WEDNESDAY, Oct. 4, 2006 (HealthDay News) -- If you're one of the millions of Americans who suffers every fall with ragweed allergies, long-term relief may be just a few years away.
In a new study from the Oct. 5 issue of the New England Journal of Medicine, researchers report that a new ragweed vaccine was effective for a year or longer in early trials. Even better, relief came from just six once-a-week injections, rather than the current schedule of several years of weekly injections required for current allergy shots.
"We can provide relief, very effective relief that lasts for at least a couple of years with a very short treatment regimen," said study author Dr. Peter Socrates Creticos, medical director of the Johns Hopkins Asthma and Allergy Center at the Johns Hopkins University School of Medicine, in Baltimore.
"You won't have to take several medicines every day of ragweed season. You won't need shots every week for years. We can turn this disease off for years with a concise six-injection regimen," he added.
"This study is very exciting, but I have to temper my excitement because it's a pilot study that has to be repeated on many more people. I'm optimistic about the future of these new immunomodulating agents," explained Dr. Rick Vinuya, an allergist at Providence Hospital in Southfield, Mich.
To develop this vaccine, Creticos and his team built on research done at the University of California San Diego. Those studies found that a certain sequence of DNA, derived from bacteria, could shut down an important immune system cell involved in the body's inflammatory response. That cell is known as a T-helper cell (Th2). Inflammation caused by Th2 is a major factor in the body's allergic response.
The Creticos team attached a DNA sequence that could shut off the Th2 response to a portion of the ragweed pollen cell to create the new vaccine. The vaccine is believed to work by shutting off the Th2 cells that are overreacting to harmless ragweed pollen. Normally, when Th2 cells in allergic people encounter ragweed pollen, they send out signals for the body to create a substance called IgE. It's IgE that causes most allergic symptoms, such as sneezing, watery eyes and itching.
But, since the vaccine effectively shuts down the Th2 response, no additional IgE should be manufactured in response to ragweed exposure.
"Its kind of like 'Let's Make A Deal,'" explained Creticos. "You know the car is behind one door, but depending on which door you choose, you might not get the car. Well, now we know which door the car is behind: We know the cell that can shut off the inflammation. Normally, the allergen wins the day, but now we redirect and shut it off."
Vinuya said current allergy medications that suppress the immune system are like big guns that shoot down everything. That can lead to unwanted side effects because many immune system functions are vital.
"[The new vaccine] is a smart bomb. It hones in on a specific target. The end effect is that the agent allows the treatment to be more effective with less side effects," said Vinuya.
For the current study, the Johns Hopkins' researchers recruited 25 people between the ages of 23 and 60 with documented ragweed allergies. During the first year of the study, 14 people received six weekly injections of the new vaccine before the ragweed season began. The remaining 11 received six weekly injections of a placebo. The volunteers kept close track of their allergy symptoms, recording when their noses ran and each time they sneezed or had watery eyes.
The vaccine group experienced a 60 percent drop in allergy symptoms during ragweed season when compared to the placebo group. In the year after the study, those in the vaccine group were still experiencing symptom relief, even though no additional vaccine was given.
Creticos said he doesn't expect any serious long-term side effects because this vaccine "restores normalcy." He said because the vaccine is so specific, only targeting the ragweed allergy, there likely won't be any long-term adverse effects. In fact, he pointed out that the vaccine is so specific that people who were vaccinated and who also have grass allergies in the spring, still experienced symptoms from that particular allergy.
He said the next step for this vaccine is phase III trials, after which the vaccine could receive government approval if all goes well. It could potentially become commercially available a few years down the road, said Creticos.
Creticos and his team are also planning phase II trials of the vaccine for people with ragweed allergy-induced asthma.
"This concept [behind this vaccine] is very important. Can we manipulate the immune system to turn off untoward inflammatory cascades? Not just for hayfever, but for other chronic inflammatory diseases, such as some forms of arthritis," he noted.
More information
To learn more about ragweed and other allergens, visit the American Academy of Allergy, Asthma and Immunology.
