Chemical glycobiology tools to decipher host-microbiota interactions

PROJECT SUMMARY The microbes that live in and on our bodies—our microbiota—represent an emerging field for precision medicine and personalized care. Microbiota composition varies significantly between individuals, with over 4,500 different species represented across broad human metagenomic analyses. This variety of species appears to have functional consequences, and correlative studies have associated specific microbes with better outcomes for multiple immune-related diseases, including cardiovascular disease, neurological disorders, and many cancers. However, translating these findings into microbiota-targeted medicines has been largely limited by the significant lack of mechanistic data that underlie these associations. In this New Innovator Award proposal, we will tackle this critical gap in knowledge by discovering precise molecular, cellular, and spatial factors that allow commensal and so-called “probiotic” microbes to modulate host immunity. Here, we will focus on exo- and capsular polysaccharides, which are well-known modulators of both innate and adaptive immunity. Although glycan extracts from multiple microbial isolates have been implicated to alter inflammatory signaling, polysaccharides remain incredibly difficult to characterize compared to other biopolymers due to a lack of high-throughput and generalizable tools. Moreover, microbial polysaccharides pose an incredible challenge for current strategies used to study mammalian glycans due to the sheer diversity of glycan composition, structure, and localization found even across closely related microbial isolates. Our proposal will address this major technical challenge through the development of diversity-oriented approaches that will directly identify the host receptors, glycan motifs, cell types, and gut regions that are involved in microbial glycan signaling to the host. These goals will be achieved through new techniques to (1) screen glycome-receptorome interactions, (2) generate libraries of homogeneous and multipurpose glycan probes, and (3) engineer functionality into the microbial glycocalyx. As validation, we will then use our approaches to (4) illuminate the molecular mechanism(s) by which structurally disparate polysaccharides can act as novel ligands for a well-known pattern recognition receptor. Together, the strategies of our innovative proposal will provide a new molecular roadmap that reveals how microbial glycans mediate pro- and anti-inflammatory signaling in the gut and beyond. The methods generated by this proposal will also be generalizable to other polysaccharides found in pathogenic bacteria and even those from other kingdoms of life, expanding our arsenal of tools in chemical glycobiology to better characterize fundamental principles of glycan signaling.