Chemical stops allergic reaction in tests. (Immunology).

Using a genetically engineered protein, researchers have short-circuited--at least in test tubes and mice--the type of allergic reaction that causes asthma, allergic rhinitis, and potentially deadly food allergies.

The scientists created the new molecule, called GE2, by fusing together snippets of two normal antibody proteins. GE2 binds to both so-called epsilon and gamma receptors on the surfaces of some immune cells. In people with allergies, ordinarily harmless substances like pollen bind to antibodies and then to the epsilon receptor. These two steps trigger the immune cells to release chemicals, such as histamine, that cause swelling, sneezing, and itching. The gamma receptor doesn't trigger allergic reactions. Instead, with certain compounds attached, it puts a brake on the release of histamine.

"One end of GE2 binds to the brake and the other to the trigger, bringing the two receptors together and defusing the [allergy] bomb," says Andrew Saxon of the University of California, Los Angeles. In his lab, GE2 slowed or stopped the release of histamine, and once injected into mice, the compound significantly reduced skin reactions to allergens to which the mice had previously been sensitized, Saxon reports in the May Nature Medicine.

"This is a therapy, not a cure," Saxon notes. To work as a drug, GE2 would have to be administered with or before every exposure to an allergen. Currently, physicians can cure some allergies by giving a patient repeated low-dose shots of specific allergens, which leads to tolerance of those substances. However, people with severe food allergies can't use such shots because of potentially deadly reactions to the therapy itself. Saxon sees the possibility of modifying GE2 to block specific allergic reactions. He says that this approach could make shots safe enough even for people with severe allergies.--D.C.