6-Deoxy-D-talan and 6-deoxy-L-talan. Novel serotype-specific polysaccharide antigens from Actinobacillus actinomycetemcomitans

Serotype-specific polysaccharide antigens from Actinobacillus actinomycetemcomitans ATCC 29523 (serotype a) and NCTC 9710 (serotype c) were extracted from whole cells by autoclaving and purified by ion-exchange chromatography and gel filtration. Analysis of component sugars by gas-liquid chromatography-mass spectrometry, high performance liquid chromatography, and NMR together with optical rotation data showed that the serotype a antigen was composed solely of 6-deoxy-D-talose, whereas the serotype c antigen consisted of 6-deoxy-L-talose. Structural analysis indicated that both of these antigens were composed of closely related repeating units, -3)-6-deoxy-alpha-D-Talp-(1-2)-6-deoxy-alpha-D-Talp-(1-(sero type a) and -3)-6-deoxy-alpha-L-Talp-(1-2)-6-deoxy-alpha-L-Talp-(1-(sero type c). 1H and 13C NMR analysis showed that both of these serotype antigens contained one acetyl group/2 sugar residues. These acetyl groups localized at the O-2 position of 3-linked 6-deoxy-D-talose (serotype a) or O-4 position of 3-linked 6-deoxy-L-talose residues (serotype c), respectively. These results coupled with our previous findings on the serotype b antigen (Amano, K., Nishihara, T., Shibuya, N., Noguchi, T., and Koga, T. (1989) Infect. Immun. 57, 2942-2946) showed that the serotype antigens from A. actinomycetemcomitans are a group of novel polysaccharides with structural features closely related biosynthetically.