Repetitive nasal allergen challenge in allergic rhinitis: Priming and Th2-type inflammation but no evidence of remodelling

Seasonal allergic rhinitis is characterized by local tissue eosinophilia and Th2-cytokines. Asthma is characterized by airway-remodeling and which conflicts with evidence for remodeling in allergic rhinitis. This study aimed to assess the relationship between allergic inflammation and features of remodeling in allergic rhinitis using a new human repetitive nasal allergen challenge.

This study included twelve patients with moderate-to-severe allergic rhinitis who underwent 5-alternate day challenges with diluent, followed after 4-weeks by 5-alternate day challenges with grass pollen extract. Nasal symptoms, Th1/Th2 cytokines in the nasal secretion, and blood were assessed. Nasal biopsies were taken one day after the first and fifth challenges with diluent and allergen. Sixteen healthy controls were challenged with diluent and allergen once. Epithelial and sub-mucosal inflammatory cells and remodeling markers were assessed by computed image analysis.

Allergic rhinitis symptoms increased after every allergen challenge compared to diluent (p<0.05), with evidence of both clinical and immunological priming. Nasal secretion tissue eosinophils and IL-5 increased significantly after nasal allergen challenge, compared to corresponding diluent challenges. Allergic rhinitis patients evidenced a correlation between submucosal mast cells and the early-phase clinical response and an association between epithelial eosinophils and IL-5 in nasal secretion. There were no differences after allergen challenge concerning epithelial integrity, reticular basement membrane thickness, glandular area, expression of markers of activation of airway-remodeling including α-SMA, HSP-47, extracellular matrix, angiogenesis, and lymphangiogenesis for allergic rhinitis compared to controls.

In conclusion, novel repetitive nasal allergen challenges in people with severe persistent allergic rhinitis yielded in tissue eosinophilia. They increased IL-5, but with no structural changes, which supports no relationship between Th2-inflammation and development of airway-remodeling in allergic rhinitis.