Imagine a world in which any protein, either naturally occurring or designed by man, could be produced safely, inexpensively and in almost unlimited quantities using only simple nutrients, water and sunlight. This could one day become reality as we learn to harness the power of plants for the production of recombinant proteins on an agricultural scale. Molecular farming in plants has already proven to be a successful way of producing a range of technical proteins. The first plant-derived recombinant pharmaceutical proteins are now approaching commercial approval, and many more are expected to follow.

A functional comparison was made between a monoclonal secretory antibody generated in transgenic plants and its parent murine IgG antibody.The affinity constants of both antibodies for a Streptococcus mutans adhesion protein were similar. However the secretory antibody had a higher functional affinity due to its dimeric structure. In the human oral cavity, the secretory antibody survived for up to three days, compared with one day for the IgG antibody. The plant secretory antibody afforded specific protection in humans against oral streptococcal colonization for at least four months. We demonstrate that transgenic plants can be used to produce high affinity, monoclonal secretory antibodies that can prevent specific microbial colonization in humans. These findings could be extended to the immunotherapeutic prevention of other mucosal infections in humans and animals.

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