Addiction, whether to alcohol, nicotine or illicit drugs, continues to be an intractable personal and societal problem despite tremendous efforts to find viable, effective solutions. Legal, pharmacological and behavioral approaches have had limited success when pitted against the power of dopamine flowing in the brain. For the past decade an innovative cadre of researchers have been pursuing the idea of vaccines to help prevent addiction.
The idea is to create antibodies to the addictive substances so that when they are introduced into the body, the immune system immediately neutralizes them. Dopamine is the brain neurotransmitter that is associated with pleasure sensations. Under normal circumstances only a limited number of brain dopamine receptors are active in response to low levels of the chemical.
However, when alcohol, nicotine or cocaine is used, a steadily increasing dopamine flow can become a torrent which can “turn on” many more receptors and greatly enhance the pleasurable sensation. An individual’s normal dopamine level fluctuates 20% to 30% over the course of a day, but cocaine makes it shoot up 500%. That powerful dopamine receptor surge may be a major factor in driving the individual to repeat and enhance the sensation, regardless of the personal or societal cost.
Trying to control the impulse to pleasure by psychological, or even chemical means would appear to be “swimming upstream” against the most powerful reinforcing sensation that evolution has built into our organism. Triggering such a dopamine flood in response to sex (i.e., reproduction) is part of nature’s design, and even those who have never experienced the effects of cocaine or heroin can understand the lure of the effect. (Click on picture of synapse below to view a video on dopamine and cocaine).
That is why an approach of blocking the effects of dopamine receptor stimulating chemicals has an appeal. Recruiting the body’s immune system as an ally to protect the brain’s delicate neurochemical balance would seem to make sense. One problem has been that chemicals like cocaine are small molecules, which easily elude the immune system’s notice, and which also easily penetrate the brain’s own defensive wall, known as the “blood brain barrier”. Normally the antibodies that protect us from viruses and bacteria would not even be formed in response to the chemicals that can cause addiction. But an effort is currently being put forth to combine those addictive chemicals with larger proteins that do generate an immune response is showing promise. Several years ago a British company, Xenova, developed an anti-cocaine vaccine code-named TA-CD appeared to reduce cocaine addition by 58% during a 12 week study. At 6 months, nearly 42% of the vaccinated participants were reportedly free of drug use.
More recently, Texas researchers at the Baylor College of Medicine developed a vaccine that teaches the immune system to attack cocaine, preventing it from producing a “high”. The vaccine was made by attaching cocaine molecules to the outside of inactivated cholera proteins, to which the body will normally produce a significant immune response. When the immune system attacks the cholera proteins, it also ‘identfies’ the cocaine molecule as an invader as well. The result is that the immune system ‘recognizes’ the addictive drug when it’s taken in to the body. The antibodies bind to the cocaine, making it too large to penetrate the “blood brain barrier” and prevent it from reaching the brain. (Click on picture of antibody below to watch video)
If the technique works as well as preliminary reports suggest, it could usher in a new approach to the problem of addiction, not only for those already compromised by chemical addictions, but also as a prevention measure for teenagers and others at risk, even prior to their exposure to the drugs. The latter suggestion raises a number of legal and ethical questions similar to ones recently faced by states who want to mandate immunization for all young women and girls against human papilloma virus infection with HPV vaccine.
Certainly there is no one “magic bullet” to cure the problem of addiction, but harnessing the body’s natural defense mechanisms certainly has an appeal.