Alexandru-Crivac, C. N.; Cartwright, J. F.; Taylor, R. M.; Sweeney, B. M.; Feary, M.; Chathoth, K. T.; Fabian, D. K.; Allsopp, H.; Brown, A. J.; James, D. C.

To comparatively evaluate cellular constraints on recombinant monoclonal antibody (mAb) production by Chinese Hamster Ovary (CHO) cells, we analysed the transcriptomes of 24 clonally derived CHO cell lines engineered with PiggyBac transposon technology to stably produce four recombinant monoclonal antibodies (mAbs) at varying specific production rates. Fed-batch cultures were sampled at exponential (day 5) and stationary (day 10) phases of culture for analysis by RNA-Seq. Recombinant mRNAs accounted for a large proportion of total mRNA across all clones, and efficient use of heavy chain (HC) mRNA to synthesise recombinant mAb (qP per HC mRNA) varied significantly with respect to both mAb product and cell line. Comparative bioinformatic analyses of CHO transcriptomes focussed on mAb specific production rate and utilised both data-driven and hypothesis-led approaches, specifically (i) production or non-production of recombinant mAb, (ii) changes in the abundance of functional groups of mRNAs abundance with mAb specific production rate and (iii) comparative analysis of informatically-mined gene subsets associated with cellular functions hypothesised to impact recombinant mAb synthesis and secretion. These analyses revealed widespread constitutive and adaptive changes in mRNA abundance associated with mAb production across a variety of cellular functions. Typically, most mechanistically consistent changes in mRNA abundance co-varying with mAb production were evident at the stationary phase sample point. These data revealed both recombinant mAb-specific limitations on cellular synthetic capacity and a generic adaptive strategy used by CHO cells to support high-level mAb production. The latter was achieved by directed and permissive regulation of endoplasmic reticulum and other processes to accommodate increased synthetic flux.