Quinoa allergenicity – identification of sensitising and cross- reactive quinoa proteins

Background: There is a need for alternative food proteins from more sustainable plant sources like quinoa to ensure future supply of high quality proteins for a growing world population. As quinoa is
gluten- free, it has gained increasingly popularity in Western diets, for example as a substitute for wheat. However, ingestion of new proteins may pose a risk of introducing new allergies. This may either be a result of de novo sensitisation and thereby induction of new allergies, or elicitation of reactions in already allergic patients due to cross- reactivity to known allergens. Cases of quinoa allergy have been reported. However, our knowledge of the allergenic proteins in quinoa remains scarce. Thus, the aim of present study was to identify the allergenic potential of quinoa. Method: Brown Norway rats were dosed either orally or i.p. with PBS as control or different doses of quinoa, without use of adjuvant, in order to evaluate immunogenicity and sensitising capacity. Before sacrifice, an ear swelling test was performed for assessment of IgE functionality and eliciting capacity of quinoa proteins. Specific IgG1 and IgE responses were analysed by means of different ELISAs. Cross- reactivity was evaluated by in silico analyses, various ELISAs and immunoblotting to peanut, hazelnut, Brazil nut, walnut, cashew nut, almond, soy, cow’s whey, wheat, grass pollen and birch pollen, using protein extracts and anti- sera raised against these products. Results: Quinoa was shown to inhere a high immunogenicity and high allergenicity, being able to sensitise as well as elicit an allergic reaction after both oral and i.p. dosing. Specific antibodies were raised against a range of quinoa proteins, with an overriding reactivity of an approximately 25 kDa protein, probably corresponding to the quinoa 11S globulin basic subunit. Quinoa showed an overall high cross- reactivity with peanut and tree nuts. Peanut and tree nut immunised rat sera had a higher cross- reactive response towards quinoa than the quinoa immunised rat sera had towards peanut and
tree nut. Results were confirmed by in silico analyses identifying a high homology between quinoa and peanut or tree nut 11S globulin, profilin or oleosin. Conclusion: This study demonstrated that quinoa contains a high inherent immunogenicity as well as allergenicity, and revealed cross- reactivity between quinoa and especially peanut and tree nut allergens.