Age-related macular degeneration (AMD) is the leading cause of blindness after age 55 in the industrialized world. Severe loss of central vision frequently occurs with the exudative (wet) form of AMD, as a result of the formation of a pathological choroidal neovasculature (CNV) that damages the macular region of the retina. We tested the effect of an immunotherapy procedure, which had been shown to destroy the pathological neovasculature in solid tumors, on the formation of laser-induced CNV in a mouse model simulating exudative AMD in humans. The procedure involves administering an Icon molecule that binds with high affinity and specificity to tissue factor (TF), resulting in the activation of a potent cytolytic immune response against cells expressing TF. The Icon binds selectively to TF on the vascular endothelium of a CNV in the mouse and pig models and also on the CNV of patients with exudative AMD. Here we show that the Icon dramatically reduces the frequency of CNV formation in the mouse model. After laser treatment to induce CNV formation, the mice were injected either with an adenoviral vector encoding the Icon, resulting in synthesis of the Icon by vector-infected mouse cells, or with the Icon protein. The route of injection was i.v. or intraocular. The efficacy of the Icon in preventing formation of laser-induced CNV depends on binding selectively to the CNV. Because the Icon binds selectively to the CNV in exudative AMD as well as to laser-induced CNV, the Icon might also be efficacious for treating patients with exudative AMD.

Purpose: We characterize the progression of retinopathy in Filial 1 (F1) progeny of a transgenic (Tg) founder miniswine exhibiting severe Pro23His (P23H) retinopathy. Methods: The F1 TgP23H miniswine progeny were created by crossing TgP23H founder miniswine 53-1 with wild type (WT) inbred miniature swine. Scotopic (rod-driven) and photopic (cone-driven) retinal functions were evaluated in F1 TgP23H and WT littermates using full field electroretinograms (ffERGs) at 1, 2, 3, 6, 9, 12, and 18 months of age, as well as the Tg founder miniswine at 6 years of age. Miniswine were euthanized and their retinas processed for morphologic evaluation at the light and electron microscopic level. Retinal morphology of a 36-month-old Tg miniswine also was examined. Results: Wild type littermates reached mature scotopic and photopic retinal function by 3 months, while TgP23H miniswine showed abnormal scotopic ffERGs at the earliest time point, 1 month, and depressed photopic ffERGs after 2 months. Rod and cone photoreceptors (PR) exhibited morphologic abnormalities and dropout from the outer nuclear layer at 1 month, with only a monolayer of cone PR somata remaining after 2 months. The retinas showed progressive neural remodeling of the outer retina that included dendritic retraction of rod bipolar cells and glial seal formation by Müller cells. The TgP23H founder miniswine showed cone PR with relatively intact morphology exclusive to the area centralis. Conclusions: The F1 Tg miniswine and the TgP23H founder miniswine exhibit similar retinopathy. Translational Relevance: TgP23H miniswine are a useful large-eye model to study pathogenesis and preservation cone PRs in humans with retinitis pigmentosa.

Purpose: To evaluate different methods of studying cone photoreceptor structure in wild-type (WT) and transgenic pigs carrying the human rhodopsin P23H mutant gene (TgP23H). Methods: For in vivo imaging, pigs were anesthetized with tiletamine-zolazepam and isoflurane and given lidocaine-bupivacaine retrobulbar injections. Stay sutures and a custom head mount were used to hold and steer the head for adaptive optics scanning light ophthalmoscopy (AOSLO). Six WT and TgP23H littermates were imaged at postnatal day 30 (P30), P90, and P180 with AOSLO and optical coherence tomography (OCT), and two additional sets of littermates were imaged at P3 and P15 with OCT only. AOSLO imaging and correlative differential interference contrast microscopy were performed on a P240 WT pig and on WT and TgP23H littermates at P30 and P180. Results: AOSLO cone density generally underestimates histology density (mean difference ± SD = 24.8% ± 21.4%). The intensity of the outer retinal hyperreflective OCT band attributed to photoreceptors is attenuated in TgP23H pigs at all ages. In contrast, AOSLO images show cones that retain inner and outer segments through P180. At retinal locations outside the visual streak, TgP23H pigs show a heterogeneous degenerating cone mosaic by using two criteria: variable contrast on a split detector AOSLO and high reflectivity on a confocal AOSLO. Conclusions: AOSLO reveals that the cone mosaic is similar to ex vivo histology. Its use as a noninvasive tool will enable observation of morphologic changes that arise in the cone mosaic of TgP23H pigs over time. Translational Relevance: Pigs are widely used for translational studies, and the ability to noninvasively assess cellular changes in the cone mosaic will facilitate more detailed investigations of new retinal disease models as well as outcomes of potential therapies.

Purpose.: Intracameral (anterior chamber) injection of antigen inhibits the development of delayed-type hypersensitivity, a phenomenon known as anterior chamber-associated immune deviation (ACAID). The authors investigated the effect of intracameral injection of interphotoreceptor retinoid-binding protein (IRPB) peptides on the development of IFN-γ⁺ and IL-17⁺ pathogenic T cells. Methods.: A uveitogenic (IRBP1–20) or nonuveitogenic (IRBP161–180) peptide was injected into the anterior chamber (AC) of B6 mice. Seven days later, the mice were primed with a pathogenic dose of IRBP1–20 in adjuvant. Thirteen days later, the pathogenic activity of the T cells isolated from the spleens of treated and untreated mice were compared, and the numbers of Th1 and Th17 T cells were assessed by intracellular staining. Regulatory T-cell activity was assessed by antibody staining and functional assays. The authors also compared the effect of inhibition on EAU of ocular injection to various sites, including the AC, the vitreous cavity, and the subretinal space. Results.: Intraocular injection of the uveitogenic peptide (IRBP1–20), but not the nonuveitogenic peptide (IRBP161–180), inhibited the generation of IFN-γ⁺ and IL-17⁺ uveitogenic T cells and the development of experimental autoimmune uveitis (EAU). AC administration of IRBP1–20, but not IRBP161–180, significantly decreased the number of circulating γδ T cells after subsequent systemic immunization with IRBP1–20. Absence of the γδ T-cell population prohibited the development of ACAID. Conclusions.: Injection of a uveitogenic peptide into the AC inhibited the development of EAU by regulation of Th1 and Th17 IRBP-specific T cells. The circulating γδ T-cell population was reduced and was associated with decreased activation of IL-17⁺ uveitogenic T cells.