Abstract
Pre existing immunity to adeno-associated virus (AAV) poses a concern in AAV vector- mediated gene therapy. Localized administration of low doses of carefully chosen AAV serotypes can mitigate the risk of an immune response. This article will illustrate the low risk of immune response to AAV serotype 2 vector-mediated gene therapy to the brain with support from clinical trial data in aromatic L-amino acid decarboxylase deficiency and Parkinson disease.