Augmentation of resistance of mice to bacterial infection by a polysaccharide-peptidoglycan complex (PSPG) extracted from Lactobacillus casei
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K Nomoto1, M Nagaoka, T Yokokura
1Yakult Central Institute for Microbiological Research, Tokyo, Japan.
Abstract:
A water-soluble polysaccharide-peptidoglycan complex (PSPG) was prepared from heat-killed Lactobacillus casei by digesting the bacteria with N-acetylmuramidase. The molecular weight of PSPG was over 30,000, and the polysaccharide portion of PSPG, its main component was composed of rhamnose, glucose, galactose, glucosamine and galactosamine. Mice pretreated intraperitoneally with PSPG survived after a lethal infection with Listeria monocytogenes or Pseudomonas aeruginosa. The growth of infecting bacteria (L. monocytogenes, P. aeruginosa, Salmonella typhimurium, Escherichia coli) in both the peritoneal cavity and the liver was inhibited markedly in the mice that had been treated with PSPG. It was suggested that macrophages may be the main effector for the anti-infectious effect of PSPG since treatment of mice with carrageenan, a selective macrophage blocker, markedly reduced the anti-infectious effect of PSPG.
Insights
A novel polysaccharide-peptidoglycan complex (PSPG) from Lactobacillus casei enhances innate immunity. PSPG treatment protected mice against lethal bacterial infections by inhibiting pathogen growth, likely via macrophage activation.
Area of Science:
- Immunology
- Microbiology
- Biochemistry
Background:
- Lactobacillus casei is a probiotic bacterium with known immunomodulatory properties.
- Bacterial components can stimulate the host immune system to enhance resistance against infections.
Purpose of the Study:
- To investigate the anti-infectious properties of a water-soluble polysaccharide-peptidoglycan complex (PSPG) derived from Lactobacillus casei.
- To elucidate the mechanism underlying the protective effects of PSPG.
Main Methods:
- PSPG was isolated from heat-killed Lactobacillus casei using N-acetylmuramidase digestion.
- The molecular weight and composition of PSPG were analyzed.
- Mice were pretreated with PSPG and subsequently challenged with lethal doses of Listeria monocytogenes or Pseudomonas aeruginosa.
- Bacterial growth in vivo was quantified.
- The role of macrophages was assessed using carrageenan, a macrophage blocker.
Main Results:
- PSPG, with a molecular weight >30,000, was successfully prepared and characterized.
- PSPG pretreatment conferred significant survival in mice against lethal L. monocytogenes and P. aeruginosa infections.
- PSPG markedly inhibited the growth of various bacteria, including L. monocytogenes, P. aeruginosa, Salmonella typhimurium, and Escherichia coli, in the peritoneal cavity and liver.
- Carrageenan treatment significantly abrogated the anti-infectious effect of PSPG, suggesting macrophage involvement.
Conclusions:
- The polysaccharide-peptidoglycan complex (PSPG) from Lactobacillus casei exhibits potent anti-infectious activity.
- PSPG enhances host defense mechanisms, leading to improved survival against bacterial challenges.
- Macrophages are likely the primary effector cells mediating the protective effects of PSPG.