Antigens of Streptococcus mutans: Isolation of a Serotype-Specific and a Cross-Reactive Antigen from Walls of Strain V-100 (Serotype e) †

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Two cell wall-associated polysaccharide antigens were extracted from purified cell walls of Streptococcus mutans serotype e strain V-100. One of these purified antigens (I) is specific for serotype e, whereas the other (II) has antigenic determinants reactive with both heterologous anti-serotype c serum (GS-5) and the homologous (e) serum. When crude formamide extracts of V-100 cell walls were loaded onto a Cellex-D column and eluted with a linear gradient of ammonium carbonate (0.02 to 0.40 M), the two products mentioned above could be recovered. The purified, antigenically reactive products (I and II) were each composed only of rhamnose and glucose in approximately a 2:1 molar ratio. Immunoelectrophoresis of the crude formamide extract, peak I, and peak II showed the purified fractions to have opposite mobilities and the crude extract to have a mobility that encompassed both purified peaks when reacted with homologous antiserum (V-100). When these three fractions were immunoelectrophoresed and reacted with heterologous anti-serotype c serum (GS-5), only the anodic portion of the crude V-100 formamide extract and purified peak II formed precipitates. Ouchterlony analysis with homologous antiserum produced precipitin patterns between the crude formamide extract and both purified peaks, indicating complete identity. However, only crude extracts of V-100 and the purified peak II material reacted with heterologous (c) antiserum; peak I did not cross-react in these Ouchterlony assays. Hapten inhibition studies revealed that a β-glucosyl moiety is the immunodeterminant for serotype e and is present on each purified fraction. The basis of the cross-reaction between anti-c sera and the purified antigen II of e is discussed.

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