Role of Lipoteichoic Acid from the Genus Apilactobacillus in Inducing a Strong IgA Response

Lactic acid bacterium-containing fermentates provide beneficial health effects by regulating the immune response. A naturally fermented vegetable beverage, a traditional Japanese food, reportedly provides health benefits; however, the beneficial function of its bacteria has not been clarified. Apilactobacillus kosoi is the predominant lactic acid bacterium in the beverage. Using murine Peyer's patch cells, we compared the immunoglobulin A (IgA)-inducing activity of 10H to those of 29 other species of lactic acid bacteria and found that species belonging to the genus ( 10H , A. apinorum JCM30765 , and A. kunkeei JCM16173 ) possessed significantly higher activity than the others. Thereafter, lipoteichoic acids (LTAs), important immunostimulatory molecules of Gram-positive bacteria, were purified from the three species, and their IgA-inducing activity was compared to those of LTAs from Lactiplantibacillus plantarum JCM1149 and a probiotic strain, Lacticaseibacillus rhamnosus GG. The results revealed that LTAs from species had significantly higher activity than others. We also compared the LTA structure of 10H with that of JCM1149 and L. rhamnosus GG. Although d-alanine or both d-alanine and carbohydrate residues were substituents of free hydroxyl groups in the polyglycerol phosphate structure in LTAs from strains JCM1149 and GG, d-alanine residues were not found in LTA from strain 10H by H nuclear magnetic resonance (NMR) analysis. Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) analysis of the glycolipid structure of LTA revealed that LTA from strain 10H contained dihexosyl glycerol, whereas trihexosyl glycerol was detected in LTAs from other strains. These structural differences may be related to differences in IgA-inducing activity. The components of lactic acid bacteria that exert immunostimulatory effects are of increasing interest for therapeutic and prophylactic options, such as alternatives to antibiotics, cognitive enhancements, and vaccine adjuvants. LTAs act as immunostimulatory molecules in the host innate immune system by interacting with pattern recognition receptors. However, as LTA structures differ among species, detailed knowledge of the structure-function relationship for immunostimulatory effects is required. Comparisons of the IgA-inducing activity of LTAs have demonstrated that LTAs from the genus possess distinctive activities to stimulate mucosal immunity. The first analysis of the LTA struct