Chimeric Helper-Dependent Adenoviruses Transduce Retinal Ganglion Cells and Müller Cells in Human Retinal Explants

Abstract

Purpose: Despite numerous recent advances in retinal gene therapy using adeno-associated viruses (AAVs) as delivery vectors, there remains a crucial need to identify viral vectors with the ability to transduce specific retinal cell types and that have a larger carrying capacity than AAV. In this study, we evaluate the retinal tropism of 2 chimeric helper-dependent adenoviruses (HDAds), helper-dependent adenovirus serotype 5 (HDAd5)/3 and HDAd5/35, both ex vivo using human retinal explants and in vivo using rats. Methods: We transduced cultured human retinal explants with HDAd5/3 and HDAd5/35 carrying an eGFP vector and evaluated tropism and transduction efficiency using immunohistochemistry. To assess in vivo transduction efficiency, subretinal injections were performed in wild-type Sprague-Dawley rats. For both explants and subretinal injections, we delivered 10 mL (1 • 10 6 vector genomes/mL) and assessed tropism at 7-and 14-days post-transduction, respectively. Results: HDAd5/3 and HDAd5/35 both transduced human retinal ganglion cells (RGCs) and Mu ¨ller cells, but not photoreceptors, in human retinal explants. However, subretinal injections in albino rats resulted in transduction of the retinal pigmented epithelium only, highlighting species-specific differences in retinal tropism and the value of a human explant model when testing vectors for eventual human gene therapy. Conclusions: Chimeric HDAds are promising candidates for the delivery of large genes, multiple genes, or neuroprotective factors to Mu ¨ller cells and RGCs. These vectors may have utility for targeted therapy of neurodegenerative diseases primarily involving retinal ganglion or Mu ¨ller cell types, such as glaucoma or macular telangiectasia type 2.

Retinal Ciliopathies and Potential Gene Therapies: A Focus on Human iPSC-Derived Organoid Models

“…High-capacity adenoviral vectors (HC-AdV), with a packaging capacity of up to 36 kb, have been shown to effectively transduce retina cells ( Figure 2 D) [ 138 , 139 , 140 , 141 ]. Most research has focused on human adenovirus type 5 (HAdV5) and its modified variants, as the various subtypes of HAdV5 exhibit efficient transduction and diverse cellular tropism [ 142 , 143 ]. The 3rd generation of gutless adenoviral vectors are devoid of viral genes and have been demonstrated to elicit a reduced immune response [ 144 ]; however, concerns still persist around potential inflammatory responses following HC-AdV transduction [ 145 , 146 ].…”