Effective Arrestin-Specific Immunotherapy of Experimental Autoimmune Uveitis with RTL: A Prospect for Treatment of Human Uveitis

PURPOSE

To evaluate the immunotherapeutic efficacy of recombinant T cell receptor ligands (RTLs) specific for arrestin immunity in treatment of experimental autoimmune uveitis (EAU) in humanized leukocyte antigen (HLA-DR3) transgenic (Tg) mice.

METHODS

We generated de novo recombinant human DR3-derived RTLs bearing covalently tethered arrestin peptides 291-310 (RTL351) or 305-324 (RTL352). EAU was induced by immunization of HLA-DR3 mice with arrestin or arrestin peptide and treated with RTLs by subcutaneous delivery. T cell proliferation and cytokine expression was measured in RTL-treated and control mice.

RESULTS

RTL351 prevented the migration of cells outside of the spleen and the recruitment of inflammatory cells into the eye, and provided full protection against inflammation from EAU induced with arrestin or arrestin peptides. RTL351 significantly inhibited T cell proliferation and secretion of inflammatory cytokines interleukin 2 (IL-2), interferon γ (IFN-γ), IL-6, and IL-17 and chemokines (macrophage inflammatory proteins [MIP-1a] and regulated and normal T cell expressed and secreted [RANTES]), which is in agreement with the suppression of intraocular inflammation. RTL350 ("empty," no peptide) and RTL352 were not effective.

CONCLUSIONS

Immunotherapy with a single RTL351 successfully prevented and treated arrestin-induced EAU in HLA-DR3 mice and provided proof of concept for therapy of autoimmune uveitis in human patients. The beneficial effects of RTL351 should be attributed to a significant decrease in Th1/Th17 mediated inflammation.

TRANSLATIONAL RELEVANCE

Successful therapies for autoimmune uveitis must specifically inhibit pathogenic inflammation without inducing generalized immunosuppression. RTLs can offer such an option. The single retina-specific RTLs may have a value as potential immunotherapeutic drug for human autoimmune uveitis because they effectively prevent disease induced by multiple T cell specificities.

Systemic immunotherapy delays photoreceptor cell loss and prevents vascular pathology in Royal College of Surgeons rats

PURPOSE

Degenerative retinopathies, including retinitis pigmentosa, age-related retinal degeneration, autoimmune retinopathy, and related diseases affect millions of people around the world. Currently, there is no effective treatment for most of those diseases. We investigated systemic recombinant T-cell receptor ligand (RTL) immunotherapy for preventing retinal degeneration and vascular damage in the Royal College of Surgeons (RCS) rat model of retinal degeneration.

METHODS

RCS rats were treated with RTL220 tethered to interphotoreceptor retinoid binding protein (IRBP) peptide or control RTL101 without peptide by subcutaneous administration starting at the onset of photoreceptor degeneration or after the degenerative process began daily or every other day and performed for a 13-week period. The retinal cross sections and whole mounts were prepared to determine histopathology, leaking vessels, and formation of vascular complexes. Immunofluorescent studies evaluated microglia and monocyte chemoattractant protein-1 chemokine in treated retinas. Optokinetic studies were performed to determine visual acuity.

RESULTS

Systemic treatment with RTL220 prevented decreases in outer nuclear layer (ONL) thickness and showed a significantly higher number of nuclei than control rats treated with RTL101 or vehicle. RTL220 was also effective in protecting retinal vasculature from leakage and the formation of abnormal vascular complexes even when the treatment was administered after the degenerative process was initiated. Visual acuity measurement showed that rats treated with RTL220 performed significantly better than those with RTL101 and untreated age-matched controls at P60 and P90. Biodistribution studies showed that RTL220 cleared slowly from the administration site. Moreover, RTL220-treated retinas had a significantly reduced number of activated microglia in the subretinal space, decreased monocyte chemoattractant protein-1 production in the retina, inhibited T-cell responses, and reduced anti-interphotoreceptor retinoid binding protein autoantibody titers. Treatment with the control RTL101 (without a specific peptide tethered) or vehicle alone did not inhibit microglia activation or protect photoreceptors or vasculature.

CONCLUSIONS

RTL therapy augmented photoreceptor cell survival, protected vasculature, and increased visual function in the RTL rat. Targeting chronic autoimmunity with RTLs can be an effective therapeutic alternative in delaying retinal degeneration. Subcutaneous delivery of RTLs alone or combined with other drugs could be an attractive option for long-term therapy for retinal degenerative diseases.