Abstract
Purpose :
AAV ocular gene therapies can elicit inflammation and an immune response that can be detrimental to the efficacy of treatment. This study tested the hypothesis that modulating the pharmacokinetics of AAV delivery via a degradable hydrogel implant can reduce the risk of developing severe ocular inflammation and improve transgene expression by lowering vector copies and ADA titers in blood.
Methods :
AAV2.7m8-CMV-GFP loaded hydrogel implants at a dose of 3.6E+10 GC/implant were formulated to release AAVs over 4 (Fast Release) or 14 days (Medium Release). A single implant was injected intravitreally in both eyes of New Zealand White rabbits. Bilateral injections of a bolus 50µL AAV solution at the same dose were performed as a positive control. The impact of sustained AAV delivery on inflammation and green fluorescent protein (GFP) expression was investigated through ocular examinations, fundus autofluorescence (FAF) imaging, and enzyme-linked immunoassay (ELISA) quantification in ocular tissues (n=3 rabbits/6 eyes per group). Vector genomes in plasma were quantified by quantitative polymerase chain reaction and ADA titers in serum were determined by ELISA.
Results :
FAF imaging and protein quantification demonstrated greatest GFP expression in the Medium release group compared to the Bolus and Fast release groups (Figure 1). The Medium release group also resulted in lower peak inflammation at Week 3 and lower ADA titer levels at Week 13 compared to the other groups (Figure 2A & 2B). Using a controlled release strategy can also lower systemic levels of AAV as evidenced by lower copy numbers from the AAV implant groups in plasma (Figure 2C).
Conclusions :
In this study, we show that modulating AAV pharmacokinetics from hydrogel implants can impact ocular inflammation, adaptive immune response, and transgene protein expression. These data demonstrate that sustained release of AAVs provides an avenue to improve ocular gene therapies.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.