Attachment assay

De Logu et al. (2000) investigated the inactivation of HSV-1 and HSV-2 and the prevention of cell-to-cell virus spread by the EO of the Asteraceae Santolina insularis. The plaque-reduction assay showed an IC50 values of 0.88 p.g/mL for HSV-1 and 0.7 xg/mL for HSV-2, respectively, whereas another test on Vero cells showed a cytotoxic concentration (CC50) of 112 p.g/mL, which leads to a CC50/IC50 ratio of 127 for HSV-1 and 160 for HSV-2. These findings indicate that the antiviral effect of the EO was caused by direct virucidal effects. There was no antiviral activity detected in a postattachment assay. Dne to attachment assays it was shown that virus adsorption was not reduced. Additionally, the reduction of plaqne formation assay indicated that the EO reduced cell-to-cell transmission of both HSV-1 and HSV-2. 

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