High-throughput screening and selection of yeast cell lines expressing monoclonal antibodies
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- Barnard, G.C., Kull, A.R., Sharkey, N.S. et al. J Ind Microbiol Biotechnol (2010) 37: 961. doi:10.1007/s10295-010-0746-1
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The methylotrophic yeast Pichia pastoris has recently been engineered to express therapeutic glycoproteins with uniform human N-glycans at high titers. In contrast to the current art where producing therapeutic proteins in mammalian cell lines yields a final product with heterogeneous N-glycans, proteins expressed in glycoengineered P. pastoris can be designed to carry a specific, preselected glycoform. However, significant variability exists in fermentation performance between genotypically similar clones with respect to cell fitness, secreted protein titer, and glycan homogeneity. Here, we describe a novel, multidimensional screening process that combines high and medium throughput tools to identify cell lines producing monoclonal antibodies (mAbs). These cell lines must satisfy multiple selection criteria (high titer, uniform N-glycans and cell robustness) and be compatible with our large-scale production platform process. Using this selection process, we were able to isolate a mAb-expressing strain yielding a titer (after protein A purification) in excess of 1 g/l in 0.5-l bioreactors.