The Use of GM Crops in Developing Countries
Case study 8: Biopharmaceuticals
3.62 An application of genetic modification that differs considerably from the previous examples is the possibility of producing biopharmaceuticals, such as vaccines, in crops. Two distinct procedures can be identified. One option is to modify plants so that they produce substances which can be extracted from the harvested plant and then processed into refined compounds. The other option is to modify plants in such a way that they produce vaccines which can be administered by eating the crop. This is achieved by changing the genetic structure of the crop to produce DNA fragments from a specific pathogen. These fragments code for proteins which provoke an immune response in the human body. The advantages of edible vaccines are manifold: injected vaccines are expensive, require trained medical staff for their administration, and usually require constant cooling during transport and storage, which creates difficulties in many developing countries. The use of needles also brings with it the risks of spreading infections.
3.63 Development of GM crops which can produce biopharmaceuticals is at a very early stage. Scientists at Cornell University are currently working on tomatoes modified to be used as a vaccine against the Norwalk virus, which causes severe diarrhoea. Studies on mice have already shown an increased immune response. In another study, bananas have been genetically modified to produce a vaccine against hepatitis, although it has not yet been possible to produce robust levels of antigens in the fruit.96 There have also been experiments with GM potatoes aiming to develop a vaccine against rotavirus and against the bacterium E. coli which causes diarrhoea. Feeding studies involving mice have shown valid responses.97
3.64 However, a number of questions remain to be addressed. One of these is how the appropriate dose could be controlled. Another concerns the effect of such crops on insects and other animals which might feed on it. For example, it has been reported that avidin, which has been produced commercially in GM maize for use in research and diagnostics, is toxic for certain insects.98 There are also environmental issues relating to gene flow from GM crops to non-GM crops. Furthermore, it has been reported that left-over grains from GM maize, modified to express biopharmaceutical compounds, have inadvertently germinated amidst soybeans grown on the same field in the season following the trial.99 It is clear that this use of GM crops will require the provision of special agronomic facilities that restrict, for example, the spread of seed and pollen. Furthermore, appropriate regulatory oversight would need to be in place to ensure that the required standards are met.
Footnotes96 AEBC (2002) Looking Ahead - An AEBC Horizon Scan (London: Department of Trade and Industry).
97 Wong K (2001) Souped-Up Spuds Show Promise for Edible Vaccines, Scientific American. Available: http://www.sciam.com/article.cfm?chanID=sa003&articleID=00019658-ED97-1C5E-B882809EC588ED9F. Accessed on: 20 May 2003.
98 GeneWatch (2003) Briefing No. 21 Genetic Modification: The Need for Special Regulation (Derbyshire, UK: GeneWatch). Avidin is an avian egg white protein, useful due to its high affinity to biotin. The avidin-biotin reaction has now become a tool in molecular biology, with numerous applications.
99 Cohen P (2002) Stray genes spark anger, New Scientist 176 (2370): 7.