Optimization of growth methods and recombinant protein production in BTI-Tn-5B1-4 insect cells using the baculovirus expression system.

A novel insect cell line from Trichoplusia ni, BTI-Tn 5B1-4 (Tn 5), was compared to Spodoptera frugiperda, Sf 9, cells for production of two recombinant secreted proteins: truncated Epstein-Barr viral attachment protein (EBV gp105) and truncated, soluble tissue factor (sTF). Under optimum conditions for both cell lines, Tn 5 cells produced 28-fold more secreted sTF than Sf 9 cells, respectively, on a per cell basis. The total production of gp105 was similar for the two cell lines. However, Tn5 cells secreted gp105 much more efficiently, resulting in 5-fold higher levels in the extracellular medium. Despite these increases, Tn 5 cells are attachment-dependent, and protein production is sensitive to the cell density (cells/cm2), unlike the Sf9 cell line which can be easily grown and scaled up in cell suspension cultures without significantly affecting its per cell production. Thus, protein production from Tn 5 cells above 0.1 L scales was optimized with respect to cell density using standard techniques for the growth of attachment-dependent cells. Roller bottles precoated with DEAE-based microcarriers and suspension cultures employing collagen-coated microcarriers were found to be effective ways of culturing Tn 5 cells. Predetermined optimal cell densities were used to produce EBV gp105 in microcarrier-coated roller bottles or in suspension cultures using collagen-coated microcarriers at concentrations close to those observed in tissue culture flasks.