Higher immunoglobulin E antibody levels to recombinant Fel d 1 in cat-allergic children with asthma compared with rhinoconjunctivitis

Summary Background Current diagnosis of allergy and asthma to cat is confirmed using cat dander extract (CDE). We have previously engineered a recombinant major cat allergen, rFel d 1, with properties identical to the natural molecule. Objective The aim of the study was to evaluate IgE and IgG4 antibodies to rFel d 1 among sera from cat‐allergic children and adults suffering from asthma and/or rhinoconjunctivitis (RC) in populations from Sweden and Austria. Methods Cat‐allergic children and adults from Sweden (n=27 and 31, respectively) and Austria (n=41 and 41) with RC and/or asthma were selected. Sera were tested for IgE and IgG4 antibodies to CDE and rFel d 1 by CAP, and IgE to rFel d 1 by ELISA. Healthy subjects and non‐cat‐allergic patients (n=75) were included as controls. Results There was a high correlation between IgE responses to rFel d 1 and CDE among the 140 patients (rs=0.85, P