The future of human cat allergy treatment may be in changing cats with food, vaccines or gene editing
Any cat lover who has watched an allergic friend react to a beloved pet knows the dark powers that lurk in that luxurious feline fur. Within minutes, an allergic human exposed to a cat can begin sneezing and wheezing. Eyes water and itch. The misery is obvious.
Solutions for people who want to be around cats despite allergies are labor-intensive, of questionable value, and sometimes defy common sense. How many emergency department trips would ensue if we all tried to give our cats frequent baths?
This predicament has triggered the imagination of researchers, who see a lucrative market for better solutions in a country that has more than 50 million cats in more than 20 million homes. Some scientists are now taking a different approach to human pet allergies. Rather than trying to change allergic humans or their environment, they're trying to change cats.
Purina began the competition in the early days of the pandemic with a cat food—Pro Plan LiveClear—that it says can reduce the protein that most allergic people react to by 47% after three weeks.
"This is really, in my mind as a veterinarian, a ground-breaking and revolutionary pet food," said Kurt Venator, Purina's chief veterinary officer. "We truly believe this is going to help cats and people get closer together."
Another research group based in Switzerland is working on a vaccine against the offending protein, called Fel d 1. And a team from Indoor Biotechnologies in Virginia is exploring CRISPR gene-editing techniques to knock out the gene that makes Fel d 1. Those two projects are years from fruition.
Indoor Biotechnologies primarily detects, tests for, and purifies allergens. Martin Chapman, its president and CEO, had a long interest in cat allergens, but a bogus company that marketed fake hypoallergenic cats until about 2015 really got his attention.
"It sort of established there was a market for cats that would be up to $7,000 apiece," said Chapman, a former professor of medicine and microbiology at the University of Virginia.
Although some cats may wind up in shelters because allergic owners couldn't live with them, allergists said there is no doubt that many often choose their cat over their own comfort. They said it is rare that an allergic cat owner will give up the cat or even banish it from the bedroom.
"I haven't really encountered patients who are willing to get rid of their cats," said Patrick Gleeson, a Penn Medicine allergist. Of the new cat food, he added, "I think there's a huge market for this product."
Venator said one allergic cat owner who participated in a Purina focus group said he bought a new couch every six months so he could get allergens out of his house and keep his cat.
A problem that affects millions
Cat allergies affect 10% to 20% of adults. More than 90% of them react to Fel d 1. About 5% of adults are allergic to dogs, but many substances are involved in those allergies. That makes modifying dogs a more complicated project. Researchers say allergies to furry animals are increasing.
Fel d 1 is produced in salivary, skin and anal glands of cats and is found in their tears. Cats spread it when they clean themselves. It winds up all over the house when they shed fur or dander. All cats make it, including hairless cats, although amounts vary by cat or even by day. Bruce Kornreich, director of the Cornell Feline Health Center, said there is evidence that uncastrated male cats make more of it than females or neutered males. There is no such thing as a hypoallergenic cat.
And, there is no way to totally escape Fel d 1. It rides on people's clothes to work and school. "It's everywhere," James Wedner, an allergist at Washington University in St. Louis, said. He once saw five allergy sufferers who worked in a brand new office building. None had cats. He tested the building for mold, cockroaches and mice and found nothing. Then he found "incredibly high levels" of Fel d 1. Other workers were bringing it in, he said.
No one knows what role Fel d 1 plays in the cat's body, which is why any effort to get rid of it has to look at the effect on cats. Kornreich said there has been speculation that Fel d 1 might protect skin from pathogens. Another possibility is that it is involved in chemical signaling. Nicole Brackett, a postdoctoral researcher with Indoor Biotechnologies, sequenced the genes that make Fel d 1 in 50 domestic cats as well as some big and wild cats. She said the genes are not "well-conserved" in the domestic cats, a sign that they likely are not essential.
Purina says its tests show its food is safe.
LiveClear already comes in six varieties, including weight management, senior, and sensitive stomach. Chewy.com sells a 3.5-pound bag for $21.58. (A similar-sized bag of non-specialty cat food could cost less than $10.) Allergen-reducing kitten food is coming in September, Venator said.
The company's novel approach started about a decade ago when Ebenezer Satyaraj, a nutritional immunologist, learned his daughter was allergic to cats. He discovered that chickens produce an antibody to Fel d 1 that can be found in their eggs. The company added the antibody to cat food. The resulting food neutralized up to about half of the Fel d 1 some cats produced.
That means the treated cats are still making Fel d 1, of course, so it does not automatically mean allergic people will feel better around them. However, Wedner said higher doses of an allergen generally cause more symptoms.
But Gleeson, who said Purina's new food is "promising," said doctors "don't really know how much allergen reduction is necessary in order to reduce symptoms."
He said doctors often recommend getting rid of the cat—most patients won't—or washing it weekly. "I haven't talked to patients who have actually done that," he said. They can also get rid of rugs, vacuum frequently and get a HEPA air purifier. And, they can try allergy shots. "This is another area where the evidence is not very good," Gleeson said. Then there are medications.
Wedner led a small Washington University study funded by Purina that found that some people with allergies could reliably detect the difference between blankets used by cats that ate LiveClear and cats that ate other foods. These heroic volunteers sat with the blankets for three hours in enclosed chambers made for growing tomatoes. Their allergy symptoms were monitored every 15 minutes.
Wedner recently finished a larger study that used real cats in people's homes. It has not yet been published so he could not release full results, but he said, "patients were better off with the food than they were without it."
He also said that patients not in studies volunteer that the food has helped them.
Elizabeth Knighton, a veterinarian with City Cat Vets in Philadelphia, said her mother was allergic to cats. "Even though I wanted a cat my whole life, I didn't get one till I was 11," she said. Her mother wouldn't allow the cat in her room and had to get allergy shots. "She was always using an inhaler," Knighton said.
She has mentioned the new Purina food to some clients. "Because it's so new, I just don't have any feedback yet," she said. "I'd like to know if I'm recommending something that works."
Vaccines and gene editing are on the horizon
Saiba Animal Health, a Swiss company initially known as HypoPet, is taking a very different approach. It is working on a vaccine that turns the cat's immune system against Fel d 1 proteins. The company's research has shown the experimental HypoCat vaccine lowered Fel d 1 in cat tears and reduced symptoms in 10 allergic cat owners.
Saiba also hopes to produce a vaccine for dogs.
Kornreich said one worry with this type of vaccine is an errant immune reaction. "There's always a concern that that the immune system can be stimulated to start neutralizing things that are not the target of interest," he said.
As for the genetic approach, Brackett, at Indoor Biotechnologies, achieved 55% efficiency in knocking out Fel d 1 in a cat cell line. That is a good rate, she and Chapman said. "Cat cells are notoriously difficult to work with," Brackett said.
The next step will be to see whether they can reduce the allergen in cat salivary glands. Then will come the really hard part: figuring how to deliver the genetic treatment to embryos or adult cats. They'll be keeping an eye on techniques that other CRISPR researchers test.
"It does seem to be that there is a significant roadblock for CRISPR at the moment," Chapman said.
Knighton, the Philadelphia veterinarian, said she is more comfortable with the special food, which neutralizes Fel d 1 after the cat makes it, than with making bigger biological changes to cats. "I'm very wary of something that tells your body to attack something your body makes," she said.
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