Selective Targeting of Choroidal Neovascularization (CNV) with Factor VII–Fc Chimeric Antibody (ICON): Comparison withAnti–von Willebrand Antibody

Abstract

Abstract: : Purpose: To compare the affinity and specificity of mouse and humanICON to anti–von Willebrand antibody, in vitro, for laser–induced choroidal neovascular endothelium in the pig. Methods: Subretinal neovascularization was induced by laser photocoagulation in four Yucatan miniature pigs (Sus scrofa). An indirect double–frequency YAG laser (532 nm) was used to deliver 15–25 spots per eye (0.1 seconds, 1.0 W) using a 2.2 D lens. Animals were sacrificed on day 14 and serial paraffin sections of the spots revealing CNV were immunostained with equivalent amounts of human and mouseICONs, and anti–von Willebrand antibody (15pM in 50 µl). The same amount of fluorescein–tagged secondary antibody was used to visualize the binding sites. Sections without the primary antibodies were used as controls. Captured confocal images were used to quantify the signal intensity within the neovascular complex, retina and choroid. Morphometric analysis was used to calculate the affinity and specificity of binding to choroidal neovascularization, and the CNV Binding Index (%Binding to CNV / %Binding to non–CNV areas). Results: HumanICON (92%), mouseICON (92%) and anti–von Willebrand antibody (91%) had comparable specificities for ocular vascular endothelium; however both human (16%) and mouseICON (23%) were specific for choroidal neovascular endothelia, compared with anti–von Willebrand antibody (1%). The CNV Binding Index of human (2.22) and mouseICON (3.34) was significantly higher than anti–von Willebrand antibody (0.14). Conclusions: Human and mouseICON bind, in vitro, to the vascular endothelia of choroidal neovascularization in pigs with greater affinity than von–Willebrand antibody. Both of these chimeric antibodies should be helpful for selective targeting and obliteration of subretinal choroidal neovascularization.

Keywords: age–related macular degeneration • choroid: neovascularization • neovascularization