An anti-nicotine vaccine could give smokers a leg up on quitting, new research suggests. The study on mice indicates that the vaccine can deliver a gene that stops nicotine before it reaches the brain, protecting the mice from the nicotine "high" for their entire lives with just one dose.
Nicotine is a highly addictive drug found in cigarettes and other tobacco products, which also cause cancer. Smoking rates are falling every year, but about 20 percent of adults still smoke, despite high taxes and disturbing warning labels.
"If you give nicotine to a mouse, they chill out, like humans. They run around less and their blood pressure drops and heart rate drops," study researcher Ronald Crystal, of Weill Cornell Medical College in New York, told LiveScience. "With the vaccine, giving them nicotine is like giving them water; the vaccine stops nicotine from reaching the brain." [5 Bad Habits You Should Still Quit]
The vaccine is a type of gene therapy. It uses a safe virus as a shuttle to insert a gene into the mouse's liver cells. The gene codes for an antibody — a protein made by the immune system that labels (and attacks) invaders, like bacteria, viruses and toxins. In the case of the newly studied vaccine, the antibody targets nicotine.
In the new study on mice, the gene delivered by the virus was able to become a part of the liver cells and actively start making this antibody. They also saw that the antibody was able to attach to nicotine and stop it from reaching the mouse's brain; once attached to the nicotine, the mice no longer showed behavioral or physiological reactions to injections of nicotine. The nicotine-antibody combo, which is constantly pumped out by the liver cells, gets removed from the blood, then metabolized by the body and excreted.
Vaccinated mice, which are then given the amount of nicotine found in two cigarettes, don't experience the heart rate slowdown or the blood pressure drop that usually accompany the drug.
Previous attempts at creating a nicotine vaccine have failed because the immune system doesn't put up a big fight against nicotine — something these vaccines depended on. For instance, in the past, researchers have tried to tie nicotine to molecules the immune system does attack full force, like the cholera toxin; but the result still didn't make enough antibodies to protect against nicotine's effects in the brain, which are the basis of a cigarette addiction.
The researchers did this study for 18 weeks and saw high levels of antibodies the entire time. Based on previous applications of this gene-delivering virus (which has been used to deliver various genes), the researchers think the results should last for a long time, possibly even a human's entire life.
"As far as we know, it's safe to use in humans," Crystal said. "Based on results from other studies with this class of viruses, we'd expect them to function forever."
These antibodies wouldn't rid someone of their nicotine cravings, but would basically make it impossible to satisfy them with cigarettes.
"Let's say someone smokes one cigarette an hour: Could they overcome by smoking one every five minutes?" Crystal said. "Maybe, but there's probably some limit on how often some people will smoke."
The researchers have to continue with animal safety and efficacy trials before they are able to test on humans, so it will be a few years before human trials on this nicotine vaccine begin. Crystal has also developed vaccines against cocaine using similar techniques, which have shown promise in monkey and mouse trials.
The study was published today, June 27, in the journal Science Translational Medicine.