Higher Immunoglobulin E Antibody Levels to Recombinant Fel D 1 in Cat-Allergic Children With Asthma Compared With Rhinoconjunctivitis

Abstract

Grönlund H, Adédoyin J, Reininger R, et al. Clin Exp Allergy. 2008;38(8):1275–1281PURPOSE OF THE STUDY. To measure immunoglobulin E (IgE) and IgG4 antibodies to an engineered recombinant major cat allergen, rFel d 1, among sera from cat-allergic children and adults.STUDY POPULATION. One hundred forty cat-allergic children and adults with rhinoconjunctivitis and/or asthma were selected; all had positive skin-prick test results to cat dander extract (CDE). Seventy-five healthy, age-matched, CDE-skin-test–negative children and adults were selected as control subjects.METHODS. Sera from the 140 patients were tested for IgE and IgG4 antibodies to CDE and rFel d 1 by ImmunoCAP (Phadia, AB Uppsala, Sweden) and for IgE to rFel d 1 by enzyme-linked immunosorbent assay.RESULTS. Ninety-eight percent of patients (all but 1) and none of the control subjects had evidence of specific IgE to rFel d 1. Specific IgE results to rFel d 1 and CDE correlated strongly (rs = 0.85; P < .001) among the 140 patients; however, results to rFel d 1 were, on average, 30% higher (P < .0001). IgE responses to rFel d 1 among children with asthma were higher (median: 19.4 kU/L), compared with children with rhinoconjunctivitis only (median: 6.6 kU/L; P < .05) and adults with asthma (median: 3.0 kU/L; P < .01). There was a threefold increased risk of asthma for one half of the children with the highest IgE levels (odds ratio: 3.23 [95% confidence interval: 1.19–8.79]) by the enzyme-linked immunosorbent assay. Children with asthma also displayed significantly higher IgG4 levels than did adults with asthma.CONCLUSIONS. Recombinant major cat allergen (rFel d 1) seems to be at least equally sensitive for in vitro diagnosis of cat allergy, compared with the current extract-based test. Elevated specific IgE antibody levels to rFel d 1 are suggested to be a risk factor for asthma in cat-allergic children.REVIEWERS COMMENTS. In vitro diagnosis of allergic sensitization is currently confirmed by using allergen extracts derived from natural source materials. The authors previously described creation of this recombinant major cat allergen, rFel d 1. Investigation with such purified recombinant proteins is a current area of intense interest within the field of allergy and immunology, because these engineered proteins may offer improved diagnostic specificity and theoretically may offer superior therapy for type 1 hypersensitivity. Previous research showed that allergen-specific IgE levels are predictive for the likelihood of allergic disease including asthma; however, some allergen-avoidance studies failed to show significant evidence of improvement or protection. This study gives further support to cat allergy causing asthma.