COMPLEMENTARY-DNA CLONING OF THE PREDOMINANT ALLERGEN OF BOVINE DANDER - A NEW MEMBER IN THE LIPOCALIN FAMILY

Background: A number of allergenic proteins in animal danders have bee n characterized at the molecular level, but little is known of their b iologic functions. We have found that the prevalence of IgE antibodies among patients with cattle-associated asthma is highest against a dan der protein referred to as BDA20. Objective: The study was performed t o characterize the molecular structure of BDA20, the predominant alle rgen in bovine dander. Methods: Clones encoding allergens were identif ied and isolated from a complementary DNA library by immunoblotting an d DNA hybridization and sequenced. Recombinant proteins were produced in Escherichia coli. Immunoreactivity of the recombinant proteins and amino acid sequences of peptides obtained from native BDA20 after Lys- C cleavage were used to identify, clones coding for BDA20. Results: In this article we report the cDNA and amino acid sequences of BDA20. Ho mology comparisons showed that BDA20 belongs to the family of lipocali ns. Conclusions: The results link a dander allergen to a group of func tionally important proteins. Lipocalins are present in various body fl uids and secretions of several animal species in which they function a s carriers of small hydrophobic molecules, such as retinoids and phero mones. If allergenicity proves to be a property shared by lipocalins, our results will have considerable implications for allergen research.