Plants can be genetically engineered to express non-native proteins, for example, crops can be engineered to produce insect toxins in order to improve disease-resistance. However, I was not aware of their ability to express antibodies until, inspired by my expanding collection of house plants, I googled ‘plant immune systems’.
Plants don’t naturally produce antibodies – they do not possess an adaptive immune system or any circulating immune defence cells. Despite this, plants can be made to express and assemble full length antibody heavy chains and light chains. This was first published back in 1989, when Hiatt et al. [1] successfully introduced mouse immunoglobulin genes to tobacco plants and produced functional antibodies with reasonable efficiency. The excellent term ‘plantibody‘ was coined soon after, to refer to antibodies and fragments of antibodies produced by plants transformed with antibody-coding genes.
The first approved therapeutic plantibody was CaroRx from Planet Biotechnology, which binds to the bacteria Streptococcus mutans to prevent tooth decay in human and was created from tobacco plants. More recently, LeafBio have been developing Zmapp against Ebola, a mixture of three antibodies, again made in tobacco plants [2]. Approaches typically use a viral vector encoding the target antibody to infect the plant and cause antibody production, which can be harvested and extracted from the plant leaves. Compared to producing antibodies in mammalian cells, plantibodies could represent a low cost and scalable option. Antibodies may have improved safety profiles due to lower risk of animal pathogen contamination, although plant-specific toxins also exist and would need to be screened against. There may also be differences in antibody properties such as glycosylation when compared with mammalian systems, which could affect antibody function [3].
Having never heard of plantibodies, or plants being able to express antibodies, I thought this was a cool bit of science to share!
References
[1] Hiatt, A., Caffferkey, R. and Bowdish, K., 1989. Production of antibodies in transgenic plants. Nature, 342(6245), pp.76-78
[2] Zhang, Y., Li, D., Jin, X. and Huang, Z., 2014. Fighting Ebola with ZMapp: spotlight on plant-made antibody. Science China. Life sciences, 57(10), p.987.
[3] Chen, Q. and Davis, K.R., 2016. The potential of plants as a system for the development and production of human biologics. F1000Research, 5
