Clinical retroviral vector production: step filtration using clinically approved filters improves titers

Production of retroviral vectors for clinical use requires removal of cells and cellular debris. We combined a series of filters of decreasing pore size using commercially available blood banking filters approved for clinical use. The collection bag and filters can be connected to create a sterile, closed system using clinically approved tubing and sealing systems. Even when challenged with a large number of vector producer cells (2.38 x 10(9) cells), no viable cells are passed through the system. The step filtration system developed minimizes the titer reduction associated with filtration, provides rapid flow rates, and was cost effective when filtering volumes in excess of 2 liters.