Recombinant antibody production

Figure 5.8 Electrospray and transformed electrospray spectra of the light- and heavy-chain antibody fragments of recombinant ritnximab obtained by LC-MS analysis. Reprinted from 7. Chromatogr., A, 913, Wan, H. Z., Kaneshiro, S., Frenz, J. and Cacia, J., Rapid method for monitoring galactosylation levels dnring recombinant antibody production by electrospray mass spectrometry with selective-ion monitoring , 437-446, Copyright (2001), with permission from Elsevier Science.

Approximately 10-15 d from the start of selection, colonies should be visible to the naked eye, and the culture supernatants from the wells should be assayed for antibody by ELISA (see below). Select cell lines for expansion on the basis of the level of recombinant antibody production, and the number and size of the colonies in the well. Wells with single colonies should be chosen. 

A number of non-hybridoma techniques have been developed for in vitro antibody production a review of recombinant antibody production is covered in Chapter 6. 

Sellick, C.A., Croxford, A.S., Maqsood, A.R., Stephens, G. et al. (2011) Metabolite profiling of recombinant CHO cells designing tailored feeding regimes that enhance recombinant antibody production. Biotechnol. Bioeng., 108, 3025-3031. 

Product formation kinetics in mammalian cells has been studied extensively for hybridomas. Most monoclonal antibodies are produced at an enhanced rate during the Gq phase of the cell cycle (8—10). A model for antibody production based on this cell cycle dependence and traditional Monod kinetics for cell growth has been proposed (11). However, it is not clear if this cell cycle dependence carries over to recombinant CHO cells. In fact it has been reported that dihydrofolate reductase, the gene for which is co-amplified with the gene for the recombinant protein in CHO cells, synthesis is associated with the S phase of the cell cycle (12). Hence it is possible that the product formation kinetics in recombinant CHO cells is different from that of hybridomas. 

Biotechnology era beginning First recombinant DNA products Human insulin Human growth hormone Interferons, etc. Monoclonal antibodies Nucleotide blockage Growth in use of natural products and neutraceuticals... 

The first hurdle encountered during the development of alfalfa as a recombinant protein production system was the relative inefficiency of the available expression cassettes. A study in which a tomato proteinase inhibitor I transgene was expressed in tobacco and alfalfa under the control of the cauliflower mosaic virus (CaMV) 35S promoter showed that 3-4 times more protein accumulated in tobacco leaves compared to alfalfa leaves [5]. Despite the low efficiency of the CaMV 35S promoter in alfalfa, bio-pharmaceutical production using this system has been reported in the scientific literature. Such reports include expression of the foot and mouth disease virus antigen [6], an enzyme to improve phosphorus utilization [7] and the anti-human IgG C5-1 [8]. In this last work, the C5-1 antibody accumulated to 1% total soluble protein [8]. 

More recently, recombinant antibodies (mostly IgGs) have been produced in the milk of transgenic animals [21,22]. In particular, one study with transgenic mice has shown that it is possible to produce a porcine chimeric IgA that can form dimers in the presence of the J chain [23]. However, the production of fully assembled slgA has yet to be reported. 

One of the most obvious benefits of plants is the potential for production scale up, leading to the production of virtually limitless amounts of recombinant antibody at minimal cost Plants are easy to grow, and unlike bacteria or animal cells their cultivation is straightforward and does not require specialist media, equipment or toxic chemicals. It has been estimated that plantibodies could be produced at a yield of 10-20 kg per acre at a fraction of the cost associated with production in mammalian cells [2,18] The use of plants also avoids many of the potential safety issues associated with other expression systems, such as contaminating mammalian viruses or prions, as well as ethical considerations involving the use of animals. 

Mammalian cell suspension cultures are the preferred choice for large-scale recombinant protein production in stirred-tank bioreactors. The most widely used systems are Chinese hamster ovary (CHO) cells and the murine myeloma fines NSO and SP2/0. In half of the biological license approvals from 1996-2000, CHO cells were used for the production of monoclonal antibodies and other recombinant glycosylated proteins, including tPA (tissue plasminogen activator) and an IgGl fusion with the tumor necrosis factor (TNF) receptor, the latter marketed as Enbrel [7]. 

Dinnis, D. and James, D. 2005. Engineering mammalian cell factories for improved recombinant monoclonal antibody production lessons from nature Biotechnology and Bioengineering 91(2), 180-189. 

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