MODELING AND OPTIMIZATION OF THE BACULOVIRUS EXPRESSION VECTOR SYSTEMIN BATCH SUSPENSION-CULTURE

A mathematical model has been developed that predicts the cell populat ion dynamics and production of recombinant protein and infective extra cellular virus progeny by insect cells after infection with baculoviru s in batch suspension culture. Infection in the model is based on the rate of virus attachment to suspended insect cells under culture condi tions. The model links the events following infection with the sequenc e of gene expression in the baculovirus replicative cycle. Substrate d epletion is used to account for the decrease in product yield observed when infecting at high cell densities. Model parameters were determin ed in shaker flasks for two media: serum-supplemented IPL-41 medium an d serum-free Sf900II medium. There was good aggreement between model p redictions and the results from an independent series of experiments p erformed to validate the model. The model predicted: (1) the optimal t ime of infection at high multiplicity of infection; (2) the timing and magnitude of recombinant protein production in a 2-L bioreactor; and (3) the timing and magnitude of recombinant protein production at mult iplicities of infection from 0.01 to 100 plaque-forming units per cell . Through its ability to predict optimal infection strategies in batch suspension culture, the model has use in the design and optimization of large-scale systems for the production of recombinant products usin g the baculovirus expression vector system. (C) 1994 John Wiley & Sons , Inc.