Subretinal Delivery Of Eiav-based Lentiviral Vectors In The Shaker1 Mouse Model For Usher Syndrometype 1b : Development Of Ushstat®

Abstract

Purpose: : Usher syndrome type 1B is a combined deaf-blindness condition caused by mutations in the MYO7A gene. We have evaluated the impact of subretinally delivered UshStat^®, a recombinant minimal equine infectious anaemia virus- (EIAV) based vector expressing human MYO7A, on photoreceptor function in response to different light intensities in shaker1 mice, a mouse model of Usher type 1 B.

Methods: : The UshStat^® vector was generated in HEK293T cells by transient co-transfection of three plasmids including vector genome, gag/pol and envelope (VSVG) genes. Subretinal injections of EIAV CMV GFP or EIAV CMV MYO7A (UshStat^®) were performed in shaker1 mice. Control eyes were administered with formulation buffer. Photoreceptor function in EIAV CMV MYO7A treated eyes was determined histologically by evaluating alpha-transducin translocation in response to low and high light levels. In addition, the neuroprotection from photoreceptor degeneration in response to chronic light intensity as well as protection from light induced superoxide accumulation were measured. UshStat^® tolerability was also evaluated in the rhesus macaque following subretinal injection.

Results: : Subretinal delivery of EIAV vectors in the mouse lead to gene transfer and expression in photoreceptors and RPE cells. In the shaker1 mouse model, subretinal delivery of the UshStat^® protected photoreceptors from intense light damage as indicated by reduced photoreceptor cell loss, a reduction in DHE staining, and restored threshold for translocation of alpha-transducin in the photoreceptors.

Conclusions: : Subretinal delivery of UshStat^® is able to restore the alpha-transducin translocation phenotype in the shaker1 mouse model and neuroprotect the photoreceptors from high light intensity damage. These data support the development of an EIAV-based gene replacement therapy to treat Usher type 1B syndrome.

Keywords: gene/expression • immunohistochemistry • oxidation/oxidative or free radical damage