THIRD WORLD NETWORK BIOSAFETY INFORMATION SERVICE
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Cry1Ab protein triggers immunogenic and allergenic reactions in mice
The most commonly grown genetically modified (GM) maize, MON810, expresses an insecticidal Cry1Ab protein originating from the soil bacterium Bacillus thuringiensis (Bt).
A study exposed mice to purified Cry1Ab proteins extracted from the bacterium and to Cry1Ab-containing MON810 pollen and leaf extracts via nasal inhalation. It found that exposure to the purified proteins resulted in immunogenic and allergenic reactions in the mice. This study is believed to be the first that has demonstrated a Cry1Ab-specific antibody production after airway exposure to Cry1Ab proteins. The findings are congruent with those of other studies showing immunogenic reactions to Cry1Ab administration through other routes. Taken together, the results indicate that Cry1Ab has a general immunogenic as well as a specific allergenic potential.
Although similar reactions were not seen in the case of the mice exposed to the MON810 plant materials, the researchers caution that this could, at least in part, be because these delivered a considerably lower dose of Cry1Ab proteins than the purified form. They also point out that immunisation with low doses of allergens has been shown to induce more severe allergic responses than high doses; it is not a simple linear dose–response relationship. The findings of this study for the MON810 plant materials are therefore inconclusive.
The authors conclude: “Although no Cry protein immunogenicity could be observed at the present dose of MON810 pollen or leaf extract, the specific antibody response against the purified Cry1Ab protoxin and toxin preparations demonstrates the principle that these proteins may affect the immune system, i.e. act as immunogens, after intranasal administration. The elicitation of specific IgE antibodies indicates allergenicity of the purified Cry1Ab proteins. However, this was not observed after exposure to (lower doses of) Cry1Ab in plant materials. Notably, the observed immune responses were elicited in the absence of an adjuvant. Given the importance of Bt-transgenic maize as food and feed across the world, a considerable number of individuals may be exposed to Cry1Ab by inhalation, in the field as well as along the food/feed chain. Thus, our results warrant further clarification and testing, both in animal models and in humans, including emphasis on vulnerable age groups and hypersensitive individuals.”
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Humoral and cellular immune responses in mice after airway administration of Bacillus thuringiensis Cry1Ab and MON810 Cry1Ab-transgenic maize
Monica Andreassen, Elena Rocca, Thomas Bøhn, Odd-Gunnar Wikmark, Johnnie van den Berg, Martinus Løvik, Terje Traavik & Unni Cecilie Nygaard (2014). Food and Agricultural Immunology, DOI: 10.1080/09540105.2014.988128
http://www.tandfonline.com/doi/abs/10.1080/09540105.2014.988128?journalCode=cfai20
Genetically modified (GM) crops may bring new proteins with immunogenic and allergenic properties into the food and feed chains. The most commonly grown GM maize, MON810, expresses a modified version of the insecticidal Cry1Ab protein originating in the soil bacterium Bacillus thuringiensis (Bt). Immune reactions following inhalation of pollen and debris from such plants have been scarcely studied. We exposed BALB/c mice to purified Cry1Ab proteins and Cry1Ab-containing MON810 plant materials by intranasal installation. No anti-Cry1Ab antibodies were detected following exposure to the plant materials. Exposure to purified Cry1Ab resulted in specific anti-Cry1Ab IgG1 and IgE production, indicating inherent immunogenicity and allergenicity. Mice exposed to leaf extracts from both MON810 and unmodified maize demonstrated influx of lymphocytes and eosinophils in the broncho-alveolar lavage, and increased cytokine release in mediastinal lymph node cells. The results indicate that the airway exposure to Cry1Ab proteins may be a route of practical relevance.