A friend once told me that it was 100 times harder for him to quit smoking cigarettes than to quit drinking alcohol. Clearly nicotine is highly addictive. About 45 million people in the U.S. smoke cigarettes, even though cigarette smoking leads to 1 of every 5 deaths each year.
In a National Health Interview Survey, over half of the smokers reported trying to quit in the past year without success. In the future, these smokers may get a vaccine to help protect them from nicotine addiction.
Researchers from Weill Cornell Medical College and Scripps Research Institute have developed a new vaccine that may treat nicotine addiction by blocking the pleasurable sensations that nicotine creates in the brain. At the early stage of animal testing, Dr. Ronald Crystal and his colleagues have demonstrated that they can prevent nicotine from reaching the brain in mice using a single injection of vaccine, as described in the latest issue of Science Translational Medicine.
Common active vaccines, like flu shots, work by introducing a small amount of virus so your immune system responds against the intruder. However, Crystal’s team created a different type – a genetic vaccine.
Their vaccine genetically modifies the liver to continuously produce high levels of an anti-nicotine antibody, in addition to normal liver production. These antibodies bind to nicotine in the blood, preventing it from reaching the brain. The trick is that you need anti-nicotine antibodies to be continuously present in the blood at sufficient levels.
Crystal’s team tested the effectiveness of their vaccine by injecting inoculated and control mice with nicotine at a level equal to smoking two cigarettes. When they measured the resulting nicotine levels, inoculated mice had seven times more nicotine in their blood than control mice and antibodies had captured nearly all (83%) of the nicotine. Inoculated mice also had 85% less nicotine in their brain than control mice.
This indicates that the vaccine produced sufficient levels of anti-nicotine antibodies, which bound to the nicotine in the blood and prevented it from entering the brain.
In addition, inoculated mice didn’t appear to experience any of the physical effects of nicotine. When given nicotine that reached the brain, control mice were less active and their blood pressure and heart rate reduced. In contrast, inoculated mice had no apparent reaction to the nicotine injection.
“Smoking affects a huge number of people worldwide, and there are many people who would like to quit, but need effective help,” Dr. Crystals said in a press release, “This novel vaccine may offer a much-needed solution.”
However, a vaccine for humans is at best years away. In the current study, the mice weren’t previously exposed to nicotine. Researchers now plan to study nicotine-addicted rats with free access to the drug, testing whether a reduction in the amount of nicotine in the brain alters nicotine-seeking behaviors. Ultimately they hope to test the vaccine in humans.
Even if the vaccine works perfectly with rodents, it may not translate into an effective vaccine for humans. The vaccine also doesn’t address the behavioral habits and psychological addiction to smoking. Finally, people may hesitate to genetically modify their bodies, even if it would help them quit smoking.