Rye flour allergens associated with baker's asthma. Correlation between in vivo and in vitro activities and comparison with their wheat and barley homologues

Background A number of wheat and barley flour proteins that belong to the cereal alpha-amylase/trypsin inhibitor family have been identified as major allergens associated with baker's asthma. However, the allergenic role of this protein family had not been investigated in rye. Objective To study the allergenicity of five purified proteins from rye flour which belong to the same inhibitor family, as well as to compare their properties with those of their wheat and barley homologues. Methods In vivo skin-prick tests were carried out in 21 patients with radioallergosorbent test (RAST) 2-3 to rye and allergic sensitization mainly to this cereal flour. In addition, sera from all these patients were used to assay the IgE binding capacity of dot blotted purified proteins. Results Three of the rye proteins tested, namely Sec c 1, RDAI-1 and RDAI-3, provoked positive skin-prick tests in more than 50% of patients, although their in vitro reactivity was lower. Different reactivities were found for the rye components compared with their wheat and barley homologues. Statistical analyses showed a significant correlation between the results of in vivo and in vitro tests for seven out of the nine purified proteins considered in this study. Conclusion Members of the rye alpha-amylase inhibitor family are main allergens involved in allergic reactions to cereal flours. However, different allergenic behaviours were found between homologous allergens from rye, barley, and wheat.