NEW YORK (Reuters) -- A new cat allergy vaccine can effectively reduce allergic symptoms with far fewer injections than traditional allergy shots, a study shows.
Four weekly injections of the vaccine significantly reduced sneezing, itchy and watery eyes, running nose, shortness of breath, and wheezing of cat-allergic people exposed to two felines in the same room for one hour. The report of the study appears in the December issue of the American Journal of Respiratory and Critical Care Medicine.
"This new treatment, while not a cure, appears to improve allergic responses to cats," says Dr. Philip S. Norman, study lead-author and professor of medicine at Johns Hopkins University.
"Traditional allergy shots inject water and extracts from allergens like cat dander or pollen," he explains. "This vaccine only injects very specific parts of cat allergens selected for their ability to favorably stimulate the immune system."
To produce results, allergy shots typically call for an initial series of at least 25 injections over three months or more, followed by booster shots every two weeks, sometimes for years, Norman says.
He also points out that shots pose a small risk of a serious allergic reaction.
"In contrast, patients receiving the vaccine occasionally have mild symptoms on the injection day, but they require only simple treatment," Norman says.
The researchers divided 95 cat-allergic people into four groups: three different dose levels and one placebo (inactive shot). Before getting the shots, and one week and six weeks after treatment, participants spent an hour in a room with two cats who had occupied the room for at least five months. During that exposure, they recorded their cat-allergy symptoms.
The treatment proved most effective for people who received the highest vaccine dose. They reported the least severe symptoms, and more people in this group were able to stay in the cat room for the full hour six weeks after treatment, compared to the other groups.
Norman says the vaccine is designed to suppress the immune system response to a protein found in cat dander and saliva. (Cats transfer the protein to their fur when they lick themselves.)
The vaccine contains a synthetic version of peptide molecules, or parts of this allergy-provoking protein.
In their report, the Hopkins team notes this is the first human study to demonstrate that peptides designed to favorably stimulate immune system T-cells can alter the symptoms of an immune system disease, such as allergies.
But they say more studies are needed to further define the risk of adverse reactions to the vaccine, the duration of the vaccine's effect, and the optimum dosages.
"If we're correct, this could make vaccines a superior approach for controlling many allergies," Norman says.
The Hopkins team developed the vaccine, ALLERVAX CAT, together with the pharmaceutical company ImmuLogic, Waltham, Massachusetts.
SOURCE: American Journal of Respiratory and Critical Care Medicine, (1996;154:1623-1628)
