Structural property of soybean protein P34 and specific IgE response to recombinant P34 in patients with soybean allergy.

Soybean allergy is one of the important food allergies because soybean is widely used in processed foods. P34 has been identified as the main allergen in soybeans. The main objective was to analyze the structural property of recombinant P34 and the P34 antigen-specific IgE response in soybean allergy using recombinant P34. Recombinant P34 was expressed by the BL21 (DE3) strain of Escherichia coli. Purified recombinant P34 showed oligomerization and binding to endotoxin. The binding of recombinant P34 to endotoxin was confirmed by LPS pull-down assay. High-density SDS treatment dissociated oligomeric recombinant P34 and removed endotoxin. Both native P34 and purified recombinant P34 showed almost identical structural properties as determined by circular dichroism analysis. We analyzed recombinant-P34-specific IgE antibodies by the ImmunoCAP System. In ImmunoCAP using recombinant P34, all sera from healthy controls were classified as negative. A correlation was found between the specific IgE antibodies to whole soybean and recombinant P34 (r=0.526, P<0.05). The sera from 3 of 9 (33%) patients with outgrown soybean allergy and 6 of 9 (66%) patients with soybean allergy were classified as positive. SDS-treated recombinant P34 retained its structure and biological activity. Recombinant P34 is a useful tool for the analysis of antigen-specific response in soybean allergy. It may be possible to develop a modified form of recombinant P34 for the diagnosis or treatment of soybean allergy using specific immunotherapy techniques.