Fel d 1

Variation in cats

Kittens produce less Fel d 1 than adult cats. Female cats produce a lower level of Fel d 1 than (unneutered) males, while neutered males produce levels similar to those of females. Both intact and spayed females produce similar levels. Although females and neutered males produce Fel d 1 in lower levels, they still produce enough to cause allergic symptoms in sensitive individuals.

Researchers have been investigating reports from cat owners that certain breeds of cats either do not produce Fel d 1 or are thought to do so at significantly lower levels than other breeds. For instance, individual cats from the naturally occurring Siberian breed, native to the Siberian region for which the breed is named, have been shown to have genetic variants that result in a lower production of Fel d 1. Another breed thought to have a possible genetic disposition not to produce this allergen or to produce less of it is the Balinese, an offshoot of the Siamese breed. Several other breeds are widely referenced as causing a diminished immune reaction in cat allergy sufferers, including Sphynx, Russian Blue, Cornish Rex, Devon Rex, Siamese, Javanese, Oriental Shorthair, Burmese, and LaPerm.

Fairly reliable tests for their Fel d 1 protein production is available for individual cats, but research regarding entire breeds continues, hampered by the lack of a thoroughly accessible and accurate genetic test for production of the antigen.

Structure

The complete quaternary structure of Fel d 1 has been determined. The allergen is a tetrameric glycoprotein consisting of two disulfide-linked heterodimers of chains 1 and 2. Fel d 1 chains 1 and 2 share structural similarity with uteroglobin, a secretoglobin superfamily member; chain 2 is a glycoprotein with N-linked oligosaccharides. Both chains share an all alpha-helical structure.

Presence in other species

Proteins matching the family signature for Fel d 1 parts, from the InterPro database, is widespread among Theria, a subclass of mammals amongst the Theriiformes (the sister taxon to Yinotheria.) Theria includes the eutherians that includes the placental mammals and the metatherians that includes the marsupials. More specifically, the InterPro profiles link the two components of Fel d 1 to the rodent androgen-binding protein (ABP; not to be confused with the human SHBG), a salivary pheromone.

A homolog of Fel d 1 protein is also present in the venom of the slow loris (Primate: Nycticebus). Slow lorises are one of only a few venomous mammals and the only known venomous primate. They possess a dual-composite venom of saliva and brachial gland exudate (BGE). The BGE possesses a protein resembling Fel d 1, which may affect host species as an allergen as a constituent of the venom. BGE is hypothesized to repel predators.

References

References

1. (September 2003). "The crystal structure of the major cat allergen Fel d 1, a member of the secretoglobin family". The Journal of Biological Chemistry.
2. (November 1991). "Amino acid sequence of Fel dI, the major allergen of the domestic cat: protein sequence analysis and cDNA cloning". Proceedings of the National Academy of Sciences of the United States of America.
3. (April 1992). "Expression and genomic structure of the genes encoding FdI, the major allergen from the domestic cat". Gene.
4. (October 1990). "Cat skin as an important source of Fel d I allergen". The Journal of Allergy and Clinical Immunology.
5. (July 1996). "Sex difference in Fel d 1 allergen production". The Journal of Allergy and Clinical Immunology.
6. (December 2017). "Polymorphism Analysis of Ch1 and Ch2 Genes in the Siberian Cat". Veterinary Sciences.
7. (April 2024). "Allergy to Cats - Cat DNA Test Kit {{!}} Basepaws".
8. Myers, P.. "Subclass Theria". Animal Diversity Web.
9. InterPro taxonomy view, IPR006178 and IPR015332
10. (2018). "Another cat and mouse game: Deciphering the evolution of the SCGB superfamily and exploring the molecular similarity of major cat allergen Fel d 1 and mouse ABP using computational approaches". PLOS ONE.
11. (September 2013). "Mad, bad and dangerous to know: the biochemistry, ecology and evolution of slow loris venom". The Journal of Venomous Animals and Toxins Including Tropical Diseases.