Immune cells notice allergens and attack with antibodies, leading to symptoms… (Glenn Koenig, Los Angeles…)
Allergy sufferers may soon be able to face ragweed season and even hyper-shedding cats without so much sniffling and sneezing — that is, if Mark Larché has anything to say about it.
Larché, an immunologist at McMaster University in Hamilton, Canada, is developing vaccines that he hopes will diminish allergies more quickly and safely than current therapies. He calls the vaccines a "next-generation allergy shot."
His first two targets are ragweed allergy, which affects 10% to 20% of Americans, mostly in the Midwest and East; and cat allergy, which afflicts some 10% of the U.S. population.
Doctors currently treat severe cases with allergy shots, also called allergy immunotherapy. It's an effective but somewhat risky approach that involves giving a person tiny, escalating doses of the very thing they're allergic to in the hopes of getting the body used to the substance. The therapy requires injections as frequently as three times a week for up to seven months, with continued monthly shots for five years or more. And because it involves exposure to the actual allergen, there's always a risk of an allergic reaction, ranging from swelling to potentially fatal anaphylactic shock.
"Allergy shots work," says Dr. Andrew Saxon, an immunologist at UCLA. "The overarching problem is they're dangerous," not to mention "expensive and slow."
Instead of using the entire allergen, Larché puts only pieces of it in his vaccine. In theory, it's enough to make the body take notice but not enough to cause an allergic reaction. Instead of months of regular shots, he plans a schedule of one shot a month for four months. Since the treatment is so new, no one knows whether an annual booster might be needed to keep up the benefits.
The vaccine represents an exciting approach to a "common and ever-increasing medical problem," says Alessandro Sette, an immunologist at the La Jolla Institute for Allergy & Immunology. "If it works, it would lead to something that is safer and less cumbersome."
Scientists have been working on the basic strategy for more than a decade; Larché predicts his first vaccines might reach the market in 2014. He's already given 350 people the cat vaccine and is planning to test it in several hundred more people later this year. An additional 300 allergy sufferers have tried the ragweed version. So far, recipients report that after vaccination, their symptoms — when inside a chamber with circulating allergen — drop by approximately half.
While it's no "magic bullet," Larché says, "you're basically taking the edge off."
The idea behind the vaccines is to change a person's immune response to an allergen, such as the protein Fel d 1 that cats spread all over their fur when they wash themselves. The right response is tolerance — immune cells recognize the allergen but decide it is not a threat. But in the case of an allergy, immune cells notice the allergen and attack it with antibodies. This leads to a decidedly intolerant response: sneezing, sniffling, swellingor rashes.
The antibodies go on the attack only if they see a whole allergen. Larché creates small chunks of the allergen by artificially manufacturing strands of protein called peptides. These peptides are recognized by the tolerant immune system cells but ignored by the cells that start allergies. By turning on the right cells, the peptides seem to retrain the body to have a more tolerant response.
Researchers are still uncertain just how this happens; Larché examines blood samples from his subjects before and after vaccination in an ongoing effort to understand the process.
Larché first targeted cat allergies because they're a relatively straightforward problem. Most people who sneeze around cats are allergic to one particular protein, Fel d 1. Ragweed pollen also has one main allergy-causing protein, called Amb a 1, which breaks down sugars. Dust mites, by contrast, have a dozen or more proteins that can cause trouble. The challenge will be designing the right mix of peptides for each situation, Saxon notes.
Scientists think cats might use Fel d 1 as a pheromone to attract mates. It's sticky stuff that attaches to the cat's dander, which then floats in the air and gets, well, everywhere.
The problem doesn't affect just those who live with a feline. People who regularly visit other people's homes, such as police officers, can't avoid it. The dander sticks to cat owners and infiltrates offices and other public places. Larché's wife, a physician, sometimes gets sick for a full day after seeing a patient who has a cat.
In addition, cat allergy seems to be a sort of "gateway" allergy. Kids bothered by cats often go on to develop asthma or even more allergies. Although Larché has tried his vaccine only in adults so far, he hopes it would work for children too and perhaps stave off future health problems.
He is also working on vaccines for dust mites and grass and would like to tackle cockroach and peanut allergies as well. Eventually, he hopes, the same strategy might work for diseases in which the immune system attacks other parts of the body — Type 1 diabetes and rheumatoid arthritis, for example.
"Traditionally, shots have been the domain of people who have quite severe [allergies]," he says. "I think this will increase the number of people who think, 'I'm going to give this a try.'"
That population includes Larché himself, who is sensitive to grass, dust mites and ragweed.
"I'm queuing up for the shot when it comes out," he says.