Immunobiochemical characterization of Putranjiva roxburghii pollen extract and cross-reactivity with Ricinus communis

Putranjiva roxburghii (PR) pollen has been found to be an important aeroallergen for type I hypersensitivity. In the present study, the IgE binding proteins of PR pollen have been characterized and compared with pollen allergens of Ricinus communis (RC) belonging to family Euphorbiaceae. On isoelectric focusing, PR pollen extract resolved into 35 bands (pI 3-9), whereas SDS-PAGE separated it into 18 protein components (MW 14-100 kD). Pooled patient's sera (ID +ve to PR) recognized 12 allergenic proteins in Putranjiva and five of them (MWs 92, 80, 55, 43 and 30 kD) showed immunologic reactivity to most of the sera samples tested individually by immunoblot. A number of shared allergenic proteins (MWs 92, 80, 66, 50, 43 and 14 kD) were observed between PR and RC pollen extracts on immunoblot using Putranjiva allergic serum pool. Inhibition in the binding for most of PR pollen allergenic proteins was obtained with higher concentration of RC extract than PR itself, depicting the presence of cross-reacting allergens in both. Putranjiva pollen extract was fractionated by a combination of DEAE Sephadex-A 50 and Sephadex-G 200 column chromatography. Periodate deglycosylation of western blotted PR extract and Put I fraction indicated the involvement of carbohydrate moieties in the allergenic activity. Of the two fractions from Put I (Ia and Ib), Put Ib was found to be the most allergenic protein by ELISA inhibition. Dot blot analysis with individual patients sera identified it as a major allergen of PR.