Growth, Viral Production and Metabolism of a Helicoverpa Zea Cell Line in Serum-free Culture

Insect cell cultures have been extensively utilised for means of production for heterologous proteins and biopesticides. Spodoptera frugiperda (Sf9) and Trichoplusia ni (High Fivetrade mark) cell lines have been widely used for the production of recombinant proteins, thus metabolism of these cell lines have been investigated thoroughly over recent years. The Helicoverpa zea cell line has potential use for the production of a biopesticide, specifically the Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus (HaSNPV). The growth, virus production, nutrient consumption and waste production of this cell line was investigated under serum-free culture conditions, using SF900II and a low cost medium prototype (LCM). The cell growth (growth rates and population doubling time) was comparable in SF900II and LCM, however, lower biomass and cell specific virus yields were obtained in LCM. H. zea cells showed a preference for asparagine over glutamine, similar to the High Fivetrade mark cells. Ammonia was accumulated to significantly high levels (16 mM) in SF900II, which is an asparagine and glutamine rich medium. However, given the absence of asparagine and glutamine in the medium (LCM), H. zea cells adapted and grew well in the absence of these substrates and no accumulation of ammonia was observed. The adverse effect of ammonia on H. zea cells is unknown since good production of biologically active HaSNPV was achieved in the presence of high ammonia levels. H. zea cells showed a preference for maltose even given an abundance supply of free glucose. Accumulation of lactate was observed in H. zea cell cultures.