Role of tear exosomes in the spread of herpes simplex virus type 1 in recurrent herpes simplex keratitis

BackgroundHerpes 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.MethodsTear fluids collected from total 59 participants were 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.ResultsTear exosomes were indeed enriched in tear fluids. Collected exosomes own normal diameters consistent with related reports. The exosomal biomarkers existed in tear exosomes. 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.ConclusionsTear exosomes should be the latent sites of HSV-1 in recurrent HSK and might be involved in the spread of HSV-1. Besides, 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.