Purpose: The purpose of this study was to examine the intrinsic susceptibility of cultured human corneal endothelial cells (HCEC) to herpes simplex virus-1 (HSV-1) infection. We compared HSV-1 adsorption, kinetics of HSV-1 production, and pattern of viral plaque formation in cultured HCEC with those of a cell line used routinely for laboratory HSV propagation (African green monkey kidney fibroblast CV-1 cells).
Methods: Cultured HCEC and CV-1 cells were exposed to the McKrae strain of HSV-1 at 5 and 0.0001 multiplicities of infection (MOI). Using the 50% tissue culture infectious dose (TCID(50)) titration method, viral adsorption (at 5 MOI) and total virus production (at 5 and 0.0001 MOI) were compared to assess both susceptibility to viral attachment and productive viral infection, respectively. Additionally, visual observations were made at 0.0001 MOI using bright-field microscopy and immunofluorescence staining of viral antigens to compare patterns of viral spread in confluent monolayers of both cell types.
Results: The percentage of HSV-1 virion particles adsorbed by cultured HCEC and CV-1 cells was similar (35.9% and 33.0%, respectively, p = 0.07, NS), indicating similar susceptibility of the two cell types to initial HSV-1 attachment and adsorption. However, maximum total virus production was more than 3-fold higher for HCEC than for CV-1 cells (p < 0.005), suggesting higher susceptibility of HCEC cells to productive viral infection. Immunofluorescence studies of infected cell monolayers corroborated these quantitative findings, with HCEC monolayers demonstrating more rapid progression of cytopathic effect than CV-1 monolayers.
Conclusions: In comparison to reference CV-1 cells, cultured HCEC show similar susceptibility to HSV-1 adsorption, but higher capacity to support productive HSV-1 infection. Our results suggest that human corneal endothelial cells may be inherently susceptible to HSV-1 infection.