Plantibody

Passive immunization is a medical strategy long employed to provide temporary protection against pathogens. Early implementations involved recovering ostensibly cell-free plasma from the blood of human survivors or from non-human animals deliberately exposed to a specific pathogen or toxin. These approaches resulted in crude purifications of plasma-soluble proteins including antibodies.

Antibodies (also known as an immunoglobulins) are complex proteins produced by vertebrates^[1] that recognize antigens (or molecular patterns) on pathogens and some dangerous compounds in order to alert the Adaptive immune system that there are pathogens within the body.^[2]

A plantibody is an antibody that is produced by plants that have been genetically engineered with animal DNA encoding a specific human antibody known to neutralize a particular pathogen or toxin. The transgenic plants produce antibodies that are similar to their human counterparts, and following purification, plantibodies can be administered therapeutically to acutely ill patients or prophylactically to at-risk individuals (such as healthcare workers). The term plantibody and the concept are trademarked by the company Biolex.

Production

A plantibody is produced by insertion of genes encoding antibodies into a transgenic plant. The plantibodies are then modified by intrinsic plant mechanisms (N-glycosylation).^[3] Plantibodies are purified from plant tissues by mechanical disruption and denaturation/removal of intrinsic plant proteins by treatment at high temperature and low pH, as antibodies tend to be stable under these conditions. Antibodies can further be purified away from other acid- and temperature- stable proteins by capture on commercially produced protein A resins. Production of antibodies in whole transgenic plants, such as species in the genus Nicotiana, is cheaper and safer than in cultured animal cells.^[4]