Purpose: Extracellular vesicles (EVs) are lipid-bilayered nanoparticles that play an important role in cellular cross-talk, and as received attention for their role as diseases biomarker. Aquaporin-5 (AQP5) is a small integral membrane protein that help in the migration of cells, proliferation, and invasion. However, the association of AQP5 with fungal diseases is still unknown. The aim of this study was to evaluate the expression of AQP5 in EVs (EV-AQP5) extracted from the vitreous of patients with Fungal Endophthalmitis (FE).
Methods: Vitreous fluid was collected from 20 patients clinically suspected as FE, 10 patients from non-infectious conditions, and 10 patients with bacterial endophthalmitis as controls. EVs were isolated from human vitreous and characterized by dynamic light scattering, and scanning electron microscopy. Human Aquaporin-5 levels were evaluated using a commercial ELISA Kit. The Receiver Operating Characteristic (ROC) curves and its significance were correlated with microbiology data.
Results: Isolated EVs size were approx.250-380 nm in diameter. The measured levels of EV-AQP5 resulted significantly higher in FE patients (mean=216±15pg/ml; 95% confidence interval (CI): 182-250) in comparison to controls (mean=130±12pg/ml; 95%CI: 111-166)(p = .001). However, AQP5 levels in EVs derived from culture-proven bacteria patients were insignificant compared to controls (mean=169±4 pg/ml; 95%CI: 161-177). ROC curve was used to define the optimal cut-off level of the test at 180 pg/ml with an AUC of 98% (95%CI: 95-100) (p = .03), with a sensitivity of 100% and specificity of 90%. Additionally, the AQP5 level in EVs derived from culture-negative vitreous was above the threshold value (200 ± 10 pg/ml (95%CI: 180-230) in comparison to the control group (p < .001) However, no significant association was found between age or visual acuity and the level of AQP5 in FE.
Conclusion: Our results reveal that the vitreous EV-AQP5 levels can aid in differentiating FE from non-infectious retinal conditions, mainly when the cultures are negative.
Keywords: Aquaporin-5; ROC curve; extracellular vesicles; fungal endophthalmitis; vitreous.