Allergenic Activity of Individual Cat Allergen Molecules

Abstract

More than 10% of the world’s population suffers from an immunoglobulin E (IgE)-mediated allergy to cats which is accompanied mainly by respiratory symptoms such as rhinitis and asthma. Several cat allergen molecules have been identified, but their allergenic activity has not been investigated in depth. Purified cat allergen molecules (Fel d 1, Fel d 2, Fel d 3, Fel d 4, Fel d 6, Fel d 7 and Fel d 8) were characterized via mass spectrometry and circular dichroism spectroscopy regarding their molecular mass and fold, respectively. Cat-allergen-specific IgE levels were quantified via ImmunoCAP measurements in IgE-sensitized subjects with (n = 37) and without (n = 20) respiratory symptoms related to cat exposure. The allergenic activity of the cat allergens was investigated by loading patients’ IgE onto rat basophils expressing the human FcεRI receptor and studying the ability of different allergen concentrations to induce β-hexosaminidase release. Purified and folded cat allergens with correct masses were obtained. Cat-allergen-specific IgE levels were much higher in patients with a respiratory allergy than in patients without a respiratory allergy. Fel d 1, Fel d 2, Fel d 4 and Fel d 7 bound the highest levels of specific IgE and already-induced basophil degranulation at hundred-fold-lower concentrations than the other allergens. Fel d 1, Fel d 4 and Fel d 7 were recognized by more than 65% of patients with a respiratory allergy, whereas Fel d 2 was recognized by only 30%. Therefore, in addition to the major cat allergen Fel d 1, Fel d 4 and Fel d 7 should also be considered to be important allergens for the diagnosis and specific immunotherapy of cat allergy.

A human monoclonal antibody based immunoenzymetric assay to measure Fel d 1 concentrations in cat hair and pelt allergenic extracts

“…In 2023, Trifonova et al used recombinant cat allergens and the basophil activation test to demonstrate that among 37 children and adolescents who were both sensitized and allergic (displayed objective symptoms) to cat allergens, 36 (97%) were reactive to Fel d 1, ∼70% were reactive to Fel d 4 and Fel d 7. Additionally, the median concentration to reach the plateau of basophil activation by Fel d 1 was 0.1 ng/ml, at least 10-fold lower than the other allergens tested ( 22 ). These studies support the view that Fel d 1 is the major cat allergen and an ideal protein to serve as an indicator of cat allergen extract potency.…”

Advancing diagnostic precision: Unveiling sensitization relationships between cat, dog, and horse allergen molecules

“…The concept of a “marker allergen molecule” becomes complex in animal allergies due to the ubiquity of many animal allergens as pan‐allergens 8,9,17 . Some lipocalins and serum albumins exhibit intricate cross‐reactivity patterns, emerging as a significant contributor to polysensitization 2,16,19–23 . Multiplex molecular allergy platforms present a valuable opportunity to comprehensively document the sensitization profile of these AMs 24–26 .…”

Non-Specific Lipid Transfer Protein Amb a 6 Is a Source-Specific Important Allergenic Molecule in Ragweed Pollen

“…Patients tended to report more symptoms when sensitized to pan-allergens in addition to Amb a 1 [ 18 , 19 ]. Importantly, the allergenic activity of the individual ragweed allergens needs to be evaluated in more detail because the frequency of IgE recognition does not take into consideration this important parameter for the clinical relevance of a given allergen [ 20 , 21 , 22 ].…”