Tyrosine capsid-mutant AAV vectors for gene delivery to the canine retina from a subretinal or intravitreal approach

Abstract

Recombinant adeno-associated viruses are important vectors for retinal gene delivery. Currently utilized vectors have relatively slow onset and for efficient transduction it is necessary to deliver treatment subretinally, with the potential for damage to the retina. Amino-acid substitutions in the viral capsid improve efficiency in rodent eyes by evading host responses. As dogs are important large animal models for human retinitis pigmentosa, we evaluated the speed and efficiency of retinal transduction using capsid-mutant vectors injected both subretinally and intravitreally. We evaluated AAV serotypes 2 and 8 with amino-acid substitutions of surface exposed capsid tyrosine residues. The chicken beta-actin promoter was used to drive green fluorescent protein expression. Twelve normal adult beagles were injected, 4 dogs received intravitreal injections, 8 dogs received subretinal injections. Capsid-mutant viruses tested included AAV2(quad Y-F) (intravitreal and subretinal), and self-complementary scAAV8(Y733F) (subretinal only). Contralateral control eyes received injections of scAAV5 (subretinal) or scAAV2 (intravitreal). Subretinally delivered vectors had a faster expression onset than intravitreally delivered vectors. Subretinally delivered scAAV8(Y733F) had a faster onset of expression than scAAV5. All subretinally injected vector types transduced the outer retina with high efficiency, and the inner retina with moderate efficiency. Intravitreally delivered AAV2(quad Y-F) had a marginally higher efficiency of transduction of both outer retinal and inner retinal cells than scAAV2. Because of their rapid expression onset and efficient transduction, subretinally delivered capsid-mutant AAV8 vectors may increase the efficacy of gene therapy treatment for rapid photoreceptor degenerative diseases. With further refinement, capsid-mutant AAV2 vectors show promise for retinal gene delivery from an intravitreal approach.

Insight into the mechanisms of enhanced retinal transduction by the engineered AAV2 capsid variant ‐7m8

“…One of the benefits of this administration route is the immune privilege in this compartment. AAV2, -5, -7, -8, -9 have been successful in gene transfer to photoreceptors when delivered into the subretinal space (Allocca et al, 2007;Auricchio et al, 2001;Mowat et al, 2014;Natkunarajah et al, 2008). However, retinal detachment can be associated with mechanical damage, especially in the fragile degenerating retina (Jacobson et al, 2012).…”

Retinal gene delivery by adeno-associated virus (AAV) vectors: Strategies and applications

“…However, the special transduction properties of tyrosinemutant AAVs after intravitreal application have to be confirmed in different species. For instance, the transduction efficacy of a quadruple tyrosine-mutant AAV2 vector for photoreceptors after intravitreal injection in the canine retina was only marginally superior to wildtype AAV2 [70].…”

Highly Efficient Delivery of Adeno-Associated Viral Vectors to the Primate Retina

“…50 In macaques, AAV2 transduction is restricted primarily to the inner retina within the foveal ring. 19 Our own experience in this study, using the same vector (AAV2-CBA-GFP) delivered by intravitreal injection, was consistent with that previously seen in macaques.…”