Subconjunctival Administration of Adeno-associated Virus Vectors in Small Animal Models

Ocular diseases include a wide range of inherited genetic and acquired disorders that are appealing targets for local drug delivery due to their relative ease of accessibility via multiple administration routes. Subconjunctival (SC) injections offer advantages over other intraocular administration routes as they are simple, safe, require only local anesthesia, and are usually performed in an outpatient setting. Although SC injections in small animals usually require the assistance of an operating microscope due to the size of the eye, they are widely utilized for drug delivery, including gene therapy vectors. Previous work has demonstrated that SC injection of specific adeno-associated virus (AAV) serotypes is a valid gene delivery strategy for targeted transduction of the ocular surface, eye muscle, cornea, and optic nerve, providing a potential approach for the treatment of many ocular diseases. Herein, a detailed protocol is presented for SC injections in a mouse model using an injection system consisting of a programmable infusion/withdrawal syringe pump (which allows for consistent and precise injection speed and pressure) and a gastight removable syringe coupled with microinjection needles. The injection system is also adaptable for other intraocular administration routes such as intrastromal, intracameral, intravitreal, and subretinal injections in small animals. Although the delivery of adeno-associated viral vectors for ocular gene therapy studies is described, the protocol herein can also be adapted for a variety of ophthalmic solutions in small animal models. The key practical steps in the administration route, setup for the injection platform, preparation of the injection, and tips from direct experience will be discussed in detail. In addition, common validation techniques for AAV delivery confirmation to the desired tissues will also be briefly discussed.