Characterization of narrow-leaf lupin (Lupinus angustifolius L.) recombinant major allergen IgE-binding proteins and the natural β-conglutin counterparts in sweet lupin seed species

β-conglutin has been identified as a major allergen for Lupinus angustifolius seeds. The aim of this study was to evaluate the binding of IgE to five recombinant β-conglutin isoforms (rβ) that we overexpressed and purified and to their natural counterparts in different lupin species and cultivars. Western blotting suggested β-conglutins were the main proteins responsible for the IgE reactivity of the lupin species and cultivars. Newly identified polypeptides from “sweet lupin” may constitute a potential new source of primary or cross-reactive sensitization to lupin, particularly to L. albus and L. angustifolius seed proteins. Several of them exhibited qualitative and quantitative differences in IgE-binding among these species and cultivars, mainly in sera from atopic patients that react to lupin rather than peanut. IgE-binding was more consistent to recombinant β2 than to any of the other isoforms, making this protein a potential candidate for diagnosis and immunotherapy.
This work was supported by the European Research Program MARIE CURIE (FP7-PEOPLE-2011-IOF) for the grant ref. number PIOF-GA-2011-301550 to JCJ-L, KBS and JDA. JCJ-L and JDA thank the Spanish Ministry of Economy, Industry and Competitiveness for the grants ref. number RYC-2014-16536 (Ramon y Cajal Research Program), BFU2016-77243-P, RTC-2015-4181-2 and RTC-2016-4824-2. Authors thank W. Smith (Royal Adelaide Hospital), M. Stuckey (St John of God Pathology) and R. Loblay (Royal Prince Alfred Hospital) for providing sera and L. Wienholt (Royal Prince Alfred Hospital) for doing the ImmunoCAP analysis of lupin- and peanut-specific IgE in some serum.