Molecular and immunologic characterization of new isoforms of the Hevea brasiliensis latex allergen Hev b 7: Evidence of no cross-reactivity between Hev b 7 isoforms and potato patatin and proteins from avocado and banana

Background: Hev b 7 is a Hevea brasiliensis latex allergen with sequence id entities of 39% to 42% to patatins recently identified as potato allergens. The complementary DNAs encoding 2 different Hev b 7 isoforms were previous ly reported. Objective: The aim of this study was to determine the sequence variation of Hev b 7 and to compare the IgE reactivity of individual isoforms in vitro and in vivo. A further objective was to evaluate possible cross-reactivitie s between Hev b 7 and patatins and proteins from banana and avocado. Methods: An H brasiliensis lambda ZAP complementary DNA (cDNA) Library was screened with use of a Hev b 7 cDNA probe. Four Hev b 7 isoforms Here produ ced in recombinant form and their IgE-binding capacities a ere compared. Ig E immunoblot inhibitions and ELISA inhibition assays were used to investiga te the possible cross-reactivity between Hev b 7 and recombinant potato pat atin and proteins from avocado and banana. Results: Two new isoforms, S2 and D-2, were identified by sequencing 32 cDN A clones with full-length coding regions. All 4 recombinant isoforms displa yed esterase activity and identical IgE-binding capacities. The new isoform s S2 and D-2 were evaluated in skin prick tests and provoked responses equi valent to natural Hev b 7, No cross-reactivity was observed between Hev b 7 isoforms and potato patatin and proteins from avocado and banana. Conclusions: All 4 recombinant Hev b 7 Isoforms have equivalent IgE-binding capacity and therefore represent suitable reagents for the development of in vitro and in vivo diagnostic tests. Hev b 7, patatins, and their homolog s appear not to contribute to cross-reactivity in the Inter-fruit syndrome.