Isolation and characterization of the early nodule specific protein homologue (Hev b 13), an allergenic lipolytic esterase from Hevea brasiliensis latex*1

Rationale Identification of Hev b 7, a 43 kDa latex allergen homologue of patatin, did not adequately explain the frequent observations of IgE antibody reactivity to a 42–46 kDa protein in serum from latex-allergic patients. We thus hypothesized the existence of another allergenic Hevea protein of a similar molecular weight. We report on the isolation and purification of a 42.98 kDa latex glycoprotein showing homology to Early Nodule Specific Protein in legumes. Methods Hev b 13 was isolated from Hevea brasiliensis latex B-serum by gel filtration and ionic exchange chromatography. Binding of human IgE to Hev b 13 and inhibition of IgE binding by patatin were studied by Western immuno-blots analysis. The cDNA encoding Hev b 13 was isolated by RT-PCR and cloned. Results The protein predicted from the Hev b 13 cDNA sequence has 391 amino acids. The mature protein possessed a deduced molecular weight of 40.40 kDa and pI of 5.0. Prevalence of IgE antibody reactivity to native Hev b 13 was 78% (51/65) in latex-sensitized healthcare workers and 77% (10/13) in latex-sensitized spina bifida children. IgE-binding to Hev b 13 was inhibited by the potato tuber patatin but lost when the carbohydrate moiety of patatin was removed. This suggested that the IgE-specific epitope might reside on the glycan. Conclusions The lipolytic esterase, Hev b 13, is a major allergen of Hevea brasiliensis latex. The principal IgE-specific epitope of the glycoprotein appears to be located on its carbohydrate moiety.