Allergenicity and cross‐reactivity of Russian olive pollen (Eleagnus angustifolia)

Background: The purposes of this study were: to determine the prevalence of sensitization and immunochemical characterization of Eleagnus angustifolia pollen (Russian olive) that belongs to the family Eleagnaceae. Methods: A total of 134 patients with rhinoconjunctivitis and/or asthma were studied. Its allergenicity, cross‐reactivity with olive pollen and the presence of Ole e 1 and Ole e 4‐like molecules were evaluated. Results: Eleagnus angustifolia pollen was detected from May to June. Seventy‐three of 134 (30.5%) had positive skin test to E. angustifolia, all of them were positive to olive. There was a good correlation between specific immunoglobulin (Ig)E levels to E. angustifolia and Olea europaea (r = 0.77, P = 0.002). Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE) immunoblots revealed major IgE‐binding bands in the E. angustifolia extract of 43 and 63.7 kDa. The E. angustifolia extract was not able to inhibit olive, whereas O. europaea inhibited E. angustifolia up to 41%. The presence of Ole e 1‐ and Ole e 4‐like allergens in E. angustifolia extract was confirmed by enzyme‐linked immunosorbent (ELISA) inhibition assays. Nasal challenge with E. angustifolia was positive in three of six patients with positive skin test to both pollens and negative in five patients with positive skin test only to O. europaea. Conclusions: This study confirms that E. angustifolia is capable of sensitizing individuals in Madrid. A minimal‐to‐moderate cross‐reactivity with olive pollen was established, suggesting some cross‐reactivity but not excluding co‐sensitization.