In a world where whiskers and purrs captivate the heart, cat allergies hide in the shadows, eager to pounce. Approximately 10–30% of the population is sensitive to cat dander, saliva, and urine, with sneezing, coughing, and itchiness being common symptoms. The primary allergen produced by cats is a globular protein called Fel d1 (Bonnet, et al., 2018).

Fel d1 is a tetrameric glycoprotein comprised of two heterodimers (Figure 1) (Kaiser, et al., 2003). When bound with immunoglobulin E (IgE), an allergenic effect is produced, which triggers symptoms in sensitive humans (Matulka, Thompson and Corley, 2019).

These chains of amino acids are formed through dehydration synthesis (Figure 2). After the peptide chains are formed, they are linked together by three interchain disulphide bonds (Kaiser, et al., 2003).

Chickens could be the solution for combatting the allergenic nature of the Fel d1 protein, as they are able to pass antibodies on to their offspring. When chickens are in the presence of cats and therefore the Fel d1 protein, they naturally produce antibodies to combat the allergen (Satyaraj, et al., 2019). The antibodies, classified as immunoglobulin Y (IgY), are condensed in the egg yolk of chicken eggs and provide passive immunity – antibodies transferred to prevent disease or infection – to baby chicks (Romeo, 2021). These eggs can then be incorporated into cat food. The IgY antibodies bind to active sites of Fel d1 (Satyaraj, et al., 2019). Unbound Fel d1 becomes an active allergen when bound with IgE, whereas bound Fel d1 is unable to bind to IgE, which neutralizes the effect of the allergen (Matulka, Thompson and Corley, 2019).

With this discovery, the possibility of reducing cat allergies worldwide is not far-fetched. It has been demonstrated that consumption of IgY antibodies is non-toxic for cats. In one study, 80% of cats fed IgY-containing food showed at least a 20% reduction in salivary Fel d1 production (Figure 2) (Satyaraj, et al., 2019). A separate study showed analogous findings, where 86% of cats had at least a 20% reduction in salivary Fel d1 after being fed IgY-containing food, compared to only 38% of control cats (Matulka, Thompson and Corley, 2019). This implies consistent reduction of Fel d1 production in cats after being introduced to IgY.

Some brands, such as Purina, have already introduced cat food that incorporates IgY. Purina food has been studied and determined to be safe consumption and harmless to cats (Matulka, Thompson and Corley, 2019). 

With a decrease in cat allergenicity, more individuals would be able to own and interact with cats. Avoidance of cats due to fear of allergic reaction would be diminished; the frequency of feline abandonment and their relinquishment to animal shelters would effectively be reduced. The impact on the human-animal bond would be lessened, as those with cat allergies would no longer be forced to limit physical contact with their cat to prevent allergic reactions. Contact is vital to a meaningful bond, and the elimination of Fel d1 allows physical contact to be achieved (Satyaraj, Wedner and Bousquet, 2019). The annihilation of Fel d1 also poses the possibility of eradicating other allergens through the usage of chickens, or through other animals that provide passive immunity.

References

Bonnet, B., Messaoudi, K., Jacomet, F., Fauquert, J.L., Caillaud, D., and Evrard, B., 2018. An update on molecular cat allergens: Fel d 1 and what else? Chapter 1: Fel d 1, the major cat allergen. Allergy, Asthma & Clinical Immunology, [e-journal] 14(14). https://doi.org/10.1186/s13223-018-0239-8

Chapman, D., Pomes, A., Breiteneder, H. and Ferreria, F., 2007. Nomenclature and structural biology of allergens. Environmenal and Occupational Respiratory Disorders, 119(2), pp.414–429. https://doi.org/https://doi.org/10.1016/j.jaci.2006.11.001.

Flatt, P.M., 2020. CH450 and CH451: Biochemistry – defining life at the molecular level. [online] Chapter 2: Protein Structure. Available at: <https://wou.edu/chemistry/courses/online-chemistry-textbooks/ch450-and-ch451-biochemistry-defining-life-at-the-molecular-level/> [Accessed 26 Sep. 2023].

Kaiser, L., Gronlund, H., Sandalova, T., Ljunggren, H.G., van Hag-Hamsten, M., Achour, A., and Schneider, G., 2003. The crystal structure of the major cat allergen Fel d1, a member of the secretoglobin family. The Journal of Biological Chemistry, [e-journal] 278(39), pp. 37730-37735. https://doi.org/10.1074/jbc.M304740200.

Liliya, 2020. Peptide bond. [image online] Available at:<https://www.alamy.com/peptide-bond-formation-of-amide-bonds-from-two-amino-acids-as-a-result-of-protein-biosynthesis-reaction-it-is-process-is-a-dehydration-synthesis-rea-image356547165.html> [Accessed 26 September 2023].

Romeo, M., 2021. A neat trick- passive immunization using chicken antibodies.[online] Available at: <https://sparkmed.stanford.edu/blog/passive-immunization-using-chicken-antibodies/> [Accessed 17 September 2023]

Matulka, R., Thompson, L., and Corley, D., 2019 Multi-level safety studies of Fel d1 IgY ingredient in cat food. Frontiers in Veterinary Science, [e-journal] 6(477). https://doi.org/10.3389/fvest.2019.00477

Satyaraj, E., Li, Q., Sun, P., and Sherrill, S., 2019. Anti-Fel d1 immunoglobulin Y antibody-containing egg ingredient lowers allergen levels in cat saliva. Journal of Feline Medicine and Surgery, [e-journal] 21(10), pp. 875-881. https://doi.org/10.1177/1098612X19861218

Satyaraj, E., Wedner, H., and Bousquet, J., 2019. Keep the cat, change the care pathway: A transformational approach to managing Fel d1, the major cat allergen. Allergy, [e-journal] 74(107), pp. 5-17. https://doi.org/10.1111/all.14013