Specific IgE and IgG1 responses to subtilisin Carlsberg (Alcalase) in mice : Development of an intratracheal exposure model

The primary objective of this study was to examine the feasibility of using a mouse model to evaluate the immunogenicity of proteins as a potential method to determine occupational exposure guidelines. Mice were intratracheally administered a benchmark protein allergen, subtilisin Carlsberg (Alcalase) in detergent matrix once a week for 4 to 6 weeks and specific IgE and IgG1 levels were determined. In all experiments, specific IgE levels were determined by using a rat basophilic leukemia cell (RBL) release assay, while specific IgG1 was measured by an ELISA. A good correlation was observed between IgE titers determined by the RBL assay and rat passive cutaneous anaphylaxis assay. Intratracheal administration of protease with detergent matrix was found to result in significant IgE and IgG1 responses that were dose related. Detergent matrix was found to enhance the Alcalase-specific IgE and IgG1 response when administered by the intratracheal route. The IgG1 response was much more robust, easier to measure, and found to follow the IgE response. These results suggest that a mouse intratracheal model is a feasible approach to examining the immunogenic potency of enzymes using specific IgE or IgG1 as the end points. Additional development and validation of the mouse model with other types of proteins will be pursued.