Structural analysis and mucosal immune regulation of exopolysaccharide fraction from Bifidobacterium animalis RH

ABSTRACTAn exopolysaccharide fraction (EPSa) produced by Bifidobacterium animalis RH was purified to dissect its chemical structure and to investigate its ability to modulate the mucosal immunity. Our results showed that EPSa had a backbone of (1→6)-linked glucose, (1→3)-linked galactose, (1→4, 6)-linked mannose, (1→3, 4)-linked mannose and (1→4)-linked glucose, branched with glucose and arabinose, and terminated with glucose residues. Scanning electron microscopy identified spherical particle to be the basic structural component of EPSa. The Congo red test indicated that EPSa was not in triple-helical conformation. Our in vitro results showed that EPSa was able to stimulate the proliferation of peripheral blood mononuclear cells and intestinal Peyer’s patch lymphocytes in the presence of concanavalin A. Our in vivo results demonstrated that EPSa can enhance the mucosal immunity by maintaining the Peyer’s patch number in small intestine and the IFN-γ level in serum, and balancing the Th1/Th2 responses.