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Kenton Woodard, Katharine J Liang, Thomas Lentz, William Bennett, Aravind Asokan, Richard Samulski; Transduction of Mouse Retina by Intravitreal Delivery Using Chimeric Capsids with Altered Glycan Interactions. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):252.
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© ARVO (1962-2015); The Authors (2016-present)
Intravitreal (IVit) delivery of recombinant adeno-associated virus (rAAV) has advantages over subretinal delivery, which is the clinic standard. This study sought to correlate capsid-receptor interaction to transduction using a panel of variants with modulated glycan interactions.
Serotypes with altered heparan sulfate (HS) binding were evaluated using the GFP reporter gene. Dual glycan interaction of HS and galactose binding was evaluated using the chimera rAAV2G9. Fundus imaging documented fluorescence onset and pattern. Eight weeks post-injection, histological analyses were conducted to identify cell tropism and retinal transduction. Fluorescence in situ hybridization (FISH) was used to detect viral genome location and immunohistochemistry was used to detect viral transduction.
Mutations in HS binding residues of rAAV2 resulted in a loss of transduction of the inner retina. The addition of HS binding to rAAV1 showed a trend towards increased fluorescence over rAAV1, but tropism was unaltered and similar to published results with rAAV6. rAAV2G9 had similar GFP intensity to rAAV2; however, histology revealed an increase in Muller glia tropism with the chimera. This tropism difference was not due to damage to the retina or reactivation of glial cells. FISH results suggest viral genomes are present in the retina even in the absence of GFP fluorescence.
HS binding is required for IVit transduction of rAAV2, and may enhance the transduction of other serotypes. Galactose binding on rAAV2 alters infectivity towards Muller glia cells through receptor interactions with the capsid. The absence of rAAV9 expression, but the presence of genomes in the retina, indicate additional cellular barriers which restrict expression. The development of rAAV receptor heatmaps of the retina will improve the rational engineering of vectors for targeted, and more efficient, retinal gene transfer.
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