D1.49 - Component-Resolved Pet Allergen Sensitization Identifies Adolescents With Airway Inflammation and Bronchial Hyperresponsiveness

Sensitization to furry pets is common in adolescence, yet conventional allergy testing using whole allergen extracts does not capture heterogeneity in IgE responses to individual allergenic proteins. At the same time, it remains unclear whether sensitization to specific molecular pet allergen components is associated with differences in airway inflammation, bronchial responsiveness, and lung function.

We used data from the Copenhagen Prospective Studies on Asthma in Childhood 2000 mother-child cohort. Sensitization to molecular cat, dog, and horse allergen components was measured using the ImmunoCAP Immuno Solid phase Allergen Chip (ISAC). Component sensitization was defined as an ISAC Standardized Unit (ISU) value ≥0.30. Sensitization patterns and co-sensitization were described using UpSet plots, and relationships between individual allergen components, extract-based specific IgE, skin prick tests, and rhinitis symptoms were assessed using Spearman correlation analyses. Associations between component sensitization and spirometric measurements (forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), FEV₁/FVC ratio, and maximum mid-expiratory flow (MMEF)), specific airway resistance (sRaw), fractional exhaled nitric oxide (FeNO), and methacholine challenge (PD₂₀) at 18 years of age were examined using linear regression models adjusted for house dust mite sensitization, smoking, and current pet exposure. Sensitivity analyses included continuous component-specific IgE levels and asthma-restricted models.

Among 347 adolescents at 18 years of age, 73 (21.0%) were sensitized to at least one pet allergen component measured by ISAC. Component sensitization patterns were dominated by monosensitization (64% of sensitized), most frequently to the cat allergen Fel d 1, which accounted for 86% of sensitized individuals, while polysensitization was less frequent and heterogeneous. 

Across individual ISAC components, sensitization was not associated with baseline lung function, including calibrated spirometric indices (FEV₁, FVC, FEV₁/FVC, and MMEF) or specific airway resistance. In contrast, sensitization to several specific ISAC components was associated with higher airway inflammation and bronchial hyperresponsiveness, as reflected by higher FeNO and lower methacholine PD₂₀ values (Figure). Component-sensitized adolescents had approximately 1.3–2.0-fold higher FeNO levels and 40–80% lower PD₂₀ compared with those without component sensitization. See Figure 1.

These associations were robust to adjustment for house dust mite sensitization and showed similar directionality in sensitivity analyses, including models restricted to adolescents with asthma. No differences in lung function, airway inflammation, or bronchial responsiveness were observed between mono- and polysensitized component profiles.

In adolescence, pet allergen component sensitization is dominated by monosensitization, most frequently to Fel d 1. Sensitization to individual pet allergen components is associated with airway inflammation and bronchial hyperresponsiveness, but not with impaired baseline lung function. Component-resolved diagnostics provide refined information on inflammatory airway phenotypes beyond conventional lung function measures.