Stirred cultures: Cells were grown in 6-well low binding plates (Costar) and in spinner flasks; cultures were inoculated at a cell density of 2x10 5 cells/ml. The Working volume was equal to 3 ml for the 6-well plate and 200 ml when cultures were performed in spinner flask. Cells were grown on 2 g/l Cytodex 1 at 37°C and 30 rpm.