Scientists have identified gene recombination in neurons that produces thousands of new gene variants within Alzheimer’s disease brains. The study reveals for the first time how the Alzheimer’s-linked gene, APP, is recombined by using the same type of enzyme found in HIV. The findings provide rationale for evaluating HIV antiretroviral therapies in people with Alzheimer’s. It also provides an explanation for why clinical trials for Alzheimer’s have failed to date.