The major dog allergens, Can f1 and Can f2, are salivary lipocalin proteins:: cloning and immunological characterization of the recombinant forms

Canis familiaris allergen 1 (Can f1) and Canis familiaris allergen 2 (Can f2) are the two major allergens present in dog dander extracts. We now report the isolation of cDNAs encoding both proteins and present their nucleotide and deduced amino acid sequences. Can f1, produced by tongue epithelial tissue, has homology with the von Ebner's gland (VEG) protein, a salivary protein not previously thought to have allergenic properties. Can f2, produced by tongue and parotid gland, has homology with mouse urinary protein (MUP), a known allergen. Both VEG protein and MUP are members of the lipocalin family of small ligand-binding proteins. Recombinant forms of Can f1 and Can f2 were produced and tested for immunoglobulin E (IgE) reactivity. Among dog-allergic subjects, 45% had IgE directed exclusively to rCan f 1, and 25% had IgE to both rCan f1 and rCan f2. In addition, both recombinant proteins were able to cross-link IgE and elicit histamine release from peripheral blood leucocytes in vitro. These findings confirm that Can f1 and Can f2 are major and minor dog allergens, respectively, and demonstrate that recombinant forms of dog allergens retain at least some IgE-binding epitopes.