Domestic cats are among the animals most prone to triggering allergies. Allergy to cats affects roughly 15% of both children and adults, with symptoms ranging from nasal and eye irritation to full-blown asthma in some cases. The vast majority of reactions, about 95%, are tied to Fel d 1, a protein produced in the cat’s saliva, sebaceous glands, perianal glands, and lacrimal glands. While the levels of Fel d 1 vary by breed, sex, and other traits, there is currently no truly hypoallergenic cat available on the market.
New possibilities are emerging through genetic engineering. Researchers at the American biotech company ImBio have identified a method to curb Fel d 1 production using gene editing. The work has been published in the CRISPR Journal.
Earlier approaches to lowering Fel d 1 included special diets and vaccines based on viral vectors, as well as attempts to breed entirely hypoallergenic cat lines. The recent study, however, pursues a different aim: a path that could render existing cats less allergenic rather than creating new lines of animals.
“Producing a separate hypoallergenic cat line for consumers and patients is very costly,” notes ImBio researcher Nicole Brackett, the study’s lead author. “We believe it makes more sense, both commercially and ethically, to develop a treatment that can work for cats that are already in homes.”
The exact role of Fel d 1 in feline biology remains not fully clear. Analyses comparing the Fel d 1 genes in wild and domestic cats suggest these genes do not critically affect survival and may not be essential for the cat’s life history.
In their experiments, scientists used tissue from 50 domestic cats that had been sterilized, including testicular, ovarian, and uterine samples. Using the CRISPR/Cas9 technique, which enables precise DNA cutting and the addition or removal of fragments, researchers removed the CH1 and CH2 gene segments that encode Fel d 1 from the cat genome. They observed no unintended changes in the expression of other proteins as a result.
The study authors acknowledge that it is not yet clear how much Fel d 1 reduction is needed for a cat to avoid provoking allergies. Prior work with a protein-reducing cat food indicated that about a 47% drop in Fel d 1 in secretions could lessen allergy symptoms by around 30%. Yet this effect mainly matters when there is direct contact with the animal; if Fel d 1 accumulates in house dust, allergic reactions can persist.
“Given that most cat- allergy patients experience symptoms at a threshold of about 8 micrograms of Fel d 1 per gram of house dust and that the allergen can accumulate in dust at levels exceeding 1000 micrograms per gram, the clinical impact of a modest reduction could be limited,” the researchers note. Another experimental approach being explored involves injections of monoclonal antibodies that bind to Fel d 1, preventing it from attaching to immunoglobulins. In past studies, this method reduced symptom severity by roughly 60% in about half of participants. The goal is to block Fel d 1 production in a way that could protect most people from allergic reactions.
“Our findings demonstrate a practical application of CRISPR technology in allergy and veterinary research, highlighting how evolutionary biology, genomic engineering, and therapeutic development can intersect,” the authors state.
The team hopes to move toward a drug that could be administered to cats, perhaps via injection. For now, they have transitioned from cell cultures and tissues to trials in live cats and plan to study more closely how the absence of Fel d 1 impacts the animals themselves.