Background: Pollen food allergy syndrome (PFAS) related to PR10 from vegetables is common in northern Europe, whereas in Mediterranean countries PFAS has been preferentially associated with profilins. However, there are pollen-allergic patients reactive to Bet v 1 in birch-free regions. Since it cannot be the primary sensitizer, there has to be another culprit. Quercus ilex is a good candidate as it belongs to the order Fagales. This order includes trees with highly sensitizing pollen such as alder, hazel, hornbeam, oak and chestnut because of the presence of PR10 allergens. PR10 allergens have indeed been described in other Quercus species.
Objective: Our goals were to determine the rate of sensitization to Q. ilex in central Spain and the associated frequency of PFAS; secondly to identify and clone the Q. ilex allergen PR10.
Methods: We included 224 allergic patients with respiratory symptoms to estimate the rate of sensitization. A skin prick test (SPT) and ImmunoCAP were performed. A total of 38 Q. ilex-sensitized patients were tested using Western blotting to determine the rate of Que i 1. Peptides from Que i 1 were analysed by MALDI-TOF/TOF and Orbitrap LC-MSMS. The Que i 1 sequence was first obtained from the Holm oak transcriptome then cloned and expressed in bacteria.
Results: 59.8% of pollen-allergic children were sensitized to Q. ilex. We described and cloned the Q. ilex PR10, Que i 1, which has a sensitization rate of 60.5% and was recognized by 65.4% patients reporting PFAS.
Conclusion and clinical relevance: Sensitization to Q. ilex pollen has increased significantly since 1995. This sensitization could be important, as the presence of PFAS in this population is higher than in patients not sensitized to Q. ilex. The first Q. ilex allergen has been described and is related to PFAS in Spanish patients sensitized to PR10 but not exposed to birch pollen.
Keywords: Quercus ilex; PR10; Que i 1; oral allergy syndrome; pollen food allergy syndrome.
© 2020 John Wiley & Sons Ltd.