Molecular characterization of dog albumin as a cross-reactive allergen,☆☆,,★★

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Abstract

Indoor allergens comprise a group of allergenic proteins that are commonly derived from house dust mite and cat and dog dander. In addition to the two major dog allergens (molecular weights: 19 and 23 kd), dog albumin represents an important allergen for up to 35% of patients who are allergic to dogs. In IgE immunoblot inhibition studies and histamine release tests it has been demonstrated that patients who react to dog albumin exhibit IgE reactivity with purified albumins from cat, mouse, chicken, and rat. The proportion of dog-specific IgE directed against dog albumin was determined for patients allergic to dog albumin, and it ranges from 70% to 90%. By IgE immunoscreening of a lambda gt11 expression library from a dog salivary gland, we identified a number of reactive complementary DNA clones. All patients with IgE reactivity against natural dog albumin displayed IgE reactivity to the β-galactosidase fusion protein encoded by clone 54c, which was therefore assumed to contain major IgE epitopes of dog albumin. The deduced amino acid sequence of clone 54c was compared with the Swiss-Prot library, and significant sequence homologies were found with albumins from different species (human: 82.6%, pig: 81.8%, cattle: 77.3%, sheep: 78.8%, mouse: 75.8%, and rat: 76.2%). Several other IgE-positive clones hybridized with oligonucleotides that were prepared according to this sequence. Partial complementary DNA coding for dog albumin fragments may be considered a useful tool for further characterization of major IgE epitopes of dog albumin. (J ALLERGY CLIN IMMUNOL 1994;93:614-27.)

Section snippets

Characterization of allergic patients' sera

Sera from 110 patients were selected for this study according to case history, positive skin prick test results and positive RAST results, as described by Jarolim et al. 21 All patients showed reactivity to other allergens (e.g., tree pollen, grass pollen, mite, cat and horse dander, guinea pig epithelia). Sera from 22 healthy persons with a negative case history of any type I allergy and negative skin prick test and RAST results to dog allergens were pooled (normal human serum pool) and used

Determination of the percentage of patients allergic to dog albumin

. IgE reactivity of selected patients allergic to albumin with dog hair/dander extract. IgE Immunoblot with dog hair/danDer proteins that were blotted to nitro cellulose. Six patients with IgE reactivity to dog albumin had been selected and were compared with a human serum pool prepared from nonallergic patients (N). P represents the buffer control.

. IgE reactivity of patients allergic to dogs with different albumins. The same group of individuals (patient 1 to 6) as in Fig. 3A was tested for IgE

DISCUSSION

Type I allergies to mammalian proteins, in particular to dog and cat allergens, are frequently related. 17, 18, 19 Although the major dog allergens Can f I 7, 13 and Can f II 7, 14 and the major cat allergen Fel d I 15, 16 show similar molecular weights, these allergens are neither immunologically nor structurally related. However, albumin was identified as a relevant IgE-binding structure in dog and cat hair/dander extracts. 7, 12, 20 About 35% of patients allergic to dogs display IgE

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  • Cited by (0)

    From aInstitute of Medical and Chemical Laboratory Diagnostics; bDepartment of Hematology and Hemostaseology; c Institute of General and Experimental Pathology, AKH, University of Vienna, Austria.

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    Supported by grants S06703 and S06712-Med of the “Fonds zur Förderung der wissenschaftlichen Forschung and grant 3/8603 of the “Fonds zur Förderung der gewerblichen Wirtschaft,” Vienna, Austria.

    Reprint requests: Rudolf Valenta, MD, Institute of General and Experimental Pathology, AKH, University of Vienna, Währingergürtel 18-20, A-1090 Vienna, Austria.

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