Detailed Structural Analysis of the Immunoregulatory Polysaccharides from the Mycobacterium Bovis BCG

Area of Science:

• Immunology
• Biochemistry
• Pharmacology

Background:

• Bacillus Calmette-Guérin polysaccharide and nucleic acid (BCG-PSN) is an established immunoregulatory medicine derived from *Mycobacterium bovis*.
• The specific structural features and pharmacological roles of polysaccharides within BCG-PSN have not been fully elucidated.
• Understanding these components is crucial for optimizing BCG-PSN's therapeutic applications.

Purpose of the Study:

• To isolate and structurally characterize polysaccharides from BCG-PSN.
• To investigate the immunomodulatory effects of these purified polysaccharides.
• To identify the active ingredients responsible for BCG-PSN's efficacy.

Main Methods:

• Purification of two distinct polysaccharides, designated BCG-1 and BCG-2.
• Structural elucidation using monosaccharide composition analysis, methylation analysis, and Nuclear Magnetic Resonance (NMR) spectroscopy.
• In vitro bioactivity assays using RAW264.7 cells to assess the production of inflammatory mediators (NO, TNF-α, IL-6, IL-1β, IL-10) and their corresponding mRNA levels.

Main Results:

• BCG-1 was identified as an α-D-(1→4)-mannan with (1→2)-linked branches, representing the first report of mannan from BCG-PSN.
• BCG-2 was characterized as an α-D-(1→4)-glucan with (1→6)-linked branches.
• Both BCG-1 and BCG-2 demonstrated potent, dose-dependent increases in inflammatory mediators and their mRNA expression in RAW264.7 cells, exhibiting effects comparable to or stronger than BCG-PSN injection.

Conclusions:

• BCG-1 (mannan) and BCG-2 (glucan) are the primary active polysaccharides within BCG-PSN.
• These polysaccharides exhibit significant immunomodulatory activity by stimulating the production of key inflammatory mediators.
• The findings identify BCG-1 and BCG-2 as the likely active ingredients responsible for the therapeutic effects of BCG-PSN.