Patricia F. Fitzpatrick Dimond Ph.D. Technical Editor of Clinical OMICs President of BioInsight Communications
The solution likely lies in controlling complex immune reactions rather than creating hypoallergenic pets.
If you are even thinking of getting a nonallergenic pet for your allergic child for a holiday gift, forget it. Authoritative pet owner assertions about dogs with hair being less allergenic than dogs with fur turns out to be drivel. Generally, experts say, one dog and another of the same breed can give off very different levels of allergen, but they all give off allergens. If you were hoping to purchase kitties or puppies with allergenicity bred out of them, you missed the boat as Allerca stopped selling its pets for suckers in 2010.
According to Daniel More, M.D., commenting on the website allergies.about.com, “Unfortunately, the whole idea of a hypoallergenic dog is a myth. There have never been any studies showing that a poodle or nonshedding dog produces less dog allergen than a nonhypoallergenic breed. Multiple recent studies show that there is no difference in the amount of major dog allergen produced by various breeds of dogs—and, in fact, one study showed that the popular labradoodle produced the most dog allergen of any breed in the study.”
Pet bodily products that cause the most significant allergic reactions include dander (skin scales)—not the length or amount of hair/fur on the pet—as well as saliva and urine. The allergies occur chiefly in response to the presence of specific glycoproteins encoded by the genes Can d1 in dogs, Fel d 1 in cats, and Der p 2 in dust mites that are expressed on surfaces of dendritic cells.
The resulting immune overreaction can results in symptoms including coughing, sneezing, itchy eyes, runny nose, and scratchy throat and, in severe cases, can result in rashes, hives, lower blood pressure, difficulty breathing, asthma attacks, and even death. Allergists say that pets causing significant allergic reactions should be removed from the home of the allergic patient to avoid possible symptom progression.
And they say “trial” removal of a pet for a few days or even weeks may be of little value since an average of 20 weeks is required for allergen levels to reach levels found in petless homes. About 17% of pet owners in the U.S. and 5% of dog owners have allergies to their pets, but many who view their animals as part of the family are reluctant to give them up, despite the potential need for constant medication to control their symptoms.
Too Good To Be True
In 2004 Allerca started offering its Lifestyle Pets, kitties and puppies, that the company claims did not cause allergies because the animal were bred either not to express allergy-causing antigens, or to express them at extremely low levels. The animals could be purchased for prices ranging from $6,950 for an Allerca GD cat, an Allerca Ashera GD cat at $26,950, or a Jabari GD dog at $15,950.
But the company supplied no information about the process behind the pets except what is available on its website, nor does much in the way of scientific provenance exist. According to Allerca, it had “spent much time and energy in achieving its final goal of delivering consistently hypoallergenic cats to our customers, and therefore our protocols and procedures remain proprietary and confidential.”
According to Simon Brodie, president of Allerca, in a 2004 interview with WebMD, “Many people think they’re allergic to cat hair or dander, but they’re really allergic to the protein. And the nice thing about this [Allerca’s breeding] process, it doesn’t completely suppress the protein production. If the cat still needs this protein, it’s still expressing it, so it can produce the protein, but in such tiny amounts that it won’t cause problems.
“It’s like hypoallergenic makeup. The allergens are still there, but in very small amounts that don’t trigger allergic reactions.”
A British shorthair cat was chosen for the first line of hypoallergenic cats, and every kitten is sold pre-spayed and neutered. “We don’t want our cat to breed with a nonhypoallergenic cat and [have] someone attempt to sell the kittens as hypoallergenic,” said Brodie.
“That’s like buying a knockoff Gucci purse that hurts someone’s health,” he told WebMD.
But, would you buy a pet, much less a knockoff Gucci bag, from a guy like Simon Brodie, alias Simon Campbell? The Scientist magazine, after Allerca cancelled several interviews conducted its own investigation in 2009, and found highly favorable testimonials posted on the company website from customers who claim to have received hypoallergenic pets. The publication also found several disappointed customers who were essentially told that they were “too allergic” to receive Allerca cats.
Later that year, the company announced on its website shortly thereafter that effective January 1, 2010, it would “focus exclusively on developing its animal genetic technologies” and would “NO LONGER offer our hypoallergenic pets for sale.”
Mr. Brodie/Campbell’s history would suggest that buying anything from him probably would be ill-advised. Among his other enterprises was Geneticas, which claimed it would provide customers an allergy-free cat based on RNAi and had already accepted hundreds of nonrefundable $250 deposits. Geneticas also predicted it could bring the cost of cloning a cat below $10,000. The cats never came and Geneticas disappeared, The Scientist reported in its article, “Felix Enigmaticus”.
Pet suckering aside, scientists are beginning to define and confirm molecular differences between highly pet-allergic and normal individuals’ immune responses, and to define in particular the role of the antigen presenting cells, dendritic cells, in allergic disorders.
Investigators at the Institut Pasteur de Lille compared uptake of Der p 1, the major house mite dust allergen, by human dendritic cells (DCs) between DCs from patients with house dust mite allergy and DCs from healthy donors.
They found that DCs took up labeled Der p 1 antigen in a dose-, time-, and temperature-dependent manner. Uptake was mediated by the mannose receptor (MR), a C-type lectin expressed by dendritic cells that mediates internalization of diverse allergens from mite (Der p 1 and Der p 2), dog (Can f 1), cockroach (Bla g 2), and peanut (Ara h 1) through their carbohydrate moieties. In their studies, the investigators found that, compared with DCs from healthy, non-allergic donors, DCs from allergic patients expressed more MR and were more efficient in Der p 1 uptake.
Using a gene-silencing strategy, the investigators specifically inhibited the expression of MR on human monocyte-derived DCs. They showed that silencing MR expression on monocyte-derived DCs reversed the Der p1 allergen-driven Th2 cell polarization bias, or the cascade of immune cell events leading to the production of cytokines associated with allergic responses. Their work, they conclude, demonstrated a major role for MR in glycoallergen recognition, in the development of Th2 responses, and in a potential anti-allergen drug target, the MR receptor.
Controlling pet allergies is less likely to be a matter of finding the perfect hypoallergenic pet and more about discovering and controlling the complex immune mechanisms that underlie severe allergic reactions. Better yet, if you are allergic, forget the kitty or puppy altogether and consider a pet tuna.
Patricia Fitzpatrick Dimond, Ph.D. ([email protected]), is a principal at BioInsight Consulting.