Defining host:microbe interactions driving pro-fibrotic macrophages

About This Grant

Project Summary Intracellular bacteria interact and interfere with host cell signaling to drive phenotypic changes in the cells they inhabit. Bacteria are known to manipulate host signaling pathways to influence host metabolism, evade phagocytosis and killing, and promote distinct cell morphologies and physiologies. Although traditionally studied in the context of infectious disease, we now appreciate that interactions between resident intestinal bacteria – our microbiota – and host cells drive chronic inflammatory diseases. The extent of bacteria:host interaction is particularly intimate in cases of intracellular bacteria, such as adherent-invasive Escherichia coli (AIEC) linked to inflammatory bowel diseases (IBD) and co-morbidities including IBD-associated fibrosis and colorectal cancer. While several important secreted effector molecules have been discovered in the interaction of AIEC and macrophages, the activity of these secreted molecules within individual macrophage cells remains poorly understood. Here we will systematically investigate these interactions using fluorescent reporters, cell sorting and microscopy and develop a simple yet powerful microfluidic tool for high-throughput analysis of thousands of single mammalian cells along with the collective transcriptome of their intracellular bacterial cargo. We will use this approach to link the response of human macrophages to the activity of bacteria in the context of IBD-associated fibrosis mediated by an AIEC strain associated with colorectal cancer (E. coli NC101). We recently discovered this strain re-programs macrophages to a pro-fibrotic phenotype through the production of the metallophore yersiniabactin, thus contributing to fibrotic lesions that develop in the context of IBD. Our proposed work will define what bacterial effectors are induced upon AIEC infection and associated with distinct macrophage phenotypes and determine which of these actions are associated with host cells experiencing bacterial adherence/invasion vs. bystander exposure. This work has both technical and conceptual innovation, where we will establish and share our new single cell dual sequencing approach and also reveal mechanisms of single cell bacteria:host interactions that drive chronic inflammatory disease phenotypes.