A durably colonising engineered native symbiont enables sustained intestinal delivery for metabolic dysfunction and...

Engineered bacterial therapeutics represent a promising strategy for sustained intestinal delivery of therapeutic molecules, but their efficacy is limited by inefficient colonisation, safety concerns and the need for repeated administration or auxiliary delivery systems.

To develop a safety-optimised native bacterial chassis capable of long-term gut colonisation and sustained therapeutic delivery for intestinal inflammatory and metabolic diseases.

Native murine Escherichia coli isolates were screened for antibiotic susceptibility, genetic tractability and long-term intestinal colonisation. The selected strain, MEc30, was further optimised by deleting the putative virulence-associated clb and irp loci. MEc30 was then engineered to produce nicotinic acid (MEc30-NA) or deliver murine interleukin-10 (MEc30-mIL-10), and therapeutic efficacy was evaluated in a high-fat diet-induced metabolic dysfunction model as well as Il10 ^-/- and dextran sulphate sodium (DSS)-induced colitis models.

MEc30 achieved stable lifelong colonisation of the murine intestine after a single oral administration, without antibiotic preconditioning or auxiliary delivery systems and did not detectably disturb host physiology or gut microbial ecology. Deletion of clb and irp abolished potential colibactin- and yersiniabactin-associated biosafety risks while preserving bacterial growth and colonisation capacity. MEc30-NA continuously produced nicotinic acid in the gut, activated epithelial GPR109a-associated barrier signalling, improved glucose and lipid metabolism, reduced systemic inflammation and avoided the sharp peak exposure associated with conventional nicotinic acid administration. MEc30-mIL-10 enabled sustained intestinal interleukin-10 delivery, suppressed inflammatory macrophage activation, improved barrier integrity and alleviated colitis in both Il10^{- / -} and DSS-induced mouse models.

This study identifies MEc30 as a durable and safety-optimised native E. coli chassis for sustained intestinal therapeutic delivery. Engineered native symbionts may provide a long-acting live biotherapeutic strategy for metabolic diseases and chronic intestinal inflammation.