Investigations of immunogenic, allergenic and adjuvant properties of Cry1Ab protein after intragastric exposure in a food allergy model in mice.

Monica Andreassen,Martinus Løvik,Terje Traavik,Johanna Bodin,Thomas Bøhn,Unni Cecilie Nygaard,Odd-Gunnar Wikmark

doi:10.1186/s12865-016-0148-x

Abstract

BackgroundIn genetically modified (GM) crops there is a risk that the inserted genes may introduce new allergens and/or adjuvants into the food and feed chain. The MON810 maize, expressing the insecticidal Cry1Ab toxin, is grown in many countries worldwide. In animal models, intranasal and intraperitoneal immunisations with the purified Cry1Ab proteins have induced immune responses, and feeding trials with Cry1Ab-containing feed have revealed some altered immune responses. Previous investigations have primarily measured antibody responses to the protein, while investigations of clinical food allergy symptoms, or allergy promotion (adjuvant effect) associated with the Cry1Ab protein are largely missing. We aimed to investigate immunogenic, allergenic and adjuvant properties of purified Cry1Ab toxin (trypCry1Ab, i.e., trypsin activated Cry1Ab) in a mouse model of food allergy.MethodFemale C3H/HeJ mice were immunized by intragastric gavage of 10 μg purified, trypsin activated Cry1Ab toxin (trypCry1Ab) alone or together with the food allergen lupin. Cholera toxin was added as a positive control for adjuvant effect to break oral tolerance. Clinical symptoms (anaphylaxis) as well as humoral and cellular responses were assessed.ResultsIn contrast to results from previous airway investigations, we observed no indication of immunogenic properties of trypCry1Ab protein after repeated intragastric exposures to one dose, with or without CT as adjuvant. Moreover, the results indicated that trypCry1Ab given by the intragastric route was not able to promote allergic responses or anaphylactic reactions against the co-administered allergen lupin at the given dose.ConclusionThe study suggests no immunogenic, allergenic or adjuvant capacity of the given dose of trypCry1Ab protein after intragastric exposure of prime aged mice.Electronic supplementary materialThe online version of this article (doi:10.1186/s12865-016-0148-x) contains supplementary material, which is available to authorized users.

Highlights

In genetically modified (GM) crops there is a risk that the inserted genes may introduce new allergens and/or adjuvants into the food and feed chain
Assessment of adjuvant capacity of trypCry1Ab Anaphylactic responses During the 30 min after i.p. challenge with allergen extract (Lupex) on day 35, the rectal temperature dropped significantly in mice i.g. immunised with lupin extract (Lupex) + cholera toxin (CT) and Lupex + CT + trypCry1Ab compared to mice immunised with Lupex or Lupex + trypCry1Ab
There was no significant difference in rectal temperature between the Lupex + CT and Lupex + CT + trypCry1Ab immunised mice, or the Lupex and Lupex + trypCry1Ab immunised mice (Fig. 1a)

Summary

Introduction

In genetically modified (GM) crops there is a risk that the inserted genes may introduce new allergens and/or adjuvants into the food and feed chain. We aimed to investigate immunogenic, allergenic and adjuvant properties of purified Cry1Ab toxin (trypCry1Ab, i.e., trypsin activated Cry1Ab) in a mouse model of food allergy. The introduction into the food chain of GM plants containing new food allergens or proteins with adjuvant potential is unwanted and an expressed concern [2]. Intranasal (i.n.) and intraperitoneal (i.p.) immunisations with the purified Cry1Ab proteins have been reported to elicit immune responses in mice [11] and we have previously demonstrated capacity of the trypsin activated Cry1Ab (trypCry1Ab) toxin to elicit specific immunoglobulin (Ig) E and IgG1 antibodies after i.n. exposure [12]. No experimental studies have investigated whether Cry proteins have adjuvant properties in relation to clinical food allergy responses

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