Identification of immunoglobulin E (IgE)-binding epitopes and recombinant IgE reactivities of a latex cross-reacting Indian jujube Ziz m 1 allergen

摘要

Ziz m 1 is a major Indian jujube (Zizyphus mauritiana) allergen involved in latex-fruit syndrome, and cDNA of the allergen has been cloned, sequenced and expressed in yeast by our laboratory previously. In this study, we performed an immunoglobulin E (IgE)-binding epitope analysis of Ziz m 1 using overlapping recombinant fragments. Eight overlapping recombinant fragments were generated from the recombinant Ziz m 1 allergen. The fragments were expressed in Escherichia coli and IgE-binding activities were evaluated by sera of latex–Indian jujube-allergic subjects and normal subjects using immunoblotting. Human allergic sera are not able to recognize fragments consisting of amino acid sequences 26–71, 119–280 and 119–291. However, residues at positions 26–199, 26–105, 26–86, 119–320 and 238–330 were found relevant in the IgE-binding. Our results indicate that ⁷²NISGHCSDCTFLGEE⁸⁶ and ²⁹²VWNRYYDLKTNYSSSIILEYVNSGTKYLP³²⁰ of Ziz m 1 are the sequences required for human IgE binding. Four corresponding peptides, ⁷²NISGHCSDCTE⁸⁶, ²⁹²VWNRYYDLKT³⁰¹, ³⁰⁰KTNYSSSIILEY³¹¹ and ³⁰⁹LEYVNSGTKYLP³²⁰, were synthesized, and these peptides reacted with 70%, 100%, 70% and 70% of 10 allergic sera tested, as revealed by enzyme-linked immunosorbent assay. Sensitization to ²⁹²VWNRYYDLKT³⁰¹ correlated significantly with the presence of allergic symptoms (P < 0·001). These findings will be useful in designing diagnostic and therapeutic approaches, thereby contributing to the development of specific immunotherapy for subjects with latex–fruit syndrome.