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Inhalation of pollens from different species of Acacia is a common cause of respiratory allergy in tropical areas of the world. Acacia farnesiana is commonly used as street trees in towns and ornamental shade trees in parks and gardens throughout arid and semi-arid regions of Asia. This study aimed to produce and purify the A. farnesiana pollen profilin (Aca f 2) and evaluate its nucleotide sequence homology with profilins of common allergenic plants to predict allergenic cross-reactivity.

Thirty-nine patients who were allergic to Acacia pollens were included in the study. Cloning of Acacia profilin-coding sequence was performed by polymerase chain reaction using primers from Acacia pollen RNA. The cDNA of Acacia pollen profilin was then expressed in Escherichia coli using pET-21b(+) vector and purified by metal affinity chromatography. Immunoreactivity of the recombinant Acacia profilin (rAca f 2) was evaluated by specific ELISA, immunoblotting, and inhibition assays.

The coding sequence of the Acacia profilin cDNA was recognized as a 399-bp open reading frame encoding 133 amino acid residues. Eighteen patients (18/39, 46.15%) had significant specific IgE levels against Aca f 2. Immunodetection and inhibition assays indicated that purified Aca f 2 might be the same as that in the crude extract.

Aca f2, the first allergen from A. farnesiana pollen, was identified as belonging to the family of profilins. The amino acid sequence homology analysis showed high cross-reactivity between Aca f 2 and other profilins from botanically unrelated common allergenic plants.