Microbial Bioengineering for Therapeutic Applications

Abstract

Engineered microorganisms -- bacteria, yeast, and bacteriophages modified through synthetic biology -- are emerging as programmable therapeutic agents capable of sensing disease biomarkers, producing therapeutic molecules at the site of disease, and modulating the immune system with spatial and temporal precision unachievable by conventional pharmaceuticals. However, clinical translation of microbial therapeutics is constrained by biocontainment safety, genetic stability over successive generations, unpredictable pharmacokinetics in the human host, and regulatory uncertainty. This study engineered and evaluated five microbial therapeutic platforms -- Escherichia coli Nissle 1917 (EcN) secreting anti-TNF-alpha nanobodies, Lactobacillus reuteri producing interleukin-10 (IL-10), Saccharomyces boulardii expressing anti-Clostridioides difficile toxin-binding proteins, an engineered bacteriophage targeting vancomycin-resistant Enterococcus (VRE), and a proposed dual-circuit EcN chassis (DC-EcN) combining tumour-homing with hypoxia-activated prodrug conversion for colorectal cancer -- in validated murine disease models (n = 180 total). DC-EcN achieved the highest tumour growth inhibition (72.8 +- 6.4% in CT26 colorectal xenografts) with genetic circuit stability maintained over 200 generations in vitro and 14 days in vivo. The thymidine auxotrophic biocontainment system achieved 10^-9 escape frequency, meeting the NIH Guidelines threshold for engineered microorganisms. EcN-anti-TNF reduced colitis severity by 64.2 +- 8.4% (DAI score), outperforming systemic anti-TNF antibody (48.6 +- 10.2%; p = 0.008). These results establish engineered microbial therapeutics as a viable drug modality and provide a systematic safety and efficacy framework for preclinical evaluation.