Transgenic milk

Parker MH, Birck-Wilson E, Allard G, Masiello N, Day M, Murphy KP, Paragas V, Silver S, Moody MD (2004), Purification and characterization of a recombinant version of human a-fetoprotein expressed in the milk of transgenic milk, Prot. Express. Purif. 38 177-183. 

Transgenic milk 1-10 30-40 Removal of casein and lipids Low cost heavy pretreatments... 

Due to discrimination from species to species, protein A resins can be used to separate monoclonal antibodies from transgenic milk. Autologous antibodies are not adsorbed if the animal is well chosen. For instance, monoclonal humanized IgG expressed in goat milk can be separated. 

As detailed in Section III, initial raw materials for the production of antibodies are very different. Animal sera, transgenic milk, bovine colostrum, cell culture (hybridomas or other recombinant cells), ascites fluid, and egg yolk are the best known. Each raw material represents a potential carrier for adventitious agents. All of them can contain viruses. More specifically, animal sera used as source of antibodies, or as a cell culture medium supplement, can additionally carry mycoplasma and pyrogens depending on the method of collection. 

Fulton, S. (1999). Production of antibodies in transgenic milk. Proc. Antibody Prod. Downstream Process., San Diego, CA, 1999. 

Scott Fulton (Genzyme Transgenics) presented a paper on the production and recovery of protein products in transgenic milk. Recovery of proteins... 

Pollock DP, Kutzko JP, Birck-Wilson E, et al. Transgenic milk as a method for the production of recombinant antibodies. J. Immunol. Methods, 1999 231(1/2) 147-157. 

Table 2. Pharmaceuticals Produced in Milk or Blood of Transgenic Farm Animals...

Van Berkel, P.H., Welling, M.M., Geerts, M. et al. (2002) Large scale production of recombinant human lactoferrin in the milk of transgenic cows. Nature Biotechnology, 20 (5), 484—487. 

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. 

Table 5.6 Proteins of actual/potential therapeutic use that have been produced in the milk of transgenic animals...

A number of additional general characteristics may be cited that render attractive the production of pharmaceutical proteins in the milk of transgenic farm animals. These include ... 

Figure 5.2 The production and purification of tPAfrom the milk of transgenic goats. (WAP promoter murine whey acid promoter). The downstream processing procedure yielded in excess of an 8000-fold purification factor with an overall product yield of 25 per cent. The product was greater than 98 per cent pure, as judged by sodium dodecyl sulfate (SDS) electrophoresis...

High expression levels of proteins are potentially attained. In many instances, the level of expression exceeds 1 g protein/litre milk. In one case, initial expression levels of 60 g l-1 were observed, which stabilized at 35 g L1 as lactation continued (the expression of the arantitrypsin gene, under the influence of the ovine P-lactoglobulin promoter, in a transgenic sheep). Even at expression levels of 1 g L1, one transgenic goat would produce a similar quantity of product in 1 day as would be likely recoverable from a 50-1001 bioreactor system. 

Table 5.7 Typical annual milk yields as well as time lapse between generation of the transgene embryo and first product harvest (first lactation) of indicated species...

In addition to milk, a range of recombinant proteins have been expressed in various other targeted tissues/fluids of transgenic animals. Antibodies and other proteins have been produced in the blood of transgenic pigs and rabbits. This mode of production, however, is unlikely to be pursued industrially for a number of reasons ... 

Figure 12.10 Outline of the production and purification of antithrombin from the milk of transgenic goats. Purification achieves an overall product yield in excess of 50 per cent, with a purity greater than 99 per cent...

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