Repeatability of nasal allergen challenge results: Further validation of the allergic rhinitis clinical investigator collaborative protocols

Abstract Background Nasal allergen challenge (NAC) models have been used to study allergic rhinitis and new therapies. Symptoms and biological samples can be evaluated at time points after allergen exposure. Objective To verify protocol repeatability and adequate interval between allergen exposures. Methods Ten ragweed allergic participants were exposed to incrementally increasing dosages of ragweed allergen intranasally until they achieved a total nasal symptom score (TNSS) of 8 of 12 and a peak nasal inspiratory flow (PNIF) of 50% reduction or more from baseline. Three weeks later, participants were challenged with a cumulative dose equal to the sum of all the allergen doses received at screening. TNSS and PNIF were recorded at regular intervals, including a 24-hour assessment. A subsequent visit was conducted after a further 3 weeks. Nasal secretion samples were collected for cytokine and eosinophil quantification. Results Nine participants completed all visits. TNSS and PNIF responses followed previous patterns, with an initial peak at 30 minutes followed by a gradual decline. Most participants reported similar patterns at both NAC visits, although some did not demonstrate the same phenotype at both visits. Some experienced a secondary symptom increase 24 hours after NAC. Eosinophil and cytokine sections followed a similar pattern at both NAC visits. Conclusion NAC is an adequate method for modeling AR in humans, demonstrating appropriate repeatability of symptoms, nasal mucosal eosinophil, and cytokines. The 24-hour time point, previously not studied in our model, may be beneficial in evaluation of long-acting medications. This three-week interval NAC model will be beneficial for studies in which before and after treatment comparisons are desired.