Background Lupin has been introduced as a new food ingredient in an increasing number of European countries, resulting in reports of allergic reactions mostly due to cross-reactions in peanut-allergic individuals. Some cases of primary lupin allergy have also been reported.
Objective The aim of our study was to develop a food allergy model of lupin in mice with anaphylaxis as the endpoint and further, to develop an approach to estimate the allergen dose inducing maximal sensitization using a statistical design requiring a limited number of animals.
Methods Mice were immunized by intragastric gavage using cholera toxin as an adjuvant. A two-compartment response surface design with IgE as the main variable was used to estimate the maximal sensitizing dose of lupin in the model. This estimated dose was further used to evaluate the model. The mice were challenged with a high dose of lupin and signs of an anaphylactic reaction were observed. Antibody reactions (IgE and IgG2a), serum mast cell protease [mouse mast cell protease-1 (MMCP-1)] and ex vivo production of cytokines (IL-4, IL-5 and IFN-γ) by spleen cells were measured. An immunoblot with regard to IgE binding was also performed.
Results The dose that elicited the maximal sensitization measured as IgE was 5.7 mg lupin protein per immunization. Mice that received this dose developed anaphylactic reactions upon challenge, IgE against several proteins in the lupin extract, and high levels of MMCP-1, and showed a general shift towards a T-helper type 2 response. Post-challenge serum MMCP-1 levels corresponded to the seriousness of the anaphylactic reactions.
Conclusion We have established a mouse model with clinical symptoms of lupin allergy, with an optimized dose of lupin protein. A statistical design that can be used to determine an optimal immunization dose with the use of a minimum of laboratory animals is described.