Plant Antibodies for lmmunotherapy

The use of transgenic plants for the expression of therapeutic recombinant proteins is gradually gaining acceptance in the scientific community (Moffat, 1995). There are many attractions to this technology, including the possibility of manufacture on an agricultural scale for bulk production and to reduce costs, as well as the range of plant hosts available and the stability of transgenic lines in seeds that might allow export of transgenic crops (containing, for example, medicinal compounds) to deprived areas of the world. These could then be grown within the existing agricultural infrastructure rather than require the funding of new pharmaceutical factories. From a technical viewpoint, the general capabilities and adaptability of plants are exciting. For example, the processing and assembly of proteins in plants appear to match closely that found in mammalian cells, which might be a particular advantage over the more commonly used microbial expression systems. In addition, because transformation techniques result in the stable integration of the foreign DNA into the plant genome, genetic recombination by sexual crossing of transgenic plants is a simple method to introduce new genes or to accumulate multiple foreign genes into plants. The original description of antibodies produced in plants demonstrated the principle of co-expression of two recombinant gene products in plants that were correctly folded and assembled into a molecule that was functionally identical with its mammalian counterpart (Hiatt et al., 1989). Severa1 groups have since expressed antibody molecules in plants, either to modify or improve plant performance and characteristics or with a view to harnessing plants as bioreactors for large-scale production of antibodies. In this Update we shall review briefly the developments in the field of antibody engineering in transgenic plants and address the potential of plant antibodies for immunotherapy.