Construction of human granulocyte-macrophage colonystimulating factor expression system using Lactococcus lactis MG1363

Lactic acid bacteria (LAB) have been used in a wide variety of industrial fermentation processes. Generally, LAB have regarded as safe status, making them potentially useful organisms for the production of commercially important proteins. Here, we developed protein expression systems using Lactococcus lactis MG1363 for which the protein of interest is targeted to a defined cell location, e.g., cytoplasm, cell wall, and medium. The expression system of human granulocyte-macrophage colony-stimulating factor (hGM-CSF) was successfully constructed, and the expression of hGM-CSF in the cytoplasm of L. lactis was detected by Western blotting. Efficient translocation was obtained using the signal peptide from lactococcal Usp45 protein and covalently anchored to the peptidoglycan by using the cell wall anchor motif of Streptococcus pyogenes M6 protein. These results suggest that L. lactis containing a new expression system can deliver many other useful genes to the intestine of human and mammalian to stimulate local mucosal immunity.