471216 A Metabolic Flux Based Dynamic Model for Antibody Producing Mammalian Cells
Mathematical models have been significant tools for combining cell physiology and engineering to predict the behavior of cell metabolism and optimize culture conditions by identifying process parameters that significantly impact cell growth and target metabolite productivity. The cell metabolism can be described and characterized using a metabolic network that accounts for biotic phase reactions. Metabolic flux analysis is a widely used approach to characterize the state of cellular metabolism and activities of various metabolic pathways. The analysis enables computation of intracellular fluxes from information on experimentally determined metabolite uptake and excretion rates by using the stoichiometry of an identified metabolic network. The analysis enables identification of all significant fluxes and significant metabolites influencing cell metabolism so that it is possible to obtain a set of macro-reactions linking the substrates to the end-products, the so-called elementary flux modes. In this work, a novel dynamic model is developed on the basis of these macro-reactions involving extracellular substrates and products for a mammalian cell culture with a MAB as the target product. The processes accounted for in the model are cell growth and death, uptake of key nutrients, glucose and glutamine, accumulation of lactate and ammonia, and MAB synthesis. In the end, the cell-specific kinetics of growth and death of mammalian cells, utilization of glucose and glutamine, and generation of MAB, ammonia, and lactate are expressed in terms of concentrations of glucose, glutamine, lactate, and ammonia. The model incorporates a structured kinetic representation of MAB synthesis. The model accounts for the impact of glutamine availability and ammonia accumulation on translation rates and stability of mRNAs involved in assembly of MAB. Glutamine provides remarkable metabolic energy for cell growth and protein synthesis and is an important precursor of proteins and peptides, as well as amino sugars, purines and pyrimidines. It has been observed that glutamine depletion in the culture greatly influences the overall antibody synthesis rate and increases the apoptotic death rates of mammalian cells. This is accounted for in the dynamic model. Performance of batch and fed-batch cultures with intermittent or sustained addition of glucose and/or glutamine is simulated. The model predictions are in good agreement with experimental data reported in the literature for Immunoglobulin G (IgG) antibodies.