The gel microdrop secretion assay: Identification of a low productivity subpopulation arising during the production of human antibody in CHO cells |
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Authors: | Linda Hammill Jacqueline Welles Gerald R. Carson |
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Affiliation: | (1) Department of Molecular Biology, BASF Bioresearch Corporation, 100 Research Drive, Worcester, MA, 01605, U.S.A.;(2) Department of Molecular Biology, BASF Bioresearch Corporation, 100 Research Drive, Worcester, MA 01605, U.S.A. |
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Abstract: | The long-term stability of high-level expression is the mostimportant factor to consider when choosing cell lines for the expression of recombinant proteins. Declining volumetricyields in large-scale fermentation can be caused by changes affecting the cell population as a whole such as loss in viability, depletion of nutrients or accumulation of metabolites affecting cell growth. Alternatively, geneticinstability may lead to the outgrowth of a less productive,metabolically favored sub-population. Currently a variety ofparameters are measured to monitor the condition of cells infermenters including glucose uptake, lactate accumulation andoxygen consumption; in addition, periodic viable cell countsallow the determination of the growth rate and viability of the population. All of these methods measure the condition ofthe cell population as a whole and changes must involve a significantly large proportion of the total culture in orderto be detectable. Here we report on a method that allows theevaluation of the productivity of individual cells. Using the gel microdrop secretion assay, we detected the appearance ofa sub-population of cells with lower productivity. Subsequentanalysis of the culture confirmed the existence of lower productivity cells with a lower vector copy number. Therefore,the single cell secretion assay proved to be a rapid method todetect and isolate a low productivity variant of the producer cell line. |
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Keywords: | CHO cells gel microdrops human antibody population parameters productivity stability |
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