A novel pathogenic RBP‐3 peptide reveals epitope spreading in persistent experimental autoimmune uveoretinitis

Abstract

SummaryExperimental autoimmune uveoretinitis (EAU) in the C57BL/6J mouse is a model of non-infectious posterior segment intraocular inflammation that parallels clinical features of the human disease. The purpose of this study was to analyse the immune response to the four murine subunits of retinol binding protein-3 (RBP-3) to identify pathogenic epitopes to investigate the presence of intramolecular epitope spreading during the persistent inflammation phase observed in this model of EAU. Recombinant murine subunits of the RBP-3 protein were purified and used to immunize C57BL/6J mice to induce EAU. An overlapping peptide library was used to screen RBP-3 subunit 3 for immunogenicity and pathogenicity. Disease phenotype and characterization of pathogenic subunits and peptides was undertaken by topical endoscopic fundal imaging, immunohistochemistry, proliferation assays and flow cytometry. RBP-3 subunits 1, 2 and 3 induced EAU in the C57BL/6J mice, with subunit 3 eliciting the most destructive clinical disease. Within subunit 3 we identified a novel uveitogenic epitope, 629-643. The disease induced by this peptide was comparable to that produced by the uveitogenic 1-20 peptide. Following immunization, peptide-specific responses by CD4 + and CD8 + T-cell subsets were detected, and cells from both populations were present in the retinal inflammatory infiltrate. Intramolecular epitope spreading between 629-643 and 1-20 was detected in mice with clinical signs of disease. The 629-643 RBP-3 peptide is a major uveitogenic peptide for the induction of EAU in C57BL/6J mice and the persistent clinical disease induced with one peptide leads to epitope spreading.

Are Anti-Retinal Autoantibodies a Cause or a Consequence of Retinal Degeneration in Autoimmune Retinopathies?

“…The study of EAU have shown that it is important to use human protein sequences in epitope mapping for human immune responses because the amino acid differences between experimental animals and human sequences may affect the identification of novel pathogenic epitopes and the determination of epitope spreading. In the EAU model, epitope spreading from the immunizing to the non-immunizing peptide was demonstrated for both IRBP 1–20 and 629–643 sequences and was consistent with the destruction of retinal tissue, increasing repertoire of antigen-specific effector T-cell with disease progression ( 102 ).…”

Stochastic Effects in Autoimmune Dynamics

“…From a practical perspective, future work could focus on validating theoretical results presented in this paper using experimental measurements of the progress of autoimmune disease in animal hosts, with experimental autoimmune uveoretinitis (EAU), an autoimmune inflammation in the eyes, being one interesting possibility. In one such recent experiment, all animals were genetically identical C57BL/6 mice, but once the EAU was induced in them through inoculation, the autoimmune disease then progressed at slightly different rates [77], (Boldison and Nicholson, 2012) and the measured variability in the numbers of infected cells and T cell responses could be compared to theoretical estimates of the variance as predicted by our model. From a clinical perspective, comparison of variance in the measured populations of different cells with the model conclusions will facilitate an efficient parameter identification and provide a set of prognostic criteria for the progress of autoimmunity, which can be used for risk stratification and assessment of patients with autoimmune disease.…”

Combined Deficiency of the Melanocortin 5 Receptor and Adenosine 2A Receptor Unexpectedly Provides Resistance to Autoimmune Disease in a CD8+ T Cell-Dependent Manner

“…Others have demonstrated the importance of minimally activated CD8 + T cells in uveitis in rats and mice (16)(17)(18)(19), and CD8 + T cells are present in eyes of uveitis patients (20,21). While it is clear that effector CD8 + T cells are involved in the inflammatory immune response, the connection with activation of these cells with the melanocortin-adenosinergic pathway is paradoxical.…”

“…It is well documented that CD8 + T cells have a role in uveitis through observations in rodent models of EAU (16)(17)(18)(19), and analysis of aqueous humor from uveitis patients (20,21). MC5r transcript expression has been reported in CD8 + T cells from human PBMCs (22) but protein expression was not confirmed and the role of MC5r in this cell subset has not been further examined.…”