Ocular Tolerability and Immune Response to Corneal Intrastromal AAV-IDUA Gene Therapy in New Zealand White Rabbits

Abstract

The chronic ocular toxicity, tolerability, and inflammation following corneal intrastromal injection of saline or escalating doses of an adeno-associated virus (AAV) containing a codonoptimized a-L-iduronidase (AAV-opt-IDUA) expression cassette were evaluated in New Zealand White rabbits. Corneal opacity following corneal intrastromal injection resolved by 24 h. Mild elevation of clinical ocular inflammation was observed 24 h after injection, but it returned to baseline by day 7 and no abnormalities were noted through 6 months of observation after injection. Vector genomes and IDUA cDNA were detected in the injected corneas in a dose-dependent manner. Both the lowest administered AAV-opt-IDUA dose, shown to be effective in mucopolysaccharidosis type I (MPS I) dogs, and a 10fold higher dose of AAV-opt-IDUA resulted in no detectable immunologic response or adverse effect in rabbits. Vector genomes outside of the eye were rarely detected following corneal intrastromal injection of AAV-opt-IDUA, and neutralizing antibodies to the AAV capsid were not present at the experimental conclusion. This study, combined with our previous studies in MPS I dogs, suggests that AAV-opt-IDUA corneal gene therapy following corneal intrastromal injection of AAV-opt-IDUA has the potential to prevent and reverse blindness in MPS I patients in a safe and effective manner.

Adeno-Associated Virus Mediated Gene Therapy for Corneal Diseases

“…Additionally, alkaline gel electrophoresis of packaged genomes informs of packaged genome integrity and the overall titer. Once the purified virions were obtained, studies were conducted to show rAAV8G9-opt-IDUA viral transduction in ex vivo human keratocytes [ 45 ], and relevant animal cornea models such as rabbits [ 55 ] and MPS I canines [ 49 ]. It is important to note that rAAV viral transduction is a multi-step process, which include viral binding to the cell surface, viral entry, endosomal trafficking, endosomal escape, nuclear import, uncoating, and second strand synthesis (reviewed in [ 49 , 56 , 57 ]).…”

“…Corneal transplantation may be beneficial for some patients with significant corneal opacity [ 120 ]. Additionally, AAV8G9-opt-IDUA (AAV8 and 9 chimeric capsid-optimized- IDUA ) gene therapy shows great promise to prevent and potentially reverse MPS I-associated corneal blindness [ 45 , 49 , 55 ]. Likewise, adenoviral-mediated expression of β-glucuronidase (GUSB) transgene in the stromal region has been shown to reduce corneal clouding in MPS VII mouse models, and similar results were reported in canine MPS VII models following adenovirus-mediated transgene expression of human GUSB [ 110 , 111 ].…”

“…This local AAV vector administration to the cornea likely can complement the defects in treating MPS diseases by bone marrow transplantation and perhaps be used in conjunction with an AAV vector approach to treat other disease symptoms (either local or systemic) [ 114 , 119 ]. Of particular note is that redosing of AAV vectors has been observed in mice and administration of AAV vectors to the rabbit cornea resulted in minimal to no serum capsid neutralizing antibodies [ 46 , 55 ]. These combined results suggest that AAV vector treatment of lysosomal storage diseases can be used in combination with AAV vectors to treat other disease aspects outside the cornea.…”

“…Compartmentalization of the eye in general and the use of a restricted intrastromal delivery route allows for low therapeutic AAV vector doses and minimal to no peripheral organ (or systemic) vector genome distribution. For instance, AAV vectors were not found outside the ocular compartment following intrastromal injection of AAV-opt-IDUA in a WT rabbit model [ 55 ]. Additionally, even at a relatively high vector dose, WT rabbits administered rAAV completely tolerated the production of a human protein in the corneal stroma with no signs of adverse reactions attributed to a deleterious innate immune response [ 55 ].…”

“…For instance, AAV vectors were not found outside the ocular compartment following intrastromal injection of AAV-opt-IDUA in a WT rabbit model [ 55 ]. Additionally, even at a relatively high vector dose, WT rabbits administered rAAV completely tolerated the production of a human protein in the corneal stroma with no signs of adverse reactions attributed to a deleterious innate immune response [ 55 ]. In the same context, 6 months post-injection to the corneal stroma, only a single animal demonstrated a weak capsid neutralizing serum antibody response, with no neutralizing antibodies found in the aqueous or vitreous humor [ 55 ].…”