Abstract
Purpose:
The cell membrane of corneal epithelial cells encompasses abundant heparan sulfate proteoglycans, which are used by herpes simplex virus (HSV-1) for entry into host cells. During egress, however, virus has developed a process that enables it to escape the grasp of these proteoglycans and spread to neighboring cells efficiently. We hypothesize that heparanase, the sole human enzyme that cleaves heparan sulfate can facilitate extensive infection in the cornea.
Methods:
Human corneal epithelial cells were used for all the experiments described. Western blot analysis and qPCR were performed to detect active protein and mRNA of heparanase respectively. Flow cytometry analysis was used to study the cell surface expression of heparanase and heparan sulfate of HSV-1 infected cells. Images of infected cells were taken with Carl Zeiss LSM 710 confocal microscope using 100X oil magnification. Overexpression and knockdown studies of heparanase were performed using heparanase expression plasmid and shRNA against heparanase protein respectively. Viral release in supernatant was measured by performing a plaque assay in Vero cells.
Results:
(1) We have found that expression of heparanase transcripts and active protein is regulated by HSV-1 infection. (2) Modulation of heparanase expression contributes directly to the availability of heparan sulfate on cell surface. (3) Heparanase knock down by shRNA results in the loss of HSV-1 infection. (4) Images of infected cells reveal heparanase localization at the trans Golgi network.
Conclusions:
Our study identifies a new host protein and demonstrates a novel mechanism for the growth of herpes simplex virus infection in corneal epithelial cells. The host protein could be used as a target against HSV infection in the cornea.
Keywords: 545 herpes simplex virus •
482 cornea: epithelium •
529 flow cytometry