Effect of grass pollen immunotherapy on clinical and local immune response to nasal allergen challenge

Allergic rhinitis is common, troublesome, costly and associated with asthma 1, 2, 3. Specific allergen immunotherapy is an effective treatment 4, particularly for seasonal allergic rhinitis. Clinical trials of allergen immunotherapy face several challenges, including standardization of allergen exposure between individuals, seasons and locations. Additionally, the primary outcome – combined symptom and medication score – may be subject to poor compliance, the result being that large numbers of participants are typically required. We have previously described nasal challenges with grass pollen, accompanied by collection and analysis of mediators in nasal fluid 5. Response to nasal challenge may serve as a surrogate for seasonal symptoms 6, allowing assessment outside of pollen seasons, control of doses, and real‐time recording of symptoms. As such, nasal challenges and, more recently, environmental exposure chambers have been used to assess responses to allergen immunotherapy 7, 8. The effects of allergen immunotherapy on mediators in nasal fluid have also been investigated, with regard to ragweed 9, cat dander 7, grass pollen 10 and silver birch pollen 11, demonstrating suppression of histamine 9, kinins 12, tryptase, eosinophil cationic protein (ECP) 10 and IL‐5 11. Combining clinical and immunological outcomes has the benefit of providing insight into the mechanisms of allergic inflammation and immunotherapy. We aimed to elaborate on this approach, investigating clinical outcomes of nasal challenge, their biological correlates, and relationship with seasonal symptoms. We hypothesized that patients receiving grass pollen immunotherapy would show blunted clinical and immunological responses to nasal challenge compared with untreated grass pollen allergics. We describe the results of a pilot, proof‐of‐concept, cross‐sectional study.