In television commercials, allergy suffers pop a pill and play in wildflower fields with nary a sneeze. Cures are tougher to come by. A new genetically engineered allergy vaccine, however, cut people's allergic reactions, and it could point the way toward a new type of vaccine that heads off hay fever.
About one in four people in industrialized countries suffer from respiratory allergies. Unfortunately, antihistamines, including the prescription drugs hawked on TV, treat only the symptoms. Weekly vaccinations with allergens treat the underlying problem, but the current vaccines don't work for everyone and sometimes cause allergic reactions of their own.
To come up with a safer and more effective vaccine, immunologist Rudolf Valenta of the University of Vienna and colleagues built on an old idea. Allergens stimulate production of a special type of antibody called immunoglobulin E (IgE), which triggers immune cells to release substances such as histamine that cause wheezing and other symptoms. Decades ago, immunologists proposed that vaccines containing allergens might trigger production of normal antibodies called immunoglobulin G (IgG), which could then help quickly mop up allergens. Valenta's team had discovered that different parts of a potent birch-pollen allergen spurred IgG and IgE production, and they'd rebuilt the protein to trigger only the IgG response. Then, 4 years ago, they began a clinical trial to test whether the engineered pollen protein eased allergies.
It did. People vaccinated over the winter with the modified allergen showed three times the anti-birch-pollen IgG levels as placebo-immunized patients, demonstrating that modified allergen spurred a normal immune response instead of an allergic response. In test tube experiments on histamine-producing immune cells, serum from 39 immunized patients--but not the 27 sham-immunized patients--cut histamine release 10-fold. And immunization reduced IgE levels by about 25% the following spring, an effect that remained the following autumn, according to results in published online 13 August in the Proceedings of the National Academy of Sciences. Vaccinated subjects reported less severe symptoms during allergy season than those vaccinated with placebo. The researchers plan to engineer vaccines based on a combination of allergy-triggering proteins from cat dander, grass, and other allergens--a strategy that could lead to a safe and effective childhood vaccination against respiratory allergy, Valenta says.
The vaccine's ability to dampen cellular responses to allergens is encouraging, says allergist William Busse of the University of Wisconsin, Madison. If the group can better document the vaccine's safety and effectiveness at cutting allergic symptoms, he adds, "there's a real chance that this is a major step forward."