3.2.2 LVV productivity
A comparison of the LVV productivity in the 24-DSW plate and 2 L STR is shown in Figure 6. Several methods were used to characterise the LVV productivity. The infectious titre method was used to measure the number of functional LVV particles produced whilst the physical titre method was used to estimate the total number of virus particles generated, whether infectious or not, by measuring p24 concentration. In Figure 6, both titres were normalised relative to the STR to facilitate easier comparison between both systems. Dividing the infectious titre with the physical titre gives an infectivity ratio in terms of the number of transducing units per pg of p24 protein (TU/pg p24). This ratio provides an indication of the quality of LVV particles produced. A higher ratio of TU per pg p24 signifies a higher infectivity since there are more transducing units in a given quantity of virus particles. Lastly, the cell specific productivity normalises LVV production relative to the cell density at induction. This way, any bias relating to differences in induction cell densities between conditions is removed thus providing a more accurate measure of comparison. According to Figure 6, all four measures of LVV productivity showed good similarity between both vessel formats. In addition, a t-test confirmed any differences between the two systems were statistically insignificant at 95 % confidence level. Overall, mixing time proved to be a good basis for scale translation and yielded comparable LVV productivity.