MOLECULAR-CLONING AND IMMUNOLOGICAL CHARACTERIZATION OF THE HOUSE-DUST MITE ALLERGEN DER-F-7

Background The allergen Der p 7 from Dermatophagoides pteronyssinus ha s been defined by molecular cloning and shown to be an important speci ficity in 50% of mite-allergic patients. Objective This study compares the cDNA sequence and serological reactivity of Der f 7 from D. farin ne with Der p 7. Method cDNA encoding Der f 7 was amplified by polymer ase chain reaction, sequenced and expressed as a fusion with glutathio ne-S-transferase for IgE and monoclonal antibody binding studies. Resu lts Der f7 cDNA encoded a 213 polypeptide containing a predicted 17 am ino acid leader sequence, no cysteines and a single N-glycosylation si te similar to Der p 7. The predicted 196 residue mature polypeptide ha d 86% identity to Der p 7 and a calculated molecular weight of 22 348D a. No homologues were found in searches of the data banks. The Der f 7 fusion protein showed a single band of 46 kDa by sodium dodecyl sulfa te-polyacrylamide gel electrophoresis (SDS-PAGE) and reacted with IEE antibodies in 19/41 (46%) of sera from asthmatic children. The degree of binding was usually 30% of that to Der p 7 consistent with the expo sure of the patients to D. pteronyssinus. Monoclonal antibodies (WH9 a nd WH22) against Ber p 7 reacted with Der f7 but inhibition studies sh owed a 10-fold difference in reactivity. Conclusion Der f7 has a predi cted 213 residue polypeptide with 86% homology and serological crossre activity to Der p 7.