DETERMINING THE SAFETY OF TRANSGENIC INSECTS
Mark S. Hoddle
September, 2004

Genetically modified insects (GMI) have generated intense interest among a number of interested parties: the lay-public and environmental communities because of potential adverse ecosystem and health impacts; scientific circles that envision revolutionary construction and application of novel organisms for pest and health management; legislators facing challenging new ideologies regarding the assessment of risk, philosophy of creation issues, and identification and protection of intellectual property rights as this new technology develops and reaches field application phases; and multi-national business concerns that may realize huge financial gains from the development of novel organisms that benefit agricultural industries or alleviate human health threats. The controversy surrounding the potential pros and cons of genetic engineering is so well entrenched in mainstream media that it is commonly the subject of discussion in newspapers, magazines, popular books, television, and radio.

Genetic engineering (GE) of plants, insects, animals, and microorganisms differs from traditional genetic selection for desirable traits in a number of ways: (1) GE by necessity involves in vitro genomic manipulations of the target organism; (2) GE requires the molecular engineer to have certain information (DNA sequences, or position or restriction enzyme sites) for the relevant region of DNA that is to be manipulated; (3) GE requires physical isolation of small useful pieces of DNA from the donor region of interest for manipulation and insertion; (4) GE typically involves the characterization of genotypes prior to the analysis of phenotypes, whereas in traditional breeding programs phenotypes are usually analyzed for desirable traits; (5) viruses, plasmids, microinjection, or gene guns are used to introduce foreign DNA into the target organism rather than recombination using gametes or compounds that induce mutagenesis from which viable organisms are then screened. Often the genetic constructs inserted into the recipient genome contain material that originated from organisms in different phyla or even kingdoms and the resulting organisms express traits that could never have been achieved with traditional genetic manipulations. Consequently, this new technology may present sets of unique inherent risks that have not been seen before with traditional genetic modification strategies.

There is intense intellectual and practical interest in creating insects that are refractory to disease, in particular arthropod borne pathogens that cause human maladies. Several research laboratories are attempting to develop transgenic mosquitoes that contain novel genetic constructs that interfere with the transmission of pathogens that cause malaria, and dengue and yellow fevers in humans. Limited critical laboratory examination of the fitness of these transgenic mosquitoes has begun, and it is envisioned that field trials are still several years away. As potential future field trials with GMIs (e.g., mosquitoes and pink boll worms) become more likely, the movement of these organisms from secure laboratory facilities for release and establishment in natural systems raise critical issues regarding regulatory oversight, safety evaluation, risk assessment, and potential non-target impacts. With respect to these preceding issues, classical biological control, the deliberate introduction and release of exotic organisms for the control of non-native invasive pests, may provide guidance in developing protocols for issues pertaining to GMI releases. Many issues that proposed GMI releases will eventually face are fundamentally similar to releases of non-GMI classical biological control agents from secure quarantine facilities and include: (1) assessment of the potential benefits and hazards arising from release; (2) procedural assessments to adequately determine safety and explore risk to receiving ecosystems; (3) identification of non-target species that would be at risk from GMIs (i.e., either direct attack, food web perturbations, or gene transfer); (4) development of mechanisms that can be adopted to mitigate potential risk; and (5) assessment of public opinion on the acceptability of GMIs as a necessary management strategy in support of or replacement of traditional control practices such as pesticide applications for mosquito control.

Regulatory Oversight of Proposed GMI Releases
Currently in the US, there is no agreed upon process for assessing safety of GMIs and their risk to the receiving ecosystem prior to release, nor has it been definitively determined which state and federal regulatory agencies will be involved with deciding what constitutes acceptable data concerning safety and risk assessment and how these data should be assessed scientifically1. Given the diversity of GMIs that could potentially be created for pest, vector, and disease management in a variety of ecosystems including natural, agricultural, and urban settings, the Food and Drug Administration (FDA), Environmental Protection Agency (EPA), and the US Department of Agriculture (USDA), may have input into regulatory oversight. As scientists begin the application process for permission to conduct field trials, overlapping jurisdictional boundaries across government agencies are likely to cause confusion, duplication of effort, and anxiety as to whether the necessary paperwork has been completed to satisfy all regulatory requirements. Coordination of oversight and division of responsibility across several government agencies is seen as an impediment in need of resolution before field testing of GMIs can be made possible2.

New Zealand and Australia have some of the most stringent legislative requirements for regulating genetically modified organisms (GMOs which include plants, animals, and microbes). New Zealand's Hazardous Substances and New Organisms Act 1996 (HSNO) places incumbent obligations on proponents of GMOs requiring them to provide adequate data on which assessments for release can be based, and this includes consideration of international concerns that incipient programs may raise. This legislation (i.e., HSNO) provides a solid framework within which risks and benefits of proposed GMO use can be weighed, and decisions made in accordance with presented data. The Environmental Risk Management Authority (ERMA) administers the review process for the release of GMOs which includes extensive public consultation and consideration of concerns raised by Maoris, New Zealand's indigenous peoples. ERMA and HSNO also provide guiding frameworks for proposed importation and releases of exotic biological control agents in New Zealand.

In Australia, the Gene Technology Bill (2000) is the cornerstone legislative act that provides a national regulatory structure governing GMOs. Within this framework, the Gene Technology Regulator prepares a risk assessment and management plan for every proposed GMO release into the environment. Risk assessment includes the potential of the GMO of concern to cause adverse environmental impacts, to persist for inordinate periods of time, and to spread geographically or via exchange of genetic material. As with ERMA, extensive consultation with stakeholders is mandatory3. The regulatory frameworks adopted by New Zealand and Australia may provide legislative inspiration to federal regulators in the US who are facing similar hurdles as releases of GMIs draw near.

Safety Evaluations and Risk Assessment
Major concerns surrounding permanent establishment of GMIs in nature include the potential for creating new pests and for disrupting ecosystems, because they may transmit novel genetic material to wild relatives or exhibit an increased ability to inhabit areas that exclude non-transformed conspecifics. Realization of these negative impacts will depend on the fitness and competitiveness of GMIs, the dispersal ability of the GMI and its environmental tolerances, and the permissiveness of the receiving environment. Additionally, adverse effects may manifest themselves via non-target organisms that use the GMI as a resource or are displaced by competition. These issues are similar to those posed by the importation and release of exotic biological control agents. Evaluation of traits likely to enable GMIs to become pestiferous need to be identified and evaluated prior to release. Rigorous protocols similar to those used for weed biological control agents may provide important starting points for deliberation in the development of novel testing regimens for GMIs. A major new area of investigation will be concerning scenarios facilitating unwanted gene flow into unintended recipient populations and the outcomes should this occur. Consideration of factors promoting gene flow is a major departure from testing protocols for biological control agents. Interpretation of what constitutes acceptable levels of safety and risk will undoubtedly be interpreted differently depending on varying tolerance perspectives of the analyzing parties in the country of release and adjacent neighbors.

Mitigating Non-Target Impacts
Despite rigorous applied laboratory tests, small-scale field trials, and modeling of results, there is the potential for unintended consequences to manifest themselves, as answers to questions pertaining to safety and risk are influenced by temporal, spatial, and myriad biotic and abiotic factors that cannot be easily replicated experimentally. A logical step for mitigating non-target effects from GMIs would be built in mechanisms to prevent continued persistence and spread. One safeguard would be the inclusion of marker genes to readily identify GMIs from non-transformed conspecifics. This technology is already in place and would allow population monitoring and measurement of spread. An additional safeguard would be incorporation of safety devices that could be activated to disable GMIs thereby countering their adverse effects should they arise. Greater research into the development of safety options will most likely occur as GE technology advances and field trials become more likely.

Conclusions

Legislative guidelines and protocols for scientifically addressing issues of safety and risk of GMIs is in need of increasing attention, as organisms developed in the laboratory steadily approach the field testing phase. Similar issues concerning the outdoor release of GMIs have faced the biological control community. Growing disquiet generated by prominent ecologists and conservationists have increased awareness of non-target impacts and the difficulty of predicting unforeseen ecosystem perturbations caused by exotic natural enemies used for the biological control of exotic pests. Recognition of these issues has increased research effort by biological control practitioners to experimentally address factors pertaining to safety and unforeseen risk within prescribed experimental and regulatory arenas. Where consideration of analogous issues pertaining to the release and use of GMIs in the environment is necessary, lessons learned by the biological control community could form a sound starting basis for molecular biologists and vector ecologists developing good practice guidelines.

References

1. Minkel, J.R. 2004. Bugging for guidance. Scientific American 291 (1): 34.

2. Pew Charitable Trusts 2004. Bugs in the system? Issues in the science and regulation of genetically modified insects. http://www.pewtrusts.com/pdf/pifb_bugs_012204.pdf.

3. Henzell, R., and Murphy, E. 2002. Rabbits and possums in the GMO potboiler. Biocontrol News and Information 23: 89N-96N.

Mark S. Hoddle
Biological Control Specialist
Department of Entomology
University of California