Nasal epithelium biomarkers in young children: associations with allergic sensitization and environmental stressors.

Background: Recent studies suggest that allergic diseases might have their onset in early epithelial barrier defects. To test this hypothesis, we assessed associations between nasal epithelium biomarkers, environmental stressors, and the risks of allergic sensitization.

Methods: In a cross-sectional study of 288 kindergarten children (mean age, 5.7 years), we measured aeroallergen-specific IgE in nasal mucosa and the concentrations of urea, albumin, and Clara cell protein (CC16) in nasal lavage fluid (NALF). Albumin and CC16 in NALF were expressed per liter or as a ratio to urea. We also calculated the NALF CC16/albumin ratio as an index integrating the permeability and the secretory function of the nasal epithelium.

Results: Median NALF concentrations of CC16 and albumin were 8.2 µg/L and 34.5 mg/L, respectively. While there were no significant gender differences when proteins were expressed per liter, the CC16 to albumin and CC16 to urea ratios in NALF were higher in girls than in boys (P = 0.02 and 0.055, respectively. The nasal epithelial barrier function, as reflected by these NALF biomarkers, was positively influenced by probiotics and age, and negatively by environmental stressors such as pool chlorine. The risk of house dust mite (HDM) sensitization increased with decreasing log NALF CC16 concentration, whether expressed per liter (2.59, 95% CI: 1.15-5.82, P = 0.02), as a ratio to urea (1.98, 95% CI: 0.96-4.06, P = 0.06), or as a ratio to albumin (OR, 2.03, 95% CI: 1.10-3.74, P = 0.02). Children in the highest and intermediate tertiles of the NALF albumin/urea ratio were three times more likely to be sensitized to HDM than those in the lowest tertile (both P = 0.04).

Conclusion: Defects in the nasal epithelium barrier function of young children, as reflected by the concentrations of CC16 and albumin in NALF, are associated with environmental factors, including pool chlorine, and with increased risks of HDM sensitization.