Ab1361 Proteomic Analysis of Tear Fluid and Aqueous Humor of Children With and Without Uveitis

Background: Changes in the biochemical and protein composition of ocular fluid may reflect inflammation due to disruption of the blood-retinal barrier (BRB), as in uveitis. Tear fluid is studied as a source of biomarker discovery in ocular and non-ocular diseases. Tear sampling is non-invasive and tolerated by children. Objectives: We aim to compare proteins in tears and aqueous humor (AH) of children with and without uveitis. Methods: Our cross-sectional study collected tears and AH in 4 patients with uveitis (1 JIA-uveitis, 1 chronic anterior uveitis, 2 ADNIV) and 3 pediatric non-inflammatory controls. Tears were collected by Schirmer strip, and AH during routine eye surgery. Advanced proteomic strategies (iTRAQ labeling and nanoLC-MS/MS) quantified proteins and normalized by total peptide amount. Log of the mean of the ratios was derived from 2 abundance readings per protein/subject. We used Wilcoxon rank sum exact test to compare proteins in tears and AH of uveitis patients and controls (P-value <0.05). Results: Seven patients (71% females, median age 17 y [R 2-59] at collection) contributed 10 paired tear and AH samples. 145 proteins were identified at medium 95% or higher FDR confidence with at least 1 high confidence peptide. Protein abundance was significantly different in tears vs AH of children with uveitis (median 607.8 vs 5012.0, P value 0.009), but not in controls (median 634 vs 121, P value 0.175) (Figure 1A/1B). Further analysis only included proteins detected in 100% of samples. Proteomic analysis showed significantly different expression of 31 of 63 (49%) proteins in tears and AH of children with uveitis, and of 10 of 18 proteins (45%) in controls (Figure 2A/2B). Some of these proteins have already been reported to be associated with the immune response or as inflammatory markers (Immunoglobulins heavy constant alpha 1, protein S100A9, and lysozyme), in the retinal pigment epithelium (Pigment epithelium derived factor), and in inflammatory uveitis (as vitamin D-binding protein, lactotransferrin, ceruloplasmin or apoliprotein I). Conclusion: Uveitis is a vision-threatening disease that warrants exploration of techniques for early detection. The eye is an immune-privileged organ immunologically shielded by the BRB. Around 50% of proteins overlapped in tear fluid and AH. Of those that were differentially expressed, mammoglobin-B, cystatin-S, and secretoglobin family 1D member have been reported in pediatric uveitis tear biomarker studies. Lysozyme, lactoferrin, lipocalin, albumin, and lactotransferrin are common major tear proteins. As tear sampling is feasible in children compared to AH, use of tears in uveitis biomarker studies is promising. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.