Herpes simplex keratitis (HSK) is the most common but serious infectious keratitis with high recurrence. It is predominantly caused by herpes simplex virus type 1 (HSV-1). The spread mechanism of HSV-1 in HSK is not entirely clear. Multiple publications indicate that exosomes participate in the intercellular communication process during viral infections. However, there is rare evidence that HSV-1 spreads in HSK by exosomal pathway. This study aims to investigate the relationship between the spread of HSV-1 and tear exosomes in recurrent HSK.
Researchers at Wenzhou Medical University collected tear fluids from total 59 participants to be included in this study. Tear exosomes were isolated by ultracentrifugation, then identified by silver staining and western blot. The size was determined by dynamic light scattering (DLS). The viral biomarkers were identified by western blot. The cellular uptake of exosomes was studied using labelled exosomes. Tear exosomes were indeed enriched in tear fluids. Labelled exosomes were successfully taken up by human corneal epithelial cells (HCEC) in large numbers in a short time. After cellular uptake, HSK biomarkers were detectable by western blot in infected cells.
Confocal laser scanning micrograph of HCEC co-incubated with tear exosomes
A The cellular uptake of tear exosomes by HCEC. Three samples per group were used for testing, 10 μg/mL labelled exosomes were used for cellular uptake observation. B Enlarged view of the image in row 3, column 2, the yellow arrows point to the membrane fusion parts during cellular uptake of exosomes. C The experiment was repeated for three times and the relative fluorescence intensity determined by the ImageJ software and the statistical analysis, **p < 0.01, ****p < 0.0001 are for the other groups compared with the 24 h uptake group.
Tear exosomes should be the latent sites of HSV-1 in recurrent HSK and might be involved in the spread of HSV-1. Also, this study verifies HSV-1 genes can be indeed transferred between cells by exosomal pathway, providing new inspiration for the clinical intervention and treatment as well as the drug discovery of recurrent HSK.