Novel Intravitreal Retina-Targeting and Immune-Evading Adeno-Associated Virus Capsid Variant

Retinal diseases are an important focus of in vivo gene therapy, for which adeno-associated virus is a preferred vector. Intravitreal injection is a highly desirable delivery route because it is much simpler, safer and inexpensive than the main alternative subretinal injection. However, existing capsids have low efficiency, require high doses and are susceptible to neutralization by antibodies that are present in the vitreous. Using AAV5 as starting material, we applied a combination of directed evolution and rational design to develop PT1, a novel AAV capsid capable of efficiently transducing the retina after intravitreal injection. The most striking property of PT1 is its remarkable ability to evade preexisting neutralizing antibodies, thanks to its multiple mutations spread over large areas of the capsid surface, disrupting several epitopes. Our results suggest that PT1 has a strong potential as a useful candidate capsid for human retinal gene therapy.