A novel apoptotic interaction between HSV-1 and human corneal epithelial cells.
OBJECTIVE
Herpes simplex virus type 1 (HSV-1) infects the cornea possibly causing blindness. The specific mechanisms of herpetic keratitis are unclear. We aimed to investigate whether HSV-1 would up- or down-regulate the apoptotic pathway of human corneal epithelial (HCE) cells.


METHODS
HSV-1 infection of HCE and Vero cells was demonstrated (immunofluorescence) and apoptotic gene expression was quantified (ribonuclease protection assay). Caspase 8 protein activity (colorimetric assay) was quantified and compared to caspase 8 mRNA amounts from RPA experiments. The apoptotic index of HSV-1 infected HCE and Vero cells (apoptotic index = % of apoptotic cells in infected samples/mock treated samples) was obtained and compared to gene expression.


RESULTS
A down-regulation in apoptotic gene expression was observed in HSV-1 infected HCE cells in contrast to Vero cells (infected and mock treated). Caspase 8 protein levels mirrored caspase 8 mRNA levels in HSV-1 infected HCE cells. The apoptotic index also supports this down-regulation. HSV-1 infected human corneal epithelial cells and Vero cells at similar rates.


CONCLUSIONS
HSV-1 down-regulates the apoptotic pathway of human corneal epithelial cells. This down-regulation of apoptotic gene expression seems to be cell specific. Also infectivity is excluded in playing a role in regulation of the apoptotic pathway because HSV-1 replicated at similar rates in HCE and Vero cells.
Miles
D
D
The Cooperative Research Centre for Eye Research and Technology, University of New South Wales, Sydney, New South Wales, Australia.
Athmanathan
S
S
Thakur
A
A
Willcox
M
M
D000818:Animals; D017209:Apoptosis / Q000235:genetics; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D002461:Cell Line, Transformed; D002522:Chlorocebus aethiops; D015536:Down-Regulation; D019573:Epithelium, Corneal / Q000473:pathology / Q000503:physiopathology*; D015870:Gene Expression; D018259:Herpesvirus 1, Human; D006801:Humans; D016849:Keratitis, Herpetic / Q000473:pathology / Q000503:physiopathology*; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D014709:Vero Cells
D012333:RNA, Messenger; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases