Micro-abnormalities in the retina and choroid induced by anti-CTLA4 treatment

Anti-Cytotoxic T-Lymphocyte Associated protein 4 agents, such as ipilimumab, are widely applied to various cancers. However, they cause immune-related adverse effects throughout the body, including the eye. This study examined whether ipilimumab induces retinal and choroidal abnormalities in rodents, and investigated potential underlying mechanisms. Female wild-type mice were injected with ipilimumab three times/week for 5 weeks. The mice underwent optical coherence tomography (OCT) on the first day of the 6th week. Retinal function and morphology were evaluated by light microscopy, immunohistochemistry and electroretinography (ERG). On OCT, the lines indicating the ellipsoid and interdigitation were obscure in treated mice, suggesting outer retina destruction. Haematoxylin-eosin staining revealed destruction, shortening, and outer segment vacuolization. Treated mice exhibited weaker, fragmented rhodamine peanut agglutinin staining in outer photoreceptor structures. The choroid of treated mice showed severe infiltration of CD45-positive cells. In addition, CD8-positive cells invaded into the outer retina. On ERG, rod, maximum responses of combined rods and cones, and cone response wave amplitudes were significantly reduced in treated mice. Ipilimumab may induce impairments in outer photoreceptor architecture accompanied with CD8- positive infiltration in the retina and CD45-positive cell infiltration in the choroid, which may contribute to retinal function deterioration.