Heimo Breiteneder

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

BACKGROUNDnHev b 7 is a Hevea brasiliensis latex allergen with sequence identities of 39% to 42% to patatins recently identified as potato allergens. The complementary DNAs encoding 2 different Hev b 7 isoforms were previously reported.nnnOBJECTIVEnThe 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-reactivities between Hev b 7 and patatins and proteins from banana and avocado.nnnMETHODSnAn H brasiliensis lambda ZAP complementary DNA (cDNA) library was screened with use of a Hev b 7 cDNA probe. Four Hev b 7 isoforms were produced in recombinant form and their IgE-binding capacities were compared. IgE immunoblot inhibitions and ELISA inhibition assays were used to investigate the possible cross-reactivity between Hev b 7 and recombinant potato patatin and proteins from avocado and banana.nnnRESULTSnTwo new isoforms, S2 and D2, were identified by sequencing 32 cDNA clones with full-length coding regions. All 4 recombinant isoforms displayed esterase activity and identical IgE-binding capacities. The new isoforms S2 and D2 were evaluated in skin prick tests and provoked responses equivalent to natural Hev b 7. No cross-reactivity was observed between Hev b 7 isoforms and potato patatin and proteins from avocado and banana.nnnCONCLUSIONSnAll 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 homologs appear not to contribute to cross-reactivity in the latex-fruit syndrome.

Structure, Allergenicity, and Cross-Reactivity of Plant Allergens

Within the last two decades, hundreds of allergenic proteins from diverse sources have been identified. The availability of numerous allergen sequences provided the basis for classifying allergens into families of evolutionary and structurally related proteins. This chapter gives an introduction into the protein family classification of allergens of plant origin. Our analysis showed that the majority of plant allergens could be grouped into a small number of protein families. The most important families of plant allergens are the prolamin superfamily, which contains several groups of important food and respiratory allergens, the profilins and the Bet v 1-related proteins, two families of allergens responsible for cross-reactivity between pollen and plant foods, and the seed storage globulins, major allergenic components of legumes, tree nuts, and other dicotyledonous seeds. The molecular classification of allergens can be used to establish a correlation between sequence and structural similarity and cross-reactivity among homologous allergens, delineate common properties of allergens, and deduce possible factors that make proteins allergenic.