Introducing streptococcal M6 protein into Lactobacillus gasseri and characterizing the probiotic traits of the engineered strains

• Published in: Advances in Food Sciences 2010-12
• Main Authors: Mansour, N M, el Raoof, SMA, Zakaria, M, Nosseir, M
• Format: Article
• Language: English
• Subjects: Bile; Bile salts; Cell surface; Colonization; Electroporation; Enzymes; Hydrophobicity; Immune response; Lactobacillus gasseri; M6 protein; Mucosa; Operons; Pancreas; pH effects; Plasmids; probiotics; Promoters; protective antigen; Rheumatic fever; Streptococcus pyogenes; Vaccines; Xylose
• ISSN: 1431-7737

The probiotic bacterium Lactobacillus gasseri ATCC 33323 was selected as a bacterial carrier for the development of mucosal vaccine targeting Streptococcus pyogenes to block colonization leading to a prevention of rheumatic fever. This would serve as a model for the delivery of other vaccines. The conserved region of streptococal M6 protein encoded by (emm6 fragment) was used as the protective antigen. Two inducible expression systems, namely, pSLP111.1 of the cell-surface expression system based on the xylose operon promoter and pLB210 based on bile salts-inducible promoter issued from Lb. plantarum, were used to express the M6 protein. The expression plasmids carrying the emm6 fragment were constructed and introduced into Lb. gasseri by optimizing the electroporation method. Before going further, we characterized the genetically modified Lb. gasseri strains for their probiotic properties and plasmid stability. The engineered strains harbouring the expression plasmids showed satisfying plasmid stability, in addition to good resistance to low pH of 2.5, 0.3% bile salts, and pancreatic enzymes. The hydrophobicity re-sults confirmed that the engineered strains are still keeping their probiotic properties, the vital factor as antigen carrier system. We are now testing the M6 protein expression by Lb. gasseri strains on their cell surface, and then will test the immune response.