Gene Therapy For Gucy2d Leber Congenital Amaurosis (LCA1)

Abstract

 

Purpose:

 

We have previously shown that subretinal injection of serotype 5 Adeno-associated viral (AAV) vectors containing the murine GC1 cDNA driven by either the photoreceptor-specific human rhodopsin kinase (hGRK1) or the ubiquitous (smCBA) promoter were capable of restoring cone-mediated function and visual behavior and preserving cone photoreceptors in the GC1KO mouse for at least three months. In the present series of experiments, we evaluated whether long term therapy was achievable in this mouse model. Additionally, we examined whether delivery of GC1 to photoreceptors of the GC1/GC2 double knockout mouse (GCdko), a model which exhibits loss of both rod and cone structure and function and phenotypically resembles human LCA1, would confer therapy to these cells.

 

Methods:

 

Subretinal injections of AAV5-hGRK1-mGC1, AAV5-smCBA-mGC1 or the highly efficient capsid tyrosine mutant AAV8(Y733F)-hGRK1-mGC1 were performed in one eye of GC1KO or GCdko mice between postnatal day 14 (P14) and P25. Rod and cone photoreceptor function were assayed electroretinographically. Localization of therapeutic GC1 expression and extent of cone photoreceptor preservation were determined by immunohistochemistry. Biodistribution studies were used to evaluate the presence of vector genomes in optic nerves and brains of treated animals.

 

Results:

 

Cone photoreceptor function was restored in GC1KO mice treated with all vectors, with AAV8(733) being the most efficient. Responses were stable for at least 10 months post-treatment. Therapeutic GC1 was found in photoreceptor outer segments. By 10 months post-injection, AAV5 and AAV8(733) vector genomes were detected only in the optic nerves of treated eyes of GC1KO mice. AAV8(733)-vectored mGC1 restored function to both rods and cones in treated GCdko mice.

 

Conclusions:

 

We demonstrate for the first time that long-term therapy is achievable in a mammalian model of GC1 deficiency, the GC1KO mouse. Importantly, therapy is also achievable in the GCdko mouse which mimics the LCA1 rod/cone phenotype. Our results provide proof-of-principle information for the development of an AAV-based gene therapy vector for treatment of LCA1.

 

Keywords: gene transfer/gene therapy • retinal degenerations: hereditary • photoreceptors