it is a promising step towards finding an edible vaccine against the neuro-degenerative disease.

Alzheimer's disease is the commonest cause of dementia, when human beta-amyloid, a toxic insoluble fibrous protein in the brain, accumulates and chokes neurons.

Reducing their accumulation may inhibit the degeneration of the nervous system and, therefore, prevent or delay the onset of Alzheimer's. One approach is to stimulate the immune system to reduce beta-amyloid in the brain.

Kim and colleagues' aim was to develop a plant-derived vaccine against Alzheimer's, since beta-amyloid is toxic to animal cells.

Tomatoes would serve as ideal vaccine carrier because they can be eaten directly, minimising risks of eroding immune stimulation potential of the foreign protein.

The researchers inserted the beta-amyloid gene into the tomato genome and measured the immune responses to the tomato-derived toxic protein in a group of 15-month-old mice.

They immunized the mice orally with the transgenic tomato plants once a week for three weeks, and also gave the mice a booster seven weeks after the first tomato feed.

Blood analyses showed a strong immune response after the booster, with the production of antibodies to the human foreign protein.

The authors concluded that 'although we did not reveal a reduction of existing plaques in the brain of mice challenged with tomato-derived beta-amyloid... this study represents a unique approach in which transgenic plants expressing beta-amyloid protein are used to produce a vaccine.'

The team is currently looking at strategies to increase the potency of the tomato-based vaccine, because fresh sample contain only 0.7 percent protein and levels of foreign protein are even lower.