D1.05 - Bet v 6 as a Marker of Pollen Cross-Reactivity in Southern Europe: Insights from a Birch-Free Region

Birch pollen is one of the main respiratory allergy elicitor sources. Its principal allergenic component is Bet v 1, which is predominant in northern and central Europe. Minor allergens such as Bet v 2 and Bet v 6 are more frequent in areas with complex pollen profiles in southern Europe, where there is a high burden of olive and cypress pollen.

To study the prevalence and clinical relevance of Bet v 6 as a potential biomarker of pollen cross-reactivity and its role in the sensitization profile to birch pollen in a geographical area free of birch trees (Valencia, Spain).

A retrospective and descriptive study was conducted on sensitization to Bet v 6 and the molecular sensitization profile to birch pollen. Samples from 2,120 patients treated at the Allergy Service of Hospital La Fe between 2021 and 2024 were analyzed. The molecular study was performed using the ALEX2® diagnostic platform (MAD®, Vienna). Clinical information (skin prick test (SPT) and symptoms) was obtained from the hospital's electronic medical record system (Orion Clinic®). Image 1

One hundred and twenty-three patients (5.8%) were positive for at least one of Bet v 1, Bet v 2, and/or Bet v 6. The predominant sensitization was to Bet v 2 (33.3%), followed by Bet v 6 (26%) and Bet v 1 (23.6%) Table 1. The most frequent combination was Bet v 2 + Bet v 6 (13%). In samples positive only to Bet v 6 (31 patients), SPTs to olive and cypress pollen were positive in 96.7% and 59.3% of patients, respectively, with all of them presenting respiratory symptoms.

This study demonstrates that a positive result for Bet v 6 in a region without birch trees is likely due to cross-reactivity with other pollen allergens, mainly olive and cypress. This finding could be relevant for the success of immunotherapy, highlighting the need for closer follow-up and further studies on this issue.