The diagnosis and monitoring of inflammatory bowel disease (IBD) relies on histologic and endoscopic analysis, as well as measurements of generic markers of inflammation. However, there are no specific tests that report on T cell-mediated immune responses as a key driver of IBD pathogenesis. Here we detect increasing granzyme A (GzmA) in gut biopsies and confirm that CD8 + T cells secrete its active form to induce interleukin (IL)-8. We then rationally design a non-invasive chemiluminescence assay for measuring active GzmA in stool supernatants from patients with IBD. For our assay, we synthesize peptide-based GzmA-specific inhibitors and chemiluminescent reporters and use them to characterize biosamples from ~150 human patients with IBD and healthy controls. Our results demonstrate that GzmA activity is an indicator of gut inflammation that can enhance the identification of patients with IBD over existing tests and potentially act as a mechanistic biomarker for the dominance of T cell activity. We envision that the selectivity and sensitivity of our GzmA activity-based optical assay will accelerate the design of additional biomedical approaches to enhance precision medicine in IBD.
Scott et al. (Tue,) studied this question.