Allergenic profile of Quercus rotundifolia pollen in Alentejo, Portugal

Background and Aim: Grasses and olive are the most relevant allergenic species in the Alentejo region. However, aggravation of allergic symptoms has been reported in the early spring, before grass and olive pollen seasons. Quercus pollen is the most abundant pollen type in the early spring in Alentejo, nonetheless its allergen profile has not yet been evaluated. The aim of this work was to characterize the allergen profile of pollen from Quercus rotundifolia among the most representative species showing pollination in April, prior to the main pollen season in Alentejo. Methods: Pollen from Quercus rotundifolia, Olea europaea and Dactylis glomerata was extracted with ammonium bicarbonate buffer, lyophilized and stored at -80ºC until analysis. Extract from Quercus ilex pollen was kindly offered by Bial. Protein content was determined by the Bradford method. SDS-PAGE followed by western blot, using allergic patient sera (obtained from the Hospital do Espírito Santo de Évora – HESE), were performed to evaluate the allergen profile of the pollen. Sensitization and cross-reactivity was assessed by solid phase immunoblot. Results: Most of the patient evidenced sensitization to pollen extracts of Q. rotundifolia. Protein profile of Q. rotundifolia has shown several bands in the Mr 10-90 kDa, mostly overlapping with Q. ilex. Western blot have shown several immunoreactive bands. Immunoreactive bands were also observed in the protein profile according to the pI in the range 4.0-6.1. Cross-reactivity between Q. rotundifolia with O. europaea and D. glomerata was found. Conclusion: These results evidenced allergens found in Q. rotundifolia pollen. It also shows that protein profile of Q. rotundifolia and Q. ilex are mostly alike suggesting that similarities in allergen profile are expected. Moreover, cross–reactivity between Q. rotundifolia and highly allergenic species such as O. europaea and D. glomerata was found which probably contributes to the aggravation of pollinosis in the early spring. Acknowledgments: This work was supported by FEDER through the “Programa Operacional Fatores de Competitividade – COMPETE” (Strategic projects of ICAAM and ICT 2013-2015). We also aknowledge Bial-Aristegui for supplying pollen and extract samples of Q. ilex.