IgE Reactivity of the Dog Lipocalin Allergen Can f 4 and the Development of a Sandwich ELISA for Its Quantification.
OBJECTIVE
Divergent results on the IgE reactivity of dog-allergic subjects to Can f 4 have been reported. The aim of this study was to evaluate the significance of Can f 4 in dog allergy and to develop an immunochemical method for measuring Can f 4 content in environmental samples.


METHODS
We purified the natural dog allergen Can f 4 from a dog dander extract by monoclonal antibody-based affinity chromatography and generated its variant in a recombinant form. Sixty-three dog-allergic patients and 12 nonallergic control subjects were recruited in the study. The IgE-binding capacity of natural Can f 4 and its recombinant variant was assessed by ELISA, immunoblotting, and skin prick tests (SPT).


RESULTS
Eighty-one percent of the dog-allergic patients showed a positive result to the immunoaffinity-purified natural Can f 4 in IgE ELISA, but only 46% in IgE immunoblotting. Respective results with the recombinant Can f 4 variant were 54% and 49%. SPT results reflected those obtained in ELISA and immunoblotting. The overall IgE reactivity of the immunoaffinity-purified natural Can f 4 was found to depend strongly on the integrity of the allergen's conformation. A sandwich ELISA based on monoclonal antibodies was found to be functional for measuring Can f 4 in environmental samples.


CONCLUSIONS
Can f 4 is a major allergen of dog together with Can f 1 and Can f 5. In combination with other dog allergens, it improves the reliability of allergy tests in dog allergy.
Department of Clinical Microbiology, Institute of Clinical Medicine and Biocenter Kuopio, University of Eastern Finland, Kuopio Campus, Finland.; Institute of Dentistry, School of Medicine, University of Eastern Finland, Kuopio Campus, Finland. Marja.Rytkonen-Nissinen@uef.fi.
Marja
M
Rytkönen-Nissinen
Department of Clinical Microbiology, Institute of Clinical Medicine and Biocenter Kuopio, University of Eastern Finland, Kuopio Campus, Finland.
Soili
S
Saarelainen
Department of Pulmonary Diseases, Kuopio University Hospital, Kuopio, Finland.
Jukka
J
Randell
Institute of Biomedicine, University of Eastern Finland, Kuopio Campus, Finland.
Jukka
J
Häyrinen
Institute of Biotechnology, Viikki Biocenter, University of Helsinki, Finland.
Nisse
N
Kalkkinen
Department of Clinical Microbiology, Institute of Clinical Medicine and Biocenter Kuopio, University of Eastern Finland, Kuopio Campus, Finland.
Tuomas
T
Virtanen
Allergen; Can f 4; Canis familiaris; IgE; dog; lipocalin