Production of Choristoneura fumiferana nucleopolyhedrovirus in C. fumiferana (CF-2C1 cells) in a 3 litre bioreactor using serum-free medium

The purpose of this study was to develop a cell culture process in a bioreactor for the production of a viral insecticide for the spruce budworm, Choristoneura fumiferana. Several cell lines were tested for their growth in serum-free medium suspension cultures. One cell line, CF-124T-2C1 (CF-2C1), was successfully adapted to grow in suspension cultures in SFM. Serum-free Ex-Cell 405 medium produced a much higher cell density (6.3 x 10⁶ cells ml^-1) than the Grace's medium supplemented with 10% fetal bovine serum (2.5 x 10⁶ cells ml^-1). Also, a higher yield of virus was obtained in the former medium. Ex-Cell 405, was used to study the growth of CF-2C1 cells and the production of C. fumiferana nucleopolyhedrovirus (CfMNPV) in a 3 l bioreactor. Under these conditions, a specific growth rate (μ) of 0.027 h^-1 was obtained during the exponential growth phase, and the specific carbon dioxide evolution rate, as determined by on-line measurement, was 0.9 x 10^-16 mol cell^-1 s^-1 and 1.78 x 10^-16 mol cell^-1 s^-1 during growth and infection phases, respectively. Virus production in bioreactor cultures infected at 1.3 x 10⁶ cells ml^-1 was consistently lower than that obtained in Erlenmeyer shake flasks. Only 26% of the cells were infected in the bioreactor compared to 44% in the shake flasks. However, a higher yield of occluded virus was obtained in the bioreactor cultures than in shake flasks. The production of occlusion bodies (OB) achieved in bioreactor cultures was 2 x 10⁶ OB ml^-1.