In this study, we evaluated three cell retention devices, an alternating tangential flow (ATF) system, a spin-filter, and a Centritech Lab III centrifuge, for the production of recombinant human Factor VIII co-expressed with von Willebrand factor. From the results, it was found that the FVIII activity in bioreactor was significantly higher in the ATF perfusion culture than two other perfusion cultures. Moreover, the FVIII activity yield was unexpectedly low in the ATF perfusion culture. We have, therefore, studied the reasons for this low FVIII activity yield. It was revealed that the inactivation and the surface adsorption of FVIII onto the harvest bag were not the main reasons for the low yield in the ATF perfusion culture. The FVIII activity yield was not increased by the use of a hollow fiber filter with 0.5 μm pore size instead of 0.2 μm pore size. Additionally, the retention of FVIII molecules by the hollow fiber filter was a dominant factor in the low FVIII activity yield in the ATF perfusion culture. We demonstrated that FVIII yield was significantly improved by controlling transmembrane pressure (TMP) across the hollow fiber filter membrane. Taken together, these results suggest that TMP control could be an efficient method for the enhancement of FVIII yield in an ATF perfusion culture.
Keywords: ATF perfusion culture; FVIII activity yield; FVIII/vWF complex; Hollow fiber filter membrane; Molecular sieving; Transmembrane pressure.