Life

A California company has turned to conventional breeding to deliver the non-allergenic kittens it promised two years ago. But allergists warn the new cats may still be something to sneeze at.

In 2004, Allerca, then based in Los Angeles, announced plans to genetically engineer cats so they would not produce the most common cat allergen, a protein called FEL D1 (See Doubts over plan for allergen-free cats). Now based in San Diego, Allerca has abandoned genetic engineering to focus on selectively breeding cats that lack the version of the FEL D1 protein that triggers allergic reactions.

A spokeswoman says the company will deliver the first 400 to 500 "GD" (for genetically divergent) kittens in 2007.

Allergists consider the approach scientifically plausible. "It's been known for a long time that some cats are very low allergen producers", producing just one-thousandth the FEL D1 of a normal cat, says Robert Wood, director of Pediatric Allergy and Immunology at the Johns Hopkins University School of Medicine in Baltimore, US.

Allerca says that is because those cats lack the gene to produce the allergenic form of FEL D1, and instead produces a different, non-allergenic protein. They genetically screened cats to identify low-FEL D1 animals for a breeding population.

Potent allergen

In a statement, Allerca says "individuals with known feline allergies were fully exposed to the Allerca GD cats without demonstrating any allergic reactions", but that the same people suffered swollen eyes, asthmatic symptoms, and hives when later exposed to ordinary cats.

Cats are among the most common pets but also among the most widely blamed for allergic reactions because FEL D1 is the most potent pet allergen. Specific to cats, FEL D1 is found in fur, saliva, urine, and skin glands. Worse, it sticks to furniture, carpets and clothing, triggering allergies even when the cat is absent. Allergists typically tell people with severe asthma or allergies to get rid of cats to ease their symptoms.

But some still want pets. Allerca reports a two-year backlog of orders, with US residents paying $3950, and residents of other countries paying €4950 to €9950 ($6300 to $12,700, respectively). Kittens are to be shipped at 12 weeks old. "It's plausible that some people could benefit - if they have $4000 for a cat," Wood says.

The original breeding stock was based on the Shorthair breed, but Allerca says the current stock is closest to the Ragamuffin breed.

Most sensitive

But allergies are tricky, and specialists are cautious about the prospects. "This approach is scientifically valid, but that doesn't mean it's going to work," says Norman Edelman, chief medical officer of the American Lung Association.

Although FEL D1 is the dominant cat allergen, Wood told New Scientist that about 10% of people with cat allergies react to cat albumin, a protein released in increasing amounts in the urine as the cat ages.

Another concern is that allergic reactions are notoriously sensitive and can vary widely. Wood has found that reducing allergen exposure by 75% does not reduce symptoms in sensitive people. "Individual sensitivity varies well over a hundred-fold," he says, so breeding "may not reduce FEL D1 enough to protect the most sensitive people."

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