Differential homing of monocytes and neutrophils in the epithelial layer of HSV-1 infected cornea regulates viral dissemination and wound healing

Purpose: To ascertain the homing of monocytes and neutrophils in the epithelium versus stroma of HSV-1 infected corneas at different stages of infection and functional significance of their anatomical location in virus-infected corneas. Methods: The corneas of C57BL/6J mice were infected with HSV-1 McKrae. Mice were euthanized on different days post-infection. The epithelium and stroma were separated from the infected corneas, and flow cytometry was performed to characterize the myeloid cell subsets in the epithelium versus the stromal layers of an infected cornea. MACS columns were used to purify neutrophils or deplete myeloid cells from infected corneas. Corneal epithelial scratch assay was performed to ascertain the impact of neutrophils on epithelium wound healing. Results: Our results showed a biphasic influx of monocytes in the epithelial but not the stromal layer of HSV-1infected corneas. Furthermore, we noted the predominance of monocytes over neutrophils in the epithelium and the stromal layer of the cornea during the pre-clinical stage of corneal HSV-1 infection. However, neutrophils were the major myeloid cell subset in the epithelium and stroma during the clinical disease period of infection. Removal of monocytes from the infected epithelial layer during the pre-clinical stage promotes the dissemination of the virus. Interestingly, neutrophils localized in the corneal epithelium inhibit corneal epithelial wound healing. Conclusions: Together, our data suggest that differential kinetics of monocytes and neutrophils homing in the epithelial layer regulate viral dissemination and epithelial wound healing in HSV-1-infected corneas.