Food Safety Evaluation The Allergy Check

Every GM plant submitted for authorisation is tested for its potential to trigger allergies. Every novel protein produced in a transgenic plant undergoes a rigorous allergy check.

The allergy check consists of tests and data comparisons to find out if a new protein is likely to trigger allergies. These tests and evaluations are carried out with the help of a decision tree.

The most important tests are:

• Degree of similarity to other allergens

• Stability of the protein during digestion

• Tests with blood from individuals who are sensitive to allergies

• Animal tests

The decision tree

The evaluation begins by seeing if the new gene comes from an organism that is known to trigger allergies.

A concrete example for this was the development of a GM soybean that contained a gene from the Brazil nut, a plant that is known to cause allergies in some people. It was determined that a protein responsible for causing allergic reactions in the Brazil nut had been transferred. The development programme was abandoned.

The case with most GM plants, however, is that the gene source is an organism that has unknown allergenic potential. Most of the time, GM plants contain genes from bacteria, as is the case with herbicide tolerance and insect resistance. When this is the case, the next steps on the decision tree are needed.

Amino acid sequence similarity

Making a chemical comparison of a new protein with known allergens is a useful method for assessing the new protein’s allergenic potential. All proteins are made up of a long chain of amino acids that is bent and folded into a three-dimensional structure. The allergenic properties of a specific protein are determined by only a few amino acids that form the docking point for antibodies from the immune system. If antibodies can bind themselves to a new protein, there is a high chance that an allergic reaction can occur.

The amino acid sequences of new proteins are therefore compared with the sequences of known allergens to see if any parts of the sequences correspond (homology). An area of high similarity could potentially be a docking point for antibodies. Indications of allergic potential are:

• Correspondence of four to eight consecutive amino acids

• Correspondence of 35 percent over a span of 80 amino acids

Databases containing the amino acid sequences of numerous allergens are now available. With the massive amount of information that is collected on proteins, and considering the complexity of their three-dimensional structures, more powerful computers will make this evaluation more precise in the future.

Blood tests

Blood serum collected from people with known sensitivity to a specific allergen can be used to find out if a new protein in a food contains that allergen.

• If the new protein reacts with the blood serum it means that the new protein is an allergen.

• If homology tests on the amino acid sequences are positive for similarity to known allergens, a test is performed with the blood serum from someone sensitive to that allergen. For example, if a new protein shows similarity to an allergen found in celery, tests will be done with the new protein against blood serum from people who are allergic to celery.

• If the new protein’s amino acid sequence has no similarity to known allergens, tests with serum sensitive to a wide range of allergens may be conducted. This type of serum contains antibodies against most common allergens.

Further limiting the likelihood of allergies If reaction tests with blood serum do not identify a threat, more investigations are carried out. Digestive stability: Many classic food allergens do not break down easily in the digestive tract. New proteins that remain stable in a test with artificial digestive juices could be allergens. This test is only useful for identifying a specific type of allergen that interacts with particular intestinal cells. Animal testing: Tests on animals, mainly rats, can give indications of a protein’s allergenic potential. The relevance of these tests to humans, however, is limited.

See also on GMO-Compass:

• Allergies: What's behind them?