[Corneal herpes: what's new?]

Herpes simplex virus type 2 entry into cultured human corneal fibroblasts is mediated by herpesvirus entry mediator

Herpes simplex virus type 2 (HSV-2) infections in the eye are becoming increasingly common in adults. The most likely point of entry for HSV-2 into the eye is through the cornea. By using primary cultures of human corneal fibroblasts (CFs), a natural target-cell type for infection, it was demonstrated that CFs are highly susceptible to HSV-2 entry and replication. RT-PCR and flow-cytometry analyses demonstrated expression of herpesvirus entry mediator (HVEM), a known mediator for HSV-2 entry into cells. Blocking of virus entry into CFs by anti-HVEM antibody implicated HVEM as a potential receptor for HSV-2 infection. These results indicate that HVEM may play a crucial role in HSV-2-induced corneal infections.

Role for 3-O-sulfated heparan sulfate as the receptor for herpes simplex virus type 1 entry into primary human corneal fibroblasts

Herpes simplex virus type 1 (HSV-1) infection of the corneal stroma remains a major cause of blindness. Primary cultures of corneal fibroblasts (CF) were tested and found susceptible to HSV-1 entry, which was confirmed by deconvolution imaging of infected cells. Plaque assay and real-time PCR demonstrated viral replication and hence a productive infection of CF by HSV-1. A role for glycoprotein D (gD) receptors in cultured CF was determined by gD interference assay. Reverse transcription-PCR analysis indicated expression of herpesvirus entry mediator and 3-O-sulfated (3-OS) heparan sulfate (HS)-generating enzyme 3-O sulfotransferase 3 (3-OST-3) but not nectin-1 or nectin-2. Subsequently, HS isolated from these cells was found to contain two distinct disaccharides (IdoUA2S-AnMan3S and IdoUA2S-AnMan3S6S) that are representative of 3-OST-3 activity. The following lines of evidence supported the important role of 3-OS HS as the mediator of HSV-1 entry into CF. (i) Blockage of entry was observed in CF treated with heparinases. The same enzymes had significantly less effect on HeLa cells that use nectin-1 as the entry receptor. (ii) Enzymatic removal of cell surface HS also removed the major gD-binding receptor, as evident from the reduced binding of gD to cells. (iii) Spinoculation assay demonstrated that entry blockage by heparinase treatment included the membrane fusion step. (iv) HSV-1 glycoprotein-induced cell-to-cell fusion was inhibited by either prior treatment of cells with heparinases or by HS preparations enriched in 3-OS HS. Taken together, the data in this report provide novel information on the role of 3-OS HS in mediating infection of CF, a natural target cell type.