Fig. 4: The new formula for calculation the Reduction Ratio of free infectious-lentiviral vector particles.

In the formula the parameter ‘Wash’ represents the reduction factor upon a wash step of the transduced cells and ‘W’ signifies the number of times the cell culture was washed. The parameter ‘Tryp’ indicates the vector-dependent reduction factor for treatment of the cells with trypsin, where ‘I’ is the amount of trypsin treatments after a wash step. ‘HL’ is the reduction factor based on the half-life of the envelope-pseudotyped vector particles at 37 °C in culture medium and ‘T’ the total culture time in days since the transduction of the cells. The parameter ‘C_i’ represents the measured amount of infectious vector particles in the inoculum. The formula calculates the Reduction Ratio, the fold-decrease in the concentration of free infectious vector particles relative to the amount of infectious viral vectors added to the cell culture.