Effects of epigallocatechin-3-gallate and acyclovir on herpes simplex virus type 1 infection in oral epithelial cells.

Background/purpose: Herpes simplex virus type 1 (HSV-1) is the pathogenic agent of human diseases, including gingivostomatitis and herpes labialis. The anti-viral activities of the tea polyphenol, epigallocatechin-3-gallate (EGCG), have been demonstrated. This study examined the combined effects of EGCG and the antiviral drug, acyclovir (ACV), on infection of HSV-1 in oral epithelial cells.

Methods: Cell viability was examined using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide. Viral yields were determined using the plaque assay. Viral proteins were detected using Western blotting analysis or confocal laser scanning microscopy. Viral DNA was detected using the real-time polymerase chain reaction.

Results: Cytotoxic effects of HSV-1 on the viability of oral epithelial cells were evidently reduced in the presence of EGCG (25 μg/ml) or/and ACV (50 μg/ml). Viral yields were also significantly reduced by treatment of cells with EGCG or/and ACV. Expression of viral immediate early protein, infected cell protein 0 (ICP0), was greatly inhibited when cells were treated with EGCG. Combined effects of EGCG and ACV were more evident for the expression of viral thymidine kinase, ICP5 and glycoprotein D. EGCG, but not ACV, significantly reduced the levels of viral particles and viral DNA during viral entry phase. However, at 20 h post infection, the intracellular viral DNA was evidently reduced in HSV-1 infected cells treated with EGCG and ACV. Moreover, the stimulatory effects of HSV-1 on phosphorylation of c-Jun N-terminal kinase could be reduced by ACV.

Conclusion: The results demonstrated the additive effects of EGCG and ACV on HSV-1 infection in oral epithelial cells.