Proteomic analysis of autoimmune retinopathy implicates NrCAM as a potential biomarker.

Purpose: To identify vitreous molecular biomarkers associated with autoimmune retinopathy (AIR). Design: Case-control study. Participants: We analyzed six eyes from four patients diagnosed with AIR and eight comparative controls diagnosed with idiopathic macular holes and epiretinal membranes. Methods: Vitreous biopsies were collected from the participants and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) or multiplex ELISA. Outcome Measures: Protein expression changes were evaluated by 1-way ANOVA (significant p-value <0.05), hierarchical clustering, and pathway analysis to identify candidate protein biomarkers. Results: There were 16 significantly upregulated and 17 significantly downregulated proteins in the vitreous of three AIR patients compared to controls. The most significantly upregulated proteins included lysozyme C (LYSC), zinc-alpha-2-glycoprotein (ZA2G), complement factor D (CFAD), transforming growth factor-beta induced protein (BGH3), beta-crystallin B2, and alpha-crystallin A chain. The most significantly downregulated proteins included disco-interacting protein 2 homolog (DIP2C), retbindin (RTBDN), and amyloid beta precursor like protein 2 (APLP2). Pathway analysis revealed that vascular endothelial growth factor (VEGF) signaling was a top represented pathway in the vitreous of AIR patients compared to controls. In comparison to a different cohort of three AIR patients analyzed by multiplex ELISA, a commonly differentially expressed protein was neuronal cell adhesion molecule (NrCAM) with p-values of 0.027 in the LC-MS/MS dataset and 0.035 in the ELISA dataset. Conclusion: Protein biomarkers such as NrCAM in the vitreous may eventually help diagnose AIR.