Novel gene therapy for proliferative vitreoretinopathy.

Abstract

Purpose : Ocular trauma and retinal surgery often result in proliferative vitreoretinopathy (PVR), a form of vision-compromising intraocular fibrosis. A key process in PVR is local inflammation. We tested the hypothesis that a modified, injury-triggered interleukin-1 receptor antagonist (IL-1ra), delivered via intraocular gene therapy, can be used to prevent PVR-related tissue damage in an experimental rabbit model of traumatic eye injury.

Methods : We engineered a chimeric transmembrane protein with an extracellular IL-1ra domain that is tethered to the cell surface by a protein sequence cleavable by metalloproteinases activated by local inflammation. Upon traumatic insult, anti-inflammatory IL-1ra was released into the extracellular matrix. These proteins were expressed under either the ubiquitin or cytomegalovirus (CMV) promoters and delivered via adeno-associated viruses. A non-cleavable protein was used as a control.

The vectors were delivered in vivo as a subretinal injection (~5 x 10¹⁰ vg/eye) in rabbits. A no-treatment control group received phosphate-buffered saline injection only. PVR was then induced through a single intravitreal injection of autologous blood. Animals were sacrificed at 4 days and at 12 weeks post-PVR induction. Immunohistochemistry for ionized calcium-binding adaptor molecule 1 (Iba1) was performed on paraffin-embedded tissue. Iba1 was used to stain for microglia, which are activated and recruited during local inflammation.

We counted the mean number of retinal microglia per high-power field in each eye using confocal microscopy. Unpaired Student’s t-test was used to compare treatment groups (N=2).

Results : At 4 days post-PVR induction, the mean number of retinal microglia in the rabbits that did not receive gene therapy was 2.1 (SEM=0.3). A reduction was observed in eyes receiving CMV-IL-1ra (0.8±0.2, p=0.0598) and ubiquitin-IL-1ra (1.2±0.0, p=0.0767). However, no anti-inflammatory effect was seen with the non-cleavable protein (2.1±0.1, p=0.8698) that could not release IL-1ra. Similarly, at 12 weeks post-PVR induction, fundus photographs of eyes treated with non-cleavable protein revealed large intravitreal membranes, which represent PVR-related changes, while those with the two cleavable molecules had subjectively smaller membranes.

Conclusions : Using injury-responsive IL-1ra gene therapy, we were able to reduce post-trauma inflammation acutely and also mitigate the long-term structural changes associated with PVR.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.