Transgenic Plants for Antibodies
Immune response to produce antibodies against a pathogen is generally induced by an antigen, but as an alternative, antibodies can also be directly supplied from outside to provide for immunity. Therapeutic potential of antibodies, as a short-term relief against infectious agents, has been recognized for long, but their production has been difficult limiting their clinical use. In 1989, for the first time, it was demonstrated that transgenic plants provide for an in expensive method for the production of functional monoclonal antibodies, also described some­times as plantibodies. Depending upon the crop, these plantibodies can be targeted to the seeds (cereals, oilsseeds, or legumes) or tubers (potato) which can be stored, transported and administered directly.

These recombinant antibodies include fully assembled whole immunoglobulins, antigen-binding fragments of immunoglobulins and single chain variable fragment (scFv). Since several genes are involved in the synthesis of an antibody, transgenic plants each with a single gene are first produced and the genes are then brought together (gene stacking) by crossing such transgenic plants, each with a single gene. The resulting quadruple transgenics thus produced have been shown to assemble successfully the secretory immunoglobulin A (sIgA), which protects against microbial infection at mucosal sites.

The effectiveness of plantibodies against a variety of diseases has been demonstrated. For instance, plantibodies against cell surface antigens of Streptococcus mutans has been shown to reduce tooth decay in animal and human models. Since large doses of an antibody are required for topical passive immunotherapy, transgenic plants may prove effective in producing these large quantities.