Higher immunoglobulin E antibody levels to recombinant Fel d 1 in cat-allergic children with asthma compared with rhinoconjunctivitis.
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 (r(s)=0.85, P<0.001); however, measured levels to rFel d 1 were on average 30% higher (P<0.0001). Ninety-eight percent of patients and none of the controls showed IgE to rFel d 1 and there was a threefold increased risk of asthma for half of the children with the highest IgE levels [odds ratio 3.23; 95% confidence interval (CI), 1.19-8.79] by ELISA. IgE responses to rFel d 1 among children with asthma were higher (median 19.4 kU/L) compared with children with RC (median 6.6 kU/L, P<0.05) and adults with asthma (median 3.0 kU/L, P<0.01). Furthermore, children with asthma displayed higher IgG4 levels than the asthmatic adults.


CONCLUSIONS
A single recombinant molecule, rFel d 1, is at least as sensitive for in vitro diagnostics of cat allergy as the current extract-based test. Elevated IgE antibody levels to Fel d 1 are suggested to be a risk factor for asthma in cat-allergic children.
Grönlund
H
H
Department of Medicine, Clinical Immunology and Allergy Unit, Karolinska Institutet and University Hospital, Stockholm, Sweden. hans.gronlund@ki.se
Adédoyin
J
J
Reininger
R
R
Varga
E-M
EM
Zach
M
M
Fredriksson
M
M
Kronqvist
M
M
Szepfalusi
Z
Z
Spitzauer
S
S
Grönneberg
R
R
Valenta
R
R
Hedlin
G
G
van Hage
M
M
D000293:Adolescent; D000328:Adult; D000818:Animals; D001249:Asthma / Q000175:diagnosis* / Q000276:immunology; D002415:Cats / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D003233:Conjunctivitis, Allergic / Q000175:diagnosis / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006023:Glycoproteins / Q000276:immunology*; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood* / Q000276:immunology; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D008297:Male; D011852:Radioallergosorbent Test; D011994:Recombinant Proteins / Q000276:immunology; D012221:Rhinitis, Allergic, Perennial / Q000175:diagnosis / Q000276:immunology*; D012680:Sensitivity and Specificity
D006023:Glycoproteins; D007074:Immunoglobulin G; D011994:Recombinant Proteins; D007073:Immunoglobulin E; C059296:Fel d 1 protein, Felis domesticus