Intravitreal injection of Fc-fragments has multiple adverse effects on retina and choroid

Abstract

 

Purpose

 

Anti-VEGF drugs are used to treat neovascular eye diseases. Some of these drugs contain Fc-fragments (Fc). It is unknown how the mode of action of these drugs is influenced by their Fc. As Fc have important biological functions, these unknown effects were investigated after intravitreal injection in rats.

 

Methods

 

11 Long Evans rats were intravitreally injected with sterile, 9.1µg biotin-labelled Fc from rats in 5 µl PBS. For control 5 µl PBS were injected in another 11 rats. Animals were sacrificed between 1 day (group 1) and 7 days (group 2) after injection. Right eyes were examined by electron microscopy, left eyes were stained for distribution of Fc by immunocytochemistry with Cy3 labelled streptavidin.

 

Results

 

High amounts of Fc were detected in the anterior chamber, the vitreous and the trabecular meshwork. Smaller amounts were seen throughout the retina and close to choroidal blood vessels in both groups. Infiltrating cells within the vitreous and anterior chamber were common and contained Fc, as well as lens capsule and cornea endothelium. Ultrastructurally, there were effects on the blood vessels such as collapse of the choriocapillaris, thrombocyte activation, fibrin formation, stasis, central retinal vein thrombosis (Fig:1A&B), formation of dense bodies and microparticles in the bloodstream, loss of fenestrations, endotheliopathy plus alteration of Bruch's membrane and ILM. Granulocytes and macrophages infiltrated the vitreous and retina (Fig.1A) in 100 % (group 1) and 60 % (group 2) of the treated and in 28,5 % (group 1) and 0 % (group 2) of the control eyes. A quantitative analysis of all these effects and a method to estimate blood flow in the choroid is in progress.

 

Conclusions

 

Biotin-labelling is ideal for investigating distribution of intravitreally injected proteins. Intravitreal injection of Fc-fragments at a dose that corresponds to a dose of aflibercept and a double dose of bevacizumab as used in patients has multiple adverse effects on eye tissues within the first week of injection, needing further investigation.  

 

1 day after injection of Fc-fragments infiltrating cells are in the vitreous (arrow in A) and thrombocytes (T) aggregate within the central retinal vein (Fig.1A arrowhead in a light micrograph). In Fig. 1B an electron micrograph shows a thrombus (T) in a central vein.<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />