Comprehensive AAV capsid fitness landscape reveals a viral gene and enables machine-guided design

The fitness landscape of AAV Adeno-associated virus (AAV) is an important gene therapy vector. Using tools from synthetic biology, Ogden et al. provide a comprehensive view of how sequence changes in capsid proteins affect AAV properties. After saturation mutagenesis of the AAV2 capsid gene, the resulting library was subjected to multiplexed phenotypic analyses, including virus production, immunity, thermostability, and biodistribution. The mutant distribution to major organs in mice revealed dominant trends affecting in vivo delivery. Moreover, the findings uncovered a viral accessory protein with a role in viral production. Finally, a model built from the capsid fitness landscape enabled machine-guided design of useful variants with much higher efficiency than random mutagenesis. Science , this issue p. 1139