Imagining better treatments for cat allergies
Food, gene editing, vaccines that alter felines being tested
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 groundbreaking 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. But 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.
“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.”
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 also 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.
And there is no way to totally escape Fel d 1. It rides on people’s clothes to work and school.
“It’s everywhere,” said James Wedner, an allergist at Washington University in St. Louis.
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. Bruce Kornreich, director of the Cornell Feline Health Center, 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.
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. 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. There are also medications available.
Saiba Animal Health, a Swiss company initially known as HypoPet, is taking a 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.
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.
Elizabeth Knighton, a veterinarian with City
Cat Vets in Philadelphia, 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.