Inhibition of experimental autoimmune uveitis by intravitreal AAV-Equine-IL10 gene therapy

Abstract

Equine recurrent uveitis (ERU) is a spontaneous, painful, and vision threatening disease affecting up to 25% of equine populations worldwide. Current treatments of ERU are non-specific and have many side effects which limits them to short-term use. In order to develop an effective therapy for ERU, we investigated the use of adeno-associated virus (AAV) gene therapy, exploiting a natural immune tolerance mechanism induced by equine interleukin-10 (Equine-IL10). The purpose of this study was to evaluate the therapeutic efficacy of a single intravitreal (IVT) dose of AAV8-Equine-IL10 gene therapy for inhibition of experimental autoimmune uveitis (EAU) in rats. Each rat was dosed intravitreally (IVT) in both eyes with either balanced salt solution (BSS) (control; n = 4), AAV8-Equine-IL10 at a low dose (2.4x109 vg; n = 5) or high dose (2.4x1010 vg; n = 5). EAU was induced in all groups of rats 7 days after IVT injections and euthanized 21 days post-injection. Ophthalmic examination and aqueous humor (AH) cell counts were recorded with the observer blinded to the treatment groups. Histopathology and qPCR were performed on selected ocular tissues. Data presented herein demonstrate that AAV8-Equine-IL10 treated rats exhibited a significant decrease in clinical inflammatory scores and AH cell counts compared to BSS-treated EAU eyes on days 10, 12 and 14 post EAU induction at both administered vector doses. Mean cellular histologic infiltrative scores were also significantly less in AAV8-Equine-IL10 dosed rats compared to the BSS group. Intravitreal injection of AAV8-Equine-IL10 resulted in Equine-IL10 cDNA expression in the ciliary body, retina, cornea, and optic nerve in a dose-dependent manner. A single IVT injection of AAV8-Equine-IL10 appeared to be well-tolerated and inhibited EAU even at the lowest administered dose. These results demonstrate safety and efficacy of AAV8-Equine-IL10 to prevent EAU and support continued exploration of AAV gene therapy for the treatment of equine and perhaps human recurrent uveitis.

Developing advanced therapeutics through the study of naturally occurring immune-mediated ocular disease in domestic animals

“…Recently, AAV-equine (eq)IL-10 was demonstrated to be safe and effective in inhibiting uveitis in a well-established model of NIU-the experimental autoimmune uveitis (EAU) rat model. 49,50 In these experiments, it was shown that both low and high doses of AAV-eqIL-10 suppressed the development of ocular inflammation significantly in rats with EAU. In addition, AAV-eqIL-10 treatment led to the reduction of aqueous humor inflammatory cell counts and histopathologic scores.…”

“…[6][7][8][9] Gene transfer of therapeutic proteins to treat naturally occurring ocular diseases is becoming more feasible based on the results of research studies in models of uveitis and other ocular diseases. 41,50,54,55 These efficacy and safety studies are paving the way for clinical trials in animals with naturally occurring immune-mediated diseases, such as a therapeutic clinical trial for AAV-eqIL-10 in horses with ERU. This AAV-IL-10 clinical trial will be the first trial of AAV gene therapy for the treatment of uveitis in any species.…”

“…Vector-derived eqIL-10 cDNA was detected in relevant ocular tissues, such as the iris/ciliary body and retina. 49 Further studies are being planned to ensure safety and tolerability in horses. With regulatory approval, a clinical efficacy trial may then be conducted in horses.…”

How study of naturally occurring ocular disease in animals improves ocular health globally

“…of naturally occurring uveitis. 48,49 These studies are reviewed in more detail in the companion Currents in One Health by Gilger, AJVR, December 2022.…”

“…Immunosuppressive gene therapies are in the preclinical evaluation stages and, if determined safe, may be effective therapies for uveitis in both horses and humans. 48 If approved by the USDA, a clinical trial in horses of the use of an AAV delivering equine IL-10 will be the first of its kind in any animal for the long-term treatment in the evaluation and prevention of posterior capsular opacity (PCO), a condition that results in development of opacity in the eye and decreased vision from lens epithelial regrowth and/or posterior lens capsule fibrosis after cataract surgery. 64 Dogs develop a rapid and severe PCO after canine cataract surgery.…”