Tolerability and tropism of recombinant adeno-associated virus vectors in the African green monkey (Chlorocebus sabaeus) anterior chamber.

While many studies have investigated the use of recombinant adeno-associated vectors (rAAV) in the posterior chamber for treatment of inherited retinal diseases, fewer studies have looked at rAAV's ability to transduce cells within the anterior chamber. This study focuses on evaluating the tropism and tolerability of three rAAV serotypes-rAAV2/6, rAAV2/9, and rAAV2/2[MAX]-expressing a green fluorescent protein (GFP) reporter following intracameral injection in the non-human primate (NHP) African green monkey (Chlorocebus sabaeus) model. Injection of high dose (1 × 1012 vg/eye) rAAV vector resulted in transient inflammation characterized by aqueous flare and cellular infiltrate that resolved without intervention in all serotypes. Post-mortem histology revealed widespread expression of GFP in cells of the trabecular meshwork and iris in high dose rAAV2/6, rAAV2/9, and particularly rAAV2/2[MAX] eyes, indicating that rAAV vectors of these serotypes have broad tropism for cells of the anterior chamber and may facilitate the treatment of blinding disorders, such as glaucoma.

Matrix metalloproteinase-3 (MMP-3)-mediated gene therapy for glaucoma.

Approximately 80 million people globally are affected by glaucoma, with a projected increase to over 110 million by 2040. Substantial issues surrounding patient compliance remain with topical eye drops, and up to 10% of patients become treatment resistant, putting them at risk of permanent vision loss. The major risk factor for glaucoma is elevated intraocular pressure, which is regulated by the balance between the secretion of aqueous humor and the resistance to its flow across the conventional outflow pathway. Here, we show that adeno-associated virus 9 (AAV9)-mediated expression of matrix metalloproteinase-3 (MMP-3) can increase outflow in two murine models of glaucoma and in nonhuman primates. We show that long-term AAV9 transduction of the corneal endothelium in the nonhuman primate is safe and well tolerated. Last, MMP-3 increases outflow in donor human eyes. Collectively, our data suggest that glaucoma can be readily treated with gene therapy-based methods, paving the way for deployment in clinical trials.

Evaluation of the Dose-Dependent Inflammatory Response and No-Observable Adverse Effect Level of Intravitreal Endotoxin in the African Green Monkey.

Purpose: To evaluate the inflammatory effects and no-observed adverse effect level (NOAEL) of intravitreal endotoxin in an African green monkey model of uveitis. Methods: Fifteen green monkeys were administered intravitreal endotoxin ranging from 0.005 to 0.08 endotoxin unit (EU)/eye. Inflammation was evaluated by slit-lamp biomicroscopy, indirect fundoscopy, tonometry, color fundus photography, ocular coherence tomography, laser flare photometry, and histopathology, with analysis of cytokine levels in aqueous and vitreous humor. The inter-rater reliability of a refined nonhuman primate ophthalmic scoring system was evaluated. Results: A dose-dependent inflammatory response was observed beginning at 0.02 EU/eye; no inflammatory response exceeding the vehicle was observed at 0.005 EU/eye. Retinal pathology was minimal, and posterior visualization degraded with increasing inflammation. Inflammation was observed by histopathology at 0.04 EU/eye. Inter-rater reliability of the scoring system was high, with 99.2% of individual scores differing by 1 scale unit or less and 87.2% of summary scores differing by 2 scale units or less. Conclusions: The NOAEL for intravitreal endotoxin in the green monkey is 0.005 EU/eye, with inflammation increasing with increasing dose beginning at 0.02 EU/eye. This updated nonhuman primate ophthalmic scoring system allows for high inter-rater reliability for the quantification of mild to severe inflammation in the green monkey eye. Translational Relevance: Validation of the ophthalmic inflammation scoring system enables application of the green monkey as a valuable translational model. Candidate therapeutics should be confirmed to have endotoxin levels below this threshold before safety testing in this species to enable interpretation of inflammation and minimize impact on animal welfare.