Abstract
Purpose: :
The human cornea is a primary target for herpes simplex virus-1 (HSV-1) infection. The goals of the study were to determine the cellular and molecular modalities of HSV-1 entry into human corneal epithelial (HCorE) cells. Specific facets of the study included identifying the major entry receptors, assessing the pH dependency, and determining the trends of superinfection during HSV-1 infection of HCorE cells.
Methods: :
A recombinant HSV-1 virus, which expresses beta-galactosidase, was used to ascertain HSV-1 entry into HCorE cells. Viral replication within the cells was confirmed using a time-point plaque assay. Lysosomotropic agents were then used to test for pH dependency for entry. Flow cytometry and immunocytochemistry were utilized to determine the expression of three cellular receptors - nectin-1, HVEM, and PILR-á - on the cell membrane. The necessity of these receptors for viral entry was then tested using antibody-blocking. Finally, trends of superinfection were investigated using a viral entry assay and flow cytometry post-primary infection.
Results: :
Cultured HCorE cells show high susceptibility to HSV-1 entry and replication. Entry was also demonstrated to be pH dependent as blocking vesicular acidification significantly decreased entry. The entry receptors expressed on the surface of the cell membrane include nectin-1, HVEM, and PILR-alpha. Receptor-specific antibodies blocked the entry receptors and remarkably reduced viral entry. Blocking of nectin-1 proved to show the most dramatic decrease in entry implicating that nectin-1 is the primary receptor utilized by HSV-1. Cells super-infected with HSV-1 also showed a dramatic decrease in entry, which can be linked to the decreased levels of nectin-1 in cells with primary infection as demonstrated with flow cytometry.
Conclusions: :
HSV-1 is capable of developing an infection in HCorE cells using a pH dependent entry process that involves primarily the nectin-1 receptor, but also the HVEM and PILR-alpha receptors. Super-infected cells show decreased levels of entry, which can be explained by decreased level of nectin-1 receptor expression on infected cells.
Keywords: herpes simplex virus • cornea: epithelium • microbial pathogenesis: clinical studies