Inner Limiting Membrane Barriers to AAV-mediated Retinal Transduction From the Vitreous

Department of Chemical Engineering, The University of California at Berkeley, Berkeley, California 94720-3190, USA.
Molecular Therapy (Impact Factor: 6.23). 09/2009; 17(12):2096-102. DOI: 10.1038/mt.2009.181
Source: PubMed


Adeno-associated viral gene therapy has shown great promise in treating retinal disorders, with three promising clinical trials in progress. Numerous adeno-associated virus (AAV) serotypes can infect various cells of the retina when administered subretinally, but the retinal detachment accompanying this injection induces changes that negatively impact the microenvironment and survival of retinal neurons. Intravitreal administration could circumvent this problem, but only AAV2 can infect retinal cells from the vitreous, and transduction is limited to the inner retina. We therefore sought to investigate and reduce barriers to transduction from the vitreous. We fluorescently labeled several AAV serotype capsids and followed their retinal distribution after intravitreal injection. AAV2, 8, and 9 accumulate at the vitreoretinal junction. AAV1 and 5 show no accumulation, indicating a lack of appropriate receptors at the inner limiting membrane (ILM). Importantly, mild digestion of the ILM with a nonspecific protease enabled substantially enhanced transduction of multiple retinal cell types from the vitreous, with AAV5 mediating particularly remarkable expression in all retinal layers. This protease treatment has no effect on retinal function as shown by electroretinogram (ERG) and visual cortex cell population responses. These findings may help avoid limitations, risks, and damage associated with subretinal injections currently necessary for clinical gene therapy.

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Available from: David Vernon Schaffer, Jul 27, 2015
    • "In addition to the above indicated barriers, for the treatment of pathologies associated with the back of the eye, drugs have to diffuse through the vitreous humor, a highly dense matrix formed by collagen fibrils and glycosaminoglycans [11]. Alternatively, drugs applied onto the eye can use the trans-scleral pathway, reach the choroids and then surpass the blood–retinal barrier [12]. "
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    • "Interestingly, degenerative processes and thereby changes in the general retinal architecture and especially in the ILM can facilitate the transduction of photoreceptors and RPE after intravitreal AAV application484950. An enzymatic digestion of the ILM and local laser-induced photocoagulation both result in an enhanced capability to transduce the outer retina after intravitreal injections of different AAV serotypes [51,52]. The discussed cell tropisms of the various serotypes are mainly influenced by the capsids affinity to different cell surface receptors. "
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    • "Cite this article as Cold Spring Harb Perspect Med doi: 10.1101/cshperspect.a017418 curring adeno-associated virus serotypes do not penetrate to the outer retina effectively when injected into the vitreous (Dalkara et al. 2009). "
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