Vaccines for drug addiction

Scientists are turning to vaccines to combat addiction to drugs and tobacco, and imaging the brain to understand what drives a person to lose their will to say a ‘no’ to these substances.

Lest you think this is a problem of developed countries, think again! National surveys in India, for example, have shown a rising incidence of HIV in injecting drug users (IDUs) in cities such as Chennai, while the epidemic has been driven by IDUs in Thailand. Similarly, China has one of the highest smoking rates in the world.

Nora Volkow, director of National Institute of Drug Abuse at the National Institute of Health, Bethesda, US, who is attending the ESOF 2008 conference in Barcelona, says NIDA is funding phase II trials on vaccines to combat cocaine and nicotine addiction.

NIDA is also conducting animal studies on a vaccine to counter addiction to heroin that is widely used by IDUs in countries with a high incidence of HIV.

Molecules such as cocaine are too small to stimulate formation of antibodies produced by the body’s immune system to fight foreign substances. Researchers therefore tag cocaine to bigger protein molecules -for example, proteins involved in drug transport – to create antibodies.

Animal studies had shown cocaine-induced antibodies interfered with the movement of the drug to the brain, and eliminated the drug’s effect on it.

Volkow and Rafael Maldonado, professor of pharmacology at the University of Pompeu Fabra, Spain, who also researches on addiction, say scientists are also closer to finding the exact mechanism behind drug addiction. “Different drugs enter through different doors, but they finally come to the same place,” she observes.

Scientists are now looking at ways to block the general, non-specific mechanisms leading to addiction, and zero in on the specific molecules that play a role in addiction.

“We have identified some components that represent a specific mechanism for drug addiction and could lead to new drugs to cure addiction,” she says.

An area in the brain called the cortex, which plays a key role in memory, attention, self-awareness, consciousness, thought and language, is involved in the addiction process. A specific front area in the cortex normally regulates an area in the brain that is involved in the sensation of pleasure.

Disruption of this area in the cortex makes a person lose his or her ability to exert one’s will and resist drugs.

“We often hear of addicts saying they are not even aware they had taken a drug and were not in control of their actions,” points out Volkow.

The ongoing vaccine studies and advances in brain imaging could help throw some solutions to a problem that has a social and economic dimension, says Maldonado.

T V Padma, South Asia coordinator, SciDev.Net

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