Key word included are: ("Alzheimer's disease" OR dementia) AND ("viral" OR "non-viral vectors" OR "gene therapy" OR "gene transfer" OR "viral vector" OR "AAV" OR "lentivirus" OR "CRISPR") AND ("Neurotrophic factors" OR "NTF" OR "NGF" OR "nerve growth factor" OR "BDNF" OR "brain-derived neurotrophic factor"). The gene discussed is BDNF; the disease is Alzheimer disease.