Roller bottle process CR2 cells were cultured in roller bottles for 5 days until a cell density of 1 × 10 8 cells was typically achieved. At this density 100% cell confluency was observed. Roller bottle cultures infected with DISC-HSV at an MOI of 0.01, exhibited 100% CPE after approximately 65 h. Harvesting the roller bottles with hypotonic saline it was possible to achieve 10 9 pfu per bottle. Figure 6 . Typical growth of CR2 cells and DISC-HSV production at 1 l scale. The total DISC-HSV virus titre produced in a 1 l vessel is approximately 1.5 × 10 10 pfu. Figure 7 . Typical growth of CR2 cells and DISC-HSV production at 15 l scale. The amount of DISC-HSV virus titre able to be produced from a 15 l culture is 7 × 10 11 pfu. This demonstrates a considerable scale up potential for a microcarrier production system.