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.