As a eukaryotic gene expression system, mammalian cells benefits from the most comprehensive post-translational modifications for expressed proteins. Today, 60-70% of all recombinant protein pharmaceuticals and 95% of the currently approved therapeutic antibodies are produced in mammalian cell lines. Creative Biolabs offers HostOptim™ mammalian cell expression services for transient expression and stable cell line development.
Despite relatively high production costs and difficult in handling, mammalian cell expression system has incomparable advantages. The advanced mammalian folding, secretion and post-translational apparatus are capable of producing antibodies have closer properties to those in the human body than other expression systems. Moreover, highly efficient expression, folding and post-translation of large and complex IgGs results in high product quality which reduces efforts and costs in the subsequent and more expensive downstream processing steps.
Creative Biolabs provides two cell lines for antibody expression: HEK293 and CHO. Due to improved cell lines, optimized production media, and prolonged production processes at high cell densities, we have the ability to produce more than 12 g/L IgGs in mammalian cell culture. The antibody production levels can up to 100 pg antibody per cell per day (pcd).
The general protocol of mammalian cell expression is described below. DNA of interest is first cloned into an appropriate vector. By transfection (plasmid transient transfection, retrovirus or lentivirus transduction, modified mRNA transfection), the gene can be inserted into the host for expression. For expressing heterologous genes in mammalian cells, vectors derived from mammalian viruses are usually used, such as Simian Viruses 40 (SV40), polyomavirus, herpesvirus, and papovavirus. Fluorescent proteins and other expression tags are used for monitoring expression.
Figure 1. Mammalian cell expression systems (Lai et al. 2013)
Stable Production of Antibodies in Mammalian Cells
Stable IgG production cell lines are essential in the therapeutic sector in order to guarantee long-term production stability. In stable cell lines, the antibody gene expression cassettes are stably integrated into the host cell genome. Strong promoters like the immediate early cytomegalovirus (CMV) or the cellular elongation factor (EF) 1-alpha promoter are needed to implement into the expression vector for improved mRNA stability and translation efficiency. Besides, increasing the number of antibody gene copies in the genome through gene amplification is also applied to enhance antibody expression.
Transient Production of Antibodies in Mammalian Cells
Transient and semi-stable mammalian antibody expression allows fast and parallelized production without any need to generate producer cell lines. Transient antibody production is suitable for small-scale production in antibody screening. The production volumes of transient mammalian antibody production can be scaled up by employing batch or fed-batch bioreactor processes to more than 150 L. The human embryonic kidney (HEK) 293 cell lines have been widely used for transient protein expression.
Our HostOptim™ technology has developed from our core expertise in the field of gene expression and protein synthesis. Improved promoters, vectors and other transcriptional approaches (i.e. more protein per mRNA) are used to increase expression levels. This selection and expansion process takes about 2-3 months.
Our experienced expert will be with you in every step of your experiment. We will try every way to produce the highest level of recombinant proteins with the shortest time, lower total cost, deliver target proteins in fast turnaround time and offer technical support directly. For more detailed information, please feel free to contact us or directly sent us an inquiry.
References
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