Establishing trypsin concentration and MOI for ΔNS1 H1N1 Influenza virus production in Vero cells cultured on microcarriers with EX-CELL Vero SFM. Vero cells were first cultivated using 250 ml spinner flasks with 3 g/l Cytodex 1 microcarriers. Upon confluency, 80% of culture medium was replaced with fresh medium. 5 ml of this culture was transferred to each well on suspension 6-well plates to test the different trypsin concentrations and MOI for infection. Trypsin concentrations used were 10 μg/ml, 5 μg/ml, 3 μg/ml, 2 μg/ml/day and 1 μg/ml/day. Virus titres obtained using TCID50 (Top) and haemagglutination assays (Bottom) at (A) MOI of 0.001 and (B) MOI of 0.01. Virus titres shown represent mean values obtained from two replicate wells. Error bars indicate the standard deviation of the experiment.