TRANSGENIC BIOREACTORS

1. Although many human therapeutic proteins are currently produced in microbial fermenters using recombinant DNA techniques, it is obvious t hat microbial processing is not suitable for a large number of bioacti ve proteins owing to the inability of bacteria to carry out postsynthe tic modification reactions required for full biological activity. 2. T his disadvantage does not apply to animal cell bioreactors that can ge nerate biologically fully active entities, yet the use of large-scale animal cell cultures for production purposes is prohibitively expensiv e. 3. With the advent of transgenic technology, the production of valu able human pharmaceuticals in large farm animals (pig, sheep, goat and dairy cattle) has become more and more attractive as a high-quantity, low-cost alternative. By employing targeted gene transfer, e.g. using mammary gland-specific regulatory sequences fused with the desired pr oduction genes, it is possible to govern the expression to occur exclu sively in the mammary gland and hence the gene product is being ultima tely secreted into the milk. 4. While reviewing the remarkable progres s in this field that has even led to commercial exploitations, we will outline in somewhat greater detail our strategy for the use of dairy cattle as a bioreactor for valuable proteins of pharmaceutical interes t.