Abstract
Purpose: :
To compare the efficacy of self-complementary AAV8 capsid mutant (scAAV8-Y733F) and single-stranded AAV8 (ssAAV8) in rescue of visual deficits in a mouse model for Leber’s congenital amaurosis (LCA). Our mouse model for LCA lacks AIPL1 and exhibits severe vision loss accompanied with rapid photoreceptor degeneration.
Methods: :
Human Aipl1 cDNA driven by the short human rhodopsin kinase promoter was packaged into the scAAV8 capsid containing a point mutation in a surface-exposed tyrosine residue (Y733F). A second viral vector with human Aipl1 cDNA driven by the short human rhodopsin kinase promoter was packaged into ssAAV8 capsid. The two viruses were titer matched for injection. For each viral vector, 1 µL of virus was sub-retinally injected into one eye of the Aipl1-/- mouse at postnatal day 2, well before photoreceptor degeneration begins. The contralateral eye was left uninjected to serve as control. Animals underwent visual testing (ERG) at post-injection day 30, followed by morphological analysis to assess photoreceptor rescue.
Results: :
Our findings show that scAAV8-Y733F treated mice had better light induced scotopic and photopic electrical responses in comparison to ssAAV8 treated mice. In agreement with our ERG results, our preliminary morphological analyses of treated retina show areas of rescue, ranging from 3 to 6 photoreceptor layers, with scAAV8-Y733F showing larger areas of rescue with more photoreceptor cells. Further detailed morphological, biochemical and behavioral analysis are underway to decipher the mechanism that contributes to the functional advantage we observe with scAAV8 treatment. We are currently performing a similar comparison after administration of the virus at a later stage of degeneration.
Conclusions: :
Several studies have reported the benefits of self-complementary and capsid mutant Y733F AAV using EGFP reporter gene, as having higher and faster onset of expression. Our initial results show that there are functional benefits to using the scAAV8-Y733F, which has not been previously reported in a head-to-head rescue comparison study. The functional benefits of these viral serotypes will advance gene therapy to potentially treat a wider array of patients exhibiting rapid photoreceptor degeneration.
Keywords: gene transfer/gene therapy • retina • retinal degenerations: hereditary