Engineering Symbiotic Microbiota for in Situ Delivery of Therapeutic Proteins

As symbiotic members of the human microbiome, Lactobacilli are an emerging class of living biotherapeutic agents capable of sustained and targeted drug delivery of protein biologics to the many organs they naturally inhabit. However, progress to this end remains limited by the paucity of genetic tools for manipulating these bacteria. We used synthetic biology techniques to build a tunable, broad host range expression system, and applied in silico techniques for de novo design of robust, strain-optimized secretion signals that direct protein export. Together, these components provide an approach to rapidly engineer niche-adapted Lactobacilli for in situ delivery of therapeutic proteins. We leveraged this platform to engineer model symbionts from the gastrointestinal and female genital tracts to secrete single domain antibody fragments, as candidate vectors for IBD immunotherapy and HIV immunoprophylaxis. This work advances Lactobacillus as a vehicle for drug delivery, and serves as a platform to accelerate development of diverse, microbiome-based medicines capable of addressing myriad disease.