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

Abstract

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-center 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-h 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 min and spirometry every 20 min. 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 min ("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 multisite chamber studies for clinical validation of allergy therapies. Future work could expand its capabilities to other aeroallergens.

Keywords: Cat; Exposure chamber; Provocation challenge; Rhinoconjunctivitis.