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Australia

GM peas cause immune response – A gap in the approval process?


In late 2005, a private research institute in Australia, CSIRO Plant Industry, put a halt on the further development of a genetically modified pea cultivar responsible for causing an immune response in laboratory mice. Opposing sides of the public debate have taken these findings in conflicting directions. Some say the Australian findings confirm the effectiveness of screening processes, while for others, the results only prove that genetically modified plants are too unpredictable to reckon with.

Pea weevil

Fighting pea weevils with peas

CSIRO has been working for almost ten years on developing an insect resistant pea cultivar. Peas are commonly used as an intercrop in Australia, where the annual pea crop totals AU$120 million. However, farmers face major challenges when it comes to the pea weevil (Bruchus pisorum), an important insect pest that lays its eggs in pea pods. If no chemical pesticides are used, up to 30 percent of the crop may be destroyed.

In order to address this problem, scientists at CSIRO took a defence gene from kidney beans and transferred it to peas. This gene is responsible for producing a kind of protein known as an amylase inhibitor. Amylase inhibitors prevent the breakdown of starch in the digestive system of pea weevils, causing them to starve before they are able to cause damage. Field trials revealed that the transgenic peas were 99.5 percent resistant.

Bild vergrößern

 

Bild vergrößern

Genetically modified peas expressing a newly introduced amylase inhibitor gene are resistant to the pea weevil (above). Conventional peas (bottom) show characteristic damage caused by pea weevil larvae.

Safety testing for weevil resistant GM peas

To find out about the safety of their new genetically modified pea cultivar, CSIRO conducted several field studies. The trials were conducted under strict containment conditions, so that none of the GM peas would make their way into the food supply. Regarding the planning of safety testing, CSIRO consulted Australia and New Zealand’s food safety authority, Food Standard Australia New Zealand (FSANZ). FSANZ is responsible for conducting safety assessments of genetically modified plants. The results of the safety studies proposed by FSANZ would then have to be submitted along with an application for approval. As a part of the required safety research, CSIRO conducted a comprehensive analysis of the new protein. Additionally, substances found in the plant, especially amylase inhibitor, must be checked for potential toxic or allergenic effects. These safety research requirements for transgenic plants are in accordance with standards set by international organizations such as the Food and Agriculture Organisation of the United Nations (FAO), the World Health Organisation (WHO), as well as the European Food Safety Authority (EFSA).

Feeding experiment

Initially, long-term laboratory and field tests conducted over several years suggested that the new peas were harmless for humans and animals (excluding the pea weevil). Even independent animal feeding experiments carried out by the Hungarian scientist Arpad Pusztai in 1999 showed no negative effects.

It was only with the final molecular characterisation of the new protein and further tests on animals that scientists from CSIRO made some unexpected findings. Although the amylase inhibitor gene comes from beans, a close relative of peas, it appears that when made by transgenic peas, the protein is produced slightly differently. CSIRO researchers, working together with the John Curtin School of Medical Research (JCSMR), found that amylase inhibitor produced in peas has a slightly different surface structure than the same protein produced in beans. A different arrangement of sugar molecules was attached to the protein’s surface.

Subsequent feeding tests on laboratory mice were able to confirm this difference. For four weeks, one test group was fed transgenic peas, while the lungs of another test group was given GM pea aerosol treatments. The tests revealed immune reactions among test animals:

  • Mice fed GM peas had elevated levels of antibodies in their bloodstream.
  • The lungs of mice directly treated with the aerosol made from GM peas had above average levels of inflammation.
  • Control groups treated with conventional peas or beans did not have these changes.

Humans could potentially have allergic reactions similar to those observed in mice. Nonetheless, the Australian and New Zealand authority on food safety (FSANZ) maintains that results of animal tests do not prove the allergic potential of GM peas in humans.

Testing stopped

The safety testing mentioned above took place before an application for the genetically modified peas was ever submitted to Australian authorities for approval. Due to the results of the safety research, the research institute decided to abandon the project after 10 years of development. CSIRO will not be seeking approval for the crop. The promising method, however, will be developed for use in other plants, said Thomas Higgins, deputy chief of CSIRO. Evidence has suggested that amylase inhibitor from beans may be expressed in other varieties of peas without forming a protein that would cause immune reactions.

Is safety testing adequate?

Environmental protection organisations like Greenpeace have expressed concern about the findings of CSIRO’s safety research. According to Christoph Then, Greenpeace’s spokesperson on GMOs in Germany, the findings lend further support to the argument that the consequences of genetically modifying plants are incalculable. He has voiced fears that the disputed peas could have even received approval in the European Union, because animal feeding tests are not explicitly required for approving genetically modified plants in the EU.

A very different conclusion was made by Thomas Higgins. From his point of view, the case-by-case approach to assessing the safety of GM plants has functioned well. Rather than mandating a standardised batch of tests for each genetically modified plant awaiting approval, scientific commissions evaluate each plant individually and demand certain tests addressing specific areas of concern. This is intended to keep safety assessments in sync with the most advanced science and methodology to date. Animal models for predicting allergenic potential are being researched and developed, but they are currently not directly applicable to humans. International organisations such as WHO and FAO agree that a safe assessment is possible using existing methods.

The question of whether European authorities would have noticed the difference in the amylase inhibitor protein has aroused concern. According to the Guidance Document for the Risk Assessment of GM Plants and Derived Food and Feed, EFSA demands that novel proteins in GM plants be checked for possible size differences and surface modifications. This includes checking for modifications to the protein's glycosylation pattern, or in other words, the way sugar molecules are attached to the protein's surface. Because the immune response was thought to be caused by an altered glycosylation pattern, one can assume that European safety assessments would have discovered the unusual structure of the amylase inhibitor and called for further testing.

Furthermore, simple amino acid sequence comparisons would have identified correspondence with known allergens. Targeted blood serum reactivity tests based on the sequence information would have been conducted to detect immune reactivity. Finally, routine tests with digestive juices would have revealed that the novel amylase inhibitor is relatively stable in the presence of digestive enzymes. This is a common characteristic of problematic allergens. 

Brazil nuts. A gene from the Brazil nut was transferred to soybeans. Since the Brazil nut is a known allergenic food, the allergenicity of the newly introduced protein was assessed. It was found that this protein is probably a major Brazil nut allergen.

Not an isolated case: Other crop improvement projects have also been abandoned

The case of the Australian genetically modified peas is not the only example of a development project that was abandoned after uncovering the allergenic potential of a new protein product. A crop improvement project in the US involved transferring a gene from the Brazil nut into soybeans. In 1996, the project was abandoned after analyses revealed that the gene of interest encoded a potential allergen. Again, the risk potential posed by this GM plant was recognized before approval. As of yet, no approved transgenic plants have been known to cause allergic reactions.

To explain the abandonment of the GM pea project, Australian authorities from FSANZ referred to similar unexpected consequences that sometimes result from conventional breeding projects. For example, the potato cultivars Lenape (USA, Canada) and Magnum Bonum (Sweden) were taken off the market due to elevated levels of toxic glycoalkaloids in their tubers. These types of risks are not entirely new, and they are not limited to genetically modified plants.

 

 


An EU Research Project

What are the risks of growing GM crops?

What are the benefits?

Numerous studies have addressed the potential impacts of genetically modified (GM) plants. Yet the existing evidence on the effects of GM plants is often contradictory and the quality of scientific research varies widely.

Therefore, the GRACE project will establish new tools for assessing the quality of existing studies and will conduct comprehensive reviews to identify health, environmental and socio-economic impacts of GM plants.

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