Clinical Response to Cat Allergen in a Mobile Compared to a Fixed Naturalistic Exposure Chamber™.

Introduction: The Red Maple Trials Naturalistic Exposure Chamber™ (NEC™) is a fixed, live-cat exposure chamber wherein allergen shed from two resident cats is aerosolized using a modified robot vacuum. The EnviroMini™ is a portable allergen exposure tent, in which allergen (Fel d 1, primarily) from milled cat hair is aerosolized in a similar manner. This is a single-centre validation study designed to compare the allergic response to cat antigen provocation in the EnviroMini to the response in the previously validated NEC.

Methods: Eight cat allergic subjects were randomized to undergo sequential 2-hour allergen challenges in the EnviroMini and the NEC, 28 or more days apart. A modified robot vacuum aerosolized cat allergen in both chambers. Airborne Fel d 1 was measured using ELISA. Nasal, ocular and chest symptoms were recorded every 10 minutes and spirometry every 20 minutes. Challenges were stopped and not repeated if FEV1 fell >20% of baseline during the exposure.

Results: Fifteen subjects completed at least one challenge and eight completed both ("per-protocol"). Mean Total Nasal Symptom Score (TNSS) averaged over the last 30 minutes ("plateau") was not significantly different between the EnviroMini and NEC (paired t-test, p=0.16; mean (SE) 6.1 (1.2) and 4.5 (0.6), EnviroMini and NEC, respectively). There was no difference in FEV1 change between the two challenges (p= 0.90). The same results were found for all subjects as for the per-protocol group. TNSS plateau was not correlated with Fel d 1 exposure, and there was no difference in average Fel d 1 concentrations between the chambers (EnviroMini: 55; NEC: 54 ng/m3).

Conclusion: The EnviroMini offers comparable cat-allergen exposure and nasal and respiratory responses to the NEC. Its portability facilitates expansion to multi-site chamber studies for clinical validation of allergy therapies. Future work could expand its capabilities to other aeroallergens.