Infliximab exerts a dose-dependent effect on retinal safety in the albino rabbit.

Abstract

To assess the retinal toxicity of an intravitreal injection of infliximab, a monoclonal antibody to tumor necrosis factor α, in a rabbit model. Two groups of adult albino rabbits (n=5) received intravitreal injections of infliximab (0.1ml) in the study eye and balanced salt solution (BSS, 0.1ml) in the control eye at baseline. Group 1 was administered with 1.5mg/0.1ml, and group 2 was injected with 7.5mg/0.1ml of infliximab solution. Electroretinography (ERG) was performed at baseline and at 1, 7, 30, and 45days after the injection. Visual evoked potentials (VEPs) were recorded at 7 and 45days after the injection. After the last electrophysiological assessment, the rabbits were euthanized and retinal histopathology and immunhistochemistry for glial fibrillary acidic protein (GFAP) were performed. ERG responses demonstrated no significant deficit in retinal function in eyes injected with infliximab. Mean dark-adapted a-wave and b-wave maximal amplitude and semi-saturation constant values at baseline and throughout the 45days of follow-up after the injection indicated no remarkable difference in outer retinal function between the control and experimental eyes. VEP responses were similar at each time point (7 and 45days). No difference was seen in retinal histopathology and immunocytochemistry sections in eyes receiving the 1.5mg/0.1ml dose compared to the control eyes. However, increased GFAP labeling in retinal Müller cells was detected in rabbit eyes treated with the 7.5mg/0.1ml dose. Intravitreal injection of 1.5mg/0.1ml infliximab dose has no toxic effect on the integrity (functional or structural) of the retina in rabbits. A higher dose of 7.5mg/0.1ml may be slightly toxic as suggested by positive Müller cell GFAP expression. Additional studies of retinal toxicity at higher doses and after multiple injections are needed to establish the retinal safety of intravitreal infliximab therapy in humans.