Researchers are investigating gene therapy as a way to treat disease at its source by delivering new instructions, or genes, into cells affected by Parkinson’s disease. One approach that has emerged as highly promising over the last decade is to use an adeno-associated virus (AAV) as a vector that is naturally able to transfer genes into cells and not known to cause illness. The vector is like an envelope that carries a message (or in this case, a gene) to specific brain cells. Once the gene has been transferred inside the cell, it is then read by the cell. The brain cells then use their normal machinery to produce the gene product, with the goal of restoring typical function. It is believed that this kind of therapy could potentially be delivered in a single dose and be a long-lasting, or even lifelong treatment. AAV vectors have previously been safely used in clinical trials for investigational gene therapy products.