The goal of antiaddiction vaccines is to prevent addictive molecules from reaching the brain, where they produce their effects and can create chemical dependencies. Vaccines can accomplish this task, in theory, by generating antibodies—proteins produced by the immune system—that bind to addictive particles and essentially stop them in their tracks. But challenges remain.
Among them, addictive molecules are often too small to be spotted by the human immune system. Thus, they can circulate in the body undetected. Researchers have developed two basic strategies for overcoming this problem. One invokes so-called active immunity by tethering an addictive molecule to a larger molecule, such as the proteins that encase a common cold virus. This viral shell does not make people sick but does prompt the immune system to produce high levels of antibodies against it and whatever is attached to it. In our laboratory, we have tested this method in animal models and successfully blocked chemical forms of cocaine or nicotine from reaching the brain.
Another approach researchers are testing generates what is known as passive immunity against addictive molecules in the body. They have cultured monoclonal antibodies that can bind selectively to addictive molecules. The hurdle with this particular method is that monoclonal antibodies are expensive to produce and need to be administrated frequently to be effective.
We have tried to circumvent these issues by genetically modifying the liver of mice to produce and secrete sufficient quantities of antiaddictive monoclonal antibodies, but that work is still in its early stages. If successful, though, addiction vaccines would be a valuable aid to help addicts quit.
Question submitted by Lynne Bennetech, via e-mail
Do you have a question about the brain you would like an expert to answer? Send it to MindEditors@sciam.com