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Original Article

 

Variable Content of Fel d 1 Variants in House Dust and Cat Extracts May Have an Impact on Allergen Measurement

 

C Bienboire-Frosini,1,4 R Lebrun,2 D Vervloet,3 P Pageat,1 C Ronin4

1IRSEA, St Saturnin d’Apt, France
2Plate-forme Protéomique de l’Institut de Microbiologie de la Méditerranée, CNRS, Marseille, France
3Université de la Méditerranée, Service de Pneumologie, Hôpital Ste Marguerite, Marseille, France
4SiaMed’Xpress, Université de Provence, Marseille, France

J Investig Allergol Clin Immunol 2012; Vol. 22(4): 270-279

 

 Abstract


Background: The major cat allergen, Fel d 1, is a tetrameric glycoprotein composed of 2 heterodimers. Polymorphisms in this allergen are well documented. Recent work shows that Fel d 1 samples can contain core fragments of variable immunoreactivity.

Objectives: Our objective was to compare Fel d 1 polymorphism in cat extracts and house dust, which is used as an indicator of allergen exposure and to understand how the combination of individual Fel d 1 variants can affect cat allergen measurement.

Methods: Natural Fel d 1 allergens were water-extracted from house dust and from the chest area and anal sacs of a cat. Recombinant Fel d 1 was provided commercially. The samples were analyzed by immunoblotting; variants were isolated using gel electrophoresis and tested using enzyme-linked immunosorbent assay.

Results: Four Fel d 1 variants of 40, 30, 19-21, and 14-16 kDa were consistently identifi ed in Fel d 1 samples. Fel d 1 patterns found in house dust and the chest area wash were similar. Dimers were shown to be the major variant, while intact or truncated tetramers and core fragments were found in variable amounts. Intact and truncated dimers of Fel d 1 displayed similar antibody binding. Conversely, the intact tetramer–but not the core tetramer–was found to bind twice the antibody amount as the dimers and core fragments.

Conclusions: Despite a common pattern of Fel d 1 variants in cat extracts and house dust, variations in the tetramer-to-dimer ratio among samples may introduce major discordances in cat allergen measurements using immunoassays. Our fi ndings indicate the need for further harmonization h armonization of allergen immunoassays.

Key words: Allergen measurement. Cat. Fel d 1. House dust. Immunoreactivity. Polymorphism. Recombinant Fel d 1. Variants.