Hypersensitivity to black locust (Robinia pseudoacacia) pollen: 'allergy mirages'

Background The allergenicity of the ornamental tree Robinia pseudoacacia , or black locust, is unknown. Objective To evaluate the prevalence of sensitization to R pseudoacacia pollen, its possible allergenic cross-reactivity with other common pollens, and the potential implication of pollen panallergens (profilin, polcalcin, and 1,3-β-glucanase) as a cause of sensitization to R pseudoacacia pollen. Methods Skin prick testing with R pseudoacacia pollen was performed in 149 patients with pollinosis. Nasal challenge with R pseudoacacia pollen was performed in 10 patients. The prevalence of sensitization to the recombinant forms of profilin (rChe a 2), polcalcin (rChe a 3), and the N-terminal of the 1,3-β-glucanase (rNtD of Ole e 9) was investigated. Immunoblotting, enzyme-linked immunosorbent assay, and competitive inhibition assays were performed with R pseudoacacia pollen and recombinant pollen allergens. Results Sixty-four patients (43%) had positive skin prick test reactions to R pseudoacacia pollen. Nasal challenge results were positive in 5 sensitized patients and negative in 4 controls and 1 sensitized patient. The allergenic profile of R pseudoacacia pollen comprises at least the panallergen profilin, a calcium-binding protein, and a 1,3-β-glucanase. The prevalence of sensitization to rChe a 2, rChe a 3, and rNtD of Ole e 9 was 60%, 33%, and 87%, respectively, among patients sensitized to R pseudoacacia pollen. Binding of IgE to R pseudoacacia extract was completely inhibited by Robinia, Chenopodium, Olea, Cupressus , and Lolium extracts. Conclusions The high prevalence of R pseudoacacia pollen sensitization in patients with pollinosis is likely to be due to cross-sensitization to panallergens (profilin, polcalcin, and 1,3-β-glucanase) from other common pollens. This phenomenon may lead to a diagnosis of "allergy mirages."