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Gloriane Schnabolk, Mausumi Bandyopadhyay, Stephen Tomlinson, Baerbel Rohrer; New insights on complement inhibitor CD59 in mouse laser-induced choroidal neovascularization: reduced expression after injury and targeted delivery for protein replacement. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5459.
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Age-related macular degeneration (AMD) is the leading cause of blindness in the US. Levels of CD59, an inhibitor of the Membrane Attack Complex (MAC), the terminal product of the complement cascade, have been found to correlate with AMD severity. Here we investigated the localization of CD59 following choroidal neovascularization (CNV). We also provide further evidence for the role of CD59 in CNV progression, and demonstrate that CR2-CD59, a newly developed site-targeted inhibitor of the MAC, provides effective protection against CNV.
Laser-induced photocoagulation was used to trigger CNV in C57BL/6 and CD59a-deficient mice (CD59-/-) in the presence and absence of CR2-CD59 injections (100 µg; IP every 48 hrs). CD59 localization and MAC deposition within the retinal pigmented epithelium/choroid (RPE/C) were identified by immunohistochemistry and quantified by confocal microscopy. CNV lesion size was measured by optical coherence tomography (OCT).
Following CNV induction, polarized localization of CD59 was temporarily lost, moving from the basal to the apical side of the RPE. OCT analysis demonstrated that loss of CD59 exacerbated (in pixels; CD59-/-: 5816 ± 244.6; WT: 3475 ± 196.3; p <0.001), whereas treatment with CR2-CD59 reduced CNV development (CR2-CD59: 2777 ± 180.6, PBS: 4061 ± 231.0; p <0.0001). Using a MAC-specific antibody, we identified an increase in mean level (pixels/µm2) of C5b-9 staining in CD59-deficient compared to WT mice (CD59-/-: 139.0 ± 28.65, WT: 36.74 ± 29.29; p <0.001), whereas treatment with CR2-CD59 did not alter levels of MAC in the remaining lesions (CR2-CD59: 26.39 ± 3.396, PBS: 33.54 ± 3.396; p =0.0928).
These data further support the importance of CD59 in controlling the magnitude of the injury response and indicate that pharmacological inhibition of the MAC with CR2-CD59 may be a viable therapeutic approach for reducing complement-mediated ocular pathology.
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