Occurrence of [→3)-β-D-Manp-(1 → 4)-β-D-Manp-(1→](n) units in the antigenic polysaccharides from Leptospira biflexa serovar patoc strain Patoc I

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.