Standardizing Imperata cylindrica—source material for quality allergen preparations

Abstract

Background: Tropical countries experience wide variations in daytime temperature and relative humidity. This affects the quality of the source material used for allergen extracts. The present study was undertaken to standardize the processing and preservation conditions of Imperata cylindrica grass pollen. Methods: I. cylindrica (Ic) inflorescence were freeze-dried, pollens sieved out and stored at −70 °C (IcA). Alternatively, the inflorescence were dried at room temperature and then at 37 °C, pollens sieved out and stored at 4 °C (IcB). The extracts prepared in PBS were analyzed in vivo by skin tests and in vitro by immunochemical methods. Results: Reduced SDS-PAGE revealed 37 protein bands in IcA extract and 23 in IcB extract. IgE immunoblot with a pool of sera from Ic hypersensitive patients showed 30 allergenic bands in IcA and 14 in IcB. Immunoblot using anti-Ic rabbit sera revealed 33 antigenic bands in IcA and 22 in IcB. In both blots, the IcA extract exhibited sharp bands and the IcB extract exhibited diffuse bands. ELISA, ELISA inhibition and skin test procedures showed that IcA extracts had a higher potency than IcB extracts. Conclusions: Extracts prepared from −70 °C processed and preserved pollens (IcA) are allergenically more potent and contain a greater number of major and minor allergens than IcB extracts.