Cross-reactivity between pollens and food allergens: The importance of Bet v 1 and Bet v 2 epitopes

Pollen-related food allergy is due to cross-reactive epitopes. This study assesses the birch epitopes rBet v 1 and rBet v 2 (profilin) as markers of allergy to plant foods in pollinosic patients at low exposure to birch. Forty-three consecutive patients with skin-prick-test positivity to birch and/or olive-tree pollen were questioned with regard to symptoms of food allergy and subjected to prick tests for the most common inhalants and to prick+prick (P+P) tests for 14 plant foods. Specific IgE to allergens and to rBet v 1 and rBet v 2 were evaluated by Pharmacia CAP System. Neither prick tests nor the CAP System revealed monosensitization to birch. Of 21 patients whit food-allergy symptoms, 17 attributed them to ingestion of one or more of the 14 foods studied, with in vivo and/or in vitro positivity to the food involved when symptoms of Oral Allergy Syndrome were reported. A total of 233 CAP positivities to plant foods was found in 27 patients (20/22 positive to three pollens, 5/10 to grass and birch or olive-tree, 1/3 to grass and 1 negative to all pollens). Correlation with P+P test was 63.6%; 67.57% of the discordant results showed CAP positivity/P+P negativity. Only birch positive cases showed sIgE to recombinant allergens (24/43, 63.2%: 12 positive to rBet v 1, 11 to rBet v 2, 1 to both). Positivity to rBet v 2 occurred only in patients positive to birch, olive-tree and grass pollen. The difference between recombinant-positive and recombinant- negative cases with respect to CAP positivity to plant foods was significant. (21/24 vs. 6/19; p