Designed as a therapeutic option for those trying to break their addiction, the vaccine produces antibodies that stop heroin as well as other psychoactive compounds metabolized from heroin from reaching the brain to produce euphoric effects.

Previous efforts to create a clinically viable heroin vaccine have struggled because heroin is metabolized into multiple substances that each produce psychoactive effects. To overcome this problem the researchers, led by the study's principal investigator, Kim D. Janda, targeted not just the heroin itself, but also the chemical it quickly degrades into, 6-acetylmorphine (6AM), and morphine.

They linked a heroin-like hapten (a small molecule that elicits an immune response only when attached to a large carrier) to a generic carrier protein called keyhole limpet hemocyanin (KLH), and mixed it with Alum, a vaccine additive, to create a vaccine "cocktail." This mixture slowly degraded in the body, exposing the immune system to different psychoactive metabolites of heroin such as 6AM and morphine.

"Critically, the vaccine produces antibodies to a constantly changing drug target," said G. Neil Stowe, who is first author of the new study. "Such an approach has never before been engaged with drug-of-abuse vaccines."

Testing the vaccine on rats provided promising results. After several booster shots of the vaccine, heroin addicted rates were found to be less likely to self-administer heroin by pressing on a lever. Only three of the seven rats that received the vaccine self-administered heroin compared to all of the control rats, including those that had been given a vaccine that only targeted morphine.

The team also found that the heroin vaccine was highly specific, only producing an antibody response to heroin and 6AM and not to other opioid-related drugs tested, such as oxycodone, and drugs used to treat opioid dependence, such as methadone, naltrexone, and naloxone.

"The importance of this is that it indicates these vaccines could be used in combination with other heroin rehabilitation therapies," said Janda.

"In my 25 years of making drug-of-abuse vaccines, I haven't seen such a strong immune response as I have with what we term a dynamic anti-heroin vaccine," Janda added. "It is just extremely effective. The hope is that such a protective vaccine will be an effective therapeutic option for those trying to break their addiction to heroin."

The Scripps Research team has also recently begun collaborating with researchers at Walter Reed Army Institute of Research to see if it is feasible to develop a dual-purpose vaccine against HIV and for the treatment of heroin addiction in a single shot.

Source: GizMag