How do I determine MOI?

MOI stands for Multiplicity of Infection which refers to the number of viral particles per cell. To calculate, take the number of viral particles used per well then divide by the number of cells originally seeded in the well. This equals the MOI. An MOI of 5 indicates that there are five transducing units for every cell in the well. It is important to note that the number of viral particles should be calculated using a titer determined in the target cell line or one that has been converted based on relative transduction efficiency of your cell line compared to HEK293T cells.