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Transient expression of AAVs can be observed in HEK-293 cells as early as 24 hours post-transfection when using PolyPlus transfection reagents dedicated to viral vector production. The standard harvesting time is generally of 48-72 hours post-transfection, irrespective of whether you are using adherent or suspension adapted HEK-293 cells. Depending on the serotype, and on the gene of interest that the AAV vector carries, it can be worth harvesting at a later time point, up to 10 days post-transfection or more. We would recommend harvesting at different time points to evaluate best productivity vs. cost-effectiveness of the process.