Cells: Two cell lines are used in our study. One has been designated CR1 and the other CR2. The CR1 cell line is a line used for the assay of the virus only. It is a Vero derived cell line that has been modified to express the glycoprotein H (gH) gene derived from HSV-1 this gene is under the control of the HSV-1 glycoprotein D (gD) promoter. CR2 cells are a modified Vero cell from the WHO Vero accredited bank (No. 88020401; European Collection of Animal Cell Cultures ECACC, Porton Down, U.K.) that has been modified to express the glycoprotein H (gH) gene derived from HSV-2. This gene is under the control of the HSV-1 glycoprotein D (gD) promoter. The CR1 cells are solely used to assay the virus in the TCID 50 assay whereas the CR2 cells are the production cells for manufacture of the DISC-HSV. Cells were cultivated in Dulbecco's Modified Eagles Medium (DMEM with high glucose, Life Technologies, U.K.) supplemented with 5% Foetal Bovine Serum (PABCO, New Zealand origin).