The COGEM formula revisited, experimental validation of the reduction ratio formula for free lentiviral particles
During transduction of cells much use is made of viral vectors derived from lentiviruses. After transduction, so-called free lentiviral vector particles can be present. Exposure to these particles should be avoided, as they may lead to adverse effects.
The presence of free vector particles in transduced cell suspensions depends on a number of factors, including the half-life of the virus vector and the number of wash steps of the cells after transduction. With a formula (the ’COGEM formula’), an estimation in the reduction of free lentiviral vector particles can be calculated. Values of some parameters in this formula are based on theoretical assumptions.
COGEM has commissioned a research project to experimentally validate these values, such as the half-life of lentiviral vector particles pseudotyped with VSV-G, and pseudotyped with other envelope proteins. The results show that most values in the formula have to be adjusted. As a consequence, in practice the calculated loss of free vector particles is lower than previously assumed.
At the end of the research report an adapted COGEM formula is shown. Additionally, an overview table for the several pseudotypes is presented with reduction factors to be applied for their half-life and trypsin inactivation. The authors emphasize that the values only refer to lentiviral vectors.
The COGEM research report can be found under the “download publication” button.