The effect of cell line, phylogenetics and medium on baculovirus budded virus yield and quality

The performance of bioprocesses involving baculoviruses largely depends on an efficient infection of cells by concentrated budded virus (BV) inoculums. Baculovirus expression vector systems have been established using Autographa californica nucleopolyhedrovirus (AcMNPV), a group I NPV that displays rapid virus kinetics, whereas bioprocesses using group II baculovirus-based biopesticides such as Helicoverpa armigera nucleopolyhedrovirus (HearNPV) have the limitation of low levels of BV, as these viruses often display poor BV production kinetics. In this study, the effect of key parameters involved in the quality of progeny virions, including cell line, virus phylogenetics and medium, on viral DNA replication, virus trafficking to the extracellular environment, and the yield of recombinant protein or polyhedra were investigated in synchronous infections of HearNPV and AcMNPV. HearNPV showed higher vDNA replication in its optimum medium, SF900III, when compared to AcMNPV, but both viruses had similar specific extracellular virion content. However, the ratio of AcMNPV extracellular virions to the total number of progeny virions produced was higher, and their quality was tenfold higher than that of HearNPV extracellular virions. The results of infection of two different cell lines, High Five and Sf9, with AcMNPV, along with HearNPV infection of HzAM1 cells in three different media, suggest that the host cells and the nutritional state of the medium as well as the phylogenetics of the virus affect the BV yields produced by different baculovirus/cell line/medium combinations.