Characterization and analysis of a cDNA coding for the group 29b (Der f 29b) allergen of Dermatophagoides farinae.

This study aims to acquire a recombinant allergen of Der f 29b by cloning and expression, and to identify its immunogenicity. In this study, the total RNA of D. farinae was extracted, cloned and expressed based on the Der f 29b gene. The molecular characteristics of Der f 29b was analyzed by the procedures of Bioinformatics. The allergenicity of recombinant Der f 29b protein was examined by western-blotting, ELISA, Immune inhibitory assays and skin prick test. The gene of Der f 29b consisted of 495 bases, derived from its nucleic acid sequence and encoded 164 amino acids. Positive responses to r-Der f 29b were shown in 24.3% by means of skin prick testing with 37 DM-allergic patients. The immunoblotting assays demonstrated that serum IgE from allergic patients reacted to r-Der f 29b protein. The IgE reactivity of r-Der f 29b in the serum from r-Der f 29b allergic patients was increased by more than 2 folds compared with healthy subjects. Immune inhibition assays showed that the IgE cross-reactivity was between r-Der f 29b and DME. Bioinformatics analysis predicted four peptides (13-17, 67-71, 104-109 and 147-155) as the B cell epitopes and five peptides (5-14, 16-31, 35-43, 52-63 and 87-97) as the T cell epitopes. Secondary structure prediction of Der f 29b with software PSIPRED identified two α-helices and seven β-sheets in Der f 29b. In conclusion, Derf 29b protein was identified as a novel subtype of dust mite allergen.