Response to Ragweed Allergen Provocation in the Red Maple Trials Allergen Challenge Theatre

Abstract

Allergen challenge chambers expose allergen-sensitive subjects to predetermined concentrations of allergen in a controlled environment and provide a mechanism to induce clinical symptoms and measure the effect of medication. We evaluated the response of ragweed-allergic subjects to two ragweed challenges in the Red Maple Trials Allergen Challenge Theatre. A provincial Ethics Board approved the study. After signing informed consent, patients with a history of ragweed allergy, not on allergy medications and with positive skin prick tests (> 3 mm) to ragweed antigen were exposed to ragweed pollen in a 3-hour priming session. Total nasal (TNSS), ocular and rhinoconjunctivitis symptom scores (TRSS) were recorded at baseline and every 30 minutes during the challenge. Those with peak TNSS ≥ 5 were then selected for two further 4-hour challenges. 48/76 subjects evaluated underwent the priming challenge. Thirty-three subjects achieving a peak TNSS ≥5 underwent two subsequent 4-hour challenges. Baseline TNSS (mean± SD) was 1.70 ±1.34 and 2.53±1.76 in challenges 1 and 2, respectively. Baseline TRSS values were 2.00± 1.66 and 3.60±2.69 respectively. Symptom scores reached a plateau by 120 minutes and remained steady for the remainder of the 240-minute exposure. Plateau TNSS was 6.28±0.20 for Challenge 1 and 6.19±0.24 for Challenge 2. Similarly, plateau TRSS values were 9.10±0.20 and 9.11± 0.33, respectively. The Red Maple Trials allergen challenge theatre demonstrated the capacity to induce symptoms of appropriate intensity upon ragweed allergen challenge. The chamber with a 100-person capacity has the ability to evaluate large test groups at one time.