Felis catus allergenic proteins (Fel d)

Felis catus allergenic proteins, collectively referred to as Fel d, are a suite of proteins produced by domestic cats that serve as the primary triggers for feline-related allergic diseases (Bonnet et al., 2018). The most significant of these is Fel d 1, a secretoglobin produced in the sebaceous and salivary glands, which is responsible for the majority of IgE-mediated sensitivity in humans (Gronlund et al., 2010). Other notable allergens include Fel d 2 (serum albumin) and Fel d 4 (lipocalin), which are involved in cross-reactivity with other mammalian species (WHO/IUIS, 2024). These proteins are highly stable, easily aerosolized, and can persist in indoor environments for extended periods, leading to chronic symptoms such as allergic rhinitis and asthma (NIH, 2023). Therapeutic strategies focus on neutralizing these allergens or modifying the host immune response, including allergen-specific immunotherapy (AIT) and the use of monoclonal antibodies like REGN1908/1909 (Regeneron, 2023). Emerging approaches also include feline-targeted interventions, such as vaccines or diets designed to neutralize Fel d 1 before it is shed into the environment (Satyaraj et al., 2019).

Other names

Cat allergensFel d proteinsFelis domesticus allergensCat dander proteinsFel d 1Fel d 2Fel d 3Fel d 4Fel d 7

Allergen-specific immunotherapy (AIT) works by inducing peripheral T-cell tolerance, increasing the production of regulatory T cells (Tregs) and IL-10, and shifting the antibody response from IgE to IgG4 (Bonnet et al., 2018). Monoclonal antibodies like REGN1908 and REGN1909 bind specifically to Fel d 1, preventing it from cross-linking IgE on the surface of mast cells and basophils, thereby inhibiting the allergic cascade (Regeneron, 2023).