Plants Battle Cavity Creeps

After polishing your teeth, the dentist of tomorrow may well have you swish a mouthful of plant vaccine. Researchers have shown that antibodies from genetically engineered plants can ward off tooth-decaying bacteria for up to 4 months. The finding, reported in tomorrow's Nature Medicine, might also lead to preventive measures for other diseases.

To make antibodies cheaply, Julian K.-C. Ma of the United Medical and Dental Schools in London and his colleagues created tobacco plants that carry the gene for an antibody to a surface protein of the major tooth-rotting bacterium Streptococcus mutans. After purifying the tobacco-produced antibody from the plants, the researchers tested its ability to prevent S. mutans from recolonizing a sterilized mouth. First the researchers had six volunteers gargle with an antibiotic mouthwash that killed off most bacteria in their mouths. Next, they applied 5 microliters of the antibody solution to each tooth, repeating the application twice a week for 3 weeks. Four months after the treatments ended, the bacteria had still not regained a foothold; the bugs returned to unvaccinated mouths within 3 to 8 weeks.

Experts are impressed by the antibody's staying power. "I was shocked to see that it lasted so long," says William Langridge, a molecular biologist at Loma Linda University in California. He notes that the antibody Ma's group used is more resistant to enzyme degradation than others tried in the past. But don't expect to be munching on a cavity-fighting plant, such as a celery stalk, anytime soon: Ma says the most likely way of administering this vaccine will be as a lozenge or mouthwash.

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