Cell cultures containing 0 ~ 5 mM sodium butyrate (NaBu) and grown at 30 and 37°C were conducted to investigate the combined effect of NaBu and low temperature on the quantity and quality of an antibody production in CHO cells. Although NaBu addition decreased cell viability by apoptosis in a dose-dependent manner at both 30 and 37°C, the onset of significant apoptosis induced by NaBu was delayed by lowering culture temperature. The highest specific antibody productivity (q p ) of 23.26 pg/cell/day was obtained in the culture containing 2 mM NaBu at 30°C; however, the highest antibody concentration of 167.84 mg/L was achieved in the culture containing 1 mM NaBu at 30°C, as the detrimental effect of further NaBu addition on cell growth compromised its beneficial effect on q p . Moreover, protein quality with respect to the total sialic acid content and Nglycolylneuraminic acid (Neu5Gc) level was evaluated. There were no apparent changes regarding the total sialic acid content of the antibody, but manipulation of cultures with NaBu treatment or (and) low culture temperature did decrease Neu5Gc levels by 5 ~ 10%. Biological activity of the antibody was also assessed, and no obvious changes were observed. Collectively, the simultaneous application of NaBu and low culture temperature was an effective way to extend culture period and enhance final antibody concentration, without compromising the sialic acid content or biological activity.

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Lowering the culture temperature is often useful to improve the production of many recombinant proteins in Chinese hamster ovary (CHO) cells. Batch cultivation of GS-CHO cells expressing TNFR-Fc antibody was therefore carried out at 30, 33.5 and 37 degrees C. TNFR-Fc productivity, q(TNFR-Fc), increased as culture temperature decreased; and the maximum q(TNFR-Fc) was 20 mg/(10(9) cells.day) at 30 degrees C which was three times that at 37 degrees C. Increasing the viable cell density (VCD) to above 2.2 x 10(6) cells/ml, however, decreased the q(TNFR-Fc) at 30 degrees C, which was due to a reduction in transcription of the TNFR-Fc gene. Taken together, lowering temperature can improve q(TNFR-Fc) but the negative effect of increasing VCD compromises this effect. Further process development addressing the issue of cell density-dependent TNFR-Fc productivity is therefore needed.

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