Closed hollow-fiber bioreactor: a new approach to retroviral vector production

Background The ability to obtain high-titer and large quantities of retrovi ral vector production in a 'closed' system would have profound implications in clinical and experimental gene therapy. Methods We studied the cell growth and vector production of three retrovira l pack:aging cell lines in a variety of conditions using hollow-fiber biore actors designed as an 'artificial capillary system' (ACS) and enhanced with the application of a hermetically sealing device for sterile welding of co nnecting plastic tubings. Vector titer, fetal bovine serum (FBS) concentrat ion, volume and the duration of productivity were assessed to optimize vect or production. Results In this pilot study, we observed that retroviral vector production (frozen-and-thawed) from cultures containing as low as 2.5% FBS yielded tit ers up to 2.2 x 10(7) cfu/ml, 14.4-fold higher than titers obtained from co ntrol dish cultures. Up to 3 liters of vector supernatant were generated du ring a 2-month large-scale production run. There was a potential to double this volume of higher-titer supernatant by increasing the frequency of harv est. It seemed that a lower metabolic rate (i.e. lactate production) in the packaging cell culture was associated with higher vector producing ability . Conclusions These data demonstrated the feasibility of producing retroviral vector with enhanced titers and clinically useful quantities in a 'closed' ACS. Thus a new approach for large-scale retroviral vector production is d eveloped. Copyright (C) 1999 John Wiley & Sons, Ltd.