Lactic acid bacteria as microbial cell factories for the in vivo delivery of therapeutic proteins as secretable TAT fusion products.

Protein-based therapeutics have garnered increasing attention across various medical fields for their substantial benefits to human health. Existing strategies for intracellular protein delivery, such as cell-penetrating peptide (CPP)-based approaches, including the transactivator of transcription (TAT) peptide, have shown promising results but also present limitations, particularly due to the need for recombinant protein manufacturing and daily invasive administration. To overcome such hindrances and develop delivery tools that are able to foster the production of the protein directly inside the body of patients, we engineered the lactic acid bacterium, Lactococcus lactis, to express and secrete TATκ-GFP protein. After oral administration of the recombinant L. lactis in mice, we found the presence of the TATκ-GFP protein not only in the intestinal wall but also in the mouse liver, heart, and brain. This provides the first evidence that a recombinant TATκ-fused protein, secreted by L. lactis in the mouse host gut, by virtue of the presence of the TATκ peptide, can efficiently pass from the intestinal wall to other organs. With future research and development, this technology based on lactic acid bacteria (LAB) as a platform for the production and delivery of therapeutic proteins could offer significant advancements in the field of therapeutic protein delivery.