Sensitization to holm oak and plane tree pollen and cross- reactivity patterns with grasses of a university student population in Évora, Portugal.

Abstract

Background: Plane (Platanus hybrida) and holm oak (Quercus rotun-difolia) trees pollen are among the most prevalent in Alentejo with pollination peaks in the early spring (March and April). Despite the high level of exposure of the population, these pollen types are considered moderately allergenic and both the sensitization and their allergen profiles are yet poorly characterized in this region. In this work, we aimed characterizing the sensitization to plane and holm oak pollen among young adults’ population to holm oak and plane tree pollen and evaluate their cross- reactivity pattern with grasses (Dactylis glomerata). Method: Fifty volunteers, students in the University of Evora, aged 18- 25 years old, were enrolled in this study, after informed consent and Ethical Committee authorization (ref. 15039). A questionnaire was applied to evaluate the prevalence of pollen allergy symptoms. Serum IgE was quantified by specific ELISA. Sensitization to three pollen types (Dactylis glomerata; Platanus hybrida; Quercus rotundifolia) was assessed by EAST (Enzymoallergosorbent Assay). Allergen profiles were analysed by immunoblotting and inhibited immunob-lotting was used to assess cross- reactivity. Results: The results of the questionnaire, associated with the IgE levels, suggested that at least 36% of the individuals enrolled in the study might suffer from allergic symptoms during the pollen season. This population was sensitized to at least one pollen type; sensitization prevalence to grasses was ~45% and to holm oak and plane tree pollen types was ~30%. Several bands were identified by EAST positive sera in the range of 10 to 80 kDa, including bands with MW corresponding to Pla a 1 (<20 kDa), Pla a 2 (40 kDa) and Pla TLP (21 kDa) allergens. Positive EAST sera to holm oak pollen identified several protein bands in the MW range of 15 to 65 kDa. Both holm oak and plane tree pollen have shown significant cross- reactivity with grass pollen. Conclusion : These results evidenced a considerable prevalence of sensitization to plane and holm oak tree pollen in Alentejo, Portugal. Despite mildly allergenic, considering the high levels of exposure, these pollen types may contribute to induce pollinosis or aggravate allergic symptoms on the early spring in this region. A better un-derstanding of complex patterns of cross- reactivity between pollen types, combined with exposure data, might contribute to a better management of seasonal respiratory allergic diseases.