• Change in average daily asthma medication use between the 2007 and 2008 ragweed seasons
  

• Effect of AIC on selected secondary clinical outcome measures
  
• safety of AIC in this population
  
• mechanisms through which AIC may induce tolerance to ragweed
  

Ragweed allergy is a common trigger of asthmatic flare-ups in people with asthma. Individuals with ragweed allergy suffer increased asthma symptoms during the fall allergy season, which generally runs from August to November. These flare-ups can significantly impact an asthma patient's quality of life. AIC is an investigational medicine that combines special DNA sequences that can modify the way the immune system responds. In AIC, these sequences are linked to a piece of the ragweed pollen molecule (known as Amb a 1) that causes hay fever symptoms. Injections of AIC have been shown to change the way the immune system responds to ragweed pollen in both animals and humans in a way that may lead to reduced hay fever symptoms.

In a previous study, AIC was safe and well tolerated, and patients exhibited a decrease in allergy symptoms lasting up to 2 years after treatment on average. This study will evaluate whether short-term use of AIC during the spring can cause long-term immune tolerance to ragweed, reduce asthma symptoms, and decrease use of asthma medications for future allergy seasons.

During the 2007 fall ragweed allergy season, participants will be observed and be asked to keep a diary of their asthma symptoms and medication use. In the spring of 2008, participants will be randomly assigned to receive six weekly doses of either the experimental medicine or placebo. Participants will be observed again for the 2008 fall ragweed season. Another series of three weekly doses of the assigned study treatment will be given in spring 2009, with observation through the 2009 fall ragweed allergy season and possibly the 2010 season. During the observation periods, participants will be asked to track their asthma symptoms and medication use and report this information to study staff. Study visits will be weekly during the spring and biweekly during the ragweed season, with a maximum of 16 visits per year. Allergy and lung tests as well as blood and urine collection will occur at selected study visits; these tests are designed to measure the participants' immune response.

Inclusion Criteria:

• History of asthma
• History of asthma medication use during the 2005 fall ragweed season
• Suspected ragweed allergy
• Positive laboratory tests for ragweed allergy

Exclusion Criteria:

• Received immunotherapy for ragweed or other allergens within the 5 years prior to study entry
• Received anti-IgE (omalizumab) within the year prior to study entry
• 3 or more courses of oral corticosteroids for asthma within the year prior to study entry
• Inpatient hospitalization for asthma within the 5 years prior to study entry
• History of respiratory failure or intubation for asthma
• Smoking within the 6 months prior to study entry
• Greater than 5 pack/year history of smoking
• Clinically significant acute or chronic illness
• Chronic immunodeficiency