Abstract
Purpose :
Mutations in the cyclic nucleotide-gated channel beta 1 subunit (CNGB1) gene are known to cause retinitis pigmentosa type 45 (RP45) – an incurable blinding disease. Here, a novel recombinant adeno-associated virus vector for gene supplementation therapy of CNGB1-linked RP was developed and tested for efficacy in the preclinical Cngb1 knockout (KO) mouse model of RP45.
Methods :
A recombinant AAV vector optimized for efficient expression of full-length human CNGB1 under control of a short human rhodopsin promoter was designed and used for packaging of AAV5-pseudotyped vectors (rAAV.CNGB1). rAAV.CNGB1 was tested for efficacy after subretinal delivery in 4 week old as well as 3 and 6 month old Cngb1 KO mice representing early and advanced disease stages with short-term, mid-term, and long-term follow-up analysis at 2, 4, and 8 months. Expression of human CNGB1 protein was evaluated by immunohistochemistry using a CNGB1-specific antibody. Efficacy was assessed in vivo by electroretinography (ERG) at rod and cone specific light stimuli and by measuring morphological preservation using optical coherence tomography (OCT).
Results :
We designed and generated rAAV.CNGB1, a novel AAV vector optimized for efficient CNGB1 gene expression in human rod photoreceptors. The transgene expression assay of rAAV.CNGB1 confirmed efficient and specific human CNGB1 protein expression in rod photoreceptors at 2, 4, and 8 months post treatment. Moreover, ERG demonstrated a significant beneficial effect of the treatment at rod specific as well as at cone specific light stimuli after 2, 4, and 8 months in mice injected at early and at advanced disease stages. Furthermore, up to 8 months after treatment, we found a significant preservation of rod outer segment structure and prolonged survival of cone photoreceptors which normally degenerate secondarily to rods in a non-cell autonomous fashion.
Conclusions :
The novel rAAV.CNGB1 vector supports efficient and specific transgene expression and biological activity as well as preservation of retinal function and morphology in the preclinical Cngb1 KO mouse model of RP45 at early, mid, and late stage of the disease.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.