Immunochemical and molecular characterization of allergenic profilin (Koc s 2) from Kochia scoparia pollen

Abstract

Kochia scoparia pollen has been demonstrated as an important cause of pollinosis in tropical and sub-tropical regions of the world. The aim of this study was to characterize the IgE-binding protein of the Kochia pollen extract and production of recombinant form of allergenic profilin of this weed. To predict its allergenic cross-reactivity with profilins of common allergenic plants, nucleotide sequence homology of Kochia profilin was evaluated. Specific ELISA and immunoblotting assay were applied to determine the IgE-binding reactivity of 28 sera collected from patients who were sensitized to Kochia pollen. In cloning procedure, the Kochia profilin-coding sequence was inserted into PTZ57R/T vector and expressed using pET-21b(+) vector. IgE-binding competence of purified recombinant Kochia profilin (rKoc s 2) was analyzed by in vitro assays. There were several protein bands in Kochia pollen extract with molecular weights approximately ranging from 14.5 to 85 kDa. Nucleotide sequencing revealed an open reading frame of 399 bp encoding for 133 amino acid residues which belonged to the profilin family; 15 patients (15/28, 53.1 %) had significant specific IgE levels for the rKoc s 2. Immunodetection and inhibition assays indicated that the purified rKoc s 2 might be the same as that in the crude extract. Koc s 2, the first allergen from the Kochia pollen was identified as a member of the family of profilins. High degree of homology was found among amino acid sequences of Kochia profilin and several profilin molecules from unrelated plant families.