Nasal mist vaccine suppresses peanut allergy in mice

Researchers with the Mary H. Weiser Food Allergy Center at the University of Michigan developed the vaccine as a new form of immunotherapy to treat allergies to peanut.

"Right now, the only FDA-approved way to address food allergy is to avoid the food or suppress allergic reactions after they have already started," said lead author Jessica O'Konek, Ph.D. "Our goal is to use immunotherapy to change the immune system's response by developing a therapeutic vaccine for food allergies."

During an allergic reaction, the body's immune system overreacts to an allergen, that is, an otherwise harmless protein. Allergen immunotherapy attempts to retrain the immune system to tolerate the allergen. Other peanut allergy immunotherapies being tested in human clinical trials have been shown to improve peanut tolerance in many, but not all, peanut allergy patients. This tolerance can be lost if maintenance doses of peanut are discontinued; additionally, adverse reactions can occur during immunotherapy.

"We are committed to the development of new food allergy immunotherapies and pleased to report these promising results," said Mary Jane Marchisotto, FARE's senior vice president for research and international operations. "This serious and potentially life-threatening disease affects 15 million Americans and is becoming increasingly prevalent. Emergency care for severe allergic reactions has increased almost 400 percent during the past decade. Effective treatments are urgently needed."

The vaccine research team is working to develop a safe, durable and more widely effective new form of immunotherapy. The experimental immunotherapy vaccine consists of peanut protein and nano-emulsion, tiny droplets of highly purified soybean oil, detergents and water mixed at high speed. The average diameter of the droplets is 350-400 nanometers, roughly 200 times smaller than the average diameter a human hair.

The nano-emulsion acts as an adjuvant, a substance that is added to a vaccine to increase the body's immune response. Nano-emulsion has previously been shown to promote a strong immune response associated with fighting infection. Researchers theorized that this infection-fighting response would suppress a competing allergic response. Because the highly purified soybean oil contains no soy proteins, treatment with the nano-emulsion does not result in the development of soy allergies and does not trigger soy allergy reactions.

The mice were experimentally sensitized to peanut to mimic the effects of peanut allergy, then were given three doses of intranasal vaccine over the course of two months, receiving either peanut plus nano-emulsion or a placebo. Two weeks after the final vaccination, the mice were exposed to peanut and their symptoms and immune functions were assessed. Compared to mice who were treated with a placebo, the mice who received the nano-emulsion vaccine were protected against localized symptoms of allergic reaction, such as itchiness and puffy eyes, as well as more severe symptoms, such as wheezing and shock.

"We're changing the way the immune cells respond upon exposure to allergens," O'Konek explained. "By re-directing the immune responses, our vaccine not only suppresses the response but prevents the activation of cells that would initiate allergic reactions. Importantly, we can do this after allergy is established, which provides for potential therapy of allergies in humans."

Additional studies in mice are ongoing to determine if the vaccine's protection will endure over a longer period. Future studies in mice may reveal more details about the mechanisms responsible for that protection. If successful, these experiments could eventually lead to a clinical trial of the vaccine in humans.