Production of pharmaceutical proteins from transgenic animals

Different systems are being studied and used to prepare recombinant proteins for pharmaceutical use. The blood, and still more the milk, from transgenic animals appear a very attractive source of pharmaceuticals. The cells from these animals are expected to produce well-matured proteins in potentially huge amounts. Several problems remain before this process becomes used in a large scale. Gene transfer remains a difficult and costly task for farm animals. The vectors carrying the genes coding for the proteins of interest are of unpredictable efficiency. Improvement of these vectors includes the choice of efficient promoters, introns and transcription terminators, the addition of matrix attached regions (MAR) and specialized chromatin sequences (SCS) to enhance the expression of the transgenes and to insulate them from the chromatin environment. Mice are routinely used to evaluate the gene constructs to be transferred into larger animals. Mice can also be utilized to prepare amounts as high as a few hundred mg of recombinant proteins from their milk. Rabbit appears adequate for amounts not higher than 1 kg per year. For larger quantities, goat, sheep, pig and cow are required. No recombinant proteins extracted from the blood or milk of transgenic animals are yet on the market. The relatively slow but real progress to improving the efficiency of this process inclines to be reasonably optimistic. Predictive reports suggest that 10% of the recombinant proteins, corresponding to a 100 million dollars annual market, will be prepared from the milk of transgenic animals by the end of the century.