4.7 AAV Production Yield in STB and Wave™ Bioreactors
The favorable features of insect cell baculovirus platform are the ability of insect cells to grow in suspension culture at a high cell density, a proven linear scalability, and a history of regulatory acceptance of the platform for the production of various biologics[9], [17]. Various reports of AAV production in either conventional stirred-tank bioreactors (STB) (glass, stainless steel, or disposable vessel)[48], [58], [69] or Wave™ bioreactors[69] suggest comparable yields and quality of rAAV vector material (Table 1). The very first report of AAV production employing a Three-Bac system in a 20L bioreactor by Meghrous et al. suggested AAV material generation with around 3-fold improvement in cell-specific yield of functional AAV particles in a controlled environment of bioreactor compared to shake flask[48]. This production run generated around 5x1012 AAV transducing units (Table 1). Subsequent reports of AAV production using modified Three-Bac system in Wave and stirred tank bioreactors suggest that AAV volumetric yield was in the range of 5x109 – 3x1010 VG/mL with a comparable consistency at various scales of Wave™ and STB, respectively[69]. The lower volumetric yield of AAV in Wave™ bioreactor was attributed to poor oxygen mass transfer control in the culture. However, the vector quality, as indicated by the ratio of genomic: transducing units, was consistent in all production runs. Table 1 summarizes the AAV yield at various scales, and in different IC-BEVS production reported. A schematic overview of AAV production process using IC-BEVS platform is depicted in Figure 3.