Tale of a 'Hypoallergenic' Cat and Standby Antihistamines

SAN DIEGO, Dec. 29 -- Feline allergies' nine lives may be up.

A fluffy white cat named Joshua and brethren would have allergic tabby-lovers, long starved of feline companionship, believe the day of the litter box is just ,950 away. Some allergists are skeptical. Other are taking a wait-and-sneeze approach.

Joshua, now 20 months old, is touted by a company here called Allerca as "the world's first scientifically proven hypoallergenic cat." Others lacking a key allergenic protein have been bred since Joshua.

According to the company's Web site, "These [hypoallergenic] cats allow some of the millions of people with feline allergies to finally enjoy the love and companionship of a household pet without suffering from allergic symptoms."

Yet some skeptical allergists recommend that anyone who springs for the pricey pets keep their antihistamines at the ready.

Allerca says its cats -- Joshua was the index cat -- are bred to not express the Fel d 1 protein that is primarily responsible for feline allergy in humans. Although Allerca says that an independently conducted exposure trial it sponsored was promising, allergists decry the lack of any published data.

The small exposure study found that 10 volunteers with severe cat allergies had little or no reaction when exposed to the "genetically divergent" cats, said Ricardo A. Tan, M.D., of the California Allergy and Asthma Group in Los Angeles. He said that:

• Two of the participants had significant allergic symptoms with the normal cat but no symptoms with a hypoallergenic cat.
• One subject had a mild reaction to both types of cat but showed no allergic symptoms to a placebo room where there was a stuffed animal that felt like a cat.
• Others had either mild symptoms with the normal cat and no symptoms to the hypoallergenic cat or no allergic reaction to either type.

Participants were blindfolded during the experiment to control for psychosomatic allergic symptoms. The data have not been peer reviewed or published.

The concept seems like it would work, said Thomas A. E. Platts-Mills, M.D., Ph.D., of the University of Virginia in Charlottesville and president of the American Academy of Allergy Asthma and Immunology. Breeding animals for a specific trait, as in this case for the dominant but rare mutated form of a gene to produce modified protein, is easy compared with trying to create a Fel d 1 knockout, he said.

Evidence is increasingly pointing to Fel d 1 as the dominant allergen among the many proteins produced by a cat and shed in its dander, Dr. Platts-Mills said.

"If you would have asked me two years ago, I would have said that if you take away Fel d 1 [people] would just become allergic to another protein," he said. "What they're doing may be more helpful than we expected."

One of the unanswered questions, though, is whether the modified protein expression by the mutated gene is sufficiently dissimilar or causes low enough Fel d 1 expression to prevent allergic rhinitis, asthma and other symptoms.

"Even if they reduced it by 50% or 40% or 80%, it doesn't mean somebody with cat allergy is going to have fewer symptoms or need less medication," said allergist James M. Seltzer, M.D., of the University of California in Irvine.

He cited previous efforts like carpet spray to denature the cat allergy protein and air filters that have clearly shown a reduction in the antigen exposure but been less effective in reducing symptoms.

Furthermore, patients may find they are still experiencing allergic symptoms since Fel d 1 exposure can come from outside the home as well--at school or work or by visitors--said Lisa Vailes, M.S., of Indoor Biotechnologies in Charlottesville, a company that isolates cat allergens to produce recombinant protein for research purposes.

"Even if they do produce [the hypoallergenic cat], people are still going to be exposed to cat allergen from other sources," Dr. Vailes said. "It would be very difficult to completely isolate a person from it."

One study in as isolated a location as Antarctica showed that enough cat allergens arrived, presumably on the clothing of staffers, at Scott base to provoke symptoms in allergic individuals (Lancet 1999; 353:1942).

Cats produce also other minor allergens, such as Fel d 3, Dr. Vailes said. While Fel d 1 accounts for probably about 90% of cat allergies, some individuals have a reaction to these other proteins and "it's possible that some patients may react to [the modified protein found in the hypoallergenic cats]," Dr. Tan said.

Cats are responsible for the majority of animal allergies, according to the American College of Allergy Asthma and Immunology. For allergy sufferers, it recommends:

• Washing cats once a week with plain water or a mild veterinary shampoo reduce dander and remove dried saliva.
• Keeping pets outside or at least out of the bedroom to reduce exposure to pet allergens, and using central air cleaners to help remove pet allergens in the home.

For the ,950 (delivery in 2007), Allerca says it will provide cat-lovers a hypoallergenic kitten, plus:

• 1 x Home Environmental Allergy Test (to check for existing cat allergen in your home)
• 2 x Allergy Tests (a complete FDA approved home allergy test)
• Allerca airline-certified cat transporter
• Veterinary Health Certificate (required for travel)
• One set of nail caps already applied (these are vinyl nail caps applied to the kitten's claws that cover the claws so no damage occurs when the animal scratches)
• A starter pack (includes premium kitten food, additional nail caps, cat toys and other kitten sundries)

The company reports a two-year waiting list.