A vaccine for nicotine dependence: targeting the drug rather than the brain.

Nicotine is the principal addictive component of tobacco. Vaccination of rats against nicotine elicits the production of nicotine-specific antibodies which can bind and sequester nicotine in serum and extracellular fluid, reduce nicotine distribution to brain, and reduce many of nicotine's physiologic and behavioral effects. Vaccination reduces the distribution to brain of both a single nicotine dose and chronic nicotine infusion at rates approximating cigarette smoking. The passive transfer of nicotine-specific antibodies (from vaccinated rabbits) into rats attenuates numerous actions of nicotine: increases in blood pressure and locomotor activity, the induction of nicotine dependence, the relief of nicotine withdrawal by subsequent nicotine and the stimulus properties that allow rats to discriminate a nicotine from a saline injection. Vaccination of rats against nicotine also reduces nicotine-induced dopamine release in the reward pathway of the brain and the reinstatement of nicotine responding, a model for relapse. Because nicotine vaccines target the drug rather than the brain, and the antibodies themselves do not cross the blood-brain barrier, immunization should circumvent the central nervous system side effects that limit the usable dosage of other medications for tobacco dependence. Nicotine vaccines have not yet been tested in humans. The effects of these vaccines in rats are highly dependent upon the concentration of antibody in serum, and are more often partial than complete. If effective for treating tobacco dependence in humans, vaccination will likely benefit from concurrent use of counseling (as is the case with other medications for smoking cessation) and perhaps from its combination with other medications that act via different mechanisms.