D2.279 - Preventive capacity of single-nut sublingual immunotherapy in Brown Norway rats

Data on therapeutic approaches to treat tree nut allergies are limited. For individuals with several tree nut allergies, a multi-nut, instead of a single-nut, immunotherapeutic approach may represent a more efficient treatment strategy. This study investigated the potential induction of cross-tolerance to either pistachio, cashew or hazelnut by single-nut sublingual immunotherapy (SLIT) with pistachio, cashew and hazelnut.

Three parallel experiments were performed, where Brown Norway rats (n = 8/group) sublingually received 1 mg of either pistachio, cashew or hazelnut protein extract, or PBS as control, every day for three weeks. Subsequently, the rats were i.p. immunised four times with 50 µg of pistachio (exp. 1), cashew (exp. 2) or hazelnut (exp. 3) protein extract to evaluate the prophylactic efficacy of the individual single-nut SLIT. Prior to sacrifice, clinical reactivity was analysed by ear swelling tests (EST) with 10 µg, basophil activation tests (BAT) with 1-10,000 µg and oral food challenges with 100 mg of pistachio (exp. 1), cashew (exp. 2) or hazelnut (exp. 3) protein. Specific IgE and IgG1 levels were quantified using ELISAs and examined by immunoblotting. In addition, sequence homology among major allergen families from the tested tree nuts was explored using in silico analysis. 

Single-nut SLIT with either pistachio, cashew or hazelnut, induced pistachio-, cashew- and hazelnut-specific IgG1, respectively, and protected against sensitisation to the respective nut, as significant decreased levels of specific IgE compared to PBS treated (control) rats after i.p. immunisations were detected. Clinical reactivity by means of EST, BAT and OFC confirmed these results, suggesting preventive capacity of the pistachio, cashew and hazelnut single-nut SLIT against their respective tree nut allergy. Whereas pistachio and cashew showed partial cross-preventive capacity against each other, no such effect was seen for hazelnut. This was supported by in silico analysis showing pistachio and cashew 2S albumin, 7S globulin and 11S globulin proteins having the greatest homology compared to hazelnut, particularly 90% identity was found between pistachio and cashew 2S albumins.

Single-nut SLIT with pistachio, cashew or hazelnut primarily exhibited preventive capacity against pistachio, cashew and hazelnut allergy, respectively. Moreover, partial cross-prevention was found between pistachio and cashew.