Immunochemical characterization of Amaranthus retroflexus pollen extract: extensive cross-reactive allergenic components among the four species of Amaranthaceae/Chenopodiaceae.

The importance of Amaranthus retroflexus pollen in causing respiratory allergy has been well ascertained in many countries including Iran with a high positive rate (69%) among Iranian allergic patients. The aim of the present study is to identify the allergenic properties of A. retroflexus pollen. Sixteen patients with allergy to A. retroflexus pollen were selected for the study. The antigenic and allergenic profiles of the A. retroflexus pollen extract as well as pollen extracts from other species of the Amaranthaceae/Chenopodiaceae family, including Chenopodium album, Kochia scoparia, and Salsola kali, were evaluated by ELISA, immunoblotting, and immunoblot inhibition assays. The resolved protein fractions on SDS-PAGE ranged from 10-85 kDa. Several allergenic components (MW 85, 45, 39, 18, 15, and 10 kDa) of the A. retroflexus pollen extract were recognized by using patients' sera by specific antibody of IgE class using ELISA and immunoblot assays. The IgE reactivity of the A. retroflexus pollen extract was partially inhibited by all three pollen extracts tested. The inhibition by the S. kali pollen extract was more than those by other pollen extracts. Moreover, the wheal diameters by the A. retroflexus pollen extract were highly correlated with those by C. album, K. scoparia and S. kali pollen extracts. In conclusion, three proteins with apparent MWs of 39, 45, and 66 kDa are suggested as the common allergenic components among the four pollens from the Amaranthaceae/Chenopodiaceae family. It appears that there are some common (similar) epitopes among the four common allergenic pollens.