N E W Y O R K, Aug. 7 "?Forget the patch, the nicotine chewing gum and the cold turkey approaches to quitting smoking.
　　A shot in the arm might someday be able to stop the craving for cigarettes experienced by 60 million Americans each year.
　　Scientists at the “Tobacco Or Health"?conference, going on in Chicago this week, are reporting their results with a vaccine against tobacco that aims to reduce the amount of nicotine that gets to the brain in the hope of making it less addictive.
　　Dr. Paul Pentel, an investigator at the Hennepin County Medical Center in Minneapolis; David Malin, Ph.D., a professor of psychology and neuroscience with the University of Houston-Clear Lake; researchers at the National Institute of Drug Abuse; and Nabi, Inc., a biotechnology company in Boca Raton, Fla., are collaborating in the development of this new vaccine, called NicVAX.

Stimulates the Immune System
　　The vaccine works by stimulating the body’s own immune system, the researchers say. Although nicotine itself is too small a chemical to produce an antibody response, when it is joined to another substance the two create a molecule-a vaccine "?that induces antibodies to nicotine alone. When the antibodies and nicotine bind in the bloodstream, the new molecule is too large to enter the brain, where the addictive effects of nicotine occur.
　　The vaccine, which currently is being tested in rats, might be able to prevent people from getting hooked on cigarettes and could help people get off the cycle of dependence on nicotine, the scientists say. Clinical trials in humans may begin as early as next year.

Possible Preventive and Treatment
　　The vaccine has been able to prevent the actions of nicotine in the rats, explains Malin. It reduces nicotine’s effect on blood pressure, it limits the withdrawal effects the rats experience, it reduces their activity level and it stops the rats from selecting nicotine when given a choice.
　　Given intravenously to the rats, the dose of nicotine is analogous to what humans consume. The vaccine has been able to reduce from one-third to two-thirds the amount of free nicotine in the bloodstream, Pentel says.
　　"The goal is to bind up nicotine,"?Pentel explains. “Much of it depends on how much antibody is present, how well-immunized the animal is and how much nicotine is given."?/p>

Humans Different than Rats
　　But smoking in humans is more complex than it is in rats. Smokers who might be treated with the vaccine could conceivably smoke more to compensate for the effects of the vaccine. “The amount of nicotine intercepted needs to be high enough so that even if someone were to smoke more cigarettes the effects of nicotine would not be felt,"?Malin says.
　　Pentel says the vaccine probably wouldn’t reduce the craving that someone has after nicotine has left their body, which is why it would be only one part of a program to treat nicotine addiction.
　　 A nicotine vaccine could have a huge market as only 3 percent of smokers in the United States quit each year. “After all, 435,000 people die prematurely every year because of their nicotine addiction,"?says Dr. Alan I. Leshner, the director NIDA, which is supporting the vaccine development.
　　Other companies, including Cantab, in England, are developing similar tobacco vaccines. Vaccines against cocaine also are in development.

　　(From ABCNEWS.com)