Abstract
Purpose: :
To develop equine infectious anaemia virus (EIAV)-based lentiviral vector gene therapies for the treatment of various retinal disorders. We have previously shown evidence that the EIAV vector is able to penetrate the outer limiting membrane following subretinal delivery and transduce photoreceptors using the constitutive CMV promoter expressing the β-galactosidase reporter gene in rodent and primate eyes. However, for unequivocal demonstration of cone, as well as rod photoreceptor transduction in primates, we have now used an EIAV vector expressing green fluorescent protein (GFP) under the CMV promoter in the rhesus macaque.
Methods: :
Under general anesthesia submacular injections of EIAV CMV GFP were performed in the left eyes of rhesus macaques. A control formulation buffer was administered in the submacular area of the contra-lateral eye. Biomicroscopy and fundus examinations were performed at day 2, 7 and 15 following submacula injections. Eyes were collected, embedded, sectioned for histolology. The sections were examined under fluorescence microscopy following counter nuclear staining with propidium iodide.
Results: :
Slit-lamp biomicroscopy revealed mild transient ocular inflammation in both vector and formulation buffer treated eyes. Fundus examinations showed clearly demarcated areas where the submacular injections were administered. Histological examinations of the retina administered with EIAV CMV GFP revealed marked fluorescence in the RPE cells and outer segments of both cone and rod photoreceptors. There was also some transduction of bipolar, Mueller and ganglion cells located at the center of the subretinal injection site using this promoter construct.
Conclusions: :
Whether lentiviral vectors are able to efficiently transduce photoreceptors following subretinal delivery has recently been an area of great interest. Submacular delivery of an EIAV vector in rhesus macaques leads to predominant expression in RPE and photoreceptor cells. Both rods and cone photoreceptors are transduced by the EIAV CMV GFP vector. Although delivery causes transient mild inflammation, this resolves and does not impact on retinal integrity. These data support the potential development of an EIAV based gene therapy for photoreceptor disorders such as Stargardt’s disease.
Keywords: gene transfer/gene therapy • photoreceptors • retinal pigment epithelium