Immunochemistry of Capsular Glucans Isolated from Streptococcus Bovis

Abstract

Abstract Dextran-like capsular materials were isolated from the culture filtrates of Streptococcus bovis strains C3, C36, C48, C106, and S19 by DEAE-cellulose chromatography. Quantitative precipitin analysis revealed a marked immunologic relationship among the capsular glucans of S. bovis. Inhibition studies, employing diglucose inhibitors, indicated that isomaltose was the most effective inhibitor of the reaction between the glucans and antiserum. Isomaltose, for example, inhibited 90% of the reaction between C36 glucan and its homologous antiserum. On the other hand, maltose at a concentration of 8 µmol/mg was almost as effective as isomaltose in inhibiting the reaction between C106 glucan and its homologous antiserum. These results indicate that isomaltose is a common feature of the capsular glucans isolated from a few selected strains of S. bovis. Further, the immunologic relationship which exists among the various glucans is, in part, dependent upon the proportion of the α 1–6 linkages as well as α 1–4 linkages in the carbohydrate chains. Evidence has been presented which indicates a chemical analogy between S. bovis glucans and clinical dextran.