Baculovirus-mediated production of HDV-like particles in BHK cells using a novel oscillating bioreactor

We have recently demonstrated the assembly of hepatitis delta virus-like particles (HDV VLP) by co-transducing hepatoma cells using two recombinant baculoviruses, one encoding hepatitis B surface antigen (HBsAg), and one encoding large delta antigen (L-HDAg). In this study, we further demonstrated the assembly and secretion of VLP in other mammalian cells. The assembly efficiency varied depending on cell lines, the baculovirus constructs and the relative dosage of both recombinant viruses. The co-transduction of BHK cells led to the formation of VLPs resembling authentic virions in size and appearance. The production process was transferred to a novel oscillating packed bed bioreactor, BelloCell, in which the transduction efficiency was up to ≈90% for a high cell density of 1.5 × 107 cells/cm3 bed and a total yield of 427 μg based on HBsAg in the VLP (harvested from 940 ml medium) was obtained. The particle yield corresponded to an average volumetric yield of 454 ng ml−1 and a specific yield of 285 μg/109 cells, and is significantly superior to that can be obtained by the commonly employed transfection method. The combination of baculovirus transduction and BelloCell reactor, thus, may represent a simple and efficient approach for the production of HDV VLP and viral vectors.