Clinical Symptoms And Biomarkers Of Bermuda Grass-Induced Allergic Rhinitis Using The Nasal Allergen Challenge Model

Abstract

Bermuda grass pollen is a prevalent allergen that flourishes in subtropical climates, such as the southern United States. Bermuda grass exposure is traditionally believed to be relatively low in Ontario due to the colder environment. However, high rates of Bermuda grass sensitization have been observed in Kingston. We sought to investigate whether Bermuda grass pollen extract can provoke allergic rhinitis (AR) symptoms in sensitized participants. We also examined if the nasal allergen challenge (NAC) model is appropriate to study Bermuda grass-induced AR and biomarkers in allergic participants from south eastern Ontario. Twenty-one Bermuda grass sensitized and 12 non-allergic consenting participants successfully completed a titrated nasal challenge with increasing concentrations of Bermuda grass allergens. Total nasal symptom score (TNSS) and peak nasal inspiratory flow (PNIF) were collected before allergen exposure and 10 minutes after the delivery of each concentration. Twelve allergic participants that met the qualifying criteria (TNSS≥8 and PNIF fall≥50%) and 11 non-allergic controls returned for a single dose NAC. Peripheral blood, nasal lavage, and nasal tissue were collected before and after NAC to investigate AR biomarkers. The mean Bermuda grass wheal size was significantly greater in sensitized participants compared to healthy controls (sensitized=6.7mm, non-allergic=0.0mm). Nineteen out of 21 sensitized participants met the criteria of a clearly positive allergic response when Bermuda grass allergen was administered to the nasal cavity. During the NAC visit, Bermuda grass allergic participants had significantly greater TNSS between 15 minutes and 3 hours post NAC compared to non-allergic controls. Bermuda grass sIgE was significantly increased in allergic participants when comparing screening to NAC visits (screening=3.46 kUA/l, baseline=9.16 kUA/l, 6 hours=8.86 kUA/l). Likewise, allergic participants significantly increased in the percentage of nasal eosinophils at both 1 and 6 hours post NAC. Mean concentration of peripheral leukocytes (baseline=5.48x109/l, 6 hours=6.63x109/l), neutrophils (baseline=3.23x109/l, 6 hours=3.89x109/l), and lymphocytes (baseline=1.64x109/l, 6 hours=2.07x109/l) were significantly increased 6 hours post NAC in Bermuda grass allergic participants. Although Bermuda grass pollen is a non-native allergen in Ontario, Bermuda grass extract can induce AR symptoms in sensitized participants during allergen challenge. The NAC model is appropriate to study Bermuda grass-induced AR and associated biomarkers.