Two Newly Identified Cat Allergens: The von Ebner Gland Protein Fel d 7 and the Latherin-Like Protein Fel d 8

Abstract

Introduction: Characterization of the complete IgE binding spectrum of cat allergens is important for the development of improved diagnosis and effective immunotherapeutics. While Fel d 1 remains unchallenged as the major cat allergen, we now report the isolation of two new allergens capable of binding similar concentrations of IgE in the allergic sera of some individuals. Materials and Methods: Cat tongue and submandibular salivary gland cDNA libraries were screened by DNA hybridisation and IgE immunoassay. The isolated DNA fragments were sub-cloned into an E. coli expression system and the IgE reactivity was examined with human cat-allergic sera using a DELFIA IgE quantitation assay. Results: Fel d 7, an 18 kDa von Ebner gland protein Can f 1 homologue, was isolated from the tongue library. Fel d 8, a 24-kDa latherin-like protein with homology to Equ c 5, was isolated from the submandibular library. The frequency of IgE binding of cat-allergic sera to recombinant Fel d 1, 7 and 8 was 60.5, 37.6 and 19.3%, respectively. Inhibition studies indicated some IgE binding cross-reactivity between Fel d 7 and dog dander extracts. Discussion: The study reports the isolation and characterization of two new cat allergens. The isolation of these allergens provides the opportunity to determine the role that IgE binding proteins other than Fel d 1 play in cat-allergic disease. For cat-allergic individuals with moderate to mild rhinoconjunctivitis these allergens may play a more important role in the manifestation of their allergic disease.

The structure of latherin, a surfactant allergen protein from horse sweat and saliva

“…A latherin-like allergen protein has also been characterized from the tongue epithelium and salivary glands of cats (Fel d 8; [14]). Whether latherin and its relatives are intrinsically allergenic, or become targets of allergic responses in certain individuals responding coordinately to other allergenic stimuli, remains to be seen.…”

Distant cousins: genomic and sequence diversity within the BPI fold-containing (BPIF)/PLUNC protein family

“…We have focused on these two genes as they have both been independently studied by a number of groups [8,9,14,15,16]. Table 1 also clearly shows that two other genes, BPIFA3 (SPLUNC3) and Bpifa6 (Splunc6), diverge significantly from our rules, but at this time these two have not been studied at all.…”

“…We showed that BPIFA4 is a SPLUNC and that its closest paralogue at the time was horse latherin (GenBank ® accession number AF491288) which is 42 % identical [5,15]. The gene appears to be absent from the rodent lineage, but has been identified in cows and cats [5,6,10,16]. The predicted protein product of human BPIFA4 is significantly shorter than other single-domain-containing proteins and appears to be missing approximately 50 amino acids from the C-terminal end of the molecule, including the cysteine residue that is conserved in all other family members [4,5].…”

Mammalian Airborne Allergens

“…This may have generated the idea that understanding mammalian allergens is basically simple -lipocalins, secretoglobins and serum albumins, and possibly also cystatins [13] and latherins [14,15] -if you know these few protein families, you may think you know it (almost) all. However, having now much more precise information than we may have wished for, we are facing new questions, some of which were quite unexpected.…”