Local tissue eosinophilia and Th2-cytokines are characteristic features of seasonal allergic rhinitis. Airway-remodelling is a feature of asthma whereas evidence for remodelling in allergic rhinitis (AR) is conflicting.
By use of a novel human repetitive nasal allergen challenge (RAC) model, we evaluated the relationship between allergic inflammation and features of remodelling in AR.
Twelve patients with moderate-severe AR underwent 5-alternate day challenges with diluent which after 4-weeks were followed by 5-alternate day challenges with grass pollen extract. Nasal symptoms, Th1/Th2 cytokines in nasal secretion and serum were evaluated. Nasal biopsies were taken 24 hours after the 1 and 5 challenges with diluent and with allergen. Sixteen healthy controls underwent a single challenge with diluent and with allergen. Using immunohistochemistry, epithelial and sub-mucosal inflammatory cells, and remodelling markers were evaluated by computed image analysis.
There was an increase in early and late-phase symptoms after every allergen challenge compared to diluent (both p<0.05) with evidence of both clinical and immunological priming. Nasal tissue eosinophils and IL-5 in nasal secretion increased significantly after RAC compared to corresponding diluent challenges (p<0.01, p=0.01, respectively). There was a correlation between submucosal mast cells and the early-phase clinical response (r=0.79, p=0.007) and an association between epithelial eosinophils and IL-5 concentrations in nasal secretion (r=0.69, p=0.06) in allergic rhinitis. No differences were observed after RAC with regards to epithelial integrity, reticular basement membrane thickness, glandular area, expression of markers of activation of airway-remodelling including α-SMA, HSP-47, extracellular matrix (MMP7, 9 and TIMP-1), angiogenesis and lymphangiogenesis for AR compared to healthy controls.
Novel repetitive nasal allergen challenge in participants with severe persistent seasonal allergic rhinitis resulted in tissue eosinophilia and increases in IL-5 but no structural changes. Our data support no link between robust Th2-inflammation and development of airway-remodelling in AR.
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