In this study, we isolated three kinds of antigenic polysaccharide components (tentatively designed as AP-1 ~ 3) from cells of Leptospira biflexa serovar patoc strain Patoc I (L. biflexa patoc Patoc I) by the hot phenol-water procedure, followed by treatment with mild acid and column chromatography. Two of them (AP-1 and AP-2) were recovered from the phenol-soluble fraction whereas another (AP-3) was recovered from the aqueous fraction. All of them reacted toward an anti-L. biflexa serum and also cross-reacted in similar extents toward most of the other leptospiral antisera tested. Such immunoreactions were specifically inhibited by a β-(1 → 4)-linked mannobiose, but were not by any mono- and oligosaccharide tested. From their structural analyses including 1H and 13C NMR spectrometry, Smith degradation and methylation analysis, it was revealed that all of these antigenic polysaccharides had the same disaccharide unit →3)-β-D-Manp-(1 → 4)-β-D-Manp-(1→ in their major polysaccharide parts, but they differed in the acyl substituents. Therefore it is most likely that such mannobiose unit is a candidate for the antigenic epitopes of L. biflexa polysaccharides. (C) 2000 Elsevier Science Ltd.
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