Authors
N Tyagi1; E Farnell3; C Fitzsimmons3; S Ryan4; R Maizels4; D Dunne3; J Thornton1; N Furnham2; 1 European Bioinformatics Institute; 2 London School of Hygiene and Tropical Medicine; 3 University of Cambridge; 4 University of Edinburgh Discussion
Allergic reactions are observed to be very similar to those implicated in the acquisition of an important degree of immunity against metazoan parasites, eliciting a similar immunoglobulin E (IgE) immune response. Based on the hypothesis that IgE-mediated immune responses evolved to provide extra protection against metazoan parasites rather than to cause allergy, we predict that environmental allergens will share key molecular properties with metazoan parasite antigens that are specifically targeted by IgE. Using large-scale computational studies, we have established molecular similarity between parasite proteins and allergens and are able to predict the regions of parasite proteins that potentially share similarity with the IgE-binding region(s) of allergens. Nearly half of 2445 parasite proteins that show significant similarity with allergenic proteins fall within the 10 most abundant allergenic protein domain families. Our experimental studies support the predictions, and we present the first confirmed example of a plant pollen-like protein that is the commonest allergen in pollen in a Schistosoma worm and confirming it is targeted by IgE in those exposed to infection in a schistosomiasis endemic area of Uganda. The identification of such similarities explains the ‘off-target’ effects of the IgE-mediated immune system in allergy. 
