A vaccine to help ex-smokers.

By generating antibodies that neutralize nicotine, a vaccine could keep ex-smokers from getting the nicotine high that drives many of them back to their bad habit, according to a group of neuroscientists.

"Our focus is to prevent a relapse," says Sabina de Villiers of the Karolinska Institute in Stockholm.

Since nicotine is too small a molecule to stimulate antibody production on its own, the Swedish group attaches nicotine to larger molecules known to trigger a vigorous immune reaction. In rodents, such test vaccines generate antibodies with differing specificities for nicotine, says de Villiers. With varying efficiencies, these antibodies bind to a nicotine molecule and prevent it from reaching the brain, she explains.

In one test, nicotine administered to vaccinated male rats didn't produce the typical release of dopamine, the brain chemical thought to underlie many of the rewarding and addictive properties of tobacco. If similar results occur in people, an immunized ex-smoker who feels a craving and bums a cigarette would end up disappointed by the lack of a nicotine buzz, says de Villiers.

This new research raises the ethical issue of whether parents should immunize their children to prevent them from becoming smokers in the first place. "I'm a former smoker myself. I would have liked that," contends de Villiers.

A biotech firm, Nabi of Boca Raton, Fla., is also developing a nicotine vaccine. Both it and the Swedish group say that tests in people could begin within a year or two.