28 Chemical Structure and Immunobiological Activity of Glycoconjugate from Treponema medium
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Treponemes are anaerobic bacteria with a typical helical shape that have been associated with the induction of human chronic diseases. Glycoconjugates distributed on the cell surfaces of some treponemes have been reported to be different from lipopolysaccharide (LPS). However, the chemical and immunobiological properties of the glycoconjugates have not been well characterized. In the present study, we separated a glycoconjugate fraction from Treponema medium ATCC 700293, a medium-sized oral spirochete, to examine the chemical structure and its immunobiological activities. The glycoconjugate was separated by phenol-water extraction, followed by hydrophobic chromatography and gel filtration. The chemical structure was shown by two-dimensional NMR and MALDI-TOF-MS to he a tetrasaccharide with two amino acids, [→4]β-D-GlcpNAc3NAcA(1→4)β-D-ManpNAc3NAOrn(1→3)β-D-GlcpNAc(1→3)α-D-Fucp4NAsp(1→), as a hydrophilic part and a lysophosphatidylglycerol derivative as a hydrophobic part. The glycoconjugate showed no immunostimulating activities, but we demonstrated that the glycoconjugate inhibited the LPS-induced immunostimulation. We also noted that the inhibitory effect was attributable to blocking the binding of LPS with LBP and CD14. Further, a phosphatidylglycerol derivative, which is a treponemal membrane phospholipid, was found to be a principle of the effect. These results suggest that the glycoconjugate and membrane phospholipid may be possible virulent factors of treponemes to evade the host defense system.
