Engineering probiotics for tuberculosis therapy

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PROJECT SUMMARY The engineering of living cells and microbes is driving a new era of medicine. This transformative approach allows for the genetic programming of living cells to intelligently sense and respond healthy and diseased envi- ronments in the body. Bacteria have specifically generated significant recent interest due to their genetic tracta- bility and ability to infiltrate disease sites. A multitude of studies have shown bacterial delivery of therapeutic payloads selectively into tumor cores, demonstrating specificity and efficacy that is otherwise unattainable with molecular-based therapeutics. Given this paradigm in cancer therapy, bacteria present a unique opportunity to be engineered as intelligent delivery vehicles to inaccessible disease sites. We recently discovered that probiotic E. coli Nissle 1917 (EcN) selectively home to granulomas, pathological regions developed at infection sites including tuberculosis. Tuberculosis kills 1.5 million people each year but conventional antibiotics are limited by toxicity, long treatment courses, and drug resistance. Importantly, while difficult for conventional therapeutics to reach, granulomas possess unique necrotic and hypoxic microenviron- ment similar to tumors that supports selective bacterial colonization. The objective of this proposal is to engineer EcN to home to granulomas and locally produce therapeutics to eliminate pathogenic Mycobacterium tuberculosis. We will use synthetic biology approaches to genetically engi- neer EcN as an intelligent drug delivery vehicle. We will utilize hypoxia-sensing growth circuits that further restrict probiotic growth the hypoxic, necrotic granuloma environment. Using a novel in vitro 3D coculture assay, we will screen a library of antimicrobial proteins to identify the most potent antimycobacterial therapeutic candidates. We will test the therapeutic efficacy of engineered E. coli using mycobacterium granuloma mouse models. This fundamentally new approach to granulomatous disease will open up opportunities to utilize engineered bacteria as therapeutic agent for granulomatous infections.