Antigenic cross‐reactivity between Schistosoma mansoni and peanut: a role for cross‐reactive carbohydrate determinants (CCDs) and implications for the hygiene hypothesis

Abstract

The antigenic reactivity of constituents of Schistosoma mansoni and peanut (Arachis hypogaea) was investigated to determine whether identical antigenic epitopes possessed by both organisms provided a possible explanation for the negative correlation between chronic schistosome infection and atopy to allergens. Aqueous extracts of peanuts were probed in Western immunoblots with rabbit IgG antibodies raised against the egg, cercarial and adult worm stages of S. mansoni. Several molecules in the peanut extract were antigenically reactive with antibodies from the various rabbit anti-schistosome sera. A pair of cross-reactive peanut molecules at ~30 000-33 000 molecular weight was purified and both proteins were identified by mass spectrometric analysis as the peanut allergen Ara h 1. Anti-S. mansoni soluble egg antigen antibodies that were eluted off the peanut molecules reacted with two S. mansoni egg antigens identified by mass spectrometry as IPSE/α-1 and κ-5. Alignments of the amino acid sequences of Ara h 1 and either IPSE/α-1 or κ-5 revealed a low level of peptide sequence identity. Incubation of nitrocellulose paper carrying electrophoresed peanut molecules, six constituents of other allergic plants and S. mansoni egg antigens in a mild solution of sodium metaperiodate before probing with antibodies, inhibited most of the cross-reactivities. The results are consistent with the antigenic cross-reactive epitopes of S. mansoni egg antigens, peanut and other allergic plants being cross-reactive carbohydrate determinants (CCDs). These findings are novel and an explanation based on 'blocking antibodies' could provide an insight for the inverse relationship observed between schistosome infection and allergies.

Parasites and allergy: Observations from Africa

“…Through in vitro studies, rabbit anti‐schistosome IgG was found to cross‐react with allergens such as latex and peanut extract . The authors proposed that anti‐schistosome IgG antibodies may block IgE‐induced allergic responses and therefore prevent the manifestations of allergic disease …”

“…65,66 Through in vitro studies, rabbit anti-schistosome IgG was found to cross-react with allergens such as latex 65 and peanut extract. 66 The authors proposed that anti-schistosome IgG antibodies may block IgE-induced allergic responses and therefore prevent the manifestations of allergic disease. 66 Generally, IgE to CCDs are not thought to be biologically active, but in recent years, responses to the mammalian carbohydrate epitope galactoseα-1,3-galactose (α-gal) have been of interest in the field of allergy since this epitope has been linked to two forms of anaphylaxis.…”

“…66 The authors proposed that anti-schistosome IgG antibodies may block IgE-induced allergic responses and therefore prevent the manifestations of allergic disease. 66 Generally, IgE to CCDs are not thought to be biologically active, but in recent years, responses to the mammalian carbohydrate epitope galactoseα-1,3-galactose (α-gal) have been of interest in the field of allergy since this epitope has been linked to two forms of anaphylaxis. 67 The first being anaphylactic reactions following the infusion of the monoclonal antibody cetuximab among cancer patients undergoing therapy in the Southeastern United States 68 and the second being delayed-onset reactions hours after mammalian meat product consumption.…”

Worms: Pernicious parasites or allies against allergies?

“…High levels of anti‐ Ascaris IgG4 have been negatively associated with allergen SPT positivity, while in a S. mansoni ‐endemic area—although higher levels of both IgE and IgG4 were found in infected individuals—a higher ratio of IgE to IgG4 predicted clinical allergic symptoms, just as in allergen‐specific immunotherapy . As many helminth products are homologous to common allergens, IgG4 responses raised against helminth products may also bind and block IgE epitopes on allergens, reducing responses to allergens and directly reducing SPT responses . Mechanistic research into the role of IgE and/or IgG4 is hampered by the lack of good experimental animal models, as IgG4 does not exist in mice.…”

“…104 As many helminth products are homologous to common allergens, IgG4 responses raised against helminth products may also bind and block IgE epitopes on allergens, reducing responses to allergens and directly reducing SPT responses. [105][106][107] Mechanistic research into the role of IgE and/or IgG4 is hampered by the lack of good experimental animal models, as IgG4 does not exist in mice. of the parasitic infection.…”