Introduction: Esophageal inflammation associated with eosinophilic esophagitis (EoE) and gastroesophageal reflux disease (GERD) require invasive endoscopy and biopsy for diagnosis and testing efficacy of treatments. In the 1970's, the Enterotest, a weighted gelatin capsule filled with and attached to a 90 cm long nylon string, was introduced as a minimally invasive method to identify intestinal infections. Patients tape the string end extruding from the capsule to their cheek and swallow the capsule; the string subsequently deploys into the small intestine and the capsule released. After incubation for 15 min to overnight the string is pulled back out of the mouth. Here we present pilot data demonstrating that secretions adhering to the string may be recovered and analyzed using shotgun proteomics. Methods: Strings from the distal esophagus of patients with GERD and normal controls (n=2/group) were cut into 2cm sections and proteins recovered by incubating strings in lysis buffer. Tandem mass spectrometry analysis using a high-capacity quadrupole ion trap was performed on trypsin-digested samples and data were searched with X!Tandem through the LABKEY interface. Spectral counting provided relative quantitation of proteins between samples. Results: After removal of isoforms, 34 proteins common to all string samples (2 each from 2 patients/subjects) were identified. Annexin A1, keratins 16, 4 and 13, and MUC5B were most highly upregulated in esophageal secretions from GERD subjects as compared with normal controls. In addition, functional clustering revealed that anti-apoptotic proteins and those involved in extracellular signaling were present in only GERD and not normal controls. Conclusion: The Esophageal String Test can be used to sample esophageal secretions in health and disease. Host response proteins are present in the esophageal lumen during inflammation. This work was supported by R21-AI079925, Thrasher Foundation, CURED Foundation, Pappas Foundation and the Colorado Clinical Translational Scientific Institute (CCTSI) NIH/NCRR Grant Number 5UL1RR026314-02.
