Ebola virus currently has no licenced vaccine or cure, however several potential therapies are in development. Why does this merit mention on a blog about botany? For one good reason; scientists used plants in a bio-pharming approach to produce the potential Ebola treatment which was recently given to 3 patients infected with the virus. Bio-pharming uses genetic modification to introduce genes coding for pharmaceutical proteins (e.g. antibodies, or when produced in plants; ‘plantibodies’) into plants, the plant will then produce these proteins as if they were its own – essentially acting as a protein factory. The plants are harvested, the pharma-protein extracted and purified to a level comparable to any other medicinal protein.

Bio-pharming is currently in the news as ZMapp (Mapp Pharmaceuticals), an experimental antibody cocktail targeted against Ebola virus and produced in tobacco plants, was used in the treatment of two US aid workers and a priest infected with the virus. ZMapp is a combination of three antibodies which recognise different parts of Ebola glycoprotein; a protein present on the outside of the virus which allows the virus to attach to and enter into cells. The antibodies attach strongly to the Ebola glycoprotein thereby inactivating the virus, preventing it from entering cells and acting as a beacon to the patient’s immune system that the virus needs to be destroyed.

The starting point for this particular biopharming process was to isolate Ebola specific antibodies from mice. The genetic code of these antibodies was determined and the bits that make an antibody recognisably ‘mouse’ were swapped for the equivalent human sections whilst retaining the Ebola binding portions. Once the human versions of the Ebola antibody sequences were established they were cloned into a virus-based plant transformation system (magnICON from ICON Genetics) producing a ‘rapid antibody manufacturing system’ (RAMP). The magnICON system uses two modified plant viruses (tobacco mosaic virus and potato virus X; Giritch et al 2006) that don’t compete with each other when in the same plant, allowing high level expression of different parts of an antibody in the same cell. The RAMP system is potentially scalable, so could allow production of large amounts of target protein as some of the process can be automated. ZMapp is being produced by Kentucky Bioprocessing.