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  • Title: Molecular characterization of a cross-reactive Juniperus oxycedrus pollen allergen, Jun o 2: a novel calcium-binding allergen.
    Author: Tinghino R, Barletta B, Palumbo S, Afferni C, Iacovacci P, Mari A, Di Felice G, Pini C.
    Journal: J Allergy Clin Immunol; 1998 Jun; 101(6 Pt 1):772-7. PubMed ID: 9648704.
    Abstract:
    BACKGROUND: Species belonging to the Cupressaceae family are a relevant source of allergens that are present in a wide number of countries. OBJECTIVE: We sought to identify, purify, and characterize recombinant allergens from Juniperus oxycedrus, a species belonging to the Cupressaceae family. METHODS: Double-stranded cDNA was synthesized from mRNA and cloned into the lambda-ZAP expression vector. IgE screening of the library was performed with a pool of sera from subjects allergic to Cupressaceae. A recombinant 6xHis-tagged Juniperus oxycedrus allergen, Jun o 2, was expressed in Escherichia coli and purified by Ni2+ affinity chromatography. It was studied further by immunoblotting inhibition with pollen extracts from other Cupressaceae, Oleaceae, Urticaceae, and Graminaceae. The role of protein-bound calcium on the allergen's IgE-binding capacity was tested in a plaque assay in the presence or absence of EGTA. RESULTS: A cDNA coding for a newly identified Juniperus oxycedrus pollen allergen, rJun o 2, was isolated. The deduced amino acid sequence contained four typical Ca2+ binding sites and showed a significant sequence similarity to calmodulins. Depletion of Ca2+ in the plaque assay led to a loss of IgE-binding capacity of rJun o 2. Immunoblotting inhibition revealed that J. oxycedrus, J. ashei, Cupressus arizonica, C. sempervirens, Parietaria judaica, Olea europaea, and Lolium perenne pollen extracts were able to inhibit IgE binding to blotted rJun o 2 at different concentrations. CONCLUSION: rJun o 2 contains IgE-binding epitopes shared by taxonomically unrelated species, and therefore it can be regarded as a new panallergen. These findings could contribute to an explanation for the phenomenon of multiple positive test results in polysensitized patients and the potential symptom-eliciting role of allergenic sources previously not encountered.
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