Development of an in vitro model system for studying the interaction of Equus caballus IgE with its high-affinity FcεRI receptor

Allergy is a serious life altering disease that is increasingly affecting people in the industrialized countries. Allergic manifestations are not restricted to humans, but are also observed, example, in inbred dogs and horses. Race horses are commonly afflicted by horse allergies and we have developed a cell culture model system for studying horse allergies. We created a genetically engineered rat basophil (RBL-2H3.1) cell line that expresses the ligand binding domain of the horse IgE high-affinity Fc receptor (FcεRI) and complemented this with a mouse B (J558L) cell line that expresses the heavy chain of horse IgE antibody. This allowed assessment of mediator release when the horse IgE binds to the transfected cell surface receptor and initiates downstream signaling upon antigenic challenge. To complement these studies a soluble form of the FcεRI (sFcεRIαD1&2) was expressed which facilitate the measurement of the binding kinetics between the horse IgE and FcεRI receptor. These developments formed the basis for the design of an allergy vaccine strategy, where rats were primed with an IgE-derived peptide followed by subsequent challenge with a chimeric IgE antibody displaying canine self IgE epitopes. The immunization strategy resulted in large polyclonal antibody titer found in the serum of immunized rat. Analysis of the immune response clearly indicated that antibodies were generated which aggregated human, horse and dog IgE on the basophil cell surface indicating that this strategy would be unsafe as an anti-allergic vaccine.