Wheat lipid transfer protein is a major allergen associated with baker's asthma

Background

Baker's asthma is a frequent occupational allergic disorder mainly caused by inhalation of cereal flours. Lipid transfer proteins (LTPs) constitute a family of plant food panallergens, but their role as inhalant and wheat allergens is still unclear.

Objective

We sought to explore the involvement of wheat LTPs in baker's asthma caused by wheat flour sensitization.

Methods

Forty patients with occupational asthma caused by wheat flour inhalation were studied. Wheat LTP, Tri a 14, was purified by using a 2-step chromatographic protocol and characterized by N-terminal amino acid sequencing and 3-dimensional modeling. Its reactivity was confirmed by means of IgE immunodetection, ELISA and ELISA-inhibition assays, and skin prick tests.

Results

Specific IgE to Tri a 14 was found in 60% of 40 individual sera from patients with baker's asthma, and the purified allergen elicited positive skin prick test reactions in 62% of 24 of these patients. Tri a 14 and peach LTP, Pru p 3, showed a sequence identity of 45%, but the low cross-reactivity between both allergens detected in several individual sera reflected great differences in their 3-dimensional IgE-binding regions.

Conclusions

Wheat LTP is a major inhalant allergen associated with baker's asthma caused by wheat flour sensitization. Poor cross-reactivity with its peach homolog was found in some patients.

Clinical implications

LTPs can be considered relevant inhalant allergens linked to respiratory disorders. LTP from wheat (Tri a 14) can be used as a helpful tool for the diagnosis of baker's asthma.

Key words: Baker's asthma, lipid transfer protein, wheat, cross-reactivity, inhalant allergen, IgE epitopes, 3-dimensional modeling, electrostatic potential

Abbreviations used: LTP, Lipid transfer protein, PB, Poisson-Boltzmann, PDB, Protein Data Bank, SPT, Skin prick test