Birch-naïve, oak-allergic subjects’ response to birch pollen in an environmental chamber

Abstract

BACKGROUND: Oak and birch pollens are known to have strong\ncross-reactivity. It is unknown how robust this cross-reactivity is in\nsubjects without natural exposure to pollen of both trees. We aimed to\nassess in an Allergen Challenge Chamber (ACC), the symptomatic\nresponsiveness to birch pollen in subjects allergic to and naturally\nexposed to Virginia Live Oak (VLO) pollen and SPT-sensitive but not\nnaturally exposed to birch pollen. METHODS: Subjects underwent\nSPT and blood draw for ssIgE to oak and birch antigens. Residential\nhistorical data were obtained. Subjects were exposed to birch pollen\n(3,500 ±700 gr/m ) in 2 consecutive 3-hour\nchallenges. Symptoms were recorded at baseline and 30-minute intervals.\nRESULTS: Twenty-four subjects, 12 males, age 20-58 yrs,\ncompleted the study. Sixteen subjects (66.7%) responded with high total\nsymptom scores (TSS) ≥10 of max 21. Twelve subjects (50%) had ssIgE\n≥0.70 kU/L to oak. Subjects with a Class II ssIgE to oak pollen had a\nsignificantly higher max TSS than those without. Fifteen subjects\nwithout natural exposure to birch pollen responded with TSS equivalent\nto 9 with previous natural exposure. Those without natural birch\nexposure also responded similarly to subjects in birch endemic areas\nreported in the literature. CONCLUSION: Subjects allergic to\noak pollen residing in South Texas, responded to birch pollen in an ACC\nwith symptoms comparable to both those with previous exposure and also\nthose residing in endemic areas and reported by other researchers. This\nrobust response of cross-reactivity in oak-allergic subjects, without\nprior endemic exposure, suggests that a cross-reactive intervention\ncould be efficacious.