Dispersion of horse allergen in the ambient air, detected with sandwich ELISA

Background: The objective was to establish an ELISA to detect horse allerge n in ambient air and settled dust. Methods: Monoclonal antibodies (mAbs) were produced against extracts of hor se antigen. Two mAbs were selected and used in a sandwich ELISA. By the aid of portable pumps, air samples were collected in one stable and in the amb ient air surrounding this stable. Furthermore, settled dust was collected b y wiping spots with pieces of fabric, at sites within 500 m of the stable. Results: Extracts of horsehair could be extensively diluted and still be po sitive. Extracts of cat and dog allergen failed to be detected. Furthermore , the mAbs were shown to detect an IgE-binding component. This was demonstr ated by an ELISA using mAbs as capture antibody and sera from horse-allergi c subjects as secondary antibody with readout depending on anti-IgE antibod y. The sera with the highest RAST class to horse were positive in this ELIS A. Airborne levels of horse allergen were over 500-fold higher in the stabl e than just outside the stable and over 3000-fold hi-her than at a resident ial building located only 12 rn fro the stable. Similarly, an inverse corre lation was found between the distance to the stable and levels of "outdoor settled" horse allergen (r = -0.9, P <0.001). Conclusions: We have developed a sensitive, horse-allergen-specific, mAb as say allowing detection of low levels of horse allergens. Raised levels of h orse allergen were found outdoors only in the close vicinity of the stable.