Abstract
Purpose: :
Adeno-associated viral (AAV) vectors are the delivery system of choice for retinal gene therapy. They are effective in a variety of species including rodents, dogs and primates. The cellular tropism and speed and strength of transgene expression of AAV vector systems can be varied by utilizing different capsid serotypes. Recently the gene mutations underlying two Leber congenital amaurosis (LCA) cat models have been identified. One is due to a mutation in the CEP290 gene and the other a mutation in CRX. These mutant cats are ideal large animal models for preclinical gene therapy studies for these forms of LCA in humans. The aim of this study was to investigate the speed of transgene expression and cellular tropism of two commonly used AAV serotypes (AAV2/5 and AAV2/8) in the cat.
Methods: :
AAV2/5 and AAV2/8 vectors expressing green fluorescent protein (GFP) under control of the CMV promoter were prepared and diluted to 5 x 1011 vg/ml. Four wild-type young adult cats were used. Following 3-port pars plana vitrectomy the right eye was injected subretinally with 200µl AAV2/5 and the left eye with 200µl of AAV2/8. Ophthalmic examination and color and fluorescent fundus photography were performed regularly. Following euthanasia eyes were fixed in paraformaldehyde and processed for cryosectioning and immunohistochemistry.
Results: :
GFP expression was detected in the AAV2/8 injected eyes 2 days following treatment. Fluorescence in the AAV2/5 injected eyes developed more slowly and was not as strong as that in the AAV2/8 injected eyes. The outer retina was transduced in the injected areas by both serotypes.
Conclusions: :
AAV2/5 and AAV2/8 vectors are efficient at transducing the feline outer retina with a similar tropism to that described in other species. AAV2/8 resulted in faster and stronger transgene expression than a similar titer and dose of AAV2/5. These results show that AAV vectors can be utilized in the cat for outer retinal gene therapy.
Keywords: gene transfer/gene therapy • genetics • immunohistochemistry