Su1828 Remission in Proton Pump Inhibitors-Responsive Esophageal Eosinophilia Correlates With Downregulation of Eotaxin-3 and TH2 Cytokines, Similarly to Eosinophilic Esophagitis After Steroids

Background: In eosinophilic esophagitis (EoE), eosinophils invade the esophagus where they degranulate and release very cytotoxic proteins, including major basic protein (MBP-1). Currently the diagnosis of EoE necessitates endoscopy with biopsy that characterizes less than 2% of the esophagus. Furthermore, the inflammation is patchy, necessitating numerous biopsies to ensure that the involved area has been adequately sampled. Improved methods are needed to characterize the eosinophil density throughout the esophagus and to thoroughly understand this disease. Aim: To prepare the first MBP-1 specific ultrasound contrast agents to facilitate the detection of EoE associated inflammation by tethering EoE specific antibodies to their surfaces and demonstrating the binding of these agents to eosinophil proteins on ex vivo monkey esophagi. Method: The contrast agent was synthesized by preparing 2 mg/ mL of insulin in HCl (pH 1.6) at 65C for 12 hours. The resulting particles were incubated withmaleimide activated streptavidin. Purified antibodies specific to MBP-1 were biotinylated and reacted with the streptavidin functionalized fibers to form an insulin aggregate-steptavidin-biotin antibody complex. This complex comprises the MBP-1 specific ultrasound contrast agent. A Macaca monkey esophagus, incubated overnight in MBP-1, was filled with this solution. Ultrasound images were taken before and after washing at 15 MHz. Results: Insulin aggregates were observed using ultrasound. Incubating the insulin complex in monkey esophagi coated with MBP-1 yields an extra contrast layer at the inner wall of the esophagus, demonstrating the specific binding of these agents to eosinophil granule proteins. No such layer is visualized in control samples (not treated with MBP-1). Discussion: This is the first reported use of insulin particles as contrast agents for ultrasound. These findings indicate that insulin aggregates provide clear ultrasound contrast in liquid environments. When coupled with disease specific antibodies, these novel agents have the potential to be used for detection, minimizing the need for anesthesia or radiation associated with other diagnostic or imaging modalities. This finding is important because it provides a new avenue for clinical detection of EoE.