Immunostimulatory Activity of Solubilized Peptidoglycan Derivatives Prepared From Lactic Acid Bacteria

To develop vaccine adjuvants from bacterial peptidoglycan (PG) the immunostimulatory activity of lysozyme-solubilized PG derived from Levilactobacillus brevis and Lactiplantibacillus plantarum was investigated. Solubilized PG from both bacteria induced IL-8 in THP-1 cells, and periodate oxidation of L. plantarum PG reduced the activity, suggesting that muramyl dipeptide was partially destroyed. Periodate-oxidized L. plantarum PG showed reduced IL-8 inducing activity in NOD2-expressing cells, while it remained in NOD1-expressing cells, suggesting that γ-d-glutamyl-meso-diaminopimelic acid structure was maintained. All PG preparations stimulated RAW264.7 cells to proliferate, suggesting that they could be potent candidates for vaccine adjuvants.