British scientists have developed a successful vaccine against tooth decay from genetically modified tobacco plants, according to a recent report in the journal Nature Medicine. Results from a four-month patient trial were very encouraging, leading to speculation that the treatment should be available to the public within a few years.

Tooth decay is caused by the bacterium Streptococcus mutans, which produces acid as it feeds on sugar and other carbohydrates coating the teeth. It affects half of all children by the age of five and three quarters of all 17 year-olds. The liquid vaccine that has been developed is simply painted on the teeth. A few applications provide protection against tooth decay for at least four months. The active components are antibodies that attach themselves to the tooth decay bacteria, preventing them from becoming established on the teeth. While these impotent microbes are washed away, other ones that are harmless, colonise the teeth leaving no room for further invasions by viable cells of S. mutans.

The work is the culmination of a 25-year effort at Guys Hospital in London, UK. Initially the objective was the production of a traditional vaccine for injection into the bloodstream, but the revolution in molecular biology has allowed the production of genetically modified tobacco plants as "factories" producing large amounts of clean, safe vaccine for oral consumption. Eight small plants or one full-grown specimen are enough to produce a single course of treatment. It would cost very little to produce the vaccine on a large scale from fields of tobacco plants.

Thought to be the first effective therapeutic molecule for humans made in genetically modified plants, it is also the first time that a secretory - as opposed to a blood-borne - vaccine has been used in a human trial. Professor Tom Lehner, one of the scientists heading the research, was the first person to put the colourless, tasteless liquid in his mouth eight years ago. He said, " A field study has to be carried out first. Once we've done this we then can decide whether it should be self-administered. My own preference would be that, for the next few years, while we learn more about this therapy, it should be applied by dentists. After a few years we could start experimenting with self-application, using a tooth paste or mouthwash or even tablets."

The British Dental Association welcomed the news but also added a warning: "Even if the vaccine does come into general use, dentists would not wish the public to abandon the simple oral health messages". Good oral hygiene, brushing regularly with a fluoride toothpaste is recommended. Limiting eating occasions to regular meals and no more than two to three snacking occasions daily will also help protect and improve dental health.

FOOD TODAY 07/1998