June 28, 2012
Vaccine Developed Against Nicotine Addiction
Connie K. Ho for redOrbit.com
20 percent. This is the number of adults who smoke, according to the Weill Cornell Medical Center. Smoking can cause health problems and is related to many diseases, and these illnesses cause one out of five deaths in the U.S. With these alarming statistics, much research has been done on how to help smokers quit, notably how to help them deal with nicotine — the element that keeps smokers addicted. Notably, researchers at Weill Cornell Medical College have successful developed and tested a new vaccine on mice that blocks chemicals related to addictive nicotine chemicals.The findings, published in a recent edition of the journal Science Translation Medicine, show how a single dose of the vaccine can shield mice against nicotine addiction over a lifetime. The vaccine was designed to utilize the mice´s liver as a factory that could constantly create antibodies that eliminated nicotine once it entered the bloodstream.
“We can target almost any organ [with this type of vaccine], but the reason for using the liver is that it is a very good secretory organ,” lead investigator Dr. Ronald G. Crystal mentioned to FoxNews.com. “The liver is very good at making and secreting many proteins, so we just genetically modified the liver cells to also make antibodies against nicotine.”
As such, nicotine was stopped from reaching the brain or the heart.
"Smoking affects a huge number of people worldwide, and there are many people who would like to quit, but need effective help," commented Crystal, chairman and professor of Genetic Medicine at Weill Cornell Medical College, in a prepared statement. "This novel vaccine may offer a much-needed solution."
Previous studies of nicotine vaccines haven´t been successful as they focused on delivering nicotine antibodies. This effect would only last a few weeks, making it necessary to obtain expensive injections that would be used repeatedly. As well, the dose showed to have inconsistent results, as it was different for each person.
"While we have only tested mice to date, we are very hopeful that this kind of vaccine strategy can finally help the millions of smokers who have tried to stop, exhausting all the methods on the market today, but find their nicotine addiction to be strong enough to overcome these current approaches," explained Crystal in the statement.
Generally, there are two types of vaccine. One vaccine is active and is similar to vaccines that are used to protect people against illnesses such as polio and the mumps. Another vaccine, passive vaccine, introduces a piece of foreign substance to the immune system that can activate a lifetime immune response against the substance. Nicotine, in particular, cannot be built into an active vaccine as it is not identified by the immune system. The team of scientists created a third vaccine, a genetic vaccine that was initially tested in mice to treat particular eye diseases and tumor types. The nicotine vaccine is based off of that model.
The researchers took a genetic sequence of an engineered nicotine antibody and placed it into an adeno-associate virus (AAV). The AAV was engineered not to be harmful and included information that told the vaccine to go to hepatocytes, which are liver cells. Then, the antibody´s genetic sequence inserted itself into the hepatocytes´ nuclear and the cells started to produce a line of antibodies with the other molecules that were created.
"As far as we can see, the best way to treat chronic nicotine addiction from smoking is to have these Pacman-like antibodies on patrol, clearing the blood as needed before nicotine can have any biological effect," commented Crystal in the statement. "Our vaccine allows the body to make its own monoclonal antibodies against nicotine, and in that way, develop a workable immunity.”
In the studies with the mice, the vaccine was able to create high levels of the antibody. The researchers found that the small amount of nicotine they gave to the mice still made it to the brain when there was no vaccine and the mouse acted “chilled out.” When the mouse was given the vaccine, the mice appeared to act actively and didn´t seem to have any negative side effects. The researchers next hope to test the vaccine in rats and primates before humans. If the vaccine is successful, it could be helpful for smokers who are trying to quit the habit.
"They will know if they start smoking again, they will receive no pleasure from it due to the nicotine vaccine, and that can help them kick the habit," noted Crystal in the statement.
Crystal believes that the vaccine could possibly be used to preempt nicotine addiction and give to individuals who have never smoked, similarly to how vaccines are used to help prevent different disease-producing infections.
"Just as parents decide to give their children an HPV vaccine, they might decide to use a nicotine vaccine. But that is only theoretically an option at this point," explained Crystal in the statement. "We would of course have to weight benefit versus risk, and it would take years of studies to establish such a threshold."
Some experts believe that the findings are interesting, but note that there are already medications on the market, such as Chantix, that focus on blocking the effects of nicotine.
"I think smoking is perhaps the most complicated of addictions because there are other aspects to why people have trouble quitting smoking," explained Dr. Michael Fingerhood, medical director of the comprehensive care practice at Johns Hopkins Bayview Medical Center who´s unaffiliated with the study but reviewed it for WebMD. "Is it a good technique, absolutely, but I don't think it's going to be a panacea“¦ It may be another way to help our patients."
However, some experts aren´t sure about the benefits of the findings of the study.
“Nicotine addiction via smoking is harmful, but is it ethical to produce a major and enduring change in someone´s body to prevent it when other, less major, types of treatment are feasible?” questioned Anthony Dayan, a retired toxicologist, in an article by the Daily Mail.